Method and apparatus for congestion control in a wire less communication system

Method and device for congestion control in wireless communication systemTechnical field

[0001] The present invention relates to a communication system. The present invention particularly relates to a method and device for congestion control in a wireless communication system.

Background technique

[0002] In a wireless communication system, a base station communicates with multiple mobile users. Wireless communication may include low-latency data communication, such as voice or video transmission, or high-data-rate communication, such as packetized data transmission. U.S. Patent Application No. 08963386, titled^uMETHOD AND APPARATUS FOR HIGH RATE PACKETDATA TRANSMISSION", submitted on November 3, 1997, describes high-rate packet data transmission, which is incorporated herein by reference.

[0003] In a wireless communication system, especially in a system suitable for packetized transmission, congestion and overload may reduce the throughput of the system. Congestion is a measure of pending and active traffic relative to the rated capacity of the system. The overload of the system occurs when the pending and active traffic exceeds the rated capacity. The system may achieve the target congestion level to maintain uninterrupted traffic conditions, that is, avoid resource overload and underload.

[0004] One problem with overload is the delayed transmission response. The increase in response time often causes the application layer to time out. At this time, the waiting time of the application that needs data exceeds the time allowed by the application. Then the application will unnecessarily resend the message after the timeout, further causing congestion. If this situation continues, it may result in a situation where the system can no longer serve any users. Therefore, when there is no congestion control, the performance of the system will be much lower than its rated capacity. Therefore, there is a need for congestion control that increases the efficiency of the wireless system and reduces the possibility of overload or error.

Summary of the invention

[0005] The embodiment disclosed herein satisfies the requirements described above. It is achieved by providing an effective congestion control method that determines a congestion indication by comparing the measured congestion metric with a threshold value, where the threshold value is used relative to the expected value. The threshold of the outer loop threshold with a certain margin. According to one aspect, the method of generating a congestion indication includes determining the outer loop threshold as a function of the desired threshold, measuring the congestion metric, comparing the congestion metric with the desired threshold, and updating the outer loop based on comparing the measured congestion metric with the desired threshold. Road threshold.

Description of the drawings

[0006] FIG. 1 is a wireless communication system;

[0007] FIG. 2 is a flowchart of a congestion control method at an access network in a wireless communication system for packetized transmission;

[0008] FIG. 3 is a flowchart of a method for making a congestion control decision in a wireless communication system for packetized transmission; [0009] FIG. 4 is a timing diagram of an expected congestion threshold for an outer loop congestion threshold;

[0010] FIGS. 5A and 5B are flowcharts of a congestion control method at an access terminal in a wireless communication system for packetized transmission;

[0011] FIG. 6 is an access network in a wireless communication system;

[0012] FIG. 7 is an access network that implements congestion control in FIG. 3; and

[0013] FIG. 8 is an access terminal that implements the data rate control in FIG. 4.

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Detailed ways

[0014] The word "example" only means "serving as an example, instance, or illustration" herein. Any embodiment described herein as an "example" is not necessarily construed as the most optimal or superior to other embodiments.

[0015] A mobile subscriber station, referred to herein as an access terminal AT, may be mobile or stationary, and may communicate with one or more base stations. The access terminal transmits and receives data packets to the base station controller through one or more modem pool transceivers, which is referred to herein as the modem pool controller MPC. The modem pool transceiver and modem pool controller are part of the access network. The access network transmits data packets among multiple access terminals. The access network may also be connected to other networks outside the access network. Such as the corporate intranet or the Internet, and may transmit data packets between each access terminal and this kind of external network. An access terminal that has established an active traffic channel connection with one or more modem pool transceivers is called an active access terminal, and is said to be in a traffic state. It is worth noting that the access network may include base stations, where the base stations are used to communicate with multiple access terminals and a base station controller.

[0016] An access terminal that is establishing an active traffic channel connection with one or more modem pool transceivers is said to be in a connection establishment state. The access terminal may be any data device that communicates through a wireless channel or a wired channel, for example, using optical fiber or coaxial cable. The access terminal may also be one of many types of equipment, including but not limited to PC cards, small flash memory, external or internal modems, or wireless or wired phones. The communication link through which the access terminal sends signals to the modem pool transceiver is called the reverse link. The communication link through which the modem pool transceiver sends signals to the access terminal is called the forward link.

