HK1081758A - Acknowledging broadcast transmissions - Google Patents

Description

Acknowledgement of broadcast transmissions

Background

FIELD

The present invention relates generally to communications, and more particularly to improving reliable transmission of orthogonal spatial information used to identify code channels in a spread spectrum communication system.

Background

The field of wireless communications has many applications including, for example, cordless telephones, wireless paging, wireless local loops, Personal Digital Assistants (PDAs), internet telephony, and satellite communication systems. One particularly important application is cellular telephone systems for mobile subscribers. As used herein, the term "cellular" system includes both systems operating on cellular and Personal Communication Services (PCS) frequencies. Various air interfaces have been developed for such cellular telephone systems including, for example, Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). In connection with them, various national and international standards have been established including, for example, Advanced Mobile Phone Service (AMPS), global system for mobile positioning (GSM), and interim standard 95 (IS-95). IS-95 and its derivatives IS-95A, IS-95B, ANSI J-STD-008 (often collectively referred to herein as IS-95), and proposed high data rate systems are promulgated by the Telecommunications Industry Association (TIA) and other well-known standard entities.

Mobile telephone systems configured in accordance with the use of the IS-95 standard use CDMA signal processing techniques to provide efficient and robust mobile telephone service. Exemplary mobile telephone systems configured substantially in accordance with the use of the IS-95 standard are described in U.S. patent nos. 5103459 and 4901307, which are assigned to the assignee of the present invention and incorporated herein by reference. An exemplary system using CDMA techniques is the CDMA2000ITU-R Radio Transmission Technology (RTT) candidate proposal, referred to herein as CDMA2000, issued by the TIA. The standard for cdma2000 IS given in the draft version of IS-2000 and has been passed by the TIA. Another CDMA standard is the W-CDMA standard, which is incorporated in3rd Generation Partnership Project“3GPP”In (2), the file numbers are 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214.

The telecommunication standards cited above are only some examples of the many communication systems that can be implemented. Some of these various communication systems are configured so that a remote station can transmit information about the quality of the transmission medium to a serving base station. This channel information is then used by the serving base station to optimize the power level, transmission format, and timing of forward link transmissions, and thus control the power level of reverse link transmissions.

As used herein, the "forward link" refers to transmissions from a base station to a remote station, and the "reverse link" refers to transmissions from a remote station to a base station. The forward and reverse links are uncorrelated, meaning that the observation of one does not contribute to the prediction of the other. However, for stationary and slowly moving remote stations, the characteristics of the forward link transmission path will be observed to be statistically similar to the characteristics of the reverse link transmission path.

The forward link is a shared resource between remote stations. To ensure simultaneous transmission to multiple remote stations, channelization using orthogonal codes may be implemented. The number of orthogonal codes is a finite system resource and must be dynamically assigned and reassigned. The selection of which orthogonal code to use is part of the optimization process implemented by the base station.

Transmissions to a remote station may be sent on a dedicated channel, with transmissions to a group of remote stations being sent in a broadcast fashion. The transmission on the dedicated channel is encoded using a set of parameters chosen from a large selection of potential parameters. If the remote station does not know the set of parameters used by the base station, the remote station will have to attempt to demodulate and decode the transmission using each set of parameters until the transmission is decoded correctly. This is a non-efficient method. Thus, the transmission format information is typically transmitted on a broadcast channel so that the remote station can receive the transmission format information. The remote station is configured to use the specified transmission format information to decode the broadcast channel.

For example, if data is transmitted to a remote station, the base station will packetize, i.e., "packetize," the data in accordance with a given transmission format and transmit the packetized data and information about the type of packet used to the remote station. Information such as packet type allows the remote station to quickly and efficiently turn on packet data. However, there may be problems in transmitting the packet information.

To increase the data throughput rate, the transport format information must be transmitted in a manner that is easily demodulated and decoded by the remote station. Typically, the transport format information is transmitted as a broadcast so that the remote station can demodulate and decode the information quickly and without an established delay. However, there are common and unavoidable drawbacks to all broadcast transmissions: reliability and effectiveness. For broadcast transmissions, the base station cannot easily determine who has received the broadcast and who has lost the broadcast. Thus, if the broadcast transmission format information is lost, the remote station may also lose the corresponding transmission on the dedicated channel.

