HK1067250A - Method and apparatus for controlling gain level of a communication channel in a cdma communication system - Google Patents

Description

Method and apparatus for controlling gain level of communication channel in CDMA communication system

FIELD

The present invention relates generally to the field of communications, and more particularly to communications in a cellular communication system.

Background

In a Code Division Multiple Access (CDMA) communication system, excessive transmission by a user can cause interference to other users in addition to reducing system capacity. Thus, the power levels and/or data rates of the communication channels transmitted by the different users of the system are controlled for controlling the interference level and for maintaining sufficient system capacity, while at the same time allowing sufficient reception quality at the receiving end. The power level and/or data rate of the communication channel may establish a gain level of the communication channel. Communication services may include radio transmission of digitized voice, still or moving images, text messages, and other data types. Such communication services may be required at different quality levels and at different mobility levels.

To this end, and for other purposes, there is a need for efficiently controlling the power level and/or data rate of a communication channel at various levels of mobility in a communication system.

SUMMARY

In a code division multiple access communication system, a method and accompanying apparatus provide for efficient control of gain levels of a communication channel at various levels of mobility. In accordance with various aspects of the invention, a rate of change of a carrier-to-interference ratio (C/I) of a communication channel received at a receiver is determined. The rate of change of C/I may be directly related to the level of mobility experienced by the communication channel. Thus, according to one embodiment, the gain level of a communication channel may be based on the rate of change of the C/I of the communication channel. Thus, communication services are provided at effective channel data rates and/or power levels at various levels of mobility.

Brief Description of Drawings

The features, nature, 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 elements have like numerals wherein:

FIG. 1 illustrates a communication system capable of operating in accordance with various embodiments of the invention;

FIG. 2 illustrates an exemplary forward link channel structure;

FIG. 3 illustrates an exemplary reverse link channel structure;

fig. 4 illustrates a communication system receiver operable in accordance with various embodiments of the present invention for operation within a mobile station and a base station;

FIG. 5 illustrates exemplary channel C/I conditions and associated channel gain levels;

FIG. 6 illustrates exemplary channel average C/I conditions and instantaneous channel C/I levels over a period of time at different levels of mobility; and

fig. 7 illustrates a flow diagram for controlling gain levels of a communication channel in accordance with various embodiments.

Description of The Preferred Embodiment

Various embodiments of the invention may be incorporated in a system for wireless communication in accordance with the Code Division Multiple Access (CDMA) technique, which has been disclosed and described in various standards published by the Telecommunications Industry Association (TIA). These criteria include: the TIA/EIA-95 standard, the TIA/EIA-IS-2000 standard, the IMT-2000 standard, and the WCDMA standard, all of which are incorporated herein by reference. A system for data communication is described in the following titled documents: "TIA/EIA/IS-856 cdma2000 High Rate Packet Data air interface Specification," which IS incorporated herein by reference, IS particularly capable of incorporating various embodiments of the present invention. Copies of these criteria may be obtained by accessing the following web addresses:http：//www.3gpp2.orgor by writing to TIA, standards and technology department, 2500 wilson boulevard, Arlington, VA 22201, usa. The standard identified as the WCDMA standard, which is incorporated herein by reference, is available by contacting the 3GPP support office (SupportOffice), 650 Route des Lucioles-Sophia Antipolis, Valbonne-France.

Generally, a novel and improved method and accompanying apparatus provide for efficient control of power levels and/or data rates of communication channels at various levels of mobility in a CDMA communication system. One or more embodiments described herein are set forth in the context of a digital wireless data communication system. Although advantageous for use in this environment, various embodiments of the invention may be incorporated in different environments or configurations. In general, the various systems described herein may be formed using software-controlled processors, integrated circuits, or discrete logic. Data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Further, the modules illustrated within each block diagram may represent hardware or method steps.

