HK1088140A

HK1088140A - Method and system for a data transmission in a communication system

Info

Publication number: HK1088140A
Application number: HK06108274.4A
Authority: HK
Inventors: R．A．阿塔尔; N.布尚; A.阿格拉瓦尔
Original assignee: 高通股份有限公司
Priority date: 2003-03-13
Filing date: 2004-03-11
Publication date: 2006-10-27

Description

Method and system for data transmission in a communication system

Technical Field

The present invention relates to communication in a wired or wireless communication system. More particularly, the present invention relates to a method and system for data transmission in such a communication system.

Background

Communication systems have been developed to allow transmission of information signals from an originating station (authorization station) to a physically different destination station. When an information signal from an origination station is transmitted over a communication channel, the information signal is first converted into a form suitable for efficient transmission over the communication channel. The conversion or modulation of the information signal involves changing the parameters of the carrier wave in accordance with the information signal in such a way as to confine the spectrum of the resulting modulated carrier wave within the communication channel bandwidth. At the destination station, the initial information signal is reconstructed from the modulated carrier wave received over the communication channel. Typically, this reconstruction is achieved by using the inverse of the modulation process employed by the origination station.

Modulation also simplifies multiple-access, i.e., the simultaneous transmission and/or reception of several signals over a common communication channel. Several multiple access techniques are known in the art, such as Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA). Another type of multiple access technique IS a Code Division Multiple Access (CDMA) spread Spectrum System, which conforms to the "TIA/EIA/IS-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wide-Bandspread Spectrum Cellular System", hereafter referred to as the IS-95 Standard. The use of CDMA technology in multiple ACCESS COMMUNICATION SYSTEMs is disclosed in U.S. Pat. No. 4,901,307, entitled "SPREAD SPECTRUM APPARATUS-ACCESS COMMUNICATION SYSTEM USENSATELLITE OR TERRESTRIAL REPEATERS," and U.S. Pat. No. 5,103,459, entitled "SYSTEM AND METHOD FOR GENERATING WAVEFORMING CDMA A CDMA CELLULAR TELEPHONE SYSTEM," both of which are assigned to the present assignee.

Multiple-access communication systems may be wireless or wired and may carry voice traffic and/or data traffic. An example of a communication system that carries both voice and data traffic IS a system in accordance with the IS-95 standard, which details the communication of voice and data traffic over a communication channel. One method FOR transmitting DATA in fixed-size code channel frames is described in detail in U.S. patent 5,504,773, entitled "method and APPARATUS FOR THE FORMATTING OF DATA FOR transmission," which is assigned to THE present assignee. According to the IS-95 standard, data traffic or voice traffic IS divided into 20 millisecond wide code channel frames having a data rate of 14.4 Kbps. Further examples of communication systems carrying both voice and data traffic include communication systems that comply with the "third generation partnership project (3 GPP)" which 3GPP is incorporated in a group of documents including: including documents No.3G TS 25.211, 3G TS 25.212, 3G TS 25.213 and 3G TS 25.214(W-CDMA standard), or "TR-45.5 Physical Layer Standard for CDMA2000 Spread Spectrum Systems" (IS-2000 standard).

The term base station is an access network entity with which subscriber stations communicate. With reference to the IS-856 standard, a base station IS also referred to as an access point depending on the context in which the term IS used. A cell is referred to as a base station or a geographic coverage area served by a base station. A sector is a portion of a base station that serves a portion of the geographic area served by the base station.

The term "subscriber station" is used herein to refer to the entity with which the access network communicates. Referring to the IS-856 standard, a base station IS also referred to as an access terminal. The subscriber station may be mobile or stationary. A subscriber station may be any data device that communicates through a wireless channel, such as fiber optic or coaxial cables, or through a wired channel. A subscriber station may also be any of several types of devices including, but not limited to, PC card, compact flash, external or internal modem, or wireless or wireline phone. A subscriber station in the process of establishing an active traffic channel connection with a base station is said to be in a connection setup state. A subscriber station that has established an active traffic channel connection with a base station is referred to as an active subscriber station and is considered to be in a traffic state.

The term access network is a collection of at least one Base Station (BS) and a controller of one or more base stations. The access network transports information signals between a plurality of subscriber stations. The access network may also be connected to additional networks outside the access network, such as a corporate intranet or the internet, and may carry information signals between each base station and such outside networks.

In the above-described multiple access wireless communication system, communication between users is performed through one or more base stations. The term user relates to both animate and inanimate entities. A first user on one wireless subscriber station communicates with a second user on a second wireless subscriber station by transmitting information signals on a reverse link to a base station. The base station receives the information signal and transmits the information signal on a forward link to the second subscriber station. The base station transmits data to another base station if a second subscriber station is not in an area served by the base station, the second subscriber station being located in a service area of the other base station. The second base station then transmits the information signal on the forward link to the second subscriber station. The forward link refers to transmissions from the base station to the wireless subscriber stations, and the reverse link refers to transmissions from the wireless subscriber stations to the base station. Likewise, communication may be between a first user at a wireless subscriber station and a second user at a landline (landline) station. The base station receives data from a first user at a wireless subscriber station on a reverse link and transmits the data to a second user at a landline station over a Public Switched Telephone Network (PSTN). In many communication systems, such as IS-95, W-CDMA, and IS-2000, the forward and reverse links are assigned respective frequencies.

The study of voice only traffic services and data only traffic services reveals some substantial differences between the two service types. One difference relates to the delay in the delivery of the information content. The voice traffic service imposes stringent and fixed delay requirements. Typically, the total one-way delay of a predetermined number of speech traffic information, called speech frames, must be less than 100 ms. Instead, the total unidirectional data traffic delay may be a variable parameter used to optimize the efficiency of the data traffic service provided by the communication system. For example, multi-user diversity requiring delays far greater than that which can be tolerated by voice traffic services, data transmission delays up to more favorable conditions, more efficient error correction coding techniques, and other techniques may be used. An exemplary efficient encoding scheme FOR data is disclosed in U.S. patent application serial No. 08/743,688, filed 11/6/1996, entitled "SOFT decision making device FOR DECODING consistent encoded codewards", which is now U.S. patent 5,933,462, issued to Sindhushayana et al at 8/3/1999, and assigned to the present assignee.

Another significant difference between voice traffic services and data traffic services is that the former requires a fixed and common Grade of Service (GOS) for all users. Typically, for digital communication systems providing voice traffic services, the requirements translate into a fixed and equal transmission rate for all users and a maximum allowable value for the error rate of the voice frames. In contrast, the GOS for the data service may be different for each user and may be a variable parameter, the optimization of which increases the overall efficiency of providing the data traffic service of the communication system. A GOS providing a data traffic service of a communication system is typically defined as a total delay incurred in transmitting a predetermined amount of data traffic information, which may comprise, for example, data packets. The term packet is a set of bits, including data (payload) and control elements, arranged into a specified format. The control elements include, for example, headers, quality metrics, and the like as known to those skilled in the art. Quality metrics include, for example, Cyclic Redundancy Check (CRC), parity bits, and the like as known to those skilled in the art.

Yet another significant difference between voice traffic services and data traffic services is that the former require a reliable communication link. When a subscriber station communicating voice traffic with a first base station moves to the edge of a cell served by the first base station, the subscriber station enters a region overlapping another cell served by a second base station. Subscriber stations in the region establish voice traffic communication with the second base station while maintaining voice traffic communication with the first base station. During such simultaneous communication, the subscriber station receives signals carrying the same information from both base stations. Likewise, both base stations also receive information-bearing signals from the subscriber station.

This simultaneous communication is called soft hand-off. When the subscriber station finally leaves the cell served by the first base station and interrupts the voice traffic communication with the first base station, the subscriber station continues the voice traffic communication with the second base station. Since soft handoff is a "make before break" mechanism, it minimizes the possibility of dropping a call. Methods and systems for providing communication with subscriber stations through more than one base station during a SOFT handoff procedure are disclosed IN U.S. patent No. 5,267,261, entitled "mobile handoff method-OFF IN a CDMA CELLULAR telecommunications system," assigned to the present assignee.

Softer handoff is a similar process whereby communication occurs over at least two sectors of a multi-sector base station. The softer handoff process is described in detail in pending U.S. patent application serial No. 08/763,498, filed 12/11/1996, entitled "METHOD and apparatus FOR PERFORMING AND OFF BETWEEN SECTORSOFF A COMMON BASE STATION", which is now U.S. patent 5,933,787, entitled "METHOD and apparatus FOR PERFORMING handoff on a patient" issued to Gilhousen et al on 3/8/1999, and assigned to the present assignee. Thus, soft and softer handoffs for voice traffic result in redundant transmissions from two or more base stations to improve reliability.

This additional reliability is not very important for data traffic communication, since erroneously received data packets may be retransmitted. Important parameters for data services are the transmission delay required to transmit data packets, and the average throughput of the data traffic communication system. The transmission delay does not have the same effect in data communication as in voice communication, but the transmission delay is an important metric for measuring the quality of a data transmission system. The average throughput rate is a measure of the efficiency of the data transmission capability of the communication system. Due to relaxed transmission delay requirements, the transmit power and resources used to support soft handoff on the forward link may be used for the transmission of additional data, thus increasing the average throughput rate by increasing efficiency.

The situation is different on the reverse link. Several base stations may receive signals transmitted by subscriber stations. Because packet retransmissions from a subscriber station require additional power from a power limited source (battery), it may be effective to support soft handoff on the reverse link by allocating resources at several base stations to receive and process data packets transmitted from the subscriber station. This use of Soft Handoff Increases coverage and reverse Link Capacity as discussed in the Andrew j. viterbi and klein s. gilhousen papers entitled "Soft Handoff CDMA coverage and industries Link Capacity" published in IEEE Journal on selected Areas in Communications, vol.12, No.8, 10.1994. The term soft handoff is communication between a subscriber station and two or more sectors, where each sector belongs to a different cell. In the case of the IS-95 standard, reverse link communications are received by two sectors and forward link communications are simultaneously carried on two or more sectors of the forward link. In the case of the IS-856 standard, data transmission on the forward link IS performed non-simultaneously between one of the two or more sectors and the access terminal. In addition, soft handover may be used for this purpose. The term softer handoff is communication between a subscriber station and two or more sectors, where each sector belongs to the same cell. In the case of the IS-95 standard, reverse link communications are received by two sectors and forward link communications are simultaneously carried on the forward link of one of the two or more sectors. In the case of the IS-856 standard, data transmission on the forward link IS performed non-simultaneously between one of the two or more sectors and the access terminal.

It is known that the quality and efficiency of data transmission in a wireless communication system depends on the condition of the communication channel between the source terminal and the destination terminal. This condition, expressed for example as a signal-to-interference-and-noise-ratio (SINR), is affected by several factors, such as the change in pathloss and pathloss of the subscriber station within the coverage of the base station, interference from other subscriber stations both in the same cell and other cells, interference from other base stations, and other factors known to those skilled in the art. To maintain a certain level of service under varying conditions of the communication channel, TDMA and FDMA systems separate users by different frequencies and/or time slots and support frequency reuse to mitigate the interference. Frequency reuse divides the available spectrum into a number of sets of frequencies. A given cell uses frequencies from only one group; cells immediately adjacent to the cell cannot use frequencies from the same group. In a CDMA system, the same frequency is reused in each cell of the communication system, thereby improving overall efficiency. The interference is mitigated by other techniques such as orthogonal coding, transmission power control, variable rate data, and other techniques known to those skilled in the art.

The above concepts are used in the development of Data-only communication systems known as High Data Rate (HDR) communication systems. Such a communication system is disclosed in pending patent application serial No. 08/963,386 filed on 3.11.1997 entitled "METHOD AND APPARATUS FOR HIGH RATE PACKET datan transmission", which is now us 6,574,211 issued to Padovani et al on 3.6.2003, assigned to the present assignee. The HDR communication system IS standardized to the TIA/EIA/IS-856 industry standard, hereinafter referred to as the IS-856 standard.

The IS-856 standard defines a set of data rates from 38.4kbps to 2.4Mbps at which an Access Point (AP) may transmit data to a subscriber station (access terminal). Since an access point is similar to a base station, the terminology with respect to cells and sectors is the same as with respect to voice systems. According to the IS-856 standard, data to be transmitted on the forward link, which IS divided into intervals, IS divided into data packets, with each data packet being transmitted in one or more intervals (slots). In each time slot, data transmission is from an access point to one and only one access terminal, which is within the coverage area of the access point, at the maximum data rate that can be supported by the forward link and communication system. The access terminal is selected based on the forward link condition between the access point and the access terminal. The forward link condition depends on interference and path loss between the access point and the access terminal, both of which are time-varying. Pathloss and changes in pathloss are created by scheduling transmissions by an access point within an interval during which forward link conditions for access terminals to a particular access point meet certain criteria that allow transmissions to occur with less power or at higher data rates relative to transmissions to the remaining access terminals, which thus improves the spectral efficiency of forward link transmissions.

In contrast, according to the IS-856 standard, data transmission on the reverse link IS initiated from multiple access terminals located within the coverage area of the access point. Moreover, because the antenna pattern of the access terminal is omni-directional, any access terminal within the coverage area of the access point can receive these data transmissions. Thus, the reverse link transmission suffers from several sources of interference: code division multiplexed overhead channels for other access terminals, data transmissions from access terminals located within the coverage of the access point (same cell access terminals), and data transmissions from access terminals located within the coverage of other access points (other cell access terminals). Multiplexing or multiplexing refers generally to the transmission of multiple data streams over a communication channel.

With the development of wireless data services, there has been emphasis on increasing data throughput on the forward link according to a model of internet services; where the server provides high-rate data in response to a request by the host. The server-to-host direction is analogous to a forward link requiring high throughput, while host-to-server requests and/or data transfers are accomplished at lower throughput. However, this development is indicative of the development of reverse link data convergence (intense) applications such as File Transfer Protocol (FTP), video conferencing, gaming, and other fixed rate data services. Such applications require improved reverse link efficiency to achieve higher data rates, such that the applications require higher throughput on the reverse link. There is therefore a need in the art to increase data throughput on the reverse link, ideally providing symmetric forward and reverse link throughput.

