HK1091079A - Method and apparatus for controlling data rate of a reverse link in a communication system - Google Patents

Description

Method and apparatus for controlling data rate of reverse link in communication system

Priority 35U.S.C. § 119

This patent application claims priority from provisional application No. 60/448,269 entitled "reverse link data communication" filed on month 2 and 18 of 2003 and provisional application No. 60/469,376 entitled "method and apparatus for controlling data rate of a reverse link in a communication system" filed on month 5 and 9 of 2003, which are assigned to the assignee and are expressly incorporated herein by reference.

Technical Field

The present invention relates generally to the field of communications, and more specifically to controlling the data rate of a reverse link from a mobile station in a communication system.

Background

In a wireless communication system, unnecessary and excessive transmissions by a user may cause interference to other users in addition to reducing system capacity. Inefficient selection of reverse link data rates in a communication system can result in unnecessary and excessive transmissions. Data communicated between two end users may pass through some protocol layers that ensure that the data flows through the system normally. Typically, a mobile station receives a block of data from an application for transmission on the reverse link. The data block is divided into a number of frames and transmitted over the communication link. Proper delivery of data is ensured in at least one aspect by a system that checks each data frame for errors and requests retransmission of the same data frame if unacceptable errors or error rates are detected in the data frame. The data blocks may be of any type, e.g. music data, video data, etc. The data blocks may have different sizes and different transmission requirements. Such data transfer requirements are often linked to quality of service. The quality of service may be measured by the communication data rate, the acceptable packet loss rate for the service, the consistency of the data transfer delay, and the acceptable maximum delay for data communication. In general, if the data rate selected for transmission is insufficient, the required packet loss and communication delay parameters cannot be obtained.

In forward link communications, a base station often has sufficient information about the quality of the forward link for a number of mobile stations. Thus, the base station can centrally manage the forward link communication data rate. On the reverse link, however, the mobile station has no information about transmissions from other mobile stations. Thus, the mobile station may make a request to be granted transmission at one data rate. The base station accepts or rejects the requested data rate after checking each mobile station request. If the requested data rate is rejected, the mobile station may request a lower data rate until the base station accepts the requested data rate. The mobile station may be granted permission to transmit at less than one data rate without being subject to request and acceptance processing. Such data rates are typically very low data rates. The mobile station needs to complete the communication for the data rate request prior to the reverse link transmission. This communication overhead between the mobile station and the base station may reach unacceptable levels and affect the desired quality of service.

Accordingly, it is desirable to provide a system, method, and apparatus for reverse link data rate selection in a communication system.

Drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

FIG. 1 depicts a communication system for transmitting and receiving data in accordance with various aspects of the present invention;

fig. 2 depicts a receiver system for receiving data in accordance with various aspects of the invention.

FIG. 3 depicts a transmitter system for transmitting data in accordance with various aspects of the invention; and

fig. 4 depicts a flow of messages and processing for determining a data rate for reverse link communications.

Detailed Description

One or more exemplary embodiments described herein are illustrated in the context of a digital wireless data communication system. Although advantageous for use in this environment, different embodiments of the present invention may be included in different environments or configurations. In general, the various systems described herein may be constructed using software-controlled processors, integrated circuits, or discrete logic. Data, instructions, commands, information, signals, symbols, and chips that may be referenced throughout the application are advantageously represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or a combination thereof. Further, the blocks shown in each block diagram may represent hardware or method steps.

More particularly, various embodiments of the invention may be included in a wireless communication system operating in accordance with Code Division Multiple Access (CDMA) techniques that have been disclosed and described in various standards published by the Telecommunication Industry Association (TIA) and other standards organizations. These standards include the TIA/EIA-95 standard, TIA/EIA-IS-2000 standard, IMT-2000 standard, UMTS and WCDMA standard, all incorporated herein by reference. The system for data communication IS also detailed in the "TIA/EIA/IS-856 cdma2000 high-speed packet data air interface Specification," which IS incorporated herein by reference. Copies of these standards may be made by being located at a web sitehttp：//www.3gpp2.orgAccess to the world wide web, or by writing to TIA, Standard and Technology Department, 2500Wilson Boulevard, Arlingeton, VA22201, United States of America (Arlington, Wilson Dairy 2500, TIA, department of standards and technology, 22201, USA). The standard, generally identified as the UMTS standard, incorporated herein by reference, is available by contacting 3GPP Support Office, 650 routes Lucioles-Sophia Antipolis, Valbonne-France.

Fig. 1 illustrates a general block diagram of a communication system 100 capable of operating in accordance with any of the Code Division Multiple Access (CDMA) communication system standards while incorporating various embodiments of the present invention. The communication system 100 may be used for communication of voice, data, or both. In general, the communication system 100 includes a base station 101 that provides communication links between a number of mobile stations, such as mobile station 102 and 104, and between the mobile station 102 and 104 and a public switched telephone and data network 105. The mobile stations in fig. 1 may be referred to as data Access Terminals (ATs) and the base stations may be referred to as data Access Networks (ANs) without departing from the main scope and various advantages of the present invention. Base station 101 may include a number of components, such as a base station controller and a base transceiver system. These components are not shown for simplicity. Base station 101 may communicate with other base stations, such as base station 160. A mobile switching center (not shown) may control various operational aspects of the communication system 100 and in relation to a backhaul 199 between the network 105 and the base stations 101 and 160.

Base station 101 communicates with the mobile stations over a forward link signal transmitted from base station 101 over its coverage area. The forward link signals targeted for mobile stations 102 and 104 may be summed to form forward link signal 106. The forward link may carry many different forward link channels. Each mobile station 102 that receives forward link signal 106 decodes the forward link signal 106 to extract the information targeted for its user. Base station 160 may also communicate with the mobile stations over the forward link signals transmitted from base station 160. Mobile stations 102 and 104 may communicate with base stations 101 and 160 via respective reverse links. Each reverse link is maintained by a reverse link signal such as reverse link signals 107 and 109 for mobile stations 102 and 104, respectively. Reverse link signals 107-109, although may be targeted for one base station, may be received at other base stations.