[0017] FIG. 1 is a diagram of a communication system 100 that supports multiple users and can implement at least some aspects and embodiments of the present invention. The system 100 provides communication for multiple cells 102A to 102G, each of which is served by a corresponding base station 104A to 104G. In an exemplary embodiment, some of the base stations 104 have multiple receiving antennas, and the others have only one receiving antenna. Similarly, some of the base stations 104 have multiple transmit antennas, while others have only a single transmit antenna. There is no restriction on the combination of the transmitting antenna and the receiving antenna. Therefore, the base station 104 may have multiple transmitting antennas and a single receiving antenna, or multiple receiving antennas and a single transmitting antenna, or a single or multiple transmitting and receiving antennas at the same time.

[0018] The terminal 106 in the coverage area may be fixed (ie, stationary) or mobile. As shown in Figure 1, multiple terminals 106 are scattered in the system. Each terminal 106 communicates with at least one and possibly multiple base stations 104 on the downlink and uplink at any time, depending on whether software is used, for example. Whether the handover or terminal is designed and used (simultaneously or sequentially) to receive multiple transmissions from multiple base stations. The soft handover in the CDMA communication system is well known in the field, and is described in detail in US Patent No. 5,101,501, entitled^uMETHOD AND SYSTEM FOR PROVIDING A SOFT HANDOFF IN A CDMA CELLULARTELEPHONE SYSTEM", hereby assigned to the assignee of the present invention and incorporated herein by reference.

[0019] The downlink refers to the transmission from the base station to the terminal, and the uplink refers to the transmission from the terminal to the base station. In an example embodiment, some of the terminals 106 have multiple receiving antennas and others have only one receiving antenna. Similarly, some of the terminals 106 have multiple transmitting antennas, while others have only one transmitting antenna. There is no restriction on the combination of the transmitting antenna and the receiving antenna. Therefore, the terminal 106 may have multiple transmitting antennas and one receiving antenna, or multiple receiving antennas and one transmitting antenna, or one or more transmitting or receiving antennas at the same time. In FIG. 1, base station 104A transmits data to terminals 106A and 106J on the downlink, base station 104B transmits data to terminals 106B and 106J, base station 104C transmits data to terminal 106C, and so on.

[0020] In a wireless communication system, such as the system of FIG. 1, where the system is used for packetized transmission, congestion and overload may reduce the throughput of the system. In addition, in a wireless communication system used for mixed voice and data traffic, the traffic in the cell

Loads may result in dropped calls and severe deterioration of voice capacity.

[0021] Congestion control is often used to solve autonomous traffic that is not well estimated by the system. Congestion control systems in wireless communication systems generally monitor multiple factors, such as channel or link occupancy, message delay, and the number of users. Based on these factors, the decision to control congestion is made when the system is overloaded (that is, when it is above the congestion standard threshold). In the case of overload, the system may start to reduce the load by rejecting the traffic and/or adjusting the data transmission rate. A given system may have a target congestion level, so that when the traffic overload of the system is roughly at the target congestion level, the system maintains the current traffic conditions. If the system is under load, the traffic situation is also adjusted.

[0022] Congestion is a measure of pending and active traffic relative to the rated capacity of the system. System overload occurs when the pending and active traffic exceeds the rated capacity. Overload may be due to too many active users or a large amount of pending data per transmission. One problem with overload is the delayed transmission response. The increase in response time often leads to application layer timeouts, where the waiting time of the application requesting data exceeds the allowable time when programming the application. The application will unnecessarily resend the message when it times out, causing further congestion. If this situation continues, it will cause the system to no longer serve any users. Therefore, without congestion control, the performance of the system will be much lower than its rated capacity, not to mention handling excess traffic.

[0023] Congestion control is to make the system run roughly at the target or rated capacity. One method of congestion control is to limit the number of users who can access the service. In one embodiment, congestion control provides satisfactory services to a small number of users, rather than providing highly degraded services to all users. Users who access the service leave after the service ends, thus reducing the load on the system so that another group of users can access the service. The goal of this kind of system is that all users can access at least a certain level of service from the system for at least a certain period of time.