Embodiments of the inventive reverse link transmission METHOD AND APPARATUS are disclosed in pending patent application Ser. Nos. 10/313,553 AND 10/313,594 filed on 6.12.2002, entitled "METHOD AND APPATUS FOR A DATA TRANSMISSIONER A REVERSE LINK IN A COMMUNICATION SYSTEM", assigned to the assignee of the present invention. As explained in detail below, the inventive reverse link transmission method and apparatus are not fully applicable to already established (legacy) communication systems due to link budget considerations. Thus, introducing the inventive reverse link transmission methods and apparatus of patent applications serial numbers 10/313,553 and 10/313,594 into a conventional communication system, there are problems related to the above link budget considerations, as well as the coexistence of the following two subscriber stations: i.e., subscriber stations capable of receiving the inventive reverse link (new subscriber stations) and subscriber stations capable of receiving only the IS-856 reverse link (legacy subscriber stations). Additionally, the inventive reverse link transmission methods and apparatus also create a need in the art for methods and apparatus for power control and data rate determination.

Accordingly, there is a need in the art for an apparatus and method that can increase data throughput on the reverse link that takes into account the above-mentioned problems.

This application relates to U.S. patent application No. 10/389,176, (attorney docket No. 030215U2), entitled "Method and System for a Data Transmission a Communication System", filed 3/13/2003; U.S. patent application No. 10/389,716 (attorney docket No. 030215U3), entitled "Method and System For estimating Parameters of a Link For Data Transmission in an A communication System", filed 3/13/2003; and U.S. patent application No. 10/389,656 (attorney docket No. 030215U4), entitled "Method and System for A Power control in A Communication System", filed 3/13/2003, which is assigned in its entirety to the assignee of the present invention.

Disclosure of Invention

In one aspect of the present invention, the above need is addressed by receiving an assignment of a sequence of intervals in each of first and second subsets of a set of access terminals, each interval being associated with a multiple access mode, wherein the second subset is mutually exclusive from the first subset; receiving, at each of a first subset of the access terminals, a scheduling decision for an interval associated with a first mode of multiple access, the interval being divided into a first portion and a second portion, the first portion comprising an overhead channel; selecting a mode for data multiplexing in each of a first subset of the access terminals, wherein the first mode includes building user data into only a first portion of the interval using a multiplexing format; the second mode comprises building user data only into at least one sub-division of a second part of the interval, wherein each of the at least one sub-division is associated with a multiplexing format; and the third mode comprises building user data into the interval in combination with the first and second modes; and transmitting user data from at least one of the first subset of the access terminals in an interval associated with a first mode of multiple access using the selected mode of data multiplexing in accordance with the scheduling decision.

In another aspect of the present invention, the above need is addressed by selecting a mode for data multiplexing in each of a second subset of the access terminals, wherein a third mode includes building user data into only a first portion of the interval using a multiplexing format; the fourth mode includes building user data into only the second portion of the interval using a multiplexing format; and the third mode comprises building user data into the interval in combination with the first and second modes; and transmitting user data from at least one of the second subset of access terminals in an interval associated with a second mode of multiple access using the selected data multiplexing mode.

In another aspect of the present invention, the above need is addressed by utilizing a first mode of data multiplexing to transmit user data from at least one of a second subset of the access terminals in an interval associated with a first mode of multiple access.

In another aspect of the present invention, the above need is addressed by transmitting user data from a third subset of the set of access terminals; the third subset is mutually exclusive from the first subset and the second subset.

Drawings

FIG. 1 illustrates a conceptual block diagram of a communication system capable of operating in accordance with an embodiment of the invention;

FIG. 2 illustrates an embodiment of a forward link waveform of the present invention;

fig. 3 illustrates a method of transmitting power control commands and packet grant (grant) commands on a reverse power control channel;

4a-4d illustrate embodiments of reverse link waveforms;

FIGS. 5a-5c illustrate embodiments of structures of reverse link channels;

FIGS. 6a-6c illustrate conceptual block diagrams of an OFDM communication system;

FIG. 7 illustrates an embodiment of reverse link data transmission; and

fig. 8 illustrates an embodiment of reverse link data retransmission;

fig. 9 shows an access terminal; and

fig. 10 shows an access point.

Detailed Description

Fig. 1 shows a conceptual diagram of a communication system. Such a communication system can be established in accordance with the IS-856 standard. The access point 100 transmits data to the access terminals 104 over a forward link 106(1) and receives data from the access terminals 104 over a reverse link 108 (1). Similarly, access point 102 transmits data to access terminal 104 over forward link 106(2) and receives data from access terminal 104 over reverse link 108 (2). Data transmission on the forward link occurs from one access point to one access terminal at or near the maximum data rate that can be supported by the forward link and communication system. Additional channels of the forward link, such as control channels, may be transmitted from multiple access points to an access terminal. Reverse link data communication may occur from one access terminal to one or more access points. The access points 100 and 102 are connected to an access network controller 110 through backhaul (backhaul)112(1) and 112 (2). The "backhaul" is the communication link between the controller and the access point. Although only two access terminals and one access point are shown in fig. 1, this is for illustration only, and the communication system may include a plurality of access terminals and access points.

After registration, which allows an access terminal to access the access network, the access terminal 104 and one of the access points, e.g., access point 100, establish a communication link using a predetermined access procedure. In the connected state, the access terminal 104 can receive data and control messages from the access point 100 and can transmit data and control messages to the access point 100 due to a predetermined access procedure. The access terminal 104 continually searches for other access points that may be added to the active set (active set) of the access terminal 104. The active set includes a list of access points capable of communicating with the access terminal 104. When such an access point is discovered, the access terminal 104 calculates a quality metric for the forward link of the access point, which may include a signal-to-interference-and-noise ratio (SINR). The SINR may be determined from the pilot signal. The access terminal 104 searches for other access points and determines the SINR of the access point. At the same time, the access terminal 104 calculates a quality metric for the forward link for each access point in the access terminal's 104 active set. If the forward link quality metric from a particular access point exceeds a predetermined increase (add) threshold or falls below a predetermined decrease (drop) threshold for a predetermined period of time, the access terminal 104 reports this information to the access point 100. Subsequent messages from the access point 100 may instruct the access terminal 104 to add or delete a particular access point from the access terminal's 104 active set.

The access terminal 104 selects a serving access point from the active set of the access terminal 104 based on a set of parameters. A serving access point is an access point that is selected for data transmission with, or is transmitting data to, a particular access terminal. The parameter set may include, for example, any one or more of current and previous SINR measurements, bit error rates, packet error rates, and any other known parameters. Thus, for example, the serving access point may be selected based on the maximum SINR measurement. The access terminal 104 then broadcasts a data request message (DRC message) on a data request channel (DRC channel). The DRC message may include the requested data rate or, alternatively, an indication of the quality of the forward link, such as a measured SINR, bit error rate, packet error rate, etc. The access terminal 104 may direct the broadcast of the DRC message to a specified access point by using a code that uniquely identifies the specified access point. Typically, the codes comprise Walsh codes. XOR the DRC message symbol exclusively with the unique code. The XOR operation is referred to as code coverage of the signal. Since each access point in the active set of the access terminal 104 is identified by a unique walsh code, the DRC message can be correctly decoded using only the selected access point performing an XOR operation equivalent to that performed by the access terminal 104 with the correct walsh code.

Data to be sent to the access terminal 104 arrives at the access network controller 110. Thereafter, the access network controller 110 may send data over the backhaul 112 to all access points in the access terminal 104 active set. Alternatively, the access network controller 110 may first determine which access point was selected by the access terminal 104 as the serving access point and then send the data to the serving access point. The data is stored in a queue at the access point. The paging message is then transmitted by one or more access points to the access terminal 104 on respective control channels. The access terminal 104 demodulates and decodes the signals on the one or more control channels to obtain the paging message.

At each forward link interval, the access point schedules data transmission to any access terminal that has received the paging message. An exemplary method for scheduling transmissions is described in U.S. Pat. No. 6,229,795, entitled "System for allocating resources in an communication System," which is assigned to the present assignee. The access point uses the rate control information received in the DRC message from each access terminal to efficiently transmit forward link data at the highest possible rate. Since the data rate may vary, the communication system operates in a variable rate mode. The access point determines the data rate at which to send data to the access terminal 104 based on the most recent value of the DRC message received from the access terminal 104. In addition, the access point uniquely identifies transmissions to the access terminal 104 by using a spreading code that is unique to that mobile station. The spreading code IS a long Pseudo Noise (PN) code, such as the spreading code defined by the IS-856 standard.

The access terminal 104 to which the data packet is to be transmitted receives and decodes the data packet. Each data packet is associated with an identifier, such as a sequence number, that the access terminal 104 uses to detect lost or duplicated transmissions. In such an event, the access terminal 104 transmits the sequence number of the missing data packet via the reverse link data channel. The access network controller 110, which then indicates to the access point which data units were not received by the access terminal 104, receives data messages from the access terminal 104 via the access point with which the access terminal 104 is in communication. The access point then schedules a retransmission of the data packet.

When the communication link between the access terminal 104 and the access point 100 operating in the variable rate mode deteriorates below a predetermined level of reliability, the access terminal 104 first attempts to determine whether another access point in the variable rate mode is capable of supporting an acceptable data rate. If the access terminal 104 determines the access point (e.g., access point 102), then a redirection (relocation) of the access point 102 to a different communication link occurs. The term redirection is the selection of a sector that is a member of the access terminal's active list, where the sector is different from the currently selected sector. The data transmission continues from access point 102 in the variable rate mode.

The above-described deterioration of the communication link may be caused by, for example: access terminal 104 moves from the coverage of access point 100 to the coverage of access point 102, shadowing, fading, and other known causes. Alternatively, when a communication link between the access terminal 104 and another access point (e.g., access point 102) becomes available, a redirection of the access point 102 to a different communication link occurs and data transmission continues from the access point 102 in the variable rate mode, which may achieve a higher throughput rate than the currently used communication link. If the access terminal 104 fails to detect an access point capable of operating in the variable rate mode and supporting an acceptable data rate, the access terminal 104 transitions to the fixed rate mode. In this mode, the access terminal transmits at one rate.

The access terminal 104 evaluates the communication link with all candidate access points for both the variable rate data and fixed rate data modes and selects the access point that yields the highest throughput.

If the sector is no longer a member of the access terminal 104 active set, the access terminal 104 will transition from the fixed rate mode back to the variable rate mode.

The above-described FIXED RATE mode AND associated METHODs FOR converting to AND from a FIXED RATE data mode are similar to the modes AND METHODs disclosed IN detail IN U.S. patent application 6,205,129 entitled "METHOD AND APPARATUS FOR VARIABLE AND FIXED FORWARD LINK RATE CONTROL IN A MOBILE COMMUNICATION SYSTEM", which is assigned to the present assignee. Other fixed rate modes and associated methods for switching to and from fixed modes are also contemplated and are within the scope of the present invention.

Forward link structure

Fig. 2 shows a forward link architecture 200. It should be appreciated that the durations, chip lengths, ranges of values described below are given by way of example only, and that other durations, chip lengths, ranges of values may be used without departing from the basic principles of operation of the communication system. The term "chip" is a unit of a code spread signal having two possible values.

The forward link 200 is defined in terms of frames. A frame is a structure comprising 16 slots 202, each slot 202 being 2048 chips long, corresponding to the duration of a 1.66ms slot, and thus a frame duration of 26.66 ms. Each time slot 202 is divided into two half-slots 202a, 202b with a pilot burst (pilot burst)204a, 204b being transmitted within each half-slot 202a, 202 b. Each pilot burst 204a, 204b is 96 chips long and is located at the midpoint of its associated half-slot 202a, 202 b. The pilot bursts 204a, 204b comprise a pilot channel signal covered by a code, e.g., a walsh code with index 0. Forward medium access control channel (MAC)206 forms two bursts that are transmitted immediately before and after pilot burst 204 of each half-slot 202. The MAC consists of up to 64 code channels that are orthogonally covered by 64-bit (64-ary) codes, such as walsh codes. Each code channel is identified by a MAC index having a value between 1 and 64 and identifies a unique 64-bit covering walsh code. A reverse power control channel (RPC) is used to adjust the power of the reverse link signal for each subscriber station. The RPC is assigned to one of the available MACs, e.g. a MAC with a MAC index between 5 and 63. A Reverse Activity (RA) channel is used to adjust the reverse link data rate for each subscriber station by transmitting a stream of reverse link activity bits (RABs). The RA channel is assigned to one of the available MACs, e.g., MAC index 4. The forward link traffic channel or control channel payload is transmitted in the remaining portion 208a of the first half-slot 202a and the remaining portion 208b of the second half-slot 202 b. The traffic channel carries user data and the control channel carries control messages and may also carry user data. The control channel is transmitted at a data rate of 76.8kbps or 38.4kbps using a cycle defined as a period of 256 slots. The term user data, also referred to as traffic, is information other than overhead data. The term overhead data is information that enables operation of entities in the communication system, such as call maintenance signaling, diagnostic and reporting information, and the like.

Packet grant channel and automatic repeat request

As discussed, the communication system may require support for access terminals that operate the reverse link in accordance with the IS-856 standard (legacy access terminals), as well as access terminals that operate the reverse link in accordance with the concepts described (new access terminals). To support such an operation, an additional channel, a Packet Grant (PG) channel, is required on the forward link. The PG channel may be provided by changing the modulation of one of the above MAC channels, e.g., RPC channel, from Binary Phase Shift Keying (BPSK) to Quadrature Phase Shift Keying (QPSK). When the second portion of the reverse link interval is dedicated to one access terminal (see below), only one PG channel, i.e., the primary PG channel, is needed.

The power control commands are modulated on the in-phase branch of the RPC channel assigned to the access terminal. The power control command information is binary, wherein a first value of a power control bit ("up") commands the access terminal to increase the transmit power of the access terminal by a first determined amount and a second value of the power control bit ("down") commands the access terminal to decrease the transmit power of the access terminal by a second determined amount. As shown in FIG. 3, the "increment" command is denoted as + 1; the "down" command is denoted as-1. However, other values may be used.

The primary PG channel is transmitted on the orthogonal branch of the RPC channel allocated to the access terminal. The information sent on the primary PG channel is ternary. As shown in fig. 3, the first value is represented by +1, the second value is represented by 0, and the third value is represented by-1. The information has the following meaning for both the access point and the access terminal:

+1 means that a new packet is allowed to be transmitted that has already been granted;

0 means that the transmission of packets that are not permitted is allowed; and

-1 means that previously sent packets (retransmissions) that have been granted are allowed to be transmitted.

The above signaling, in which the transmission of the information value 0 does not require signal energy, allows the access point to allocate energy to the primary PG channel only when an indication to transmit a packet is sent. The primary PG channel requires very little power to provide reverse link transmission information since only one or a small number of access terminals are allowed to transmit on the reverse link in the interval. Thus, sufficient power can be allocated to the primary PG channel to ensure reliable reception of the primary PG channel at the access terminal without undue interference from the power allocation. Thus, the impact on the RPC power allocation method is minimized. RPC power allocation methods are disclosed, for example, in the following patent applications: pending U.S. patent application 09/669,950, entitled "Methods and apparatus for Allocation of Power to base stations", filed on 25.9.2000 and pending U.S. patent application 10/263,976, entitled "Power Allocation for Power Control Bits in a Cellular Network", filed on 2.10.2002, both of which are assigned to the present assignee. Further, the access terminal is required to perform ternary decision on the forward (forward stream) only when the access terminal expects a response after a data transfer request or when the access terminal has a pending data transmission. However, it should be appreciated that the choice of ternary values is a design choice and that values other than those described may be used.