Abstract

Methods and apparatus are presented herein to address the above-mentioned problems. In one aspect, a method for acknowledging the output of dedicated transmissions and broadcast transmissions is presented, the method comprising: generating a first acknowledgement message in response to the dedicated transmission from the base station; generating a second acknowledgement message in response to the broadcast transmission from the base station; selecting a Walsh code used to cover the first acknowledgment message using the second acknowledgment message; and transmitting the first coverage confirmation message to the base station.

In another aspect, a method for estimating an acknowledgment message from a remote station is presented, the method comprising: decoding the acknowledgement message; determining an identity of a Walsh code sequence covering the acknowledgment message; using the acknowledgement message to determine whether the dedicated transmission was decoded by the remote station; and using the identity of the Walsh code sequence to determine whether the broadcast transmission was decoded by the remote station.

Brief description of the drawings

Fig. 1 is a diagram of a wireless communication network.

Fig. 2 is a diagram of the interaction between the signaling layers L1, L2, and L3 in the base station and the remote station.

Fig. 3 is a diagram of a process of obtaining Walsh space information.

Fig. 4 is a flow chart illustrating when a remote station should send an acknowledgement of a broadcast message.

Fig. 5A is a block diagram of a prior art channel structure for an acknowledgment channel.

Fig. 5B is a block diagram of a new channel structure for an acknowledgment channel.

Fig. 6 is a flow chart illustrating how the Walsh code sequences of a remote station are updated.

Description of The Preferred Embodiment

As illustrated in fig. 1, the wireless communication network 10 generally includes a plurality of mobile stations (also referred to as remote stations or subscriber units or for equipment) 12a-12d, a plurality of base stations (also referred to as Base Transceiver Stations (BTSs) or node bs) 14a-14c, a Base Station Controller (BSC) (also referred to as a radio network controller or packet control function 16), a Mobile Switching Center (MSC) or switch 18, a Packet Data Serving Node (PDSN) or internet function (IWF)20, a Public Switched Telephone Network (PSTN)22 (typically a telephone company), and an Internet Protocol (IP) network 24 (typically the internet). For simplicity, only four mobile stations 12a-12d, three base stations 14a-14c, one BSC16, one MSC18, and one PDSN20 are shown. Those skilled in the art will appreciate that there may be more or fewer mobile stations 12, base stations 14, BSCs 16, MSCs 18, and PDSNs 20.

In one embodiment, the wireless communication network 10 is a packet data service network. The mobile stations 12A-12D may be several different types of wireless communication devices such as a portable telephone, a cellular telephone that is connected to a laptop computer running an IP-based web browsing application, a cellular telephone associated with a hands-free car kit, a Personal Digital Assistant (PDA) running an IP-based web browsing application, a wireless communication module included in a portable computer, or a fixed location communication module such as might be found in a wireless local loop or meter reading system. In most general embodiments, the mobile station may be any type of communication unit.

The mobile stations 12a-12d may advantageously be configured to implement one or more wireless packet data protocols, as described in the EIA/TIA/IS-707 standard. In a particular embodiment, the mobile stations 12a-12d generate IP packets destined for the IP network 24 and encapsulate the IP packets into frames using a point-to-point protocol (PPP).

In one embodiment, the IP network 24 is coupled to a PDSN20, the PDSN20 is coupled to a MSC18, the MSC is coupled to a BSC16 and a PSTN22, the BSC16 is coupled to the base stations 14a-14c, coupled through a line configured for the transmission of voice and/or data packets according to any of several known protocols including, for example, E1, T1, Asynchronous Transfer Mode (ATM), IP, PPP, frame Relay, HDSL, ADSL, or xDSL. In an alternative embodiment, the BSC16 can be directly coupled to the PDSN 20.