Fig. 1 illustrates a general block diagram of a communication system 100 capable of operating in accordance with a Code Division Multiple Access (CDMA) communication system standard, while incorporating various embodiments of the present invention. The communication system 100 may be for communication of voice, data, or both. In general, the communication system 100 includes a base station 101 that provides communication links between a plurality of mobile stations, such as mobile station 102 and 104, and between the mobile station 102 and 104 and a public switched telephone network and a data network 105. Base station 101 may include a number of components such as a mobile station controller, a base station controller, and a radio frequency transceiver. These components are not shown for simplicity. Base station 101 may also communicate with other base stations (not shown). Base station 101 communicates with each mobile station 102 and 104 over a forward link. The forward link may be maintained by forward link signals transmitted from base station 101. The forward link signals directed to mobile stations 102 and 104 may be summed to form forward link signal 106. Each mobile station 102-104 that is receiving forward link signal 106 decodes the forward link signal 106 to extract the information that is directed to its user.

Mobile stations 102 and 104 communicate with base station 101 via corresponding reverse links. Each reverse link is maintained by a reverse link signal, such as reverse link signals 107 and 109 for respective mobile stations 102 and 104. Each mobile station 102-104 may transmit a pilot channel to base station 101. The pilot channel transmitted from a mobile station may be used to demodulate information conveyed by a reverse link signal transmitted from the same mobile station. The use and operation of pilot channels is well known. Each of mobile station 102 and base station 101 includes a transmitter and a receiver for communicating over the forward and reverse links. Various block diagrams of transmitters are shown and described in the IS-95, IS-2000, IMT-2000, WCDMA and IS-856 standards.

Fig. 2 illustrates a forward channel structure 200 that may be used for communication on the forward link, in accordance with one embodiment. Forward channel structure 200 may include a pilot channel 201, a Medium Access Control (MAC) channel 202, a traffic channel 203, and a control channel 204. The MAC channels 202 may include a reverse activity channel 206 and a reverse power control channel 207. The reverse activity channel 206 is used to indicate the level of activity on the reverse link. Reverse power control channel 207 is used to control the power level at which a mobile station may transmit on the reverse link.

Fig. 3 illustrates a reverse channel structure 300 that may be used for communication on the reverse link, in accordance with one embodiment. Reverse channel structure 300 includes an access channel 350 and a traffic channel 301. Access channel 350 includes a pilot channel 351 and a data channel 353. Traffic channel 301 includes pilot channel 304, MAC channel 303, Acknowledgement (ACK) channel 340, and data channel 302. The MAC channel 303 includes a reverse link data rate indicator channel 306 and a data rate control channel 305. The ACK channel 340 is used to communicate whether the data packet was successfully decoded at the mobile station. The reverse link indicator channel 306 is used to indicate the rate at which the mobile station is currently transmitting. The data rate control channel 305 indicates the data rate that the mobile station desires and/or receives on the reverse link.

Fig. 4 illustrates a block diagram of a receiver 400 for processing CDMA signals. Receiver 400 demodulates the received signal to extract the information conveyed by the received signal. Receive (Rx) samples may be stored in RAM 404. The receive samples are generated by a radio frequency/intermediate frequency (RF/IF) system 490 and an antenna system 492. Antenna system 492 receives an RF signal and passes the RF signal to RF/IF system 490. The RF/IF system 490 may be any conventional RF/IF receiver. The received RF signal is filtered, down-converted and digitized to form RX samples at baseband frequencies. The samples are provided to a demultiplexer (demux) 402. The output of demultiplexer 402 is provided to a searcher unit 406 and finger elements 408. To which the control unit 410 is also coupled. Combiner 412 couples decoder 414 to finger elements 408. The control unit 410 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 414 may be in accordance with a concatenated soft output viterbi algorithm with or without feedback.