The access terminal receives and demodulates the RPC/Primary PG channels from all access points in the access terminal's active set. Thus, the access terminal receives the primary PG channel information, which is transmitted on the orthogonal branch of the RPC/primary PG channel for each access point in the access terminal's active set. The access terminal may filter the energy of the received primary PG channel information by an update interval and compare the filtered energy to a set of thresholds. With proper threshold selection, access terminals that are not allowed to transmit decode the primary PG channel value to 0 with a high probability.

The information transmitted on the primary PG channel is also used as a means for automatic retransmission requests.

When the reverse link transmission of a packet from an access terminal is received only by the serving access point, the serving access point generates and sends a grant upon correctly receiving a previous packet from the access terminal to send a new packet in response to the access terminal's request to send a packet. In this case, this information on the primary PG channel is used as an Acknowledgement (ACK). If a previous packet from the access terminal is received in error, the serving access point generates and sends a grant to retransmit the previous packet in response to the access terminal's request to send the packet. This information on the primary PG channel is used as a Negative Acknowledgement (NACK). Therefore, a separate ACK/NACK channel is not required.

Alternatively, reverse link transmissions of packets from an access terminal may be received at multiple access points.

When a non-serving access point receives and decodes the reverse link from a transmitting access terminal, the non-serving access point provides information to the serving access point whether the user data was successfully decoded. The serving access point then sends an ACK/NACK to the access terminal on the primary PG channel.

Optionally, the access point having received the payload information transmits the payload information to a centralized entity to perform soft-decision (soft-decision) decoding. The centralized entity then informs the serving access point whether payload decoding was successful. The serving access point then sends an ACK/NACK to the access terminal on the primary PG channel.

Optionally, the non-serving access point may autonomously send an ACK/NACK to the access terminal on the primary PG channel once the reverse link is decoded. For example, an access terminal may receive conflicting information on the primary PG channel because some access points fail to correctly receive the access terminal's transmission due to information on the primary PG channel being deleted or received in error or for other known reasons. Thus, information sent in response to reverse link transmissions on the primary PG channel is interpreted differently when sent through a serving or non-serving access point. Since it is not important from the access network perspective which access point received the access terminal's transmission, when the access terminal receives information on the primary PG channel that is interpreted as an ACK from any access point, the access terminal sends a new packet at the next transmission permission, although the serving access terminal may have sent permission to resend previously sent packets.

Because the access terminal makes a ternary decision on the primary PG channel received from the serving access point and a binary decision on the primary PG channel received from the access point, the access terminal may use different thresholds for the ternary and binary decisions.

The PG channel described above provides satisfactory information when the second portion of the reverse link interval is dedicated to only one access terminal (see below). However, when the second portion of the reverse link interval is dedicated to multiple access terminals, additional information is provided in which subsection of the second portion of the reverse link interval which one of the access terminals that received the transmit grant will transmit in. Such information may be provided on the supplemental PG channel.

The structure of the supplementary PG channel is identical to that of the above PG channel except that the supplementary PG channel has a different MAC index. Referring again to fig. 3, the supplemental PG channel information is transmitted on both the in-phase and quadrature branches. The information, along with information obtained from the PG channel, is interpreted as follows:

ignoring the supplemental PG channel information when the PG channel informs the access terminal that there is no permission to transmit packets;

when the PG channel informs the access terminal that permission to send a new packet is granted or permission to send a previously sent packet (retransmission) is granted, then:

0 means that the access terminal is to use the entire second portion of the reverse link interval;

any of the remaining four values identify one of four subsections of the second portion of the reverse link interval.

Thus, the signaling described above can support four subsections of the second portion of the reverse link interval. If more sub-parts should be needed, additional supplemental PG channels can be added.

Once an access terminal accesses the communication system, the PG channel, i.e., the MAC index, may be assigned to the access terminal. Alternatively, the PG channel may be assigned to an access terminal, and the supplemental PG channel may be determined by the access terminal based on the MAC index of the PG channel, e.g., by adding a determined offset (offset) to the PG channel.

Reverse activity channel

As described above, communication systems in accordance with the IS-856 standard use a reverse activity channel to adjust the reverse link data rate for each subscriber station by transmitting a stream of reverse link activity bits (RABs). The reverse activity channel is sufficient if a new terminal transmitting only in an interval dedicated to TDMA operates in the communication system. However, to support both legacy access terminals and new access terminals transmitting in intervals dedicated to TDMA, additional channels are required on the forward link.

To support the reverse link data rate for a new access terminal transmitting in an interval dedicated to TDMA, transmission of a reverse activation channel support value may be required that adjusts the data rate, requiring more than one bit. Since it may be desirable not to change the design of the forward link too much, the additional reverse activity channel may have the same structure as the conventional reverse activity channel, but will be assigned a different MAC index. Since such reverse activity channels only support transmission of one bit, multiple bit values may be transmitted over several transmission instances of the reverse activity channel.

The forward link 200 IS a modification of the forward link of a communication system in accordance with the IS-856 standard. The modification IS considered to have minimal impact on the forward link structure and therefore requires minimal changes to the IS-856 standard. However, it should be appreciated that the teachings are applicable to different forward link architectures. Thus, for example, the forward link channels may be transmitted non-continuously but simultaneously. In addition, any forward link structure capable of communicating information may be used, the information being provided in the following channels: PG, supplemental PG, and RA channels such as separate PG and ACK/NACK code channels, a new RA channel different from the conventional RA channel.

Reverse link

As discussed above, the quality and efficiency of data transfer depends on the channel conditions between the source terminal and the destination terminal. The channel conditions depend on interference and path loss, both of which are time varying. Thus, the reverse link performance may be improved by interference mitigation. On the reverse link, all access terminals in the access network may transmit simultaneously on the same frequency (one frequency reuse set), or multiple access terminals in the access network may transmit simultaneously on the same frequency (more than one frequency reuse set). It should be noted that the reverse link described herein may utilize any frequency reuse. Thus, the reverse link transmission of any access terminal is subject to several sources of interference. The most dominant sources of interference are:

transmission of code division multiplexed overhead channels from other access terminals, the access terminals being from both the same cell and other cells;

transmission of code division multiplexed user data by access terminals in the same cell; and

transmission of code division multiplexed user data by access terminals from other cells.

Research into the performance of the reverse link in a Code Division Multiple Access (CDMA) communication system has shown that eliminating interference from the same cell can achieve significant improvements in the quality and efficiency of data transmission. Interference from the same cell in a communication system employing CDMA, i.e., a communication system according to the IS-856 standard, may be mitigated by limiting the number of access terminals that may concurrently transmit on the reverse link.

Since there are two modes of operation, limiting the number of access terminals transmitting simultaneously and allowing all access terminals to transmit simultaneously, the access network needs to instruct the access terminals which mode to use. The indication is transmitted to the access terminal in periodic intervals, i.e., in a predetermined portion of the forward link channel, e.g., each control channel period. Alternatively, the indication is communicated to the access terminal only if changed by a broadcast message in a forward link channel, e.g., a reverse power control channel.

When operating in the restricted mode, the forward link channel of the compressed grant (packet grant) described above may be used to provide permission or denial of transmission to an access terminal requesting permission to transmit.

The same-cell interference may also be mitigated by time-multiplexing the traffic and overhead channels of the reverse link, and by scheduling which of the access terminals requesting transmission is permitted to transmit user data or traffic in a reverse link interval, such as a frame, time slot, or any interval supported by the communication system. The scheduling may take into account the entire access network and may be performed by a centralized entity, such as the access network controller 110. This scheduling approach minimizes interference since the terminals transmit in neighboring sectors of the cell. Alternatively, the scheduling may take into account a part of the access network comprising only one access point and may be performed by a centralized entity or by a decentralized entity, such as an access point controller. This scheduling method only mitigates interference of the same cell. Furthermore, a combination of the two approaches may be used, where one entity schedules several access points instead of the entire network.

It should be appreciated that the number of access terminals allowed to transmit in an interval affects the interference on the reverse link and, therefore, the quality of service (QoS) on the reverse link. Thus, the number of access terminals allowed to transmit is a design criterion. Thus, this amount can be adjusted by the scheduling method according to changing conditions and/or requirements of QoS.

Additional improvements may be realized by mitigating interference from other cells. Other cell interference during user data transmission is mitigated through opportunistic (opportunistic) transmissions, maximum transmit power control, and user data rates for each access terminal within the multi-sector cell. "opportunistic transmission" (and multi-user diversity) means that transmissions for the access terminal are scheduled for an interval that exceeds a determined opportunity threshold. An interval may be considered to be correct if a metric exceeds an opportunity threshold, the metric being determined based on an instantaneous quality metric of a reverse link channel within the interval, an average quality metric of the reverse link channel, and a function that enables differentiation between users, such as an urgency function described below. The method enables an access terminal to transmit user data at a lower transmit power and/or to complete transmission of packets with fewer intervals. Lower transmit power and/or completion of packet transmissions in fewer intervals results in reduced interference from transmitting access terminals in sectors of a multi-sector cell and, thus, lower total other-cell interference to access terminals in neighboring cells. Optionally, the override of the average channel condition allows the terminal to transmit at a higher data rate with the available power, thus causing the same interference to other cells as would be caused by the access terminal transmitting at a lower data rate during an inappropriate transmission interval with the same available power.

In addition to mitigating interference on the reverse link channel, multi-user diversity can take advantage of the path loss and variations in path loss to increase throughput. "multi-user diversity" arises from the diversity of channel conditions between access terminals, e.g., due to different locations experiencing different dead zones and fading, which vary over time. Diversity in channel conditions among user terminals allows scheduling of access terminal transmissions during an interval during which the access terminal's channel conditions meet certain criteria that allow transmission at less power or higher data rates, thus improving the spectral efficiency of reverse link transmissions. Such criteria include a quality metric for the access terminal's reverse link channel that is better than an average quality metric for the access terminal's reverse link channel.

The design of the scheduler may be used to control access terminal QoS. Thus, for example, while the opportunity reported by the terminal may be lower than the opportunity reported by a terminal not belonging to the subset, the subset may be given transmission priority by biasing the scheduler toward the subset of access terminals. It should be appreciated that a similar effect may be achieved by employing the urgency function discussed below. The term subset is a set whose members include at least one member but not all members of another set.

Even with opportunistic transmission methods, transmitted packets may be erroneously received and/or deleted at the access point. The term delete is not able to determine the message content with the required reliability. The erroneous reception is due to interference from other cells and the access terminal cannot accurately predict a quality metric of the access terminal's reverse link channel. Other cell interference is difficult to quantify in a communication system where transmissions from access terminals belonging to different multi-sector cells are unsynchronized, short, and uncorrelated.

To mitigate incorrect channel estimates and provide interference averaging, an Automatic Re-transmission reQuest (ARQ) method is typically used. The ARQ method detects lost or erroneously received packets at the physical layer or the link layer and requests retransmission of these packets from the transmitting terminal.

Layering is a method, i.e. hierarchy, for organizing communication protocols in well-defined encapsulated data units between otherwise decoupled processing entities. The protocol hierarchy is implemented in both the access terminal and the access point. According to the Open Systems Interconnection (OSI) model, protocol layer L1 specifies the transmission and reception of wireless signals between base stations and remote stations, layer L2 specifies the correct transmission and reception of signaling messages, and layer L3 specifies control messages for the communication system. Layer L3 initiates and terminates signaling messages according to the semantics and timing of the communication protocol between the access terminal and the access point.

In the IS-856 communication system, the air interface signaling layer L1 IS referred to as the physical layer, L2 IS referred to as the Link Access Control (LAC) layer or the Medium Access Control (MAC) layer, and L3 IS referred to as the signaling layer. The above signaling layers are additional layers, numbered L4-L7 according to the OSI model and referred to as transport, session, presentation and application layers. Physical layer ARQ is disclosed In U.S. patent application 09/549,017 filed on 14/4/2000, entitled "Method and Apparatus for Quick Re-transmission of signals In A Communication System", assigned to the present assignee. An example of a link layer ARQ method is the Radio Link Protocol (RLP). RLP is a class of error control protocols known as Negative Acknowledgement (NAK) -based ARQ protocols. One such RLP IS described in TIA/EIA/IS-707-A.8, entitled "DATA SERVICE OPTIONS FOR SPREADS PERTRUM SYSTEMS: RADIO LINK PROTOCOL TYPE 2 ", hereinafter referred to as RLP 2. The transmission of the initial and retransmitted packets may be opportunistic.

Reverse link transmission

Reverse link user data transmissions from legacy access terminals utilize Code Division Multiple Access (CDMA), such as CDMA according to the IS-856 standard.

New access terminals may utilize several multiple access methods of the reverse link channel depending on the options implemented by the communication system. First, the new access terminal may utilize CDMA used by legacy terminals, such as CDMA according to the IS-856 standard.

In addition, the communication system may implement reverse link operation designed primarily for Time Division Multiple Access (TDMA). The operation is achieved by dividing the reverse link into intervals and associating each of the intervals with CDMA or TDMA. A control entity in the access network, such as access network controller 110, makes decisions specifying the sequence assignments for the CDMA and TDMA intervals. The decision is made based on the reverse link conditions for the given access terminal, the number and activity of legacy terminals, and other design criteria for the communication system. The reverse link condition may be determined according to an erasure rate of the DRC channel. The design criteria may include, for example, a handoff state specifying the access terminal, reverse link loading, and other criteria known to those skilled in the art. Obviously, the allocation may comprise only the interval associated with one of the multiple access methods.

A control entity in the access network then notifies all access terminals of the access network of the allocation by communicating the allocation to the access terminals. Optionally, the allocation is only communicated to the new access terminal. The allocations are transmitted in periodic intervals, i.e., in predetermined portions of the forward link channel, e.g., each control channel period. Alternatively, the assignment is communicated to the access terminal only when changed by a broadcast message in a forward link channel, such as a control channel. The number of bits in the message (indicator bits) depends on the number of different sequences.