In the normal operation of the wireless communication network 10, the base stations 14a-14c receive and demodulate sets of reverse signals from respective mobile stations 12a-12d for telephone calls, web browsing, or other data communications. Each reverse signal received by a given base station 14a-14c is processed within that base station 14a-14 c. Each base station 14a-14c may communicate with a plurality of mobile stations 12a-12d by modulating and transmitting sets of forward signals to the mobile stations 12a-12 d. For example, as shown in fig. 1, the base station 14a communicates with first and second mobile stations 12a, 12b simultaneously, and the base station 14c communicates with third and fourth mobile stations 12c, 12d simultaneously. The resulting packets are forwarded to the BSC16, which BSC16 provides call resource allocation and mobility management functions, including control for soft handoff of a call for a mobile station 12a-12d from one base station 14a-14d to another base station 14a-14 c. For example, the mobile station 12c communicates with two base stations 14b, 14c simultaneously. Finally, when the mobile station 12c moves far enough away from one of the base stations 14c, the call will be handed off to the other base station 14 b.

If the transmission is a conventional telephone call, the BSC16 routes the received data to the MSC18, and the MSC18 provides additional routing services that interface with the PSTN 22. If the transmission is a packet-based transmission, such as a data call destined for the IP network 24, the MSC18 routes the data packets to the PDSN20, and the PDSN20 sends the packets to the IP network 24. Alternatively, the BSC16 routes the packets directly to the PDSN20, and the PDSN20 sends the packets to the IP network 24.

In some communication systems, packets carrying data traffic are divided into subpackets, which occupy slots of a transmission channel. The name of the cdma2000 system is used hereafter for convenience of description only. Such use is not intended to limit implementation of the embodiments herein to cdma2000 systems. Implementations in other systems, such as WCDMA, can be implemented without affecting the scope of the embodiments described herein.

The forward link from the base station to the remote station operating within the range of the base station can include multiple channels. Some forward link channels can include, but are not limited to, pilot channels, synchronization channels, paging channels, quick paging channels, broadcast channels, power control channels, assignment channels, control channels, dedicated control channels, Medium Access Control (MAC) channels, fundamental channels, supplemental code channels, and packet data channels. The reverse link from the remote station to the base station also includes multiple channels. Each channel conveys a different type of information to the intended receiving station. Typically, voice traffic is transmitted on the fundamental channel and data traffic is transmitted on the fundamental channel or the packet data channel. The fundamental channel is typically a dedicated channel for a given party, while the packet data channel typically transports signals that are given to different parties in a time and/or code multiplexed manner. Alternatively, the packet data channel is also described as a shared fundamental channel. For the purposes of describing the embodiments herein, the fundamental channel and the packet data channel are generally referred to as the data traffic channel.

Voice traffic and data traffic are typically coded, modulated, and then spread on the forward or reverse links before transmission. Coding, modulation, and spreading can be implemented in a variety of formats. In a CDMA system, the transmission format ultimately depends on the type of channel over which voice traffic and data traffic are being transmitted and the condition of the channel, which is described in terms of fading and interference.

The predetermined transmission format corresponds to a combination of various transmission parameters and can be used to simplify the selection of the transmission format. In an embodiment, the transport format corresponds to any or all combinations of the following transmission parameters: the modulation scheme used by the system, the number and identity of orthogonal or quasi-orthogonal codes, the data payload size in bits, the duration of the message frame, and/or details regarding the encoding scheme. Some examples of modulation schemes used within communication systems are Quadrature Phase Shift Keying (QPSK), eight phase shift keying (8-PSK), and sixteen quadrature amplitude modulation (16-QAM). Some of the multiple coding schemes that can be selectively implemented are convolutional coding schemes, which can be implemented at different rates, or turbo coding, which includes multiple coding steps.

Orthogonal and quasi-orthogonal codes, such as walsh codes, are used to channelize the information sent to each remote station. In other words, walsh code sequences are used on the forward link to allow the system to cover multiple users, each assigned to a different orthogonal or quasi-orthogonal code on the same frequency during the same time duration. For example, the Walsh code sequences generated by Walsh functions can be recursively defined as follows:

where W' represents the logical complement of W, and W (1) ═ 0. Thereby to obtain

And

w (8) is as follows:

the Walsh sequence is one of the rows of the Walsh function matrix. The Walsh function of order n comprises n sequences each of length n bits. The data transmission is covered by one or several such spreading codes, thereby allowing CDMA separation between different transmissions occurring simultaneously on the same frequency. In this context, "code space" or "Walsh space" refers to the term of a set of spreading code sequences used to transmit data.