During operation, received samples are provided to the demultiplexer 402. Demultiplexer 402 provides these samples to searcher unit 406 and finger elements 408. The control unit 410 configures the finger elements 408 to perform demodulation of the received signal at different time offsets based on the search results from the searcher unit 406. The demodulation results are combined and passed to decoder 414. The decoder 414 decodes the data and outputs the decoded data. Despreading of the channels is performed by: the received samples are multiplied by the complex conjugate of the PN sequence and assigned Walsh function for a single timing hypothesis, and the resulting samples are digitally filtered, typically by an integrate and dump accumulator circuit (not shown). Such techniques are generally known in the art. Receiver 400 may be used to decode information on the reverse and forward links signals.

Each time the correlation process is started, the searcher 406 and finger elements 408 may be restarted for determining demodulation of the pilot channel to test the timing hypothesis and phase offset. Searcher 406, or finger elements 408, or a combination of searcher 406 and finger elements 408, may determine the carrier-to-interference ratio (C/I) of each received signal. The ratio Eb/I is synonymous with the ratio C/I. The ratio Eb/I is a measure of the carrier energy per data symbol or data bit unit to interference. Thus, C/I and Eb/I may be exchanged in some respects. Interference is generally defined as the power spectral density of interference and thermal noise.

To control interference and maintain sufficient system capacity while allowing sufficient reception at the receiving end, the system controls the gain level of each transmitted channel from each transmitting source. The gain level of each channel may be adjusted by adjusting the channel data rate or the power level or both. The gain level of a channel is based on the data rate of the information being encoded at the transmitter, and the power level at which the channel is signaled. Generally, channels at high data rates require higher power levels to overcome interference. Channels at low data rates require lower power to overcome the same interference level. Thus, the gain of the channel may be adjusted by adjusting the power level, the data rate, or both.

Various power control schemes for controlling the power level of a signal and various schemes for controlling the data rate of a channel are known. Various standards incorporated herein by reference provide one or more schemes for controlling signal power levels and channel data rates. The power level of a channel can be controlled with two independent power control loops, an open loop and a closed loop. Open loop power control is based on the need for the receiver to maintain an adequate communication link with the transmitter. Data rate adjustment is generally used to guarantee reception quality at the receiving end and to control interference within the coverage area. When the feedback quality measurement indicates poor reception, the data rate may be reduced while keeping the power level constant to improve the reception quality and overcome interference effects. The data rate may also be reduced to allow other users to receive communications at a higher data rate.

In accordance with at least one of the CDMA spread spectrum system standards incorporated herein by reference, the mobile station may adjust the output power level based on the properties of the code channel. The mobile station may maintain a power level ratio between the code channel power level and the reverse pilot channel power level. The ratio may be set in accordance with the data rate used within the code channel. Generally, a table provides ratio values at different data rates. This ratio generally increases for higher data rates. Ratios equal to 1 or less than 1 are also possible. At a ratio equal to 1, the power control loop sets the power level of the pilot channel equal to the power level of the code channel. During data transmission on the traffic channel, the data rate and traffic channel power level may be adjusted. Once the allowable data rate is selected, the traffic channel power level is set using the corresponding channel power with respect to the reverse link pilot power level.

In the data mode, the base station may provide communication links to a large number of mobile stations at different data rates. For example, one mobile station in a forward link connected state may receive data at a low data rate while another mobile station receives data at a high data rate. On the reverse link, the base station may receive multiple reverse link signals from different mobile stations. A mobile station based on independent forward link measurements may request a desired data rate from a base station. The desired forward link data rate may be communicated to the base station via a Data Rate Control (DRC) channel 305. The data rate may also be selected by the base station based on certain metrics. These metrics may include the transmit power level of the power control subchannel and/or the power level of one or more forward traffic channels. The base station attempts to provide forward link data transmission at the requested data rate.