The new access terminal receives the allocation information and enters multiple access as specified in the allocation information if no option is given to autonomously select between CDMA and TDMA operation. If the access terminal is given the option of selecting between CDMA and TDMA operation, the new access terminal makes an autonomous decision based on the design criteria of the communication system. Such criteria can include, for example, power amplifier headroom (headroom), forward link quality metrics, handoff status of new access terminals, reverse link quality metrics, amount of data to be transmitted, urgency function values, QoS requirements, and other known design criteria. Thus, for example, the new access terminal can utilize TDMA, the link budget of the new access terminal enabling reverse link transmissions at data rates above a threshold; otherwise, the new access terminal may utilize CDMA. In addition, CDMA may be selected for new access terminals that are capable of utilizing TDMA but whose data packet size is too small for high data rates. In addition, the AT may select CDMA for low latency applications.

Reverse link channel

As discussed above, the legacy access terminals operate in accordance with the IS-856 standard, and therefore, the reverse link waveforms for the legacy terminals are identical to the reverse link waveforms of the IS-856 standard and are not described in detail herein.

In addition, those new access terminals that utilize code division multiple access utilize a reverse link waveform that IS consistent with the reverse link waveform of IS-856, such as CDMA according to the IS-856 standard.

Exemplary reverse link waveforms for a new access terminal operating in a TDMA interval are shown in fig. 4 a-c. It should be appreciated that the durations, chip lengths, ranges of values described below are given by way of example only, and that other durations, chip lengths, ranges of values may be used without departing from the basic principles of operation of the communication system.

The reverse link 400 is defined in accordance with an interval 402. An interval is a structure that includes a predetermined number of slots 404. As shown in fig. 4a, the interval includes m slots, however, the number of slots is a design decision; thus, any number of time slots may comprise a gap. Each time slot 404(1),. ·, 404(m) is divided into two portions 406, 408. The first portion 406 includes overhead channels 412 and 418, and an optional traffic channel 420 with additional overhead channels.

The reverse link overhead channels include: a Pilot Channel (PC)412, a Data Request Channel (DRC) 414, an Acknowledgement Channel (ACK)416, and a Packet Request (PR) Channel 418. Optionally, a traffic channel with a Reverse Rate Indication (RRI) channel, collectively indicated by reference numeral 420, may also be included in the first portion 406.

The second portion 408 is further divided into subsections 410, each subsection 406 carrying a traffic channel and an accompanying reverse rate indication channel (RRI)422 for the access terminal. As shown in fig. 4a, there are n sub-portions 410 in the second portion 408(1) of the first slot 404 (1); thus, n different access terminals may transmit in the second portion 408(1) of interval 404 (1); in the second portion 408(m) of the mth slot 404(m) there are/sub-portions 410; thus, n different access terminals may transmit in the second portion 408(m) of the interval 404 (m). The number of sub-parts 410 may vary depending on the access network for which the scheduler is designed. One subsection means the entire second portion of the interval used by one access terminal. The additional traffic channels and accompanying RRI channels provided in subsection 410 may utilize TDM, OFDM, CDM, or any other form of multiplexing.

Fig. 4b shows a designated TDMA interval 402. The TDMA interval includes one time slot 404. The slot 404 is 2048 chips long, corresponding to a 1.66ms slot duration. Each time slot 404 is divided into two portions 406, 408, each portion being equal to a half time slot. The second portion 408 corresponds to the first sub-portion 410 because the second portion 408 is not further subdivided.

The overhead channels as described above are distinguished by different codes, e.g., by being covered by different walsh codes, and organized in the first portion 406. An optional traffic channel, denoted collectively by reference numeral 420, with a reverse rate indication channel (RRI) may also be included in the first portion 406. The RRIs are inserted (pure) into the traffic channel and the resulting structure 420 is distinguished from the overhead channel by a different code, e.g., by being covered by a different walsh code. Thus, the traffic channel and RRI channel 420 are referred to as a CDM traffic channel, a CDM/RRI channel, respectively. Optionally, (not shown) the RRI channel is not inserted into CDM traffic. Thus, the CDM traffic channel and the RRI channel are distinguished by each being covered by a unique code.

An additional traffic channel 422(T) and an accompanying reverse rate indication channel 422(RRI) are provided in the second half-slot 408. As shown in fig. 4b, the traffic channel 422(T) and accompanying RRI channel 422(RRI) are time division multiplexed and referred to as TDM traffic channel, TDM/RRI channel, respectively.

Although not shown, the additional traffic channels and accompanying RRI channels provided in the second half-slot 408 may utilize OFDM, CDM, or any other modulation format (not shown). In addition, as described below, the additional traffic channels and accompanying RRI channels provided in the second half-slot 408 may utilize different multiplexing formats, such as TDM and OFDM depending on the data rate.

Fig. 4c shows a reverse link waveform for an access terminal operating in a TDMA interval, but carrying no data in the second half-slot 408. As shown, the overhead channel 406-.

Thus, to set up user data into an interval dedicated to TDMA, a new access terminal may utilize three different protocols (modes) for multiplexing user data within such an interval:

building user data into a first part of the interval using Code Division Multiplexing (CDM);

building user data into the second part of the interval using Time Division Multiplexing (TDM) or Orthogonal Frequency Division Multiplexing (OFDM); and

build user data into the first data portion of the interval with CDM and into the second portion of the interval with TDM/OFDM.

Fig. 4d shows the reverse link waveform for a new access terminal operating in a CDMA interval, which carries CDM user data in two half-slots 406, 408. As shown, the overhead channels 412-. An additional CDM channel 422 is transmitted in the second half-slot 408.

Although not shown in fig. 4d, the new access terminal may utilize a CDM traffic channel, i.e., CDM, to establish user data into the CDMA-dedicated intervals by:

building user data into the first part of interval 406;

building user data into the first part of interval 408; and

building user data into both the first portion 406 and the second portion 408.

The data transmitted in the CDM portion and TDM/OFDM portion of the slot may include data, such as video, for the same information content. Additionally, base video may be transmitted in the CDM portion of the slot, and enhanced video may be transmitted in the TDM/OFDM portion of the slot; thus, if the terminal fails to transmit during the second half of the time slot, acceptable video may still be received. Alternatively, each half may comprise data about different information content. Thus, for example, voice data may be sent in the CDM portion of the slot and video may be sent in the TDM/OFDM portion of the slot.

Pilot channel

In one embodiment, the pilot channel 412 is used for estimation of the reverse link channel quality. In addition, the pilot channel 412 is used for coherent demodulation of the channel transmitted in the first half-slot 406. The pilot channel 412 includes an unmodulated symbol having a binary value of "0". Referring to fig. 5, the unmodulated symbols are provided to a block 510(1) that maps the binary symbols to modulation symbols according to the selected modulation. For example, when the selected modulation is Binary Phase Shift Keying (BPSK), a binary symbol value of "0" is mapped onto a modulation symbol value of +1, and a binary symbol value of "1" is mapped onto a modulation symbol value of-1. In block 510(4), the mapped symbols are covered with the walsh function generated by block 510 (2). The walsh covered symbols are then provided for further processing.

Data request channel

The data request channel 414 is used by the access terminal to indicate to the access network the selected serving sector and the requested data rate on the forward traffic channel. The requested forward traffic channel data rate includes, for example, a four-bit DRC value. Referring to fig. 5, the DRC values are provided to a block 506(2) which encodes the four-bit DRC values to produce a bi-orthogonal (bi-orthogonal) codeword. The DRC codeword is provided to a block 506(4) which repeats each codeword twice. The repeated codeword is provided to a block 506(6) which maps the binary symbol onto a modulation symbol according to the selected modulation. The mapped symbols are provided to a block 506(8) which covers each symbol with a code such as a walsh code generated by block 506(10) according to DRCCover identified by index i. Each generated walsh chip is then provided to block 506(12) where the walsh chip is covered by a different code, such as a different walsh code generated by block 506 (14). The walsh covered symbols are then provided for further processing.

ACK channel

The ACK channel 416 is used by the access terminal to inform the access network whether the user data sent on the forward traffic channel was successfully received. The access terminal transmits ACK channel bits in response to each forward traffic channel interval associated with a detected header directed to the access terminal. The ACK channel bit is set to +1(ACK) if the forward traffic channel packet is successfully received; otherwise, the ACK channel bits are set to-1 (NAK). If the CRC protecting the transmitted user data is consistent with the CRC calculated from the decoded user data, the forward traffic channel user data is deemed to have been successfully received. Referring to fig. 5, the ACK channel bits are repeated in block 508(2) and provided to block 508 (4). Block 508(4) maps the binary symbols onto modulation symbols according to the selected modulation. The mapped symbols are then provided to block 508(6), which covers each symbol with the walsh code generated by block 508 (8). The walsh covered symbols are then provided for further processing.

Packet ready channel

Each access terminal desiring to transmit indicates to the sector that user data is available for transmission in a future interval and/or that transmission in a future interval is appropriate. An interval is deemed appropriate if the instantaneous quality metric of the reverse link channel interval, which is modified by an opportunity level determined based on additional factors, exceeds the average quality metric of the reverse link channel, which is modified by an opportunity level determined based on additional factors, or exceeds some threshold depending on the design of the communication system.

The quality metric of the reverse link is determined from a reverse pilot channel, e.g., according to equation (1):

wherein Tx _ pilot (n) is the power at which the pilot channel is transmitted during the nth interval; and

filt _ Tx _ Pilot (n) is the power of the filtered pilot signal over the past k intervals estimated in the nth interval. The filter time constant, represented by the time slot, is determined to provide an appropriate averaging of the reverse link channel.

Therefore, equation (1) indicates how good the instantaneous reverse link is with respect to the average reverse link. The access terminal performs Tx _ pilot (n) and Filt _ Tx _ pilot (n) measurements and performs a quality metric calculation according to equation (1) at each interval. The calculated quality metric is then used to estimate a quality metric for a predetermined number of intervals in the future. The predetermined number of intervals may be two. One Method for such quality estimation is described in U.S. patent application Ser. No. 09/974,933, filed 10/2001, entitled "Method and apparatus for Scheduling Transmission Control in a Communication System", assigned to the present assignee.

The above-described method of estimating the reverse link quality metric is given by way of example only. Accordingly, other methods may be used. For example, the access terminal may provide information regarding the pilot channel and traffic channel transmit power levels to the access point, which then uses the information to determine the appropriate transmission interval.

Factors that determine the level of opportunity include, for example, a maximum acceptable transmission delay t (from packet arrival at the access terminal to packet transmission), a number of packets in the queue of the access terminal/(transmit queue length), and an average throughput on the reverse link th. The above factors define the "urgency" function I (t, l, th). The urgency function I (t, l, th) is determined according to the expected influence of the input parameters. For example, the urgency function has a lower value when the first packet of the queue for transmission to the access terminal arrives, but increases if the number of packets in the access terminal queue exceeds a threshold. The urgency function reaches a maximum value when the maximum acceptable transmission delay is reached. Queue length parameters and transmit throughput parameters likewise affect the urgency function.

The use of the three parameters described above as inputs to the urgency function is given for illustrative purposes only; any number or even different parameters may be used depending on the design considerations of the communication system. Additionally, the urgency function may be different for different users, thereby providing user differentiation. Further, functions other than the urgency function may be used to distinguish between users. Thus, for example, each user may be assigned an attribute (attribute) based on the QoS of the user. The attribute itself may replace the urgency function. Optionally, the attribute may be used to modify an input parameter of the urgency function.

The urgency function I (t, l, th) may be used to modify the quality metric according to equation (2):

at the value calculated according to equation (2) and the threshold value T_JThe relationship between can be used to define the level of opportunity. A suitable set of opportunity levels is given by way of example in table 1. It should be appreciated that a different number and a different defined level of opportunity may be used instead.

Level of opportunity	Definition of
Level of opportunity	Definition of	0	There is no data to send
1	Data is available for transmission	0	There is no data to send
1	Data is available for transmission	2	Data available for transmission, channel condition "good" or urgent transmission "high"
3	Data is available for transmission, channel conditions are "very good" or urgent transmissions are "very high"	2

TABLE 1

The appropriate level of opportunity is encoded and transmitted over the PR channel. If the opportunity level is not 0, i.e., indicating "no data to transmit," the PR channel is transmitted. The four levels of opportunity may be represented as two information bits. The PR channel needs to be received at the access point with high reliability because any error during PR channel reception may result in a possible scheduling of access terminals that do not request user data transmission or report a lower chance class. Alternatively, such an error may result in an access terminal failing to schedule a higher opportunity level for reporting. Therefore, the two information bits need to be transmitted with sufficient reliability.

As described above, since both the access point and the access terminal know the predetermined number of future intervals for which the opportunity level is estimated, a suitable transmission interval is implied. Since the timing of the access point and the access terminal are synchronized, the access point is able to determine which interval is the appropriate transmission interval for which the transmitting terminal reports the opportunity level. However, it will be appreciated that other arrangements may be employed in which the appropriate transmission interval is variable and communicated explicitly to the access point.

The PR channel 418 value according to the above concept is represented as a 2-bit value. Referring to fig. 5, the PR value is provided to a block 512(2) which encodes the 2 bits to provide a codeword. The codewords are provided to a block 512(4), which repeats each codeword. The repeated codeword is provided to a block 512(6) which maps the binary symbol onto a modulation symbol according to the selected modulation. The mapped symbols are then provided to block 512(8), which covers each symbol with the walsh code generated by block 512 (10).

CDM traffic channel

The CDM traffic channel 420 is a packet-based, variable rate channel. User data packets for the access point are transmitted at a data rate selected from a group of data rates, such as data rate groups 9.6, 19.2, 38.4, 76.8, and 153.6 kilobits per second (kbps).

Referring to fig. 5, data (data bits) to be transmitted is divided into blocks of a predetermined size and provided to a block 504 (2). Block 504(2) may include a turbo encoder. The output of block 504(2) comprises code symbols. The code symbols are interleaved by block 504 (4). In one embodiment, block 504(4) includes a bit-reversal channel interleaver (interleaver). The interleaved sequence of code symbols is repeated in block 504(6) as many times as necessary to achieve a fixed modulation symbol rate, depending on the data rate and encoder coding rate, and provided to block 504 (8). Block 504(8) is provided with the CDM RRI channel symbols and inserts the CDM RRI channel symbols into the CDM traffic channel symbols. The inserted symbols are provided to a block 504(10) which maps the binary symbols onto modulation symbols according to the selected modulation. The mapped symbols are then provided to block 504(12), which covers each symbol with the walsh code generated by block 504 (14). The generated chips are provided for further processing, as will be described in detail below. The CDM traffic channel/RRI channel packet may be transmitted in one to more half slots according to user data to pilot ratio, packet size, and the given data determined.