[0024] The degree of congestion in the system can be determined by monitoring the data rate of pending and active users and the received signal strength required to obtain the desired quality of service. In CDMA wireless systems, RL capacity is limited by interference. One measure of cell/sector congestion is the total received power at the base station. The ratio of the total received power at the base station to the thermal noise gives a normalized congestion measure and is called the thermal rise ROT. ROT has limited dynamic range limitations. Another variant of ROT is the total cell load. The cell load generated by each access terminal communicating with the base station may be measured by the signal-to-interference power ratio.

[0025] In addition, the timing of congestion control actions will affect the operation of the system. If congestion control is introduced too early, traffic that can be handled will be discarded. Similarly, if the congestion control delay is too long, the system may be paralyzed due to heavy traffic.

[0026] FIG. 2 illustrates a congestion control method 150 applicable to a wireless communication system (especially a communication system for packetized transmission). The method 150 is implemented at an access network, such as a base station or a base station controller. The method starts at step 152 to determine the degree of congestion and the corresponding congestion bit CBo. The degree of congestion may be determined by a congestion metric, such as the average data rate or ROT of all users. The term congestion bit, CB, is used in this discussion to refer to the congestion indication sent from the access network to the access terminal, indicating the degree of congestion of the system. According to one embodiment, CB is a bit whose meaning is indicated by polarity. Logic 1 means that the bit is set to indicate that the system is congested and/or overloaded. Therefore, effective and accurate operation requires the reverse link RL data rate Adjust accordingly. A logic zero, that is, the bit is cleared, indicates that the system is not congested and may be underloaded, so effective operation requires adjustment of the RL data rate. Other embodiments may implement other polarity schemes.

[0027] Similarly, other embodiments may implement a codeword or multi-bit congestion indication, where additional information about the degree of congestion may be provided to the access terminal. For example, multiple bits may describe different degrees of congestion ranging from severe to mild. Each access terminal then makes a decision based on the degree of congestion. According to this multi-bit scheme, access terminals may be prioritized or classified. Access terminals with higher priority can only achieve rate adjustment for severe congestion conditions, and access terminals with lower priority may be Adjust the data rate when there is light congestion. Priority may be transmission type or access terminal

Accessed services or functions of other system-specific standards.

[0028] Another embodiment may transmit a dedicated signal to indicate the congestion situation or degree. One embodiment only transmits congestion information when the system is overloaded. Another embodiment transmits congestion information only when the system is under load, where the access terminal assumes that the system is overloaded unless other information is received. Another embodiment may set the congestion bit when the system is close to overload, where the margin is used to apply a conservative control scheme. Multiple mechanisms may be used to indicate congestion.

[0029] Continuing with FIG. 2, it is determined in step 152 that the congestion bit may be based on the current congestion situation determined by the congestion metric, or may consider historical conditions. Including past data enables smooth control decisions. In step 154, the access network transmits the CB to the access terminal.

[0030] Each access terminal communicating with the access network uses congestion bit information to control the RL transmission data rate. In step 156, each access terminal AT(i) receives and evaluates the transmitted CB. At decision diamond 158, if CB is set, ie CB=1, processing continues to step 160 in response to the overload condition. In step 162, the access terminal then determines the RL transmission rate consistent with the resolution of the overload situation. For example, according to an embodiment, when the CB is set, each access terminal will reduce the transmission data rate. Also at the decision diamond, if CB is cleared, that is, CB=0, the process proceeds to step 164 to respond to the underload condition. At step 166, the access terminal then determines a transmission rate consistent with the RL's resolution of the underload situation. For example, according to an embodiment, when the CB is cleared, each access terminal will increase the transmission data rate. Finally, at step 168, each access terminal transmits at the adjusted rate, and the process returns to step 152 to wait for the next congestion bit.

[0031] The access network periodically determines the congestion information or degree. The congestion metric is measured and compared to a congestion threshold, which may be a function of the system's rated capacity. The congestion bit then indicates whether the congestion level of the system is above or below the threshold.