Base stations 101 and 160 may simultaneously communicate with a common mobile station. For example, mobile station 102 may be in close proximity to base stations 101 and 160, which can maintain communication with base stations 101 and 160. On the forward link, base station 101 transmits on forward link signal 106 and base station 160 transmits on forward link signal 161. On the reverse link, mobile station 102 transmits on reverse link signal 107 to be received by both base stations 101 and 160. To transmit a data packet to mobile station 102, one of base stations 101 and 160 may be selected to transmit a data packet to mobile station 102. On the reverse link, both base stations 101 and 160 may attempt to decode traffic data transmissions from mobile station 102. The data rates and power levels of the reverse and forward links may be maintained in accordance with the channel conditions between the base station and the mobile station as outlined in various aspects of the invention.

Fig. 2 shows a block diagram of a receiver 200 for processing and demodulating a received CDMA signal while operating in accordance with various aspects of the invention. Receiver 200 may be used to decode information on the reverse and forward links signals. Receiver 200 may be used to decode information on the fundamental channel, control channel, and supplemental channels. Received (Rx) samples may be stored in RAM 204. The received samples may be generated by a radio frequency/intermediate frequency (RF/IF) system 290 and an antenna system 292. To take advantage of receive diversity gain, the RF/IF system 290 and antenna system 292 may include one or more components for receiving multiple signals and for RF/IF processing of the received signals. Multiple received signals propagating through different propagation paths may come from a common source. The antenna system 292 receives the RF signals and passes the RF signals to the RF/IF system 290. The RF/IF system 290 may be any conventional RF/IF receiver. The received RF signal is filtered, down-converted and digitized to form RX samples at baseband frequencies. These samples are provided to a multiplexer (mux) 252. The output of multiplexer 252 is provided to searcher unit 206 and rake finger 208. To which a control system 210 is connected. The combiner 212 couples the decoder 214 to a finger element 208(finger element). Control system 210 may be a microprocessor controlled by software and may be located on the same integrated circuit or on a separate integrated circuit. The decoding function in decoder 214 may use a turbo decoder or any other suitable decoding algorithm. The signal transmitted from the source may be encoded with a number of encoding layers. Decoder 214 may perform decoding functions according to two or more encodings. For example, the data to be transmitted may be encoded at two different layers, an outer layer and a physical layer. The physical layer may be encoded according to Turbo and the outer layer may be encoded according to reed solomon (reed solomon). As such, the decoder 214 decodes the received samples according to these encodings.

In operation, received samples are provided to multiplexer 252. Multiplexer 252 provides the samples to searcher unit 206 and rake finger 208. The control unit 210 configures the rake finger 208 to perform demodulation and despreading of the received signal based on the search results from the searcher unit 206 at different time offsets. The results of the demodulation are combined and passed to decoder 214. The decoder 214 decodes the data and outputs the decoded data. Despreading of the channels is often accomplished using an integrated circuit and dump accumulator circuit (not shown) by multiplying the received samples with the complex conjugate of the PN sequence and a given walsh function under a single timing hypothesis and digitally filtering the resulting samples. Such techniques are generally well known in the art. Receiver 200 may be used in a receiver portion of base stations 101 and 160 for processing received reverse link signals from mobile stations, and in a receiver portion of any mobile station that processes received forward link signals.

Decoder 214 may accumulate the combined energy for data symbol detection. Each data packet may carry a Cyclic Redundancy Check (CRC) field. Decoder 214 may be coupled to control system 210 and/or other control systems that check for errors in received data packets. If the CRC data does not pass, the received data packet is received in error. The control system 210 and/or other control systems may send a negative acknowledgement message to the transmitter to retransmit the data packet.

Fig. 3 shows a block diagram of a transmitter 300 for transmitting the reverse and forward link signals. The channel data for transmission is input to a modulator 301 for modulation. The modulation may be according to any commonly known modulation technique, such as QAM, PSK, or BPSK. The channel data for transmission may be encoded by one or more layers prior to modulation. The channel data for transmission is generated for modulator 301. The channel data for transmission is received by the modulator 301.

The modulated data rate may be selected by a data rate and power level selector 303. The data rate selection may be based on feedback information received from the destination. The data rate is often based on channel conditions, among other considerations and in accordance with various aspects of the present invention. The channel conditions may change from time to time. The data rate selection may also change from time to time.

The data rate and power level selector 303 thus selects the data rate in the modulator 301. The output of modulator 301 is subjected to a signal spreading operation and amplified in block 302 for transmission from antenna 304. The data rate and power level selector 303 also selects a power level for the amplification level of the transmitted signal. The combination of the selected data rate and power level allows for proper decoding of the transmitted data at the receiving destination. A pilot signal is also generated in block 307. The pilot signal is amplified to an appropriate level in block 307. The pilot signal power level may be based on the channel condition of the receiving destination. The pilot signal may be combined with the channel signal in a combiner 308. The combined signal may be amplified in amplifier 309 and transmitted from antenna 304. The antennas 304 may be in any number of combinations including antenna arrays and multiple-input multiple-output configurations.

In a CDMA2000 system, a Mobile Station (MS) is allowed some simultaneous communication services. Each communication service may have different quality of service (QoS) requirements. For service selection, data packets may be communicated with well-defined QoS parameters, such as a specific data rate or data rate range, a packet loss rate, and a maximum delay allowed for communication of a data packet or some data packets. During the service negotiation phase of the communication link, the MS and the Base Station (BS) agree on a set of QoS parameters. The QoS parameters may be defined for the duration of the defined communication service. The BS may then be requested to meet these agreed QoS, such as data rate, packet loss, and most likely maximum delay.