To recover the originally transmitted data bits of the data traffic channel, the decoder must be able to determine how many spreading codes are being used to cover the data and which spreading codes are being used. Since the channel can use several possible spreading codes and various optional coding and modulation formats, it is desirable to inform the decoder at the receiving end about the actual transmission parameters used at the transmitting end. The transmission parameters can be transmitted on one or several separate control channels, which may be implemented for sending occasionally or each time a data traffic transmission occurs. The receipt of the transmission parameters will allow the decoder to quickly begin decoding and demodulating the data traffic channel.

In a cdma2000 system, one type of data traffic channel is the forward packet data channel (F-PDCH). The F-PDCH is assigned to a single remote station of a specified duration. Generating the F-PDCH by the base station consumes a variable amount of resources. For example, a new voice call initiated within the service area of a base station reduces the number of Walsh codes available to other remote stations, while a drop of a voice call increases the number of available Walsh codes.

Layering is a method for organizing communication protocols within well-defined encapsulated data units between other decoupled processing entities (i.e., layers), as is known in the art. Fig. 2 illustrates three protocol layers L1220, L2210, and L3200 implemented within the base station 250 and the remote station 260. Layer L1220 provides for wireless signal transmission and reception between the base station and the remote station, layer L2210 provides for proper transmission and reception of signaling messages, and layer L3200 provides for control information transfer of the communication system. Layer L3200 initiates and interrupts signaling messages according to the semantics and timing of the communication protocol between base station 250 and remote station 260. In cdma2000 systems, 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. Above the signaling layer is an application layer 230, the application layer 230 containing the functionality of a certain application service.

At layer L3200, voice traffic 201, packet data traffic 203, and system services 205 are communicated over data units constructed in accordance with the previously discussed standards. Transmission parameters, such as Walsh space information, are communicated from a base station to a remote station using three layer L3 messages, referred to herein as Walsh table ID messages, Walsh mask messages, and the most recent Walsh code indicator message. The Walsh table ID message is used to identify one of a plurality of Walsh tables, where each table lists indices that can be used to establish a packet data channel between the base station and the remote station. The indices can further be stored as a function of an order of use, i.e., the order of indices indicates that a particular Walsh code sequence is used before other Walsh code sequences.

A Walsh mask message is transmitted in a forward packet data control channel (F-PDCCH) along with a MAC identifier (MAC _ ID) to indicate a bitmap of availability of Walsh codes listed in an assigned Walsh table. Some predetermined MAC _ IDS may be common to a group of remote stations, or MAC _ IDS may be unique to an individual remote station. When a remote station enters the communication system, a unique MAC _ ID can be assigned to the remote station in accordance with a unique International Mobile Station Identification (IMSI). In one implementation, the MAC _ ID value is "0 x00," which is the MAC _ ID reserved for broadcasts to all remote stations within the service range of the base station. The Walsh mask message is used to inform the Walsh table selected by the Walsh table ID message of possible "holes". These gaps occur when certain Walsh codes are assigned to other traffic channels, such as a forward supplemental channel (F-SCH), a forward fundamental channel (F-FCH), and/or a forward dedicated control channel (F-DCCH).

A Last Walsh Code Indicator (LWCI) message is transmitted on the F-PDCCH along with a MAC _ ID to indicate an index of the last Walsh code for the corresponding F-PDCH. The LWCI message is considered to convey information about which Walsh code was used to establish the most recent previous forward packet data channel.

Fig. 3 illustrates a method of obtaining Walsh space information for the F-PDCH. Portion 300 illustrates various Walsh tables 301A, 301b.. 301N stored at the base station and remote station. The Walsh table ID message, the Walsh mask message, and the last Walsh code indicator message are transmitted by the base station to the remote station. Section 310 illustrates that the mask 311 defined by the Walsh mask message overlaps with the table 301i defined by the Walsh table ID message. In fig. 3, mask 311 is represented by a sequence of "0" and "1", and this sequence is then multiplied by table 301i, where multiplication by "0" indicates that the corresponding sequence in table 301i cannot be used. The coverage of the mask 311 results in a set of Walsh codes 321 in a portion 320, which portion 320 will be used primarily for dedicated communications between the base station and the remote station. Section 320 also illustrates the index of the last Walsh code for the corresponding F-PDCH using LWCI information 322, 323.