CDM reverse rate indicator channel

The CDM RRI channel 420 provides an indication of the reverse link packet type. The packet type indication provides the access point with information that assists the access point in determining whether soft decisions from a currently received packet can be soft combined with soft decisions from a previously received packet. Soft combining utilizes energy values (soft-decision values) at bit positions obtained from previously received and decoded packets. The access point determines the bit value of the packet by comparing the soft decision value to a threshold (hard decision). A bit is assigned a first value, e.g., "1", if the energy corresponding to the bit is greater than the threshold, otherwise the bit is assigned a second value, e.g., "0". The access point then determines whether the packet is decoded correctly, for example by performing a CRC check, or by any other equivalent or suitable method after packet decoding. If such a test fails, the packet is considered for deletion. However, the access point retains the soft-decision value (if the number of retransmission attempts for the packet is less than the maximum allowed attempts), and when the access point obtains the soft-decision value for the current packet, it may combine the retained soft-decision value and the soft-decision value for the current packet and compare the combined soft-decision value to the threshold.

Some combined approaches are known and therefore need not be described here. One suitable Method is described in detail in U.S. patent 06,101,168 entitled "Method and Apparatus for Time efficient re-transmission Using Symbol Accumulation", which is assigned to the present assignee.

However, in order to soft combine packets meaningfully, the access terminal must know that the packets include information that can be combined, as well as a method of combining. Determining a set of RRI values according to the combining method. The RRI channel may be similar to an RRI channel according to the IS-856 standard. Referring to fig. 5, an RRI value, e.g., represented by 3 bits, is provided to a block 502(2) which encodes the 3 bits to provide a 7-bit codeword. An example of the encoding is shown in table 2.

RRI symbol	RRI code word
RRI symbol	RRI code word	000	0000000
001	1010101	000	0000000
001	1010101	010	0110011
011	1100110	010	0110011
011	1100110	100	0001111
101	1011010	100	0001111
101	1011010	110	0111100
111	1101001	110	0111100

TABLE 2

The codewords are provided to a block 502(4), which repeats each codeword. The repeated codeword is provided to block 502(6), which provides the codeword to block 504(8) for insertion into the CDM traffic channel. Blocks 502(8), 502(10), and 502(12) are not used.

Optionally, the codewords are provided to a block 502(4), which repeats each codeword. The repeated codewords are provided to block 502(6), which provides the codewords to block 502(8), block 502(8) mapping the binary symbols onto modulation symbols according to the selected modulation. The mapped symbols are then provided to block 504(10), which covers each symbol with the walsh code generated by block 504 (12). The generated chips are provided for further processing, as will be described in detail below.

TDM traffic channel

The TDM traffic channel 422(RRI) is a packet-based, variable rate channel. User data packets for the access point are transmitted at a data rate selected from a group of data rates, such as data rate groups 76.8, 153.6, 230.4, 307.2, 460.8, 614.4, 921.6, 1228.8, and 1843.2 kbps. Data (data bits) to be transmitted is divided into blocks of a predetermined size and supplied to block 504 (2). Block 504(2) may include a turbo encoder having a code rate 1/5. The output of block 504(2) comprises code symbols. The code symbols are interleaved by block 504 (4). Block 504(4) may include a bit-reversed channel interleaver. The interleaved sequence of code symbols is repeated in block 504(6) as many times as necessary to achieve a fixed modulation symbol rate, depending on the data rate and encoder coding rate, and provided to block 504 (8). Block 504(8) passes the symbols to block 504(10), and block 504(10) maps the binary symbols onto modulation symbols according to the selected modulation. The mapped symbols are then provided to a block 504(12) which covers each symbol with the walsh code generated by block 504(14), and the resulting chips are provided for further processing, as described in detail below.

The code symbols are converted to modulation symbols as part of the processing. The TDM traffic channel modulation symbols are then time division multiplexed with the chips of the RRI channel. However, the size of the TDM channel does not necessarily match the symbol size produced by combining the RRI channel chips and the TDM traffic channel modulation symbols representing the packet. Thus, chips representing the initial packet symbols are divided into subpackets, which are inserted into the TDM channel and transmitted. A method FOR transmission, incremental redundancy, is described in pending U.S. patent application serial No. 09/863,196, filed on 22/5/2001, entitled "ENHANCED CHANNELINTERLEAVING FOR INCREASED DATA THROUGHPUT," assigned to the present assignee.

The above sub-packet transmission is described with reference to table 3, which table 3 shows the packet parameters. The data rates and associated packet parameters are given by way of example, and thus other data rates and associated packet parameters are contemplated.

Data Rate (kbps)	Data bit	Code symbol	Modulation type	Modulation symbol	RRI chip	Modulation symbols in TDM channels
Data Rate (kbps)	Data bit	Code symbol	Modulation type	Modulation symbol	RRI chip	Modulation symbols in TDM channels	76.8	256	1280	QPSK	640	384	1280
153.6	512	2560	QPSK	1280	192	1664	76.8	256	1280	QPSK	640	384	1280
153.6	512	2560	QPSK	1280	192	1664	230.4	768	3840	QPSK	1792	128	1792
307.2	1024	5120	QPSK	1856	96	1856	230.4	768	3840	QPSK	1792	128	1792
307.2	1024	5120	QPSK	1856	96	1856	460.8	1536	7680	QPSK	1920	64	1920
614.4	2048	10240	QPSK	2560	64	1920	460.8	1536	7680	QPSK	1920	64	1920
614.4	2048	10240	QPSK	2560	64	1920	921.6	3072	15360	8-PSK	3840	64	1920
1228.8	4096	20480	8-PSK	5120	64	1920	921.6	3072	15360	8-PSK	3840	64	1920
1228.8	4096	20480	8-PSK	5120	64	1920	1843.2	6144	30720	16-QAM	7680	64	1920

TABLE 3

Considering a data rate of 1843.2kbps, data to be transmitted is divided into blocks of 6144 bits in size. Coding at the coding rate of 1/5 results in 6144 × 5 ═ 3072 code symbols. The modulation is 16-QAM, which means that one modulation symbol is generated every four code symbols. Thus 30720 code symbols yield 30720/4-7680 modulation symbols. Since the TDM channel includes two half slots, the TDM channel size is 1024 per slot. Since the number of RRI chips in a slot is 64, there is space for 2 x (1024-64) ═ 1920 modulation symbols in the TDM channel.

The first subpacket is formed by inserting a first 1920 modulation symbols from all 7680 modulation symbols into the TDM channel. Since the sub-packet includes all the information needed to recover the data bits of the packet, if the transmission is successful, the sub-packet is decoded; the next packet is sent. If the transmission fails, the next sub-packet is formed. In one embodiment, the next subpacket is formed by inserting the second 1920 modulation symbols from all 7680 modulation symbols into the TDM channel. The method is repeated until the data bits of the packet are successfully decoded, or a predetermined number of sub-packet transmissions or retransmissions are reached.

To enable the access point to soft combine subpackets transmitted by the incremental redundancy (HARQ) method, each subpacket is assigned a subpacket index. The subpacket index is transmitted on a TDM reverse rate indication channel, as described below.

The term sub-grouping is used in the foregoing description for instructional purposes, i.e., to explain the concept of incremental redundancy. Since this distinction is primarily semantic, the terms group will be used together unless necessary for a clear understanding.

TDM reverse rate indicator channel

The TDM RRI channel 422(RRI) serves a similar purpose as the CDM RRI. Thus, the TDM RRI channel provides an indication of the reverse link packet type (e.g., payload size, code rate, modulation, etc.), as well as the sub-packet index, which is used for the incremental redundancy (HARQ).

To provide the required indication, the RRI includes 5 bits of information. Referring to fig. 5, the RRI values are provided to a block 502(2) which biorthogonally encodes the 5 bits to provide a codeword. The codewords are provided to a block 502(4), which repeats each codeword. The repeated codewords are provided to a block 502(6) which maps the binary symbols onto modulation symbols according to the selected modulation. The mapped symbols are also provided to a block 502(8) which covers each symbol with the walsh code generated by block 502(10), and the resulting chips are provided for further processing, as described in detail below.

Table 4 summarizes the RRI codeword values.

RRI codeword values	Packet rate	Sub-group indexing
RRI codeword values	Packet rate	Sub-group indexing	0，1	76.8k	1，2
2，3	153.6k	1，2	0，1	76.8k	1，2
2，3	153.6k	1，2	4，5	230.4k	1，2
6，7	307.2k	1，2	4，5	230.4k	1，2
6，7	307.2k	1，2	8，9	460.8k	1，2
10，11，12	614.4k	1，2，3	8，9	460.8k	1，2
10，11，12	614.4k	1，2，3	13，14，15	921.6k	1，2，3
16，17，18，19	1228.8k	1，2，3，4	13，14，15	921.6k	1，2，3
16，17，18，19	1228.8k	1，2，3，4	20，21，22，23	1843.2k	1，2，3，4

TABLE 4

Referring to table 4, when the access point receives and decodes the RRI codeword having a value of "0", the access point attempts to decode the subpacket at a data rate of 76.8 kbps. If the sub-packet fails to decode, the access point receives the next packet and decodes the RRI codeword having a value of "1", the access point may combine the current sub-packet with the previously received sub-packet because the RRI codeword having a value of "1" identifies the currently received sub-packet having an index of "2", which may be combined with the sub-packet having an index of "1".

As discussed above, the pilot channel is a reference signal, i.e., a parameter of the pilot signal, such as structure, transmit power, and other parameters known at the access point. Upon receiving the pilot channel, the access point determines parameters of a reverse pilot signal affected by the communication link. By combining the two sets of parameters, i.e., the parameter at the time of transmission and the parameter at the time of reception, the access point can estimate the communication link and coherently demodulate the channel of the communication link. Methods of using reference signals for estimating a communication link are known in the art. See, FOR example, pending U.S. patent application Ser. No. 09/943,277 filed on 30.8.2001 entitled "METHOD AND DAPPARUTUS FOR MULTI-PATH ELEMENTATION IN A WIRELESSCOMMUNICATION SYSTEM", assigned to the present assignee.

Referring to fig. 4a-b, the reverse pilot channel is not available in the second half slot, and is used for estimation of the reverse link and coherent demodulation of the channel transmitted in the first half slot. However, the relatively high transmit power and careful encoding ensure a high probability of reception and correct decoding of the RRI channel. Further, both the access terminal and the access point are provided by the information summarized in table 4.

Thus, the access point may conceive of the assumption that: what data rate and what RRI codeword to send and attempt to decode the RRI by trying the hypothesis. The access selects the hypothesis that is the most likely hypothesis according to the metrics used for the hypothesis test. As discussed below, the reverse pilot channel is transmitted at a power determined by a power control loop so that the reverse pilot channels from all access terminals are at the same power (P) at the access point_pilot) Is received. Due to the RRI channel power (P)_t) Related to reverse link transmit power (see equation (3) below), so once the RRI channel is decoded correctly, the access point can use equation (3) to determine the parameters of the RRI channel necessary to estimate the reverse link channel quality. Thus, the RRI channel may be used as a reference signal rather than a pilot channel for estimating reverse link channel quality estimates and coherent demodulation of the channel transmitted in the second half slot.

In order to properly use equation (3), the access point must know the value of a, the Rise Over Thermal (ROT) difference between the overhead and the traffic transmission interval. As discussed further below, the access point measures the value of a.

Although the CDM traffic channel/CDM RRI channel is described as using the same structure that produces the TDM traffic channel and TDM RRI channel, this need not be the case and separate structures for the following channels may exist: CDM traffic channels, CDM RRI channels, and TDM traffic channels and TDM RRI channels.

OFDM reverse traffic channel

As discussed, the transmission of the data rate depends on the characteristics of the communication channel, such as the signal to interference and noise ratio (SINR); higher data rates require higher SINR. Since multipath interference is a significant source of interference for interference and noise, mitigating interference at higher data rates will significantly improve the performance of the communication system.

One method for mitigating multipath interference is Orthogonal Frequency Division Modulation (OFDM). OFDM is a known modulation method, the basic principle of which is explained with reference to fig. 6. OFDM communication system 600 takes user data 602 and provides it to block 604 (pre-processing of the user data prior to block 604, i.e., encoding, repeating, interleaving, etc., not shown for simplicity). Block 604 distributes user data among a number of parallel bins (bins) 606, the exact number being a function of the size of the Fast Fourier Transform (FFT) used. The parallel bins 606 are modulated by an Inverse Fast Fourier Transform (IFFT) in block 608. This modulated signal, which comprises a set of signals equal in number to the number of parallel bins, is then up-converted to a set of radio frequency sub-carriers 610, amplified and transmitted over a communication channel 612. The signal is received and demodulated using an FFT in block 614. Demodulated data 616 is then reallocated to user data 620 by block 618.

The user data is protected against frequency selective fading caused by multipath. If the subcarriers experience fading, the lost user data is only a small portion of the entire user data. Since the transmitted user data includes error correction bits, the lost portion can be subsequently recovered.

The above-described OFDM may be used for transmission in the second slot of the TDM interval as follows. When the access terminal determines that the user data rate to be transmitted on the reverse link exceeds a predetermined data rate, e.g., exceeds 614.4kbps, the access terminal transmits the user data using OFDM instead of TDM.

OFDM reverse rate indicator channel

To provide the required indication, the OFDM RRI may include 5 bits of information. The RRI values 602(2) are provided from the user data 602(1) to respective blocks 604 (of fig. 6A), which blocks 604 allocate the RRI data to at least one predetermined parallel bin 606(2) and allocate the user data on the remaining parallel bins 606(1) (pre-processing, i.e., encoding, repeating, interleaving, etc., of the user data and RRI data prior to block 604, not shown for simplicity). Further processing is performed as described in fig. 6. Referring again to fig. 6a, upon reception, the signal is received and demodulated using FFT in block 614. Demodulated RRI data 616(2) and demodulated user data 616(2) are then re-allocated by block 618 to provide user 620(1) and RRI value 620 (2).

Optionally, the user data and RRI data are multiplexed and provided to block 604 (of fig. 6) (pre-processing of the user data prior to block 604, i.e., encoding, repeating, interleaving, etc., not shown for simplicity). Thus, the RRI values and the user data are allocated among the parallel bins 606. Further processing is performed as described in fig. 6. Referring to fig. 6c, upon reception, the signal is received and demodulated with FFT in block 614. The demodulated RRI data and demodulated user data are then reallocated by block 618 to provide user 620(1) and RRI value 620 (2).

Reverse link structure

Fig. 5c further illustrates the structure of the reverse link channel. The TDM traffic channel 422(T) and TDM RRI channel 422(RRI) (of fig. 4) are time division multiplexed in block 514 and provided to a gain adjustment block 516 (1). After gain adjustment, the time-division multiplexed signal is provided to a modulator 518.