According to various aspects of the present invention, a method and apparatus for implementing QoS on the reverse link is provided, wherein updated information regarding queue length and packet delay deadlines is available at the MS, while a resource manager that allocates the negotiated QoS is in the BS. The MS requests a requested rate from the BS instead of reporting its queue length (reserve) information. The MS calculates the requested data rate and duration before requesting the data rate from the BS. The request for the data rate may take the form of a request for one or more forward link traffic channel power-to-pilot (T/P) ratios. The set of available data rates may have corresponding T/P ratios. A list may be provided for the correspondence between T/P ratio and data rate. The autonomous data rate control performed by the MS may also be based on congestion feedback from the BS. The BS may be responsible for allocating rates to the MS and for congestion management and stability of the reverse link. The BS is also responsible for admission control. The allocation of resources in response to a data rate request may be described in the flow of messages and processes illustrated below.

The actual resource managed by the BS is the traffic channel to pilot power ratio (T/P). The mapping from the data rate of the channel to T/P is an operating point selected based on the number of retransmissions allowed and the use of hybrid ARQ. The BS may assign different mappings as a function of the delayed request (allowed retransmission) for each service. Such optimization is useful for services with short-time processing and very low latency requests (e.g., interactive games). For most services, the best choice is for the BS to select the mapping that maximizes the reverse link throughput. The labels (1-8) on the left represent possible sequences of events or processes that may occur.

The BS manages admission control and allows only communication services (or flows) with acceptable and reachable QoS requests. Once the service of data packets or the flow of communication is allowed, the MS knows the agreed QoS parameters, such as the acceptable data rate, the packet loss rate and the maximum delay associated with the flow. Note that these QoS guarantees are necessarily random due to channel variations and changes.

The MS implements an (upstream) policy that drops inconsistent data packets at the ingress. In this way, the MS accepts all packets deemed to satisfy the agreed QoS for the allowed flows by implementing the policy. Packets whose requested QoS prior to the output queue stage exceeds an agreed QoS, e.g., as defined by the communication data rate, are dropped at the MS. The MS may also implement an outer loop mechanism to adjust the policy parameters based on operating conditions. The BS may "verify" that the MS actually conforms to its agreed rate.

3. The coherent packets that are allowed at the MS are queued in the output queue. A deadline is associated with each packet based on the packet arrival time and the maximum delay allowed for that service (or flow). Preferably, the MS may queue the output queues so that packets are held in order of their deadline, the earliest deadline being placed at the forefront. The MS must manage its transmission schedule to ensure that packets are transmitted before its deadline.

The MS determines the requested data rate based on the deadline associated with the packet in the output queue. This process is described more fully below. Since the data rate determined by the MS is required to meet the agreed QoS, the requested data rate is not merely an indication of "priority". If the requested rate cannot be allocated by the base station due to congestion, overload control, or any other reason, the MS may also calculate one or more congested data rates by determining which packets in its queue can be dropped to assist the BS in allocating a lower rate than the requested rate. The MS determines the congestion rate based on the requested rate and the number of packets that can be dropped in the queue. Typically, as packets are dropped from the queue, the data rate required to transmit the remaining number of packets decreases. The BS converts the requested and congested rates to the requested and congested T/P or alternatively, the MS can directly calculate the requested and congested T/P.

MS transmits the requested and congested T/P or T/P increase or decrease and transmits it to BS. Since these resources are requested by the MS to meet its QoS criteria, the BS must attempt to meet the request for the T/P increase, which is affected by the available resources. Some consecutive T/P-increase requests from the MS indicate increased priority, which if not would result in some QoS criteria not being met.

The BS scheduler stacks these T/P requests according to reverse link resources, that is, rise over thermal (rise over thermal), and time. The BS also reserves certain resources for known low-delay, constant bandwidth flows, e.g., voice calls. The BS may attempt to optimize such a stack, for example by delaying a certain T/P allocation or providing a higher T/P allocation for a shorter duration. If the BS delays the assignment to the MS, subsequent requests from the MS may request a higher T/P to satisfy the QoS for delay sensitive packets because the longer the delay to transmit data packets, the higher the data rate requested to transmit to satisfy the same QoS. Therefore, the BS has limited flexibility in scheduling. If excess bandwidth is available, the BS may choose to ignore the request for T/P reduction, or provide a higher T/P than requested.

The BS allocates the T/P to the MS. The allocation may be indicated to the MS as an increase (or decrease) to the current data rate allocation.

8. Based on the T/P assignment, the MS schedules packets for transmission. The MS is based on the earliest deadline first scheduling rule and may be modified. For example, before starting to transmit any packets, the MS determines whether data packet transmission occurred within its deadline. This determination is a function of the assigned T/P and the deadline and should address the potential for future incremental assignments. The MS drops any packets that may miss its delivery deadline. Packets that are not successfully transmitted before their deadline expires are considered to be dropped. The MS keeps track of the packet loss rate associated with the flow.

In this framework, the processing of time steps 2, 3 and 8 respectively allow the MS to manage the QoS (rate, maximum delay and packet loss guarantees) associated with its flow. The processing of time steps 4 and 5 allows the MS to combine the needs of all its flows into one T/P request. The BS admission control process at time step 1 ensures that the BS will have sufficient resources to satisfy all admitted negotiated QoS flows requests from all MSs at time step 6. The MS determines the requested data rate to satisfy the QoS. The MS merges the queues for multiple (negotiated QoS) services into one rate request. Also, typically, instead of determining the requested rate and translating to the requested T/P, the MS can operate directly at the requested T/P. This is more common because it is easier to satisfy packet transmissions from different services with different T/P to rate mappings.