[0032] FIG. 3 illustrates an outer loop method 180 for accessing a network to determine a congestion threshold, where the outer loop refers to the process of adjusting the threshold, and the inner loop refers to the use of the threshold when determining congestion. The CB is then set based on the measured congestion metric and the outer loop threshold. The outer loop threshold is called "TH_0UTERL00P" here. The process starts in step 182 by initializing the outer loop threshold to the desired threshold, which is referred to herein as "TH_DESIRED". The desired threshold is defined by the access network. At step 184, the access network measures the congestion metric of the system. According to an embodiment, the congestion metric is a measure of the thermal rise ROT function, which is defined as the ratio of the total received power to the thermal noise. Another embodiment uses a metric related to cell load. Multiple metrics may be used to determine congestion conditions.

[0033] At decision diamond 186, the access network compares the measured metric (such as ROT) to the outer loop threshold. If the measured metric is greater than the outer loop threshold, the congestion bit is set at step 190, otherwise the congestion bit is cleared at step 188. The access network compares the measured metric with the desired threshold at decision diamond 192. If the measured metric is greater than the desired threshold, the outer loop threshold is adjusted by the amount of Δ at step 194; otherwise, the access network adjusts the amount of outer loop threshold δ at step 196. The adjusted outer loop threshold value is used by the access network to compare with the congestion metric to generate congestion bits for the next congestion determination period. The access network transmits the congestion bit at step 198.

[0034] The values Δ and 6 are determined to maintain the drop probability to the desired level. The drop probability in an embodiment refers to the probability that a given congestion metric exceeds an expected threshold. In particular, the ratio of δ/Δ controls the drop probability. For a given δ/Δ ratio, smaller δ and Δ values result in less responsive congestion control, that is, slower and smoother. For a given 6/ ratio, larger values of δ and will result in a more responsive congestion control, but a larger responsive control will also have more errors. The method adapts to changes in operating conditions, where the drop probability is constant for changes in operating conditions, and these conditions include, but are not limited to, the number of users, target rate, and channel conditions. In an embodiment, when the interference from neighboring cells changes due to the dynamically changing load conditions of other cells, the outer loop threshold correction in the wireless communication system may be used to correct the cell's

Available capacity.

[0035] As illustrated in FIG. 4, one embodiment sets an outer loop threshold with room for the target threshold, so that within a predetermined probability, the transmission rate does not exceed the target threshold. In an embodiment, the outer loop threshold is calculated to maintain the measured congestion metric within the drop probability at a desired level. The dynamic adjustment of the outer loop threshold is required to adapt to changing conditions, including but not limited to channel conditions and the number of users.

[0036] Each access terminal receives the congestion bit and determines the transmission rate based on this. In one embodiment, according to the method 200 illustrated in FIG. 5A, the access terminal receives the congestion bit at step 202 and evaluates the congestion bit at the decision diamond 204. For CB=1, the processing continues to the decision diamond 206 to handle the overload situation, otherwise the processing proceeds to the decision diamond 214 to handle the underload situation. For overload conditions, the most recent rate is compared to the target rate at decision diamond 206. The target rate is determined according to the access terminal. If the most recent rate is greater than the target rate, the rate is reduced in step 208 depending on the access terminal and the probability of rate reduction. The probability is labeled Pd(i), where i is the index of the access terminal in the system, and d corresponds to the reduced probability, and each access terminal may have a unique probability. If the most recent rate is not greater than the target rate at decision diamond 206, the access terminal determines at decision diamond 210 whether there are N consecutive CBs = E. If there are N consecutive CBs = 1, then the access terminal checks in step 212 The RL transmission applies the most recent data rate; otherwise, the process continues to step 208 to reduce the rate. In this way, the access terminal adjusts the data rate to maintain the transmission data rate below the target value. If the data rate is below the target and the access terminal has received a predetermined number of N indications, indicating system congestion, then access The terminal reduces the data rate. In this case, the access terminal maintains a data rate lower than the target rate determined by the access terminal, but the system is still overloaded, that is, the congestion control of AT(i) is not sufficient to sufficiently reduce congestion. The access terminal then transmits at step 222 at the new rate.