The above approach has drawbacks due to the manner in which the Walsh mask message is transmitted to the remote station. The Walsh mask message is transmitted in a broadcast manner on the F-PDCCH. Thus, the performance of the above method is affected by the imperfections that are common to all broadcast transmissions and unavoidable. In particular, there are two problems: reliability and effectiveness.

For reliability, sending the Walsh mask message in a broadcast manner does not ensure that each remote station can receive the information even if retransmissions are used. When a remote station has difficulty acquiring the correct Walsh mask information, there is no systematic way to recover from the lack of the required Walsh mask information.

The lack of reliability results in a lack of effectiveness. System effectiveness suffers because the base station may not be able to determine that the remote station does not have the correct Walsh mask information. If the remote station does not have the correct Walsh mask information, some of the transmissions to the remote station will be wasted.

Acknowledgement of broadcast messages

In one embodiment, an acknowledgement is generated and used in response to the broadcast of the Walsh mask message. As indicated above, "broadcast" is a term in the art that indicates transmission of a message under certain conditions, i.e., an attachment to a common MAC _ ID rather than a certain user MAC _ ID transmitted on a broadcast channel, so that each remote station sharing the common MAC _ ID can demodulate and decode the broadcast transmission. This embodiment utilizes an acknowledgement channel designed to acknowledge the success or failure of a transmission on a dedicated channel. As discussed above, the intended initial use of the acknowledgment channel is for the scheduling unit in the base station to increase the data throughput rate of the system.

Fig. 4 depicts the generation of an acknowledgment to a broadcast transmission using a new acknowledgment channel, which is described in more detail below with respect to fig. 5B. The processor and the memory unit are configured in the base station to perform the method steps described in fig. 4. Alternatively, other infrastructure elements can be configured to perform these steps. This embodiment includes implementing the two program flows described in blocks 4A and 4B. In step 400, a system flag is set in the remote station according to whether an acknowledgement to the broadcast transmission must be generated. In this embodiment, the broadcast transmission is a Walsh mask message.

In step 410 of block 4A, the remote station receives the Walsh mask message and compares the newly received Walsh mask to the original Walsh mask stored at the remote station. If the received Walsh mask message is the same as the original Walsh mask message, then the remote station refrains from transmitting an acknowledgement in step 420. In one embodiment, the remote station is configured to repeat the acknowledgement if the remote station has previously acknowledged the old Walsh mask message. If the received Walsh mask message is different from the original Walsh mask message and the conditions described in block 4B are met, the remote station sends an acknowledgement on the reverse link acknowledgement channel described in fig. 5B in step 430.

In step 450 of block 4B, the remote station determines whether transmissions on the F-PDCH are scheduled during the same time as Walsh mask messages are transmitted on the F-PDCCH. If not, the remote station refrains from sending an acknowledgement in step 460. If so and the conditions of block 4A are met, the remote station sends an acknowledgement on the reverse link acknowledgement channel described in FIG. 5B in step 470.

Fig. 5A is an example of a prior art acknowledgment channel structure for acknowledging messages received on a dedicated channel. The remote station (not shown) generates a bit, either 0 or 1, for each slot to indicate whether the sub-packet has been decoded correctly. A "slot" is a duration and a "subpacket" is a transmission unit. The message may be transmitted as one or more subpackets over at least one slot period. This bit is repeated a plurality of times in the repetition unit 500. In a system transmitting at a rate of 1.2288 mega per second (Mcps), the optimal repetition factor is twenty-four (24). The term "chip" is used to describe a bit in a spreading sequence, such as a bit pattern spread by a Walsh code. The output of the repetition unit 500 is mapped to +1 or-1 by the mapping unit 510. The output of the mapping unit 510 is covered by an extension unit 520. In one embodiment, spreading element 520 may be a multiplier that spreads the mapped output by the ith 64-ary Walsh code sequence.