The pilot channel 412, data request channel 414, acknowledgement channel 416, and packet request channel 418 (of fig. 4) are provided to respective gain adjustment blocks 516(2) -516 (5). After gain adjustment, the individual channels are provided to a modulator 518.

In addition, optional CDM traffic channel/CDM RRI channel 420 (of fig. 4) is provided to gain adjustment block 516 (7). After gain adjustment, the individual channels are provided to a modulator 518.

The modulator 518 combines the incoming channel signals and modulates the combined channel signals according to an appropriate modulation method, such as Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), eight phase shift keying (8-PSK), and other modulation methods known to those skilled in the art. The appropriate modulation method may vary depending on the data rate to be transmitted, the channel conditions, and/or other design parameters of the communication system. The combination of the incoming channel signals will change accordingly. For example, when the selected modulation method is QPSK, the incoming channel signals will be combined on in-phase and quadrature signals, and the signals will be quadrature spread. The selection of the channel signals is combined on the in-phase and quadrature signals according to design parameters of the communication system, such as the assignment of the channels so that the data load between the in-phase and quadrature signals is balanced, the resulting peak-to-average value of the waveform is low, and other design parameters.

The modulated signal is filtered in block 520, upconverted to a carrier frequency in block 522, and provided for transmission.

Reverse link access method

As discussed, reverse link user data transmissions from legacy access terminals utilize code division multiple access, e.g., CDMA according to the IS-856 standard. According to the IS-856 standard, the access terminals may access the carrier frequency of the reverse link and, thus, autonomously initiate reverse link transmissions regardless of any possible reverse link assignments between TDMA and CDMA intervals. The initial reverse link transmission is at a predetermined data rate, e.g., 9.6 kbps. When a received Reverse Activity Bit (RAB) on a reverse activity channel is zero, the access terminal may increase the rate to the next higher rate with a probability p; when the RAB is one, the access terminal may decrease the rate to the next lower rate with a probability q. The probabilities p and q for each rate are communicated from the access network to the access terminal or negotiated between the access point and the access terminal, e.g., at connection time.

Thus, a new access terminal utilizing code division multiple access, e.g., CDMA in accordance with the IS-856 standard, may autonomously initiate reverse link transmissions regardless of any possible reverse link allocations between TDMA and CDMA intervals, as described above.

As described above, a new access terminal modulated with a CDMA specified interval may autonomously initiate reverse link transmissions in the CDMA specified interval.

Reverse link transmissions from new access terminals utilizing the TDMA-specified interval occur from at least one of the access terminals during a portion of the reverse link interval. To illustrate how the one-slot interval structure described above is extended to multiple slot intervals, reverse link data transmission as described below uses an interval equal to two slots. However, as noted above, any number of time slots may be used to construct the interval. Access to the carrier frequency of the reverse link for new access terminals with TDMA specified intervals depends on the pattern of data multiplexing.

As described above, new access terminals that utilize the CDM-only mode, i.e., access terminals that transmit user data using only CDM in the TDMA interval, can access the carrier frequency of the reverse link and thus autonomously initiate reverse link transmission.

Instead, the carrier frequency of the reverse link is accessed, and thus the reverse link transmission is scheduled by an entity in the access network in response to a request by an access terminal to transmit user data for a new access terminal utilizing TDM/OFDM or CDM and TDM/OFDM mode, i.e., an access terminal transmitting user data using TDM/OFDM or CDM and TDM/OFDM in the TDMA interval. The access terminal is scheduled based on the following factors: a channel quality metric for an access terminal in an interval on a reverse link, an average reverse link quality metric for the access terminal, and an urgency function. If the new access terminal is not scheduled, i.e., the transmit permission to the access terminal is denied; the access terminal must refrain from transmitting in at least the TDM/OFDM portion of the interval. Thus, the access terminal transmits no data in the interval or transmits data in the CDM portion only of the interval, i.e., with the CDM portion of the TDMA interval.

Referring to fig. 7, an example of reverse link data transmission for an access terminal requesting TDMA will be shown and described. Fig. 7 illustrates reverse link data transmission negotiation for one access terminal for understanding purposes only. Furthermore, only the serving access point is shown. However, as noted above, it should be understood that the concepts may be extended to multiple access terminals. In addition, multiple access points of the access network may receive and decode reverse links from a transmitting access terminal and provide information to the serving access point whether user data was successfully decoded. Optionally, the access point receiving the payload information sends the payload information to a centralized entity to perform soft decision decoding. The central decoder then informs the serving access point whether the payload decoding was successful. The serving access point indicates ACK over the PG channel, thus preventing unnecessary retransmissions.

As described above, the access procedure, serving sector selection, and other call setup procedures are not repeated since they are based on similar functionality of the communication system according to the IS-856 standard. The only difference is that the new access terminal does not send an access channel probe during the TDM/OFDM half slot.

An access terminal (not shown) that has received data to be transmitted and wishes to transmit in a TDMA interval estimates its reverse link quality metric and urgency function for the TDMA interval and generates an opportunity level (OL 1). For purposes of understanding only, it is assumed that all intervals are designated as TDMA. The access terminal estimates the data rate at which it can transmit and generates the data type accordingly. As discussed, the packet data type not only indicates the data rate, but also specifies whether the packet is initial or retransmitted. As described in more detail below, the rate determination method determines a maximum supportable rate based on the amount of data to be transmitted, the maximum transmit power of the access terminal, and the transmit power allocated to the pilot channel. The access terminal then determines whether a rule for sending the next value in the packet preparation channel is satisfied. The rules may include:

the next value in the packet ready channel is sent over an interval, e.g. two slots;

the next value in the packet ready channel is sent when the chance class changes;

sending the next value in the packet ready channel even if the opportunity level has not changed without receiving a packet grant for a predetermined interval; and

if the access terminal has no data to send, then no packet ready channel is sent. When the rule is satisfied, the access terminal transmits the requested data rate and opportunity level over the PR channel on time slots n and n + 1.

A serving access point (not shown) of the access network receives the reverse link and decodes the information included in time slots N and N +1 in time slot N + 1. The serving access point then provides the opportunity level, packet data type, and requested data rate for all access terminals requesting permission to send data to a scheduler (not shown). The scheduler schedules packets for transmission according to a scheduling rule. As discussed, the scheduling rules attempt to minimize mutual reverse link interference between access terminals while achieving required QoS or data allocation fairness. The rules are as follows:

i. giving a transmission priority to the access terminal reporting the highest opportunity level;

giving priority to access terminals with lower transmitted throughput if several access terminals report the same level of opportunity;

selecting an access terminal randomly if several access terminals satisfy rules (i) and (ii); and

granting a credit to one of the access terminals having data available for transmission in order to maximize reverse link utilization, even if the reported level of opportunity is low.

After the scheduling decisions have been made, the serving access point transmits scheduling decisions for each of the access terminals requesting permission to transmit on the PG channel. As shown, the serving access point sends scheduling decisions (SD 0) in time slots N +2 and N +3 that deny the access terminal from sending new packets.

Since the access terminal does not receive any response to the PR channel and the access terminal has data to transmit, the access terminal again estimates the reverse link quality metric and the urgency function of the access terminal, which results in an increased level of opportunity (OL 3). The access terminal also generates a packet data type and estimates the data rate, and provides the packet data type, the requested data rate on the RRI channel, and the level of opportunity on the PR channel of the reverse link in time slots n +2 and n + 3.

The serving access point receives the reverse link and decodes the information included in time slots N +2 and N +3 of time slot N + 3. The serving access point then provides the scheduler with the opportunity level, packet data type, and requested data rate for all access terminals requesting permission to send data. After a scheduling decision has been made, the serving access point transmits the scheduling decision for each of the access terminals requesting a transmit grant on the PG channel. As shown, the serving access point sends scheduling decisions (SD 1) in time slots N +4 and N +5 that allow new packet transmissions.

The access terminal receives the PG channel and decodes the scheduling decisions (SD 0) sent in slots N +2 and N +3 of slot N + 3. The access terminal thus avoids transmitting during time slots n +4 and n + 5. The access terminal has data to be transmitted and, therefore, estimates a reverse link quality metric and an urgency function for the access terminal. As shown, the access terminal determines an opportunity level (OL 3) that is the same as the opportunity level in the two time slots prior to the transmission, and therefore, the access terminal avoids transmitting PR channels in time slots n +4 and n + 5.

The serving access point makes scheduling decisions (SD 1) that allow access terminals to transmit, and therefore, the serving access point transmits scheduling decisions for each of the access terminals requesting permission to transmit on the PG channel. As shown, the serving access point sends scheduling decisions (SD 1) granting new packet transmissions in time slots N +4 and N + 5.

The access terminal receives the PG channel and decodes the scheduling decisions (SD 1) sent in slots N +4 and N +5 of slot N + 5. The access terminal has data to be transmitted in addition to the data transmitted in time slots n +6 and n +7, and therefore, the access terminal estimates the reverse link quality metric and the urgency function for the access terminal. As shown, the access terminal determines the opportunity level (OL 2) and, therefore, the access terminal transmits the PR channel in time slots n +6 and n + 7. Since the access terminal is allowed to transmit, the access terminal also transmits user data in the TDM/OFDM portion of the reverse link traffic channel in time slots n +6 and n + 7.

As shown in fig. 7, the access terminal receives a transmit permission after two requests. Each of the grouping requests may be associated with the same grouping or different groupings. If each of the packet requests is associated with a different packet, then in one embodiment, the access terminal autonomously determines which packet to send. Optionally, the transmit permission is associated with a first unlicensed packet request. However, other strategies are well within the scope of the present invention.

The serving access point receives the reverse link and decodes PR channel information included in time slots N +6 and N +7 of time slot N +7 and user data included in time slots N +6 and N +7 of time slots N +8 and N + 9. The serving access point then provides the schedule with the opportunity level, the packet data type, and the requested data rate for all access terminals requesting permission to send data. After the scheduling decisions have been made, the serving access point transmits scheduling decisions for each of the access terminals requesting permission to transmit on the PG channel. Since the access point successfully decoded the user data, the serving access point sends scheduling decisions (SD 1) in slots N +10 and N +11 that allow new packet transmissions.

Since the rules for transmitting the next value in the packet preparation channel are not satisfied when the access terminal estimates the reverse link quality metric and the urgency function, the access terminal transmits PR in neither time slots n +8 and n +9 nor time slots n +10 and n + 11.

The access terminal receives the PG channel at slot n +11 and decodes the scheduling decision SD 1. The access terminal is also transmitting user data in the TDM/OFDM portion of the appropriate time slots n +12 and n +13 since the access terminal is allowed to transmit.

The serving access point receives the reverse link and decodes the user data included in time slots N +12 and N +13 of time slots N +14 and N + 15. Since the access point successfully decoded the user data, but the serving access point did not have an outstanding (outstanding) packet request, the access point does not send a PG.

The case where the access network fails to correctly decode the payloads transmitted over the reverse link in time slots n +6 and n +7 is shown in fig. 8.

The serving access point receives the reverse link and decodes PR channel information included in time slots N +6 and N +7 of time slot N +7 and user data included in time slots N +6 and N +7 of time slots N +8 and N + 9. The serving access point then provides the scheduler with the opportunity level, packet data type, and requested data rate for all access terminals requesting permission to send data. After a scheduling decision has been made, the serving access point transmits the scheduling decision for each of the access terminals requesting a transmit grant on the PG channel. Since the access point failed to successfully decode the user data, the serving access point sends scheduling decisions (SD-1) in slots N +10 and N +11 that allow retransmission of previously transmitted packets.

Since the rule for transmitting the next value in the packet prepared channel is not satisfied based on the access terminal's reverse link quality metric and an estimate of the urgency function, the access terminal does not transmit PR in time slots n +8 and n + 9. However, since the opportunity level has changed based on the access terminal's reverse link quality metric and an estimate of the urgency function, the access terminal transmits PR in time slots n +10 and n + 11.

The access terminal receives the PG channel and decodes the scheduling decisions (SD-1) sent in slots N +10 and N +11 of slot N + 11. The access terminal estimates the reverse link quality metric and the urgency function of the access terminal because the access terminal is allowed to retransmit previously transmitted packets instead of new packets, which then have data to be transmitted. As shown, the access terminal determines the opportunity level (OL 3) and, therefore, the access terminal transmits the PR channel in time slots n +12 and n + 13. In addition, the access terminal retransmits the user data in the TDM/OFDM portion of the appropriate time slots n +12 and n + 13.

The serving access point receives the reverse link and decodes PR channel information included in time slots N +12 and N +13 of time slot N +13 and user data included in time slots N +12 and N +13 of time slots N +14 and N + 15. The serving access point then provides the schedule with the opportunity level, the packet data type, and the requested data rate for all access terminals requesting permission to send data. After having made a scheduling decision, the serving access point transmits the scheduling decision for each of the access terminal terminals requesting a transmit permission on the PG channel. Since the access point successfully decoded the user data, the serving access point sends scheduling decisions (SD 1) granting new packet transmissions in time slots N +14 and N + 15.

The access terminal receives the PG channel and decodes the scheduling decision SD1 in slot n + 15. Since the access terminal is allowed to transmit, the access terminal also transmits the user data in the TDM/OFDM portion of the appropriate time slots n +16 and n + 17.

The serving access point receives the reverse link and decodes the user data included in time slots N +16 and N +18 of time slots N +18 and N + 19. Since the access point successfully decoded the user data, but the serving access point did not have an outstanding packet request, the access point does not send a PG.

It should be appreciated that the serving access point may schedule access terminals based on its most recently received transmission request.

It should be appreciated that the access network may fail to receive the PR channel. Since the access terminal does not retransmit the PR channel until the opportunity level changes, to prevent communication failure, the access terminal retransmits the PR channel after a predetermined amount of time.

It should be appreciated that the packet access network may fail to receive a packet even with a few retransmission attempts. To prevent excessive retransmission attempts, the communication system may abandon retransmission attempts after a certain number of retransmission attempts (a sustained interval). The lost packets are then processed by different methods, such as Radio Link Protocol (RLP).

Reverse link power control

As discussed, at least one access terminal in a sector transmits data traffic on the reverse link using TDMA. Since in a CDMA communication system all terminals transmit on the same frequency, each transmitting access terminal acts as an interferer to access terminals in neighboring sectors. To minimize interference on this reverse link and maximize capacity, the transmit power of the pilot channel for each access terminal is controlled by two power control loops. The transmit power of the remaining overhead channels and CDM traffic channels is then determined as a fraction of the transmit power of the pilot channel. The transmit power of the TDM traffic channel is determined as the traffic-to-pilot power ratio for a given data rate, which is corrected by the thermal noise rise difference between the overhead and the traffic transmission interval. The thermal noise rise is the difference between the receiver background noise (noise floor) and the total received power as measured by the access terminal.