Let us assume that at time t₀MS queue is formed by size s_iPacket P of_i1, N, by term d_iAre arranged in the order of (a). Each packet P_iAssociated with a data service k (i). For data service k, the known mapping of data rate to T/P is defined as: r_k(T/P). Then, the following equation is used to assign the T/P value T₀May be defined and determined. At a rate R_k(i)(T₀) Packet P_iTransmission time over radio, x_iIs composed of

x_i＝s_i/R_k(i)(T₀) (1)

Since the packets have been arranged in their order of deadline, the packet P_iWill complete its transmission to

z_i＝t₀+∑s_j/R_k(j)(T₀) Wherein in [1,....... -, i]Shanghai (2)

That is, having a deadline before d_iPacket P of₁，...，P_i-1At P_iIs previously transmitted. Thus, the process can determine whether any packet in the output queue of the MS will miss its deadline, i.e., whether it will miss its deadline

z_i＞d_iFor 1. ltoreq. i.ltoreq.N (3)

If the MS determines that any packets in its queue at the current rate will miss its deadline, it may request a higher rate to meet its QoS. Note that: this data rate calculation uses deadline information associated with each packet in the MS queue. The BS cannot make such a data rate determination based on the reservation and QoS class only.

There may be some methods of providing the requested T/P information to the BS. Depending on the design of the request channel and the frequency of transmission of the requested information from the MS to the BS, it may also be useful to calculate the duration of the request at the MS and provide an indication to the BS. Equation 2 above also allows the MS to determine the request duration. Basically, with an assigned T/P ratio T₀The last packet in the MS queue will be at time z_NIts transfer is completed. Thus, based on the current packet queue and allocation rate, the request duration is z_N. Equation 2 can be updated with very little computational load. For example, if at a subsequent time t₁In packet P₁When the transfer is completed, the allocated T/P is changed to T₁Then the updated packet completion time is written as:

z_i(t1)＝t₁+∑s_j/R_k(j)(T₁) Wherein the sum is [ 2... multidot., i]Upper computer (4)

These completion times can be calculated from the previous packet completion times by using the equation:

z_i(t₁)-t₁＝z_i(t₀)-t₀-s₁/R_k(1)(T₀)+∑s_j[1/R_k(j)(T₁)-1/R_k(j)(T₀)](5)

second, assume that it has a size s_newService k (new), and deadline d_newNew packet P of_newAt time t₂And (4) arriving. Typically, the deadline for the new packet is between the (in-order) deadlines for packets k and k +1, i.e. d for k < N_k≤d_new＜d_k+1. And, for i ≦ k, z_i(t₂) And is not changed. If the value of T/P is T₁There is no change in the shape of the lens,

z_i(t₂)＝z_i(t₁)+s_new/R_k(new)(T₁) For i > k (6)

Thus, the MS can calculate and keep updating its request T/P, the request duration, and the transmission schedule of packets in its queue.

To assist the BS in rate allocation during congestion, the MS also calculates the congestion rate by determining which packets in its queue can be dropped. The MS may use a number of criteria to determine the priority of which packets can be dropped:

packets from a service that is susceptible to dropping packets,

packets from a service whose current packet loss rate is less than the agreed packet loss rate,

if the requested T/P is not allocated packets that are likely to miss their delay deadline.

Based on the priority of dropping, the MS determines which packets can potentially be dropped while still meeting acceptable QoS at different congestion levels. The MS then applies equations (1) through (3) to the virtual queue formed by removing the packets from the MS queue to calculate the congestion T/P value. Note that from beginning to end, packet data and data blocks may be interchanged.

It is more convenient and equivalent to work with data rates if the T/P to rate mapping is fixed. A diagram illustrating requested and congestion data rate calculations is shown below. Packet size and deadline are also shown graphically. Each packet size (in bits) is shown as a vertical bar placed at its deadline on the time frame axis. The size of the vertical bar represents the packet size. Any straight line with a positive slope through the origin corresponds to the rate (expressed in bits/second). The origin is the current time or the time when the allocation starts. The requested rate is the minimum slope that satisfies all the deadlines, that is, the minimum slope below the line for all packets in the graph. Also, the MS calculates the congestion rate by assuming that the first packet in the queue can be dropped (congestion level 1) and the congestion rate associated with dropping the largest packet in the queue (congestion level 2).

At time t₀MS queues are defined by their deadlines d_iIs s_iPacket P of_iAnd { i ═ 1., N }. Then, at a dispensing rate R₀We can write the following equation. At a rate R₀Packet P_iTransmission time over radio, x_iIs composed of

x_i＝s_i/R₀ (7)

Since the packets have been arranged in the order of their deadline, the packet P_iWill complete its transmission to

z_i＝t₀+∑s_i/R₀Wherein in [1]Shanghai (8)

That is, having a deadline before d_iPacket P of₁，...，P_i-1At P_iIs previously transmitted. Thus, the process can determine whether any packet in the MS output queue will miss its deadline, i.e., it will miss its deadline

z_i＞d_iFor 1. ltoreq. i.ltoreq.N (9)

If the MS determines that any packet in its queue will miss its deadline, it requests a higher rate to meet its QoS. This data rate calculation uses deadline information associated with each packet in the MS queue. The BS cannot make such rate determinations based solely on the reserve and QoS classes.