FIG. 5B is a channel structure diagram of a new reverse link acknowledgement channel (R-ACKCH) for acknowledging transmissions sent on the dedicated packet channel and for acknowledging transmissions sent on the broadcast channel. Reverse acknowledgement channel bits 550 for the dedicated channel with repetition factor RF 3 × ACKCH _ REPS_sIs input into the repeating unit 560, wherein ACKCH _ REPS_sIs a system defined as a constant of 1, 2 or 4. In one embodiment, per ACKCH _ REPS over a 1.25ms slot_sThe 1-bit rule generates acknowledgment channel bits. The output of the repetition unit 560 is 3 symbols per slot. On a broadcast channelThe received reverse acknowledgment channel bits 555 for transmission are input to the covering unit 570. The reverse acknowledgement channel bits 555 are used by the covering element 570 to select a Walsh code sequence. The selected Walsh code sequence includes 8 symbols per slot, and the output of the repetition unit 560 is covered by using a multiplier 580 to form 24 symbols per slot. The output of the multiplier is generated at a rate of 19 kilo-symbols per second (ksps) using a time slot lasting 1.25 ms. This output is then sent to be modulated, upconverted and transmitted over the air, the details of which are not discussed in detail herein.

In one general embodiment, the new R-ACKCH channel can acknowledge any broadcast transmission in addition to acknowledging dedicated transmissions. Notably, the value of the acknowledgment bit for the broadcast transmission is used to select the Walsh code sequence that covers the acknowledgment bit for the dedicated transmission. When the base station receives the acknowledgement message, the base station will be able to identify the Walsh code sequence used to cover the acknowledgement bit for the dedicated channel.

Exchanging signaling messages

Due to the jitter of the reverse link, the acknowledgments sent on the acknowledgment channel may be misread as negative acknowledgments, as described above. In another embodiment, the base station and the remote station can exchange relevant information via L3 signaling messages. The embodiment of exchanging L3 signaling messages can be performed together with the above-described embodiments.

In order to exchange L3 signaling messages, a method must be established for the remote station to demodulate and decode the L3 signaling messages on the dedicated channel. The problem is how a remote station can demodulate and decode messages sent using a particular transmission format when the remote station has no transmission format information.

As previously described, transmissions for a particular remote station are sent on a dedicated channel, while transmissions for a group of remote stations are sent in a broadcast fashion. The transmission on the dedicated channel is encoded using a set of parameters chosen from a large selection of potential parameters. If the remote station does not know the set of parameters used by the base station, the remote station will have to attempt to demodulate and decode the transmission using each set of parameters until the transmission is decoded correctly. This is a non-efficient method. Thus, the transmission format information is typically transmitted on a broadcast channel so that the remote station can receive the transmission format information.

Using this broadcast transmission format information, the remote station will be able to demodulate and decode the transmission information on the dedicated channel quickly and efficiently. The embodiments described herein are used to enable a remote station to demodulate and decode transport format information on a dedicated channel.

In an embodiment, at least one processor and memory unit, or other infrastructure element capable of performing scheduling functions within a base station, is configured to send an L3 signaling message or other transmission using a covering set of Walsh code sequences. The covered set of Walsh code sequences is a set of Walsh code sequences that are common between the previous Walsh space and the current Walsh space. If a new Walsh space is selected to transmit information, a subset of the new Walsh set may be the same as a subset of the old Walsh set. This common subgroup is called the coverage group.

As depicted in fig. 3, a set of available Walsh code sequences is generated using Walsh masks on the Walsh table. The LWCI message indicates which Walsh code was last used. Typically, the system implements a selection rule for determining which Walsh code to use next. For example, a typical selection rule is to pick the Walsh code from the bottom of the table and then move up the table for each subsequent transmission on the dedicated channel.

In an embodiment, the processor and memory unit are configured to determine which Walsh code was last used from a previously used table and which was not. Using the information of the Walsh selection rule, the processor and memory unit select a set of Walsh codes from the previous table, wherein the set of Walsh codes comprises the Walsh code sequences least likely to be selected by the prescribed selection rule. Next, the processor and memory unit select a new Walsh code table that shares the least likely selected Walsh codes. Alternatively, the LWCI indicator is reset to point to the Walsh codes of the previous table. It is noted that the order of the Walsh code sequences in this table can be arbitrary, so long as the base station and the remote station agree upon or share the same order.