The gain level set by the transmitter by adjusting the channel power level and data rate may be based on the C/I level of the received signal at the receiving end. As described above, the receiver 400 may measure the C/I level of each received signal. The receiver reports the C/I measurement to the transmitter. The transmitter adjusts the channel gain level of the channel to maintain the target C/I at the receiver after comparing the reported C/I to the target C/I threshold. Signals between a transmitter and a receiver may propagate through a channel having various fading conditions before being received by the receiver. The C/I level may be continuously changed from one level to another. The control loop for controlling the channel gain level may use the C/I target threshold level in order to maintain the frame error rate at a sufficient level. The C/I target threshold may be selected and maintained such that the adjusted channel gain is at a level above the minimum required level for maintaining a sufficient frame error rate for at least a period of time after reporting the channel C/I condition to compensate for variations in the channel between the reporting time and the actual signal transmission time. In this way, the channel gain is maintained at a minimum level plus a margin.

There may be a delay between the time the C/I level is measured and reported and the subsequent time the channel gain level is selected and sent out from the transmitter. Thus, under fading channel conditions, the frame error rate is predictively maintained at a sufficient level for most of the time by ensuring that the channel gain is above the minimum level. The excessive gain margin allows communication at lower data rates, higher power levels, or both with respect to the minimum gain level. Communication at low data rates requires less power than communication at high data rates. Thus, to add a gain margin by changing the data rate, the data rate can be reduced while keeping the power level unchanged. If the data rate is maintained at the same level, the channel gain can be increased by increasing the power level. The power level and data rate may be varied to achieve a higher channel gain corresponding to the gain margin.

Referring to fig. 5, a graph 500 depicts an example of channel C/I conditions 502 and minimum required channel gain 501 versus time. For example, for channel C/I conditions 502 at the receiver, the minimum required channel gain 501 is sufficient to maintain an adequate communication link between the transmitter and the receiver. The channel gain is at a peak level when the channel C/I condition is at a minimum. At time 591, the channel gain for transmission to the receiver may be set to gain stage 504. The excess margin 590 between the minimum gain stage 501 and the selected gain stage 504 at time 591 ensures that communication over the channel is at a reasonable frame error rate below most fading conditions at least at some times. For example, by allowing an excessive gain margin, the selected gain level 504 is sufficient to maintain adequate communication between the transmitter and receiver for at least a period of time 550. The excess margin provides protection if channel C/I conditions degrade during time period 550. If the channel C/I conditions improve during time period 550, requiring a lower gain level, the effective excess margin is actually higher than the selected excess gain margin 504. In this way, the receiver can receive at a reasonable frame error rate under most channel conditions.

At time 592, over a period of time 551, the excess margin 590 can protect against changing channel conditions. Time period 551 is less than time period 550 due to the rate of change of the channel condition. The channel condition changes more slowly during time period 550 than during time period 551. At time 593, excess margin 590 provides protection against any change in channel conditions for a longer period of time. The corresponding C/I channel condition at time 593 is improving and therefore requires lower channel gain at actual transmission time. The rate of change of the channel C/I condition is directly related to the speed at which the transmitter and receiver are separated from each other and/or the rate of change of the propagation channel.

In general, aspects of the present invention provide for efficient gain control for communications under various conditions. In a code division multiple access communication system 100, a rate of change of a carrier-to-interference ratio (C/I) of a communication channel received at a receiver 400 is determined. According to an embodiment, the gain level of the communication channel at the transmitter may be based on the rate of change of the C/I of the communication channel. Referring to fig. 5, for example, the rate of change at time 591 is different from the rates of change at times 592 and 593. If the rate of change of C/I is positive, a gain margin is subtracted from the gain level of the communication channel to produce a final gain level for transmission of the communication channel according to an embodiment. When the rate of change of C/I is positive, the channel condition is improving. For example, the rate of change of C/I is positive at time 593. C/I increases at time 593. Thus, at time 593, a gain margin is subtracted from the gain level of the communication channel to produce a final gain level for transmission of the communication channel, in accordance with one embodiment.