[0037] It is worth noting that according to an embodiment, the probability of at least one previous data rate is adjusted, such as Pd(i) is a function of the data rate, where the reduced probability is Pd(i, R), and the increased probability is Pu( i, R) o R refers to the most recent rate used by the access terminal, or possibly a function of historical data rate information. The lower probability of the higher rate and the higher probability of the lower rate are used to smooth out the load changes experienced in the access network.

[0038] Returning to the decision diamond of FIG. 5A, when the congestion bit is cleared, the processing continues to the decision diamond 214 to deal with the underload situation. If the most recent rate is less than the target rate, the rate at step 218 is increased depending on the access terminal and for an increase within the rate. This probability is labeled Pu(i), where u corresponds to the increased probability, and each access terminal may have a unique probability. If the latest rate is not less than the target rate at decision diamond 214, the access terminal determines at decision diamond 216 whether there are N consecutive CBs = Ο. If there are N consecutive CBs = 0, the access terminal checks the latest data at step 220 The rate applies RL transmission; otherwise, the process proceeds to step 218 to increase the rate. In this way, the access terminal adjusts the data rate to maintain the transmission data rate as close to the target value as possible. If the data rate is above the target and the access terminal has received a predetermined number of N indications, that is, the system is not congested, the access terminal increases the data rate. In this case, the access terminal maintains a data rate above the target rate determined by the access terminal, but the system is still under load, that is, the congestion control of AT(i) does not fully utilize system resources. The access terminal then transmits at step 222 at the new rate.

[0039] FIG. 5B illustrates another embodiment of congestion control, where the congestion indication includes multiple bits. The first bit corresponds to the adjustment instruction to indicate the direction of the data rate adjustment, that is, increase or decrease. At least another bit corresponds to the target indication and is used to indicate whether the mobile station uses the data rate target process, that is, always adjust or compare according to the data rate target determined by the mobile station. In one embodiment, according to the method 300 illustrated in FIG. 5B, the access terminal receives the congestion bit at step 302 and evaluates the adjustment indicator CB at the decision diamond 304_1OFor CB]=1, the processing continues to the judgment diamond 306 to deal with the overload situation, otherwise the processing continues to the judgment diamond 314 to deal with the underload situation. In the case of overload, the treatment shall be evaluated in the judgment diamond 306.

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Estimate target indication CB2, where CB₂According to the value of CB], indicate that the system is seriously overloaded or underloaded. For the first value, the mobile station is instructed to adjust the rate at step 308 regardless of the target data rate. For CB₂For the second value of, the mobile station compares the latest rate with the target data rate at the decision diamond 310. The target data rate is determined according to the access terminal or mobile station. If the most recent rate is greater than the target rate, the rate is reduced at step 308 depending on the access terminal and the probability of the data rate reduction. The probability is labeled Pd(i), where i is the index of the access terminal in the system, and d corresponds to the reduced probability, and each access terminal may have a unique probability. If the final rate is not greater than the target rate at decision diamond 310, the access terminal uses the final rate in step 312. The access terminal then transmits at step 322 at the new rate.

[0040] Returning to the decision diamond 304 of FIG. 5B, when the congestion bit clears, processing continues to the decision diamond 314 to deal with the underload situation. In step 314, the evaluation target indicates CB?. For the first value, the mobile station is instructed to adjust the rate at step 318 regardless of the target data rate. For the second value of CB?, the mobile station compares the closest rate to the target data rate at decision diamond 316. The target data rate is specifically determined according to the access terminal or mobile station. If the most recent rate is less than the target rate, the rate is reduced at step 318 based on the probability of the access terminal and the data rate reduction. This probability is labeled Pu (i), where i is the index of the access terminal in the system, u corresponds to the increased probability, and each access terminal may have a unique probability. If the final rate is not less than the target rate at decision diamond 316, the access terminal uses the final rate at step 320. The access terminal then transmits at step 322 at the new rate.