Using these overlaid Walsh code sequences, the base station sends L3 signaling messages to the remote station on a dedicated channel, such as the F-PDCH, where the L3 signaling messages include transport format information for other transmissions. It is noted that the quality of the forward and reverse links often fluctuates widely, and thus the transmission formats in which information is transmitted also vary widely to optimize the data throughput of the system.

Once the base station determines the overlaid Walsh code sequence, the base station can transmit on a dedicated channel to a remote station that does not have the current transmission format information.

Fig. 6 is a flow chart of exchanging L3 signaling messages containing current transport format information. In step 600, the remote station determines that the transmission on the most recently received dedicated channel may not be decoded correctly, indicating that an erroneous Walsh mask, Walsh table, or LWCI is used. In step 610, the remote station generates a Walsh mask request message or a Walsh table ID request message or an LWCI request message whenever appropriate, and transmits the message to the serving base station. In step 620, the serving base station receives the message and sends a Walsh mask update message or a Walsh table ID update message or an LWCI update message to the remote station as long as the update response is an appropriate reply to the message. In step 630, the remote station receives the update response and updates the Walsh code sequence. Notably, the update Walsh information update message can be sent autonomously by the base station, i.e., without a response request from the remote station.

The above-described embodiments provide for transmitting transport format information to a broadcast channel on a dedicated channel instead of, or in addition to, a broadcast channel. These embodiments can be implemented when the remote station is restricted from entering the range of the serving base station. In addition, this embodiment can be implemented when the remote station sends a negative acknowledgement in response to a broadcast transmission, the process of which is described above.

Synchronization of orthogonal spatial information

The above describes embodiments of reliable convergence of orthogonal code space information, which depends on the quality of the transmission channel (broadcast channel or dedicated channel). The following embodiments for synchronizing orthogonal spatial information can be implemented together with the above embodiments if the situation arises that neither type of channel is sufficient to update the orthogonal spatial information. Typically, if the channel conditions are insufficient to deliver a message to the remote station during the extended time, the remote station will send a series of negative acknowledgements to the transmitting base station. Rather than having the base station wait for multiple negative acknowledgements before determining that the remote station has erroneous orthogonal spatial information, the embodiments described below have the base station make the determination after receiving only one negative acknowledgement.

In one embodiment, a serving base station is configured with a plurality of counters, each counter associated with a remote station operating within range of the serving base station. The format of the counter is a system-defined parameter set by the number of remote stations that the base station can serve within the quality threshold. Each remote station may also be configured with a counter that is synchronized with a corresponding counter at the base station.

In one embodiment, the counter is a 3-bit counter. A 3-bit counter will count the number of Walsh mask changes. The counter at the base station is incremented by modulo 8 by 1 when a new Walsh mask message is sent to the remote station, and the counter at the remote station is incremented by modulo 8 by 1 when a new Walsh mask message is received.

A general description of this embodiment is that the contents of the counter at the remote station will be used to select the Walsh cover that is used to cover the acknowledgment or negative acknowledgment bits sent on the new reverse acknowledgment channel (R-ACKCH), such as that depicted in fig. 5B. In the new reverse acknowledgment channel, the value of the acknowledgment bit for the broadcast transmission is used to select the Walsh code sequence covering the acknowledgment bit for the dedicated transmission. If the acknowledgement length of the broadcast transmission is 3 bits, 8 values may be embedded in the transmitted acknowledgement message. When the base station receives an acknowledgment or negative acknowledgment bit from the remote station, the base station checks the Walsh cover of the received bit and extracts the embedded counter content. If the counter content in which the received acknowledgement or negative acknowledgement is embedded differs from the local counter value, the base station determines that a synchronization problem has occurred so that the remote station does not operate using the current transmission format information. Thus, in this embodiment, the counter value serves as the sequence identifier of the Walsh mask. Once a synchronization problem has been identified, the base station can take appropriate action to correct the problem.

In one embodiment, the base station corrects synchronization problems by resetting the local counter to the embedded counter content specified by the Walsh cover of the acknowledgment or negative acknowledgment bit from the remote station. In this embodiment, the base station must have at least one counter for each remote station so that the base station can keep track of all embedded counter contents.