Pilot channel power control

The pilot channel POWER control loop is similar to that of the CDMA SYSTEM disclosed in detail in U.S. patent No. 5,056,109, entitled "method and APPARATUS FOR CONTROLLING TRANSMISSION POWER in CDMA cell MOBILE TELEPHONE SYSTEM," which is assigned to the assignee of the present invention and is incorporated herein by reference. Other power control methods are also contemplated and are within the scope of the present invention.

The first power control loop (outer loop) adjusts the set point (set point) in order to maintain the desired level of performance, as estimated at the sector receiving the reverse link with the best quality metric. The performance levels include, for example, a DRC channel erasure rate and a CDM traffic channel Packet Error Rate (PER). The set point is updated according to rules that may be:

where a CDM-RRI is specified to be successfully detected, the setpoint is lowered if the DRC erasure rate is less than a threshold, e.g., 25%, and the CDM packet is successfully decoded;

in the case where it is specified that the CDM-RRI is successfully detected, the setpoint is increased if the DRC erasure rate is greater than the threshold or the CDM packet is not successfully decoded.

The set point is periodically updated at the access point every predetermined number of frames following selection diversity. The DRC erasure rate is measured over the interval. The setpoint is updated only according to the DRC erasure rate if a CDM traffic channel is not received within the update interval. In the event that a successful detection of the CDM RRI is specified, the setpoint is updated within the update interval if the predetermined number of frames is greater than one frame, or in the event of a failure to successfully decode a CDM packet.

The second power control loop (inner loop) adjusts the transmit power of the access terminal so that the reverse link quality metric is maintained at a set point. The quality metric includes an energy-per-chip-to-noise-plus-interference ratio (Ecp/Nt) and is measured at an access point receiving the reverse link. Thus, the set point is also measured as Ecp/Nt. The access point compares the measured Ecp/Nt to the power control set point. If the measured Ecp/Nt is greater than the set point, the access point sends a power control message to the access terminal to reduce the transmit power of the access terminal. Alternatively, if the measured Ecp/Nt is below the set point, the access point sends a power control message to the access terminal to increase the transmit power of the access terminal. The power control message is implemented using one power control bit. A first value ("increase") for the power control bit commands the access terminal to increase the transmit power of the access terminal and a lower value ("decrease") commands the access terminal to decrease the transmit power of the access terminal. An access terminal receiving power control bits from multiple sectors decreases transmit power if one of the power control commands is "down," and increases transmit power otherwise.

Power control bits for all access terminals communicating with each access point are transmitted on the MAC channel of the forward link.

Remaining overhead channel and CDM traffic channel power control

Once the transmit power of the pilot channel for a slot is determined by operation of the power control loop, the transmit power of each of the remaining overhead channels and CDM traffic channels is determined as the ratio of the transmit power of the designated overhead and CDM channels to the transmit power of the pilot channel. The ratio for each overhead to CDM channel is determined from simulations, laboratory experiments, field experiments, and other engineering methods known to those skilled in the art.

Thus, for example, the power of the CDM traffic channel/RRI channel relative to the pilot channel power for the reverse traffic channel depends on the data rate as shown in Table 5.

Data Rate (kbps)	Data channel gain (dB) relative to pilot
Data Rate (kbps)	Data channel gain (dB) relative to pilot	0	Infinity (no data channel to transmit)
9.6	DataOffsetNom+DataOffset9k6+3.75	0	Infinity (no data channel to transmit)
9.6	DataOffsetNom+DataOffset9k6+3.75	19.2	DataOffsetNom+DataOffset19k2+6.75
38.4	DataOffsetNom+DataOffset38k4+9.75	19.2	DataOffsetNom+DataOffset19k2+6.75
38.4	DataOffsetNom+DataOffset38k4+9.75	76.8	DataOffsetNom+DataOffset76k8+13.25
153.6	DataOffsetNom+DataOffset153k6+18.5	76.8	DataOffsetNom+DataOffset76k8+13.25

TABLE 5

TDM traffic channel power control

The required transmit power of the traffic channel is also determined based on the transmit power of the pilot channel. In one embodiment, the required traffic channel power is calculated using the following equation:

P_t＝P_pilot·G(r)·A (3)

wherein: p_tIs the transmit power of the traffic channel;

P_pilotis the transmit power of the pilot channel;

g (r) is the traffic-to-pilot transmit power ratio for a given data rate r; and

a is the Rise Over Thermal (ROT) difference between the estimated overhead and the traffic transmission interval. The term "thermal noise rise" as used herein refers to the difference between the background noise and the total received power measured by the access terminal.

Measurements of ROT in the overhead transmission interval (ROToverhead) and traffic transmission interval (rototfaidic) are known in the art and are required for the calculation of a for the access point. Such measurements are disclosed in U.S. patent 6,192,249 entitled "method for reverse link loading evaluation", assigned to the assignee of the present invention. Once the noise in both the overhead and traffic transmission intervals is measured, a is calculated using the following equation:

A＝ROT_traffic-ROT_overhead (4)

the calculated a-value is then transmitted to the access point, e.g. over the conventional RA channel if only an access terminal operating with TDMA is present in the communication system, or over a new RA channel if both legacy and new access terminals are operating in the communication system.

Alternatively, the a value represents an estimate of the ROT difference given by equation (3). The initial value of a is determined from simulations, laboratory experiments, field tests, and other engineering methods known to those skilled in the art. The value of a is thus adjusted according to the reverse link Packet Error Rate (PER) to maintain the determined PER at the maximum allowed number of transmissions for a given packet. As described above, the reverse link packet error rate is determined based on the ACK/NACK for the reverse link packet. In one embodiment, if an ACK is received within N of a maximum of M retransmission attempts, the a value is increased by a first determined amount. Likewise, if no ACK is received within N of the maximum M retransmission attempts, the a value is decreased by a second determined amount.

It can be known from equation (3) that the traffic channel transmit power is a function of the data rate r. In addition, the access terminal is limited to a maximum amount of transmit power (P)_max). Thus, the access terminal is initially in accordance with the P_maxAnd the determined P_pilotTo determine how much power is available. The access terminal thus determines the amount of data to be transmitted and, based on the available power and the amount of data, transmits the data to the access terminalThe data rate r is selected. The access terminal then evaluates equation (3) to determine whether the effect of the estimated noise difference a does not result in exceeding the maximum available power. If the maximum available transmit power is exceeded, the access terminal decreases the data rate r and repeats the process.

By providing an access terminal with a maximum allowed value g (r) a via a conventional RA channel if only an access terminal operating in TDMA is present in the communication system, or by providing an access terminal with the maximum allowed value on a new RA channel if both legacy and new access terminals are operating in the communication system, the access point can control the maximum data rate at which the access terminal can transmit.

Optionally, the AT determines the value of G (r). A based on the traffic-to-pilot power ratio and an estimate of A adjusted based on the reverse link Packet Error Rate (PER), which is determined based on ACK/NACK, as described above.

Packet decoding improvements

The traffic-to-pilot transmit power ratio g (r) for a given data rate r is determined by considering the number of transmissions (retransmissions) of the packet for correct packet decoding. Thus, if the packet is decoded correctly with one transmission, the traffic-to-pilot transmit power ratio is greater than the traffic-to-pilot transmit power ratio if one or more transmissions are allowed.

The number of transmissions (retransmissions) determines the latency that affects the quality of service (QoS). Since different packet types, e.g., voice packets, file transfer protocol packets, etc., require different QoS, different packet types may be assigned different traffic-to-pilot transmit power ratios. Thus, for example, when an access terminal determines that voice packets requiring a certain QoS (lower latency) are to be sent, the access terminal uses a first traffic-to-pilot transmit power ratio that is greater than a second traffic-to-pilot transmit power ratio that is used when FTP packets requiring a different QoS (higher latency) are to be sent.

RRI channel power control

As discussed above, the RRI channel is time division multiplexed with traffic channel payload. To avoid the need to transmit the RRI portion of a traffic/RRI channel slot at a different power level than the traffic portion, the power allocation between the RRI channel and the traffic channel is controlled by the number of chips allocated to the RRI channel according to the data rate being transmitted.

To ensure proper decoding of a determined number of chips comprising a walsh covered codeword, the required power can be determined. Alternatively, if the power required for the traffic/payload for the transmission is known and the RRI portion of the traffic/RRI channel slot is transmitted at the same power, the number of chips suitable for reliable RRI channel decoding can be determined. Thus, once the data rate and hence the transmission power for the traffic/RRI channel slot is determined, the number of chips allocated to the RRI channel is also determined. The access terminal generates a 5-bit packet type, biorthogonally encodes the 5 bits to obtain symbols, and fills the number of chips allocated to the RRI channel with the symbols. If the number of chips allocated to the RRI channel is greater than the number of symbols, repeating the symbols until all chips allocated to the RRI channel are filled.

AT and AP architecture

An access terminal 900 is shown in fig. 9. The forward link signal is received by an antenna 902 and transmitted to a front end 904, which includes a receiver. Which filters, amplifies, demodulates, and digitizes the signal provided by antenna 902. The digitized signal is provided to a demodulator (DEMOD)906, which provides demodulated data to a decoder 908. Decoder 908 performs the inverse of the signal processing functions performed at the access terminal and provides the decoded user data to a data sink 910. The decoder is also in communication with the controller 912 to provide overhead data to the controller 912. Controller 912 also communicates with other blocks including access terminal 900 to provide appropriate control of the operation of access terminal 900, e.g., data coding, power control. Controller 912 may include, for example, a processor and a storage medium coupled to the processor and including a set of processor-executable instructions.

User data to be transmitted to the access terminal is provided by a data source 914 along with a controller 912 to an encoder 916. Controller 912 also provides overhead data to encoder 916. An encoder 916 encodes the data and provides the encoded data to a Modulator (MOD) 918. Data processing in encoder 916 and modulator 918 is performed in accordance with the reverse link generation described in the text and figures above. The processed data is then provided to a transmitter within the front end 904. The transmitter modulates, filters, amplifies, and wirelessly transmits the reverse link signal over the reverse link via an antenna 902.

A controller 1000 and an access terminal 1002 are shown in fig. 10. User data generated by the data source 1004 is provided to the controller 1000 via an interface unit (not shown), such as a packet network interface, PSTN. As discussed, the controller 1000 connects a plurality of access terminals, which form an access network (only one access terminal 1002 is shown in fig. 10 for simplicity). The user data is provided to a plurality of selector elements (only one selector element 1002 is shown in fig. 10 for simplicity). A selector element is assigned to control the exchange of user data between the data source 1004 and the data sink 1006 and one or more base stations under the control of the call control processor 1010. The call control processor 1010 may include, for example, a processor and a storage medium coupled to the processor and including a set of processor-executable instructions. As shown in fig. 10, selector element 1002 provides user data to a data queue 1014, which includes user data to be transmitted to access terminals (not shown) served by access terminal 1002. The user data is provided to channel element 1012 by data queue 1014, as controlled by scheduler 1016. Channel element 1012 processes the user data in accordance with the IS-856 standard and provides the processed data to a transmitter 1018. The data is transmitted on the forward link through antenna 1022.

The reverse link signal from an access terminal (not shown) is received at antenna 1024 and provided to a receiver 1016. Receiver 1016 filters, amplifies, demodulates, and digitizes the signal and provides the digitized signal to channel element 1016. The channel element 1016 performs the inverse of the signal processing functions performed at the access point and provides decoded data to the selector element 1012. Selector element 1012 sends user data to data sink 906 and overhead data to call control processor 1010.

Those skilled in the art will appreciate that while the flow diagrams are arranged in a sequential order for clarity of understanding, certain steps may be performed in parallel in an actual implementation.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, module circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with the following components: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof for performing the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the described embodiments. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

A part of the disclosure of this patent document includes contents subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the patent and trademark office patent file or records, but otherwise reserves all copyright rights whatsoever.

Claims

1. An apparatus for transmitting user data to a user from a set of access terminals transmitting reverse links on a same frequency, the apparatus comprising:

a first set of access terminals, each of the first set of access terminals comprising:

a receiver;

a storage medium configured to store instructions; and

at least one processor, communicatively coupled to the receiver and the storage medium, capable of processing a set of instructions to:

processing a signal provided by the receiver to obtain an allocation of a sequence of intervals, each interval being associated with a multiple access mode;

processing a signal provided by the receiver to obtain a scheduling decision for an interval associated with a first mode of multiple access; the interval is divided into a first portion and a second portion, the first portion including overhead channels;

selecting a mode for data multiplexing, wherein

The first mode comprises building user data using a multiplexing format only into a first portion of the interval associated with the first mode of multiple access;

the second mode comprises building user data only into at least one subsection of the second portion of the interval associated with the first mode of multiple access, wherein each of the at least one subsection is associated with a multiplexing format; and

the third mode comprises establishing user data into the interval associated with the first multiple access mode by combining the first mode and the second mode; and is

Causing the transmitter to transmit user data in the interval associated with the first mode of multiple access using the selected mode of data multiplexing in accordance with the scheduling decision.

2. The apparatus of claim 1, wherein each interval is associated with code division multiple access or time division multiple access.

3. The apparatus of claim 1, wherein the first mode of multiple access comprises time division multiple access.

4. The device of claim 1, wherein the receiver is configured to:

receiving at least a primary first channel;

extracting information from the received primary first channel;

optionally extracting information from the received at least one supplemental first channel; and is

Providing the extracted information to the at least one processor.

5. The apparatus of claim 1, wherein the at least one processor builds user data into only a first portion of the interval associated with the first mode of multiple access using a multiplexing format by processing a set of instructions to:

user data is built into only the first part of the interval using code division multiplexing.

6. The apparatus of claim 1, wherein the at least one processor builds user data only into at least one subsection of the second portion of the interval associated with the first multiple access mode by processing a set of instructions to:

determining the at least one sub-portion in accordance with the scheduling decision; and

building user data into the determined at least one sub-portion.

7. The apparatus of claim 6, wherein said at least one processor builds user data into said determined at least one sub-portion by processing a set of instructions to:

building user data into the entire second portion of the interval.

8. The apparatus of claim 6, wherein the at least one processor determines the at least one sub-portion from the scheduling decision by processing a set of instructions to:

processing information extracted from the at least one supplemental first channel; and

determining the at least one sub-portion from the extracted information.