[0041] The method 200 of FIG. 5A allows the use of a single congestion bit, where the processing implemented at the mobile station determines whether a predetermined number of congestion indicators have the same value. This process requires the mobile station and the system to wait at least a predetermined number of times to receive a predetermined number of congestion indications before the mobile station forces a data rate adjustment. In contrast, the method 300 of FIG. 5B provides fast-response congestion control because the access network uses target indications to force data rate adjustments at the mobile station. The mobile station therefore receives sufficient information in the congestion indicator to make a congestion decision when a single congestion indicator is received. The increase in the responsiveness of the method 300 comes at the cost of adding additional bits (or more bits) to the congestion indicator.

[0042] Another embodiment may implement other bit combinations or allow a congestion indication method for each mobile station, while allowing forced adjustment when the target adjustment is not sufficient to affect the performance of the entire system.

[0043] Another embodiment may implement another polarity scheme to identify overload and underload conditions. Similarly, another embodiment may consider the history of previous data rates, where the next data rate is calculated as an adjustment to at least one previous data rate, or based on statistical calculations of historical information. It is possible to add additional steps and decision criteria based on congestion control for the desired system or user.

[0044] The methods and devices disclosed herein provide enhanced congestion control in a wireless communication system, which is achieved by adding a data rate target process for a single mobile station or access terminal with a closed-loop resource allocation control method. In addition, congestion control may be further enhanced by directly controlling the probability of exceeding the desired congestion metric.

[0045] FIG. 6 illustrates an access network 400, which is a transceiver with a receiving circuit 402 and a transmitting circuit 404 coupled to a rate control unit 406. The AN400 also includes a congestion control unit 408. The congestion control unit 408 measures the degree of congestion of the transmission and compares the degree of congestion with the threshold described in FIG. 3. The AN400 also includes a communication bus 410, a processor 412, and a memory 414. The operations of the congestion control unit 408 and the rate control unit 406 may be controlled by hardware in these units, or may be controlled by software instructions stored on the memory 414 and operated by the processor 412. The calculation of the threshold may be implemented as described in FIG. 3, where the threshold is calculated and applied by the congestion control unit 408. Another embodiment may implement the various functions of the AN400 with another control unit and may combine the functions in one unit.

[0046] FIG. 7 illustrates an access network 500 for implementing congestion control similar to the method illustrated in FIG. 3. The access network 500 includes a receiving circuit 502 for radio frequency processing of received signals. The receiving circuit 502 is coupled to the congestion measurement unit

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Yuan 508. In step 184 of the method 180 in FIG. 3, the congestion metric measurement unit 508 may measure the rot of the received signal or may measure the cell load, or some other metric that indicates the congestion of the system. The congestion metric measurement unit 508 provides the measurement result to the outer loop threshold adjustment unit 504 and the comparator 510. The output of the congestion metric measurement unit 508 may provide information, the format of which is specific to the needs of each unit 504.510. The outer loop threshold adjustment unit 504 also receives the desired threshold to determine the congestion situation. It is worth noting that in one embodiment, a single target is used to indicate overload or underload, however, other systems use multiple target values to indicate the degree of congestion. The outer loop threshold adjustment unit 504 initializes the outer loop threshold at step 182 in FIG. 3. Initialization sets the outer loop threshold to be equal to the desired threshold. The outer loop threshold adjustment unit 504 then adjusts the outer loop threshold in steps 194 and 196 of FIG. 3. The outer loop threshold adjustment unit 504 also receives the comparison result of the comparator 510, where the result determines the adjustment type. In an embodiment, as in the decision diamond 192 of FIG. 3, the outer loop threshold is reduced by a different value depending on the comparison result of the congestion metric measured in the comparator 510 with the desired threshold. The outer loop threshold unit 504 is then coupled to the comparator 506, where the outer loop threshold generated by the unit 504 is compared with the single Element 508 is compared to the measured congestion metric. The result determines the value of the congestion indicator, which is the congestion bit in the current embodiment, and the polarity of the congestion bit is determined by this result. The output of the comparator 506 is provided to the congestion bit generator 512.

[0047] Continuing with FIG. 7, the desired threshold is also provided to the comparator 510, where the measured congestion metric of the unit 508 is compared with the desired threshold. The result of the comparator 510 is provided to the unit 504 and determines the adjustment amount of the outer loop threshold. In this way, a certain margin is reserved between the outer loop threshold and the desired threshold.