There are some methods of providing the requested rate information to the BS. Depending on the design of the request channel and the frequency of transmission of the requested information from the MS to the BS, it may also be useful to calculate the duration of the request at the MS and provide an indication to the BS. The above (equation 2) also allows the MS to determine the request duration. Basically at the distribution rate R₀The last packet in the MS queue will be at time z_NIts transfer is completed. Thus, based on the current packet queue and the assigned rate, the request duration is z_N. Equation (2) can be updated with very little computational load. For example, if in packet P₁Subsequent time t when the transfer is completed₁The dispensing rate has become R₁Then the updated packet completion time may be written as:

z_i(t₁)＝t₁+∑s_j/R₁wherein in [2]Shanghai (10)

These completion times can be calculated from past packet completion times using the equation:

z_i(t₁)-t₁＝[(z_i(t₀)-t₀)R₀-s₁]/R₁ (11)

second, assume size s_newDuration d_newNew packet P of_newAt time t₂And (4) arriving. Typically, the deadline for the new packet may be between the (in-order) deadlines for packets k and k +1, i.e. d for k < N_k≤d_new＜d_k+1. Then, for i ≦ k, z_i(t₂) And is not changed. If the rate R is₁The temperature of the molten steel is not changed,

z_i(t₂)＝z_i(t₁)+s_new/R₁for i > k (12)

Thus, the MS can calculate and keep updating its request rate, request duration, and transmission schedule of packets in its queue.

As indicated above, the MS can determine the requested rate or T/P by examining the delay bound of all packets in the MS buffer. Alternatively, if the MS checks that only the first packet is in its buffer, that is, the packet with the shortest delay bound, and applies the above-described T/P (or rate) calculation, the result is equivalent to a delay bound fed back to the BS. In this case, the value of the calculated T/P (or rate) represents the shortest term and the equivalent highest priority. An example of two-bit encoding for the reverse link channel delay period is shown in the following paragraphs and may be used.

The reverse link request may be sent to the BS by message or using a continuous low rate control channel. The following schemes may be considered and used:

use the reverse link message to provide queue length or reserve information to the BS. To support QoS, a QoS field may be added to this request message.

The MS periodically inserts a bit in the continuous T/P or rate request channel to indicate a request for a higher rate. This does not provide an indication of any QoS for the BS.

The resources managed by the BS include a traffic channel to pilot power ratio (T/P). Generally, higher T/P ratios map to higher data rates. The system may allow for more than one mapping scheme between T/P ratios and corresponding data rates. Typically, the MS always selects a mapping of data rates to T/P that maximizes reverse link throughput. For some services (e.g., interactive games) with short processing and very low latency requests, it is necessary to work with fewer retransmissions and higher T/ps. Thus, if the data packet at the head of the queue of the MS has a very short deadline (e.g., less than 40MS), the MS may select a particular rate to T/P mapping that is appropriate for low latency services. The scheme can operate using the rate and mapping it to the T/P, or directly computing the requested T/P.

To allow the BS resource manager to prioritize allocations during periods of congestion, the MS also shows one or more congested T/P values to the BS in addition to the requested T/P. The BS attempts to allocate the requested T/P fairly to all MSs. If the requested resources exceed the available resources, the BS changes the requested T/P of one MS at a time (in some order determined by the BS) using a smaller T/P associated with congestion level 1 until the entire allocation for all mobile stations falls within the available resources. If necessary, the BS may proceed to the T/P associated with congestion level 2, and so on. The indication of the requested T/P or data rate and the congested T/P or data rate may be communicated via short control messages, continuous messages, or a combination thereof.

In the request message to the BS, the requested T/P and its duration may be provided based on calculations at the MS. Such a request message may not include reservation and QoS feedback to the BS. The BS cannot calculate the requested T/P and its duration based on the backlog and QoS classes. Periodic messages requesting T/P and its duration are preferred for periodic feedback of reserve and QoS classes in order to manage QoS (rate, packet loss, maximum delay). In response, the BS allocates the T/P and the duration to the MS through the grant message. The MS continues to update its (local) rate and duration calculations. The update request is triggered whenever there is a significant change in the T/P of the request, or the duration of the request exceeds the allocation duration by a significant amount. A grant with a zero T/P assignment may indicate the expiration of the grant to the MS.

Once T/P is granted to the MS, a low bandwidth continuous reverse link request channel may be utilized in order to reduce request message overhead. The MS maintains a Current Grant variable based on the Grant from the BS. Alternatively, the permission may be implicit, that is, any MS is allowed to autonomously set its Current Grant variable to the global (initial) value of the Current Grant and thus eliminate the need for any message.

Based on the requested rate calculation, the MS continuously sends requests to increase, decrease, or not change its Current Grant. The request for increasing the T/P may also indicate whether the increase is needed to meet the T/P for different congestion levels. An encoding of a two-bit differential Rate Request (differential Rate Request) field may be included in the message. The MS indicates its Current Grant level with respect to requested rate and congestion rate, e.g., if the Current Grant is between the requested T/P and TP of congestion level 1, the MS's request includes encoded bit "10". Alternatively, a two-bit differential rate request field containing only 1 congestion level and a new level for preventing buffer underflow for delay sensitive traffic may be included.

Current admission request

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -11 request T/P- - - - - - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - -10 congestion level 1T/P- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

- - - - - - - - -00T/P request indicates to the MS the level of current grant with respect to the requested T/P and the congested T/P

Encoding of two-bit differential T/P request fields

Current admission request

Can be reduced by-11T/P-can be reduced-can

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -01 congestion level T/P- - - - - - - - - - - - - - - - - - - - - - - - - -

the-00T/P request indicates to the MS the level of current grant with respect to the requested T/P, the congested T/P and the T/P that can cause buffer underflow

Optional encoding of two-bit differential T/P request field

Optionally, a long admission threshold D is planned₀May also be defined. If the MS calculates that its request duration exceeds D₀It may represent a request for a long license. This is useful because it allows the BS to anticipate and therefore better manage its resource allocation and scheduling decisions. For the scheduler, the requests for high rates are "priority" requests, while the requests for long grants represent backups.