According to one embodiment, the magnitude of the gain margin may be proportional to the magnitude of the rate of change of C/I. If the positive rate of change of C/I is large, the channel condition improves at a faster rate than if the positive rate of change of C/I is small. Thus, in the predictive approach, the channel conditions require a final gain level that is much lower than the gain level estimated in a channel with a large positive rate of change of C/I. Thus, the magnitude of the gain margin is larger in a channel condition having a large positive rate of change of C/I than in a channel condition having a small positive rate of change of C/I. In order for the subtraction gain margin to work, the data rate of the communication channel may be increased according to an embodiment. When the rate of change of C/I is positive, the data rate may be increased since the channel conditions are improving. Thus, in a predictive manner, the channel is able to support the communication link at a higher data rate. The power level of the communication channel may be reduced to account for the subtraction of the gain margin according to one embodiment. When the rate of change of C/I is positive, the power level may be reduced since the channel conditions are improving. In order for the subtraction gain margin to work, the data rate may be increased while the power level is decreased according to an embodiment. Thus, in a predictive manner, the channel is able to support the communication link at the same data rate and at a lower power level.

If the rate of change of the C/I is negative, a gain margin is added to the gain level of the communication channel to produce a final gain level for transmission of the communication channel according to an embodiment. When the rate of change of C/I is negative, the channel condition is degrading. For example, the rate of change of C/I is negative at times 591 and 592. C/I decreases at times 591 and 592. Thus, according to an embodiment, at times 591 and 592, a gain margin is added to the gain level of the communication channel to produce a final gain level for transmission of the communication channel.

According to one embodiment, the magnitude of the gain margin may be proportional to the magnitude of the rate of change of C/I. If the negative rate of change of C/I is large, the channel condition degrades at a faster rate than if the negative rate of change of C/I is small. Thus, in the predictive mode, the channel conditions require a final gain level that is much lower than the gain level estimated in a channel with a large negative rate of change of C/I. Thus, the magnitude of the gain margin is greater in channel conditions having a large negative rate of change of C/I than in channel conditions having a small negative rate of change of C/I. The negative rate of change at time 591 is less than the negative rate of change at time 592. Thus, according to one embodiment, the magnitude of the gain margin at time 591 is less than the magnitude of the gain margin at time 592.

In order for the added gain margin to work, the data rate of the communication channel may be reduced according to an embodiment. When the rate of change of C/I is negative, the data rate may be reduced because the channel conditions are degrading. Thus, in the predictive mode, the channel is able to support the communication link at a lower data rate, while avoiding frame erasure. Further, in order for the added gain margin to work, the power level of the communication channel may be increased according to an embodiment. When the rate of change of C/I is negative, the power level may be increased since the channel conditions are degrading. In order for the added gain margin to work, the power data rate may be reduced and the power level increased simultaneously. Thus, in a predictive manner, the channel is able to support the communication link at the same data rate and at a higher power level.

The channel conditions between the transmitter and the receiver may be dynamic. Fast fading conditions may be referred to as high mobility conditions, while slow fading conditions may be referred to as low mobility conditions. Referring to fig. 6, an example of the C/I condition of the channel is shown. For example, at time 610, the channel may be in a fast fading condition, and at time 620, may be in a slow fading condition. The mean C/I601 is the average C/I of the channel over a period of time. The instantaneous C/I602 of the channel goes through the mean C/I601 at different times. In a fast fading condition corresponding to time 610, the number of times the instantaneous C/I602 passes through the mean C/I601 is higher compared to the slow fading condition corresponding to time 620. The number of times the instantaneous C/I602 passes the mean C/I601 may be proportional to the mobility level of the communication channel in the communication system 100. Thus, the mobility level of the receiver 400 may be determined by determining the number of times the instantaneous C/I602 passes the mean C/I601.