[0048] FIG. 8 illustrates an access terminal 600 for implementing the method of FIG. 5A. The access terminal 600 includes a receiving circuit 602 for radio frequency processing, wherein the receiving circuit 602 provides the congestion bit to the congestion bit counter 604 and the comparator 606. The counter 604 keeps track of consecutive congestion bits of the same value received at the access terminal 600. The counter 604 may be implemented in software, where the counter is cleared when a congestion bit of a different value is received.

[0049] The comparator 606 compares the latest data rate with the target data rate and provides the result to the data rate adjustment unit 610. The data rate adjustment unit applies the first control to the congestion situation and the second control to the underload situation. The congestion condition is indicated by the first polarity of the congestion bit, and the underload condition is indicated by the opposite polarity. The data rate adjustment unit 610 also receives the count value, that is, the number of consecutive congestion bits with the same polarity of the current congestion bit. According to the result of the comparator 606 and the count value from the unit 604, the data rate adjustment unit 610 adjusts the data rate. The count value is compared with the maximum number of allowable adjustments. As explained in steps 212 and 220 of FIG. 5A, if the count value is less than the maximum number, the access terminal maintains the most recent data rate. When the count value is equal to or greater than the maximum number, the access terminal adjusts the data rate according to the congestion bit information.

[0050] As described above, congestion control is enhanced by the outer loop adjustment of the congestion threshold, where the adjustment adds a certain margin to the threshold with a predetermined probability of exceeding the threshold. According to one embodiment, the external loop compares the measured congestion metric with the outer loop threshold and the expected threshold.

[0051] As described above, congestion control is enhanced by providing specific data rate targets for each access terminal. Each access terminal responds to an overload condition as indicated by the congestion indicator, which is achieved by reducing the most recent data rate to reduce the data rate to a data rate below the target rate specific to the access terminal. When the access terminal transmits at a data rate lower than the target rate, the access terminal responds to congestion by using the most recent rate. If the system congestion cannot be reduced, the access terminal will reduce the data rate in an attempt to reduce the system load. In this case, the access terminal reduces the data rate after receiving a predetermined number of system congestion indications.

[0052] One embodiment applies an outer loop threshold adjustment method that takes a single access terminal as a specific target to determine the data rate. The access terminal may provide historical information to the access network, where the information is used to determine the outer loop threshold or expected threshold

value.

[0053] Those skilled in the art can understand that information and signals may be represented by various technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols and chips that may be involved in the above description are preferably composed of voltages, circuits, electromagnetic waves, magnetic fields or their particles, light fields or their particles, or any combination thereof. To represent.

[0054] Those skilled in the art can also understand that the various illustrative logical blocks, modules, circuits, and algorithm steps disclosed herein in combination with the embodiments described herein can be electronic hardware, computer software, or a combination of both. to realise. To clearly illustrate the interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described according to their functionality. Whether these functionalities are implemented as hardware or software depends on the specific application and design constraints adopted by the entire system. Technicians can implement the described functions for each specific application in a variety of ways, but such implementation decisions should not cause any deviation from the scope of the present invention.

[0055] The implementation or execution of the logical blocks, modules, and circuits disclosed in various illustrative embodiments herein may be: general-purpose processors, digital signal processors (DSP) or other processors, application-specific integrated circuits (ASIC) , Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components or any combination of the above to achieve the functions described herein. The general-purpose processor is preferably a microprocessor, however, alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with DSP cores, or any such configuration.

[0056] The method steps or algorithms disclosed in the embodiments herein may be directly executed in hardware, a software module executed by a processor, or a combination of the two. The software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROM, or other storage media in any form known in the art . An exemplary processor is preferably coupled to the processor so that the processor can read and write information from the storage medium. Or, the storage medium may be integrated into the processor. The processor and the storage medium may reside in an application specific integrated circuit ASIC. The ASIC can reside in the user terminal. Alternatively, the processor and the storage medium may reside in discrete components of the user terminal.

[0057] The above description of the preferred embodiments enables those skilled in the art to make or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined here can be applied to other embodiments without using creative ability. Therefore, the present invention is not limited to the embodiments shown here, but should conform to the broadest scope consistent with the principles and novel features disclosed herein.

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