Alternatively, two bits may be used to represent the delay bound (or priority level) of a packet at the head of the queue. For example:

delay period for the beginning of priority queue packet

3 is less than X

2 is greater than X, but less than 3X

1 is greater than 3X, but less than 9X

0 is greater than 9X (i.e., best effort)

X is a system parameter whose value may be fixed by the BS, or may be fixed depending on the service mixed by each MS.

The MS sends the current grant on the reverse link using the T/P value. The BS determines the value of the current grant variable at the MS from the current transmission. The BS may determine this value by measuring the ratio of the traffic channel power and the pilot power in the MS transmission or the rate used for transmission from the MS and mapping it to the T/P.

The BS resource manager fairly allocates T/P among the MSs using the current T/P used by the MSs, along with the information in the T/P requests. For example, depending on the congestion level, it may only satisfy the congestion level 1 request for all MSs. The BS then allocates a T/P delta to the MS whose request indicates 00 or 01, with the MS indicating 00 having a higher priority. The BS assigns a T/P decrement to the MS whose request indicates 11 or 10. The BS may also use additional criteria to manage contention among MSs.

The operation of the BS resource manager can be explained by the following example. Consider the case of three MSs:

MS 1：Ec_Pilot[1]，Current Grant[1]，Request＝10

MS 2：Ec_Pilot[2]，Current Grant[2]，Request＝01

MS 3：Ec_Pilot[3]，Current Grant[3]，Request＝01

MS 4：Ec_Pilot[4]，Current Grant[4]，Request＝11

MS 5：Ec_Pilot[5]，Current Grant[5]，Request＝00

MS 6：Ec_Pilot[6]，Current Grant[6]，Request＝10

note that in the above example, all MSs except MS 4 have requested a higher T/P than the Current Grant to satisfy the request T/P. MS 4 may assign a decrement in its Current Grant. The increased allocation may or may not be provided to other MSs, depending on the further calculations. The BS resource manager can calculate the Current resource utilization from Ec _ Pilot and Current Grant for each MS as follows:

resource utilization ∑ Ec _ Pilot [ i ] - [ Current Grant [ i ] +1] (13)

BS allows for increase (up-regulation) or decrease (down-regulation) for Current Grant. The increase or decrease is a multiplication factor multiplied by the Current Grant, whose value Adjust [ i ] is defined as (1+ a) or (1-a), respectively. With allocation, the updated resource utilization can be calculated as:

resource utilization ∑ Ec _ Pilot [ i ] - [ Adjust [ i ] - [ Current Grant [ i ] +1] (14)

The resource management algorithm may proceed by the following steps. It terminates at a step where a set of adjustment values Adjust i is derived when the updated resource utilization is below a maximum resource utilization threshold Tmax.

Step 1A decrement is assigned to MS 4 and an increment is assigned to all other MSs.

Adjust [4] ═ 1-a, Adjust [ i ] ═ 1+ a, and i ═ 1, 2, 3, 5, 6. This allocation attempts to move all MSs to meet their requested T/P. An updated resource utilization is determined. This allocation is granted and may be assigned if the updated resource utilization is below a maximum threshold Tmax. If the resource utilization exceeds Tmax, step 2 is entered.

Step 2It is not possible to move all MSs to the requested T/P. For fairness, the process moves all MSs to congestion level 1T/P. This means that in addition to MS 4, MS 1 and 6 can also be assigned down-regulation. That is, Adjust [ i]1-a, 1, 4, 6 and Adjust [ i ] for i]1+ a, 2, 3, 5 for i. Again, it is determined whether this updated resource allocation can be allowed, that is, not to exceed the total allowed allocation. If not, go to step 3.

Step 3It is not possible to move all MSs to congestion level 1T/P. For fairness, the process changes all MSs to congestion level 2T/P. This means that all MSs except MS 5 will be allocated down regulation. That is, Adjust [ i]1-a, 1, 2, 3, 4, 6 and Adjust [5 ] for i]1+ a. Again, it is determined whether this updated resource allocation is allowed, that is, not to exceed the total allowed allocation. If not, go to step 4.

Step 4 the BS T/P adjustment algorithm cannot determine a satisfactory allocation. An explicit message may be requested to terminate the transmission from one or the MS. The BS selects which licenses to terminate based on various criteria, including: the metric and the size of the current assignment to the MS.

The low bandwidth continuous forward link grant channel may be used to indicate an adjustment to the CurrentGrant to the MS. The MS modifies its Current Grant variable based on the actual grants (and adjustments) it receives from the BS. Since the grant extends continuously to the MS, it is not necessary to indicate a long grant to the MS. Long grant requests (as used) only allow the BS to anticipate and thus make better scheduling decisions.

The encoding for the low bandwidth continuous forward link grant channel may be as follows:

+1if the mobile station is instructed to increase T/P by a configured amount, (also T/P related)

-1If the mobile station is instructed to decrease T/P by a configured amount, (also T/P related)

0If the mobile station is instructed to keep the T/P unchanged.

If the BS does not reliably decode the continuous request channel (e.g., the reverse pilot channel (R-PICH) is received with low power and the continuous request channel symbol is erased), the BS sets the forward grant channel symbol to 0. Otherwise, if the continuous request channel is reliably decoded, the BS sets the forward grant channel symbol appropriately.

Although the BS resource manager determines the congestion level based on the MS request rather than requesting a continuous grant channel for each MS with some loss of flexibility, it is possible to use a continuous common grant channel that represents only the currently calculated congestion level at the BS (e.g., encoded as one of the three levels shown above). Based on this indication, the MS can autonomously adjust its data rate according to the same logic. For example, when the BS common grant indicates a congestion level of 1, the MS requesting 10 must decrease their T/P, while the MS requesting 01 can increase their T/P for subsequent transmissions. Furthermore, the continuous common grant channel, while reducing overhead on the forward link, cancels the BS's ability to distinguish between competing MSs based on additional criteria. It is also possible to cancel the continuous request channel and reduce it to the autonomous operation of the MS. The congestion indication from the BS is based on current measurements of MS resource usage, rather than MS requests. Thus, there is no closed loop for each MS. In this case, the BS cannot distinguish between MSs whose QoS is satisfied and those whose QoS is not satisfied and thus cannot perform fairly.