According to one embodiment, the mobility level of a communication channel in the communication system 100 may be determined by determining the number of times the instantaneous C/I of the channel passes through the average C/I of the channel. The mobility level may be compared to a mobility threshold. The mobility threshold may correspond to a low mobility level. According to an embodiment, the gain level of the communication channel between the transmitter and the receiver 400 in the communication system 100 may be based on the rate of change of the C/I if the mobility level meets the low mobility threshold. If the mobility level is below the low mobility threshold, the channel condition corresponds to a low mobility condition. In low mobility conditions, the channel conditions change slowly, thus allowing the gain level of the channel to be based on the rate of change of C/I in a predictive manner according to an embodiment.

Referring to FIG. 7, a flow diagram 700 for implementing aspects of the present invention is shown. In step 701, a mobility level of a receiver may be determined. In step 702, the mobility level is compared to a low mobility threshold. The low mobility threshold may correspond to a low mobility level condition. If the mobility level is below the low mobility threshold, then the rate at which the channel C/I changes is determined in step 703. In step 704, a controller, such as control system 410 in receiver 400, may determine whether the rate of change of C/I is positive or negative. In step 705, if the rate of change is positive, a gain margin is subtracted from the minimum gain of the channel, according to one embodiment. In step 706, if the rate of change is negative, then a gain margin is added to the minimum gain of the channel, according to one embodiment. The channel may be transmitted with the adjusted gain level.

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 described 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 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 subscriber unit. 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 (39)

1. In a code division multiple access communication system, a method comprising:

determining a rate of change of a carrier-to-interference ratio (C/I) of a communication channel received at a receiver; and

determining a gain level of the communication channel for transmission of the communication channel to the receiver based on the rate of change of the C/I.

2. The method of claim 1, further comprising:

determining whether the rate of change of the C/I is positive; and

subtracting a gain margin from the gain level of the communication channel to generate a final gain level for transmission of the communication channel to the receiver.

3. The method of claim 2, wherein a magnitude of the gain margin is proportional to the magnitude of the rate of change of the C/I.

4. The method of claim 2, wherein the subtracting comprises increasing a data rate of the communication channel.

5. The method of claim 2, wherein said subtracting comprises reducing a power level of said communication channel.

6. The method of claim 2, further comprising transmitting the communication channel to the receiver at the final gain level.

7. The method of claim 1, further comprising:

determining whether the rate of change of the C/I is negative; and

adding a gain margin to the gain stage of the communication channel to generate a final gain stage for transmission of the communication channel to the receiver.

8. The method of claim 7, wherein a magnitude of the gain margin is proportional to the magnitude of the rate of change of the C/I.

9. The method of claim 7, wherein the adding comprises reducing a data rate of the communication channel.

10. The method of claim 7, wherein the adding comprises increasing a power level of the communication channel.

11. The method of claim 7, further comprising transmitting the communication channel to the receiver at the final gain level.

12. The method of claim 1, further comprising:

determining a mobility level of the communication channel; and

determining whether the determined mobility level satisfies a low mobility threshold, wherein the gain level of the communication channel determined from the rate of change of the C/I depends on whether the determined mobility level satisfies the low mobility threshold.

13. In a communication system, an apparatus comprising:

a receiver for receiving a communication channel; and

a controller for determining a rate of change of a carrier-to-interference ratio (C/I) of the communication channel and for determining a gain level of the communication channel for transmission of the communication channel to the receiver based on the rate of change of the C/I.

14. The apparatus of claim 13, wherein the communication system is a code division multiple access communication system.

15. The apparatus as recited in claim 13 wherein said controller is configured to determine whether said rate of change of said C/I is positive and subtract a gain margin from said gain level of said communication channel to produce a final gain level for transmission of said communication channel to said receiver.

16. The apparatus of claim 13, wherein a magnitude of the gain margin is proportional to the magnitude of the rate of change of the C/I.

17. The apparatus of claim 15, wherein the subtracting comprises increasing a data rate of the communication channel.

18. The apparatus of claim 15, wherein the subtracting comprises reducing a power level of the communication channel.

19. The apparatus of claim 15 further comprising a transmitter for transmitting said communication channel to said receiver at said final gain level.