9. The apparatus of claim 1, wherein the at least one processor builds user data only into at least one sub-portion of the second portion of the interval associated with the first mode of multiple access by processing a set of instructions to:

associating each of at least one sub-portion of the second portion of the interval associated with the first mode of multiple access with one of code division multiplexing, time division multiplexing, and orthogonal frequency division multiplexing; and is

Building data into each of the at least one sub-portion using the associated multiplexing format.

10. The apparatus of claim 9, wherein the at least one processor builds user data into the at least one subdivision associated with time division multiplexing by processing a set of instructions to:

building user data into the at least one subdivision using time division multiplexing in case the rate of user data is below a threshold.

11. The apparatus of claim 9, wherein the at least one processor further processes a set of instructions to:

user data is additionally built into the at least one sub-portion utilizing orthogonal frequency division multiplexing.

12. The apparatus of claim 1, wherein the at least one processor establishes user data into the interval associated with the first mode of multiple access by combining the first mode and the second mode by processing a set of instructions to:

user data originating from a data source is established into a first portion of the interval associated with the first multiple access mode and into at least one sub-portion of a second portion of the interval associated with the first multiple access mode.

13. The apparatus of claim 1, wherein the at least one processor establishes user data into an interval associated with a first mode of multiple access by combining the first mode and the second mode by processing a set of instructions to:

establishing user data originating from a first data source into a first portion of the interval associated with a first mode of multiple access; and is

Building user data originating from a second data source into at least one of at least one sub-portion of the second portion of the interval associated with the first mode of multiple access.

14. The apparatus of claim 1, wherein the at least one processor causes the transmitter to transmit user data in the interval associated with the first mode of multiple access using the selected mode of data multiplexing in accordance with the scheduling decision by processing a set of instructions to:

processing information extracted from the received primary first channel; and

causing the transmitter to transmit the user data according to the extracted information.

15. The apparatus of claim 1, wherein the at least one processor causes the transmitter to transmit user data in the interval associated with the first mode of multiple access using the selected mode of data multiplexing in accordance with the scheduling decision by processing a set of instructions to:

causing the transmitter to transmit the user data when the scheduling decision is to grant transmission.

16. The apparatus of claim 1, wherein the at least one processor causes the transmitter to transmit user data in the interval associated with the first mode of multiple access using the selected mode of data multiplexing in accordance with the scheduling decision by processing a set of instructions to:

causing the transmitter to transmit the user data when the first mode of data multiplexing is selected and the scheduling decision is to deny transmission.

17. The apparatus of claim 1, wherein the processor is further configured to process a set of instructions to:

transmitting user data from at least one of the second subset of access terminals in the interval associated with the first mode of multiple access using the first mode of data multiplexing.

18. The apparatus of claim 1, wherein the processor is further configured to process a set of instructions to:

ignoring processing of a signal provided by the receiver to obtain scheduling decisions for an interval associated with a second mode of multiple access; the interval is divided into a first portion and a second portion, the first portion including an overhead channel;

selecting a mode for data multiplexing at each of a second subset of the access terminals, wherein

The third mode includes building user data into only a first portion of the interval associated with the second mode of multiple access using a multiplexing format;

the fourth mode includes building user data into only the second portion of the interval using the multiplexing format; and

the third mode comprises establishing user data to the first mode and the second mode in combination

In the said interval; and is

Utilizing said selected pattern of data multiplexing cycles such that said transmitter transmits user data in said interval associated with said second mode of multiple access.

19. The apparatus of claim 18, wherein the at least one processor utilizes a multiplexing format to establish user data only into the first portion of the interval associated with the second mode of multiple access by processing a set of instructions to:

code division multiplexing is used to build user data into only the first part of the interval.

20. The apparatus of claim 18, wherein the at least one processor builds user data into the interval by combining the first mode and the second mode by processing a set of instructions to:

building user data originating from a first data source into a first portion of the interval; and is

Building user data originating from a second data source into a second portion of the interval.

21. The apparatus of claim 18, wherein the at least one processor builds user data into the interval by combining the first mode and the second mode by processing a set of instructions to:

user data originating from a first data source is built into a first part of the second part of the interval.

22. The apparatus of claim 1, further comprising:

a second set of access terminals, each of the second set of access terminals comprising:

a receiver;

a transmitter;

a storage medium configured to store instructions; and

at least one processor, communicatively coupled to the receiver and the storage medium, capable of processing a set of instructions to transmit the user data.

23. The apparatus of claim 22, wherein the user data is transmitted using code division multiple access.

24. The apparatus of claim 23, wherein the user data IS transmitted using code division multiple access according to IS-856 standard.

25. An apparatus for transmitting user data from a set of access terminals that transmit reverse links at a frequency, the apparatus comprising:

a receiver;

a transmitter;

a storage medium configured to store instructions; and

processing a signal provided by the receiver to obtain a scheduling decision for an interval, the interval being divided into a first portion and a second portion, the first portion comprising an overhead channel;

a mode is selected for data multiplexing in which,

the first mode includes building user data into only a first portion of the interval using a multiplexing format;

the second mode includes building user data only into at least one subsection of a second portion of the interval, wherein each of the at least one subsection is associated with a multiplexing format; and

the third mode comprises building user data into the interval in combination with the first and second modes; and

causing the transmitter to transmit user data in the interval using the selected mode of data multiplexing in accordance with the scheduling decision.

26. The apparatus of claim 25, wherein the receiver is configured to:

receiving at least a primary first channel;

extracting information from the received primary first channel;

optionally extracting information from the received at least one supplemental first channel; and

providing the extracted information to the at least one processor.

27. The apparatus of claim 25, wherein the at least one processor builds user data into only the first portion of the interval using a multiplexing format by processing a set of instructions to:

28. The apparatus of claim 25, wherein the at least one processor causes building user data only into at least one subsection of the second portion of the interval by processing a set of instructions to:

building user data into the determined at least one sub-portion.

29. The apparatus of claim 25, wherein said at least one processor builds user data into said determined at least one sub-portion by processing a set of instructions to:

building user data into the entire second portion of the interval.

30. The apparatus as claimed in claim 28, wherein said at least one processor determines said at least one sub-portion from said scheduling decision by processing a set of instructions to:

processing the extracted information from the at least one supplemental first channel; and is

Determining the at least one sub-portion from the extracted information.

31. The apparatus of claim 25, wherein the at least one processor builds user data only into at least one sub-portion of the second portion of the interval by processing a set of instructions to:

associating each of the at least one sub-portions of the second portion of the interval with one of code division multiplexing, time division multiplexing, and orthogonal frequency division multiplexing; and is

Building data into each of the at least one sub-portions using the associated multiplex format.

32. The apparatus as claimed in claim 31, wherein said at least one processor builds user data into said at least one sub-division associated with time division multiplexing by processing a set of instructions to:

33. The apparatus of claim 32, wherein the at least one processor further processes a set of instructions to:

34. The apparatus of claim 25, wherein the at least one processor builds user data into the interval by combining the first mode and the second mode by processing a set of instructions to:

user data originating from a data source is built into a first portion of the interval and into at least one sub-portion of a second portion of the interval.

35. The apparatus of claim 25, wherein the at least one processor builds user data into an interval by combining the first mode and the second mode by processing a set of instructions to:

Building user data originating from a second data source into at least one of the at least one sub-portion of the second portion of the interval.

36. The apparatus of claim 25, wherein the at least one processor causes the transmitter to transmit user data in the interval using the selected mode of data multiplexing in accordance with the scheduling decision by processing a set of instructions to:

processing the extracted information from the received primary first channel; and is

And enabling the transmitter to transmit the user data according to the extracted information.

37. The apparatus of claim 35, wherein the at least one processor causes the transmitter to transmit user data in the interval using the selected mode of data multiplexing in accordance with the scheduling decision by processing a set of instructions to:

38. The apparatus as claimed in claim 31, wherein said at least one processor causes said transmitter to transmit user data in said interval using said selected mode of data multiplexing in accordance with said scheduling decision by processing a set of instructions to:

39. The apparatus of claim 25, wherein the at least one processor is further configured to process a set of instructions to:

ignoring processing of a signal provided by the receiver to obtain a scheduling decision for an interval;

the transmitter is caused to transmit user data in the interval using the first mode of data multiplexing.

40. The apparatus of claim 25, further comprising:

a receiver;

a transmitter;

a storage medium configured to store instructions; and

41. The apparatus of claim 40, wherein the user data is transmitted using code division multiple access.

42. The apparatus of claim 41, wherein the user data IS transmitted using code division multiple access according to the IS-856 standard.

43. An apparatus for link parameter estimation, the apparatus comprising:

a storage medium configured to store instructions; and

measuring a parameter of a first channel;

determining a parameter of a second channel from the measured parameter of the first channel; and

estimating parameters of the link from parameters of the first channel and parameters of the second channel.

44. The apparatus of claim 43, wherein the at least one processor measures the parameter of the first channel by processing a set of instructions to:

the amplitude and phase of the first channel are measured.

45. The apparatus of claim 43, wherein the at least one processor determines the parameter for the second channel by processing a set of instructions to:

decoding the second channel to obtain a data rate and phase of the second channel;

determining a transmit power ratio of the second channel to the first channel as a function of the data rate;

adjusting the transmit power ratio in accordance with a quality metric of a third channel; and

determining an amplitude of the second channel based on the adjusted transmit power ratio.

46. The apparatus of claim 45, wherein the at least one processor decodes the second channel to obtain the data rate and phase for the second channel by processing a set of instructions to:

constructing a set of hypotheses based on a data rate and a content of the data;

decoding the second channel according to each of the hypothesis groups; and

the most likely hypothesis is selected based on the metrics used for hypothesis testing.

47. The apparatus of claim 43, wherein the at least one processor estimates the parameter of the link from the parameter of the first channel and the parameter of the second channel by processing a set of instructions to:

combining parameters of the first channel and parameters of the second channel; and

estimating the link complex channel gain from the combined parameters.

48. The apparatus of claim 47, wherein the at least one processor combines the parameters of the first channel and the parameters of the second channel by processing a set of instructions to:

the combination is performed using the maximum ratio.

49. The apparatus of claim 47, wherein the at least one processor combines the parameters of the first channel and the parameters of the second channel by processing a set of instructions to:

setting a parameter of the first channel to a value of zero.

50. The apparatus of claim 43, wherein said link comprises a reverse link;

the first channel comprises a reverse link pilot channel; and

the second channel comprises a reverse rate indicator channel.

51. The apparatus of claim 45, wherein the third channel comprises a data request channel.

52. An apparatus for power control of a channel, the apparatus comprising:

a processor; and

a storage medium coupled to the processor and comprising a set of instructions executable by the processor, the processor executing the set of instructions to:

determining a transmission power of a first channel;

determining a quality of service to be provided on the channel;

determining a transmit power ratio of the channel to the first channel for a data rate to be transmitted on the channel based on the quality of service;

adjusting the transmit power ratio in accordance with a quality metric of the channel; and

calculating the channel transmit power from the adjusted transmit power ratio.

53. The apparatus of claim 52, wherein the processor determines the transmit power of the first channel by executing a set of instructions to:

determining a set point based on the quality metric of the second channel and the presence of user data detected in the third channel; and

increasing the value of the transmit power if the current value of the transmit power is below the determined set point.

54. The apparatus of claim 53, wherein the processor executes a set of instructions to:

decreasing the value of the transmit power if the current value of the transmit power is below the determined set point.

55. The apparatus of claim 53, wherein the processor determines the set point by executing a set of instructions to:

determining a quality metric of the second channel;

detecting the presence of user data in the third channel;

decoding user data if it is detected that user data is present in the third channel; and

determining the set point based on the quality metric and a result of the detecting.

56. The apparatus of claim 55, wherein the processor determines the quality metric of the first channel by executing a set of instructions to:

determining a deletion rate of the second channel.

57. The device of claim 55, wherein the processor detects the presence of user data in the third channel by executing a set of instructions to:

constructing a set of hypotheses based on a rate of signaling data and content of the signaling data;

decoding the signaling data according to each of the hypothesis groups;

selecting a most likely hypothesis according to the metrics for the hypothesis test; and

if the selected hypothesis is greater than the first threshold, the presence of user data is declared.

58. The apparatus of claim 55, wherein the processor decodes user data in the event that the user data is detected to be present in the third channel by executing a set of instructions to:

decoding code division multiplexed user data from the third channel.

59. The apparatus of claim 55, wherein the processor determines the set point based on the quality metric and a result of the detecting by executing a set of instructions to, upon detecting the presence of user data:

lowering the setpoint if the quality metric is less than a second threshold and the decoding is successful; and

increasing the setpoint if the quality metric is greater than the second threshold and the decoding is unsuccessful.

60. The apparatus of claim 55, wherein the processor determines the set point based on the quality metric and a result of the detecting by executing a set of instructions to, when the presence of user data is not detected:

lowering the set point if the quality metric is less than a second threshold; and

increasing the setpoint if the quality metric is greater than the second threshold.

61. The apparatus of claim 53, wherein the processor adjusts the transmit power ratio based on the quality metric of the channel by executing a set of instructions to:

increasing the transmit power ratio by a first determined amount when a first determined number of retransmissions of user data on the channel fail.

62. The apparatus of claim 53, wherein the processor adjusts the transmit power ratio based on the quality metric of the channel by executing a set of instructions to:

when user data is successfully transmitted on the channel within a second determined number of retransmissions, reducing the transmit power ratio by a second determined amount.

63. The apparatus of claim 53, wherein the processor adjusts the transmit power ratio based on the quality metric of the channel by executing a set of instructions to:

determining a thermal noise rise difference between a transmission interval of the first channel and a transmission interval of the channel;

adjusting the thermal noise rise difference; and

adjusting the transmit power ratio based on the adjusted rise-over-thermal difference.

64. The apparatus of claim 63, wherein the processor determines the rise-over-thermal difference between the transmission interval of the first channel and the transmission interval of the channel by executing a set of instructions to:

measuring a thermal noise rise in a transmission interval of the first channel;

measuring a thermal noise rise in a transmission interval of the channel; and

calculating a difference between a rise over thermal noise in a transmission interval of the first channel and a rise over thermal noise in a transmission interval of the channel.

65. The apparatus of claim 63, wherein the processor determines the rise-over-thermal difference between the transmission interval of the first channel and the transmission interval of the channel by executing a set of instructions to:

estimating the thermal noise rise difference.

66. The apparatus of claim 65, wherein the processor estimates the rise-over-thermal difference by executing a set of instructions to:

estimating the rise-over-thermal difference from a quality metric of the channel.

67. The apparatus of claim 53, wherein the channel comprises a first traffic channel; and is

Wherein the first channel comprises a pilot channel.

68. The apparatus of claim 54, wherein the second channel comprises a data request channel; and is

Wherein the third channel comprises a second traffic channel.