Also, signaling errors on the continuous request and grant channels are not catastrophic. Erasure on the continuous forward Grant channel is assumed as a command to keep the Current Grant unchanged. Any signaling errors will be quickly corrected by subsequent requests and grants due to the low-delay closed-loop mechanism. Specifically, in each reverse link frame transmission, the Current Grant that changes locally at the MS is known by the BS and allows both sides of the control loop to maintain the same state.

Reverse link QoS management may operate by using only request and grant messages. However, for strict QoS management, i.e., for service management QoS with sudden arrival, varying rate, and strict delay constraints, it is necessary to use continuous request and grant channels. Note that the continuous request channel can be used without a continuous grant channel.

For negotiated QoS traffic, the MS may operate as follows:

the MS sends a request message showing the request T/P (and the congested T/P). The request message may also contain the maximum T/P (headroom at the MS)). The BS may indicate the T/P grant by a message, or the grant may be implicit (known as the initial T/P). In the latter case, no request and grant messages are required.

The requested T/P change is indicated on the low overhead continuous rate request channel. The channel may be established and released using layer 3 signaling. Only one such channel is needed per MS, since this channel represents the total rate request for the MS.

The change in T/P of the grant is indicated by the base station on a low overhead continuous grant channel on the forward link. Alternatively, a low overhead continuous common grant channel may be used that indicates a level of congestion based on the received request.

During soft handoff operations, message-based reverse resource management is handled only by the serving BS (the BS with the highest average pilot level received at the MS). The continuous request and grant channel may be received and transmitted only by the serving BS or the reduced active set of the BS. If the continuous grant channel is only transmitted by the serving BS, the operation in soft handover is the same as if the mobile station is not in soft handover. However, if the forward quick grant channel is transmitted from more than one BS in the active set, different BSs may operate independently and generate different grant instructions. The MS is then requested to adjust its Current Grant variable to the minimum of the rate adjustments granted by all BSs in the active set.

The overhead for each MS continuously requesting and granting a channel amounts to using the message-based channel once every few hundred milliseconds. Thus, to match the overhead, the rate request and rate grant messages need not be sent more frequently than, for example, 250MS per MS, including all services at the MS. The continuous feedback channel is necessary to manage the QoS for services with a maximum delay less than, for example, 100 ms. Even for services with burst arrivals whose queue sizes can vary significantly in tens of milliseconds. If the delay bound is greater than 250ms, then QoS may be managed through a message-based request and grant channel. 2-4 bits per 20-40ms may be required for a continuous reverse rate request channel. These bits indicate the requested modification of its allocated rate to the BS and/or the need for a long grant.

In general, an architecture for QoS and resource management at the reverse link is disclosed, where packet queues are distributed at the MS and a centralized resource manager is in the BS. In this architecture, the tasks of reverse link QoS management are allocated to the MS and the BS manages the total resources and admission control for the agreed QoS service. The MS provides the requested resources (rate or T/P) needed to satisfy its QoS to the resource manager. This is different from previous methods in which the MS provides queue reservation information to the resource manager. The queue reservation information is insufficient for the resource manager to meet the QoS guarantee. Reverse link QoS is managed by the MS through closed loop control of the assigned rate or T/P. QoS requests for multiple services (or flows) are combined into a compressed representation of the resource (rate or T/P). This allows for an efficient (low communication overhead) closed loop control. This allows the MS to determine the requested T/P that it is allowed to satisfy all service QoS requests. Low complexity mechanisms to recalculate rate (or T/P) and duration requirements after packet departure, packet arrival vary in allocated rate or in link quality. The low overhead continuous request and grant channel is consistent with this architecture and is adapted to manage QoS for services with maximum delay requests of less than 100 ms. Processing for calculating T/P requests for different levels of congestion by using packet drop priorities is disclosed. Compression coding of the rate request channel is disclosed which provides BS resource manager information to determine the level of congestion at the packet queues distributed to the MS. Further, it allows the BS resource manager to make intelligent allocation decisions in competing MSs. Therefore, the BS resource manager allocates resources in the competing MSs, including the operation of closed-loop rate control in soft handover.

The different aspects of the invention will be more apparent by referring to the different steps depicted in fig. 4. Fig. 4 depicts a message flow 400 and processing steps of a BS and an MS in communication system 100. The receiver and transmitter systems 200 and 300 shown in fig. 2 and 3 are operable to perform different steps when incorporated in respective base stations or mobile stations in the communication system 100. In step 401, the mobile station determines data packets for transmitting a plurality of communication services. In steps 402 and 403, the mobile station determines the transmission deadline for each data packet and queues the data packets in the queue for transmission according to the determined transmission deadline, respectively. In steps 405, 406 and 407, the mobile station determines a data rate for transmitting data packets to allow a transmission deadline of each data packet to be met based on the arrangement of the data packets in the queue, determines a duration of the determined data rate for transmitting the data packets based on the arrangement of the data packets in the queue, and transmits the data rate and the duration from the mobile station to the base station, respectively. In step 408, the base station determines whether the available resources allow for transmissions from the mobile station at the determined data rate and duration to be allocated at the base station. In step 409, the base station transmits an acceptance of the determined data rate for the transmission of data packets from the mobile station. At step 410, the mobile station transmits at the accepted data rate. In step 411, the base station may indicate a congestion level alarm to the mobile station and the determined available resources are not allowed to be allocated at the base station to transmissions from the mobile station at the predetermined data rate. In steps 412, 413 and 414, the mobile station discards at least one of the data packets in the queue to determine a new data packet queue, determines a new data rate for transmitting the new data packet queue, the new data rate being lower than the data rate determined in the past, and determines a new duration for transmitting the determined new data rate for the data packets based on the arrangement of the data packets in the new queue. The flow 400 branches to step 408 to repeat the determination for acceptance or rejection.