20. The apparatus as recited in claim 13 wherein said controller is configured to determine whether said rate of change of said C/I is negative and to add a gain margin to said gain level of said communication channel to produce a final gain level for transmission of said communication channel to said receiver.

21. The apparatus of claim 20, wherein a magnitude of the gain margin is proportional to the magnitude of the rate of change of the C/I.

22. The apparatus of claim 20, wherein the adding comprises reducing a data rate of the communication channel.

23. The apparatus of claim 20, wherein the adding comprises increasing a power level of the communication channel.

24. The apparatus of claim 20 further comprising a transmitter for transmitting said communication channel to said receiver at said final gain level.

25. The apparatus of claim 13, wherein the controller is to determine a mobility level of the communication channel, and to determine whether the determined mobility level satisfies a low mobility threshold, wherein determining the gain level of the communication channel from the rate of change of the C/I is dependent on whether the determined mobility level satisfies the low mobility threshold.

26. In a code division multiple access communication system, an apparatus comprising:

means for determining a rate of change of a carrier-to-interference ratio (C/I) of a communication channel received at a receiver; and

means for determining a gain level of said communication channel for transmission of said communication channel to said receiver based on said rate of change of said C/I.

27. The apparatus of claim 26, further comprising:

means for determining whether the rate of change of the C/I is positive; and

means for subtracting a gain margin from the gain level of the communication channel to produce a final gain level, the final gain level being used for transmission of the communication channel to the receiver.

28. The apparatus of claim 27, further comprising means for transmitting the communication channel to the receiver at the final gain level.

29. The apparatus of claim 26, further comprising:

means for determining whether the rate of change of the C/I is negative; and

means for adding a gain margin to the gain stage of the communication channel to produce a final gain stage for transmission of the communication channel to the receiver.

30. The apparatus of claim 29, further comprising means for transmitting the communication channel to the receiver at the final gain level.

31. The apparatus of claim 26, further comprising:

means for determining a mobility level of the communication channel; and

means for determining whether the determined mobility level satisfies a low mobility threshold, wherein the means for determining the gain level of the communication channel as a function of a rate of change of the C/I depends on whether the determined mobility level satisfies the low mobility threshold.

32. In a communication system, an apparatus comprising:

means for receiving a communication channel; and

means for a controller to determine a rate of change of a carrier-to-interference ratio (C/I) of the communication channel, and to determine the rate of change of the C/I to determine a gain level of the communication channel for transmission of the communication channel to the receiver.

33. The apparatus as recited in claim 32 wherein said means for said controller is configured for determining whether said rate of change of said C/I is positive and subtracting a gain margin from said gain level of said communication channel to produce a final gain level for transmission of said communication channel to said receiver.

34. The apparatus of claim 33 further comprising a transmitter for transmitting said communication channel to said receiver at said final gain level.

35. The apparatus as recited in claim 32 wherein said means for said controller is configured for determining whether said rate of change of said C/I is negative and adding a gain margin to said gain level of said communication channel to produce a final gain level for transmission of said communication channel to said receiver.

36. The apparatus of claim 35 further comprising means for a transmitter for transmitting said communication channel to said receiver at said final gain level.

37. The apparatus of claim 33, wherein the means for the controller is to determine a mobility level of the receiver, and to determine whether the determined mobility level satisfies a low mobility threshold, wherein determining the gain level of the communication channel from the rate of change of the C/I is dependent on whether the determined mobility level satisfies the low mobility threshold.

38. In a code division multiple access communication system, a method comprising:

determining a rate of change of a carrier-to-interference ratio (C/I) of a communication channel received at a receiver;

adjusting a gain level of the communication channel for transmission of the communication channel to the receiver according to the rate of change of the C/I; and

determining whether the rate of change of the C/I is positive or negative;

wherein the adjusting comprises: subtracting a gain margin from the gain level of the communication channel to