In another embodiment, the base station sends an L3 signaling message, the process of which is described in the document description of fig. 6 above. In addition to the transport format information, the L3 signaling message can be configured to further convey the content value of the appropriate base station counter. After receiving the L3 signaling message, the remote station resets its counter value to the appropriate counter value and resets the Walsh space information in accordance with the L3 signaling message.

In another embodiment, the base station forces the remote station counters to reset to a common counter value. On the broadcast channel, the base station can send a counter reset command message and attach a common MAC _ ID to the reset command instead of a certain user MAC _ ID. Thus, each remote station sharing a common MAC _ ID receives the counter value and resets the local counter appropriately.

Alternatively, the actual common MAC _ ID itself can be used as the counter reset value. For example, in a cdma2000 system, MAC _ ID values of 0-7 are specified as common values among all remote stations operating within range of the serving base station. Thus, if a MAC _ ID value of 6 is sent on the broadcast channel, all remote stations will be configured to decode the message attached to this MAC _ ID. In one embodiment, if a 3-bit counter is used at both the base station and the remote station, then 2³The value of 8 needs to be communicated to the remote station. If the value of the local counter is used to select the value of the MAC _ ID, the need for a separate reset command message is eliminated. MThe AC _ ID will serve a dual purpose: first, it is specified that the attached message is for the initial purpose of all remote stations, and second, the purpose of identifying the counter value.

It is worth noting that if the base station forces the common value to be reset, the base station only needs one local counter, since all remote stations will be reset to have the same counter content.

It is also worth noting that counters having larger or smaller sizes, such as 2-bit counters or 4-bit counters, can be used without unduly affecting the scope of the embodiments.

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, 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, modules, 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: 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 of devices designed to perform the functions described herein. A general purpose processor is preferably 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 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 other 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 preferred 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 the use of the inventive faculty. 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.

Claims (6)

1. Apparatus in a remote station for acknowledging the output of dedicated transmissions and broadcast transmissions, comprising:

a storage unit; and

a processing unit configured to execute a set of instructions stored on the storage unit, the set of instructions to:

generating a first acknowledgement message in response to the dedicated transmission from the base station;

generating a second acknowledgement message in response to the broadcast transmission from the base station;

selecting a Walsh code used to cover the first acknowledgment message using the second acknowledgment message; and

the first coverage confirmation message is sent to the base station.

2. A method for acknowledging the output of dedicated transmissions and broadcast transmissions, comprising:

generating a first acknowledgement message in response to the dedicated transmission from the base station;

generating a second acknowledgement message in response to the broadcast transmission from the base station;

selecting a Walsh code used to cover the first acknowledgment message using the second acknowledgment message; and

the first coverage confirmation message is sent to the base station.

3. Apparatus in a base station for estimating acknowledgment transmissions from a remote station, comprising:

a storage unit; and

a processing unit configured to execute a set of instructions stored on the storage unit, the set of instructions to: decoding the acknowledgement message;

determining an identity of a Walsh code sequence covering the acknowledgment message;

using the acknowledgement message to determine whether the dedicated transmission was decoded by the remote station; and

the identity of the Walsh code sequence is used to determine whether the broadcast transmission was decoded by the remote station.

4. A method for estimating an acknowledgement message from a remote station, comprising:

decoding the acknowledgement message;

determining an identity of a Walsh code sequence covering the acknowledgment message;

using the acknowledgement message to determine whether the dedicated transmission was decoded by the remote station; and

the identity of the Walsh code sequence is used to determine whether the broadcast transmission was decoded by the remote station.

5. A method for determining whether to generate an acknowledgement message for a broadcast transmission, comprising:

comparing a Walsh mask included in the broadcast transmission with a previous Walsh mask included in a previous broadcast transmission; and

if the Walsh mask is different from the previous Walsh mask, an acknowledgement message is generated whether the dedicated transmission and the broadcast transmission are scheduled during the same time.

6. An apparatus for generating a combined acknowledgement message for acknowledging dedicated transmissions and broadcast transmissions, comprising:

a repeating unit for repeating the confirmation bit value to form a symbol;

a covering unit for selecting a Walsh code symbol based on the second confirmation bit value; and

a multiplier for expanding the output of the repeating unit using the output of the covering unit.