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, 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 thereof designed to perform 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 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 (30)

1. In a communication system, a method for determining a data rate for a reverse link communication from a mobile station to a base station, comprising:

determining data packets transmitted by the mobile station for a plurality of communication services;

determining a transmission deadline for each of the data packets;

queuing the transmitted data packets in a queue according to the determined transmission deadline;

determining a data rate for transmission of the data packets based on the arrangement of the data packets in the queue that satisfies the transmission deadline for each of the data packets.

2. The method of claim 1, further comprising:

transmitting the data rate from the mobile station to the base station.

3. The method of claim 1, further comprising:

determining a duration of time to transmit the data packet using the determined data rate based on the arrangement of the data packets in the queue.

4. The method of claim 3, further comprising:

transmitting the determined duration from the mobile station to the base station.

5. The method of claim 1, further comprising:

determining whether available resources allow allocation at the base station to transmissions from the mobile station at the data rate.

6. The method of claim 5, further comprising:

indicating a congestion level alert to the mobile station when the determined available resources are not allowed to be allocated at the base station for transmission from the mobile station at the data rate.

7. The method of claim 6, further comprising:

discarding at least one of the data packets in the queue to determine a new data packet queue;

determining a new data rate for the new data packet queue transmission, wherein the new data rate is lower than the data rate.

8. The method of claim 7, further comprising:

determining a new duration for transmitting the data packets using the determined new data rate based on the arrangement of the data packets in the new queue.

9. In a communication system, a method for determining a data rate for a reverse link communication from a mobile station to a base station, comprising:

determining data packets for a plurality of communication services communicated from the mobile station;

determining a transmission deadline for each of the data packets;

queuing the data packets in a plurality of queue queues for transmission in accordance with the determined transmission deadline;

determining a plurality of data rates for the data packet transmission based on the possible plurality of queue permutations.

10. The method of claim 9, wherein the plurality of determined data rates comprises a requested data rate and at least one congestion level data rate.

11. The method of claim 9, further comprising:

transmitting the plurality of data rates from the mobile station to the base station.

12. The method of claim 9, further comprising:

determining a duration of each of the determined plurality of data rates for transmitting the data packet based on the arrangement of the data packets in the queue.

13. The method of claim 12, further comprising:

transmitting the determined duration from the mobile station to the base station.

14. The method of claim 9, further comprising:

determining whether available resources allow for transmission allocated at the base station from the mobile station at least one of the plurality of data rates.

15. The method of claim 14, further comprising:

indicating to the mobile station when the determined available resources allow allocation at the base station for transmissions from the mobile station at least one of the data rates.

16. In a communication system, an apparatus for determining a data rate for a reverse link communication from a mobile station to a base station, comprising:

means for determining data packets for a plurality of communication services transmitted from a mobile station;

means for determining a transmission deadline for each of the data packets;

means for queuing the data packet for transmission in a queue for transmission according to the determined transmission deadline;

means for determining a data rate for transmission of said data packets based on the arrangement of said data packets in said queue that meets said transmission deadline for each of said data packets.

17. The apparatus of claim 16, further comprising:

means for transmitting the data rate from the mobile station to the base station.

18. The apparatus of claim 16, further comprising:

means for determining a duration of time to transmit the data packets using the determined data rate based on the arrangement of the data packets in the queue.

19. The apparatus of claim 18, further comprising:

means for transmitting the determined duration from the mobile station to the base station.

20. The apparatus of claim 16, further comprising:

means for determining whether available resources are allowed to be allocated at the base station to transmissions from the mobile station at the data rate;

21. the apparatus of claim 20, further comprising:

means for indicating a congestion level alert to the mobile station when the determined available resources are not allowed to be allocated at the base station for transmission from the mobile station at the data rate.

22. The apparatus of claim 21, further comprising:

means for discarding at least one of the data packets in the queue to determine a new data packet queue;

means for determining a new data rate for transmission of the new data packet queue, wherein the new data rate is lower than the data rate.

23. The apparatus of claim 22, further comprising:

means for determining a new duration for the determined new data rate to transmit the data packet based on the arrangement of the data packets in the new queue.

24. In a communication system, an apparatus for determining a data rate for a reverse link communication from a mobile station to a base station, comprising:

means for determining data packets for a plurality of communication services transmitted from the mobile station;

means for determining a transmission deadline for each of the data packets;

means for queuing the data packets in a plurality of queue arrangements for transmission in accordance with the determined transmission deadline;

means for determining a plurality of data rates for transmission of the data packet based on the plurality of possible queue permutations.

25. The apparatus of claim 24, wherein the plurality of determined data rates comprises a requested data rate and at least one congestion level data rate.

26. The apparatus of claim 24, further comprising:

means for transmitting the plurality of data rates from the mobile station to the base station.

27. The apparatus of claim 24, further comprising:

means for determining a duration of each of the determined plurality of data rates for transmitting the data packet based on the arrangement of the data packet in the queue.

28. The apparatus of claim 27, further comprising:

means for transmitting the determined duration from the mobile station to the base station.

29. The apparatus of claim 9, further comprising:

means for determining whether available resources are allowed to be allocated at the base station to transmit at least one of the plurality of data rates from the mobile station.

30. The apparatus of claim 29, further comprising:

means for indicating to said mobile station when said determined available resources allow allocation at said base station to transmissions from said mobile station at least one of said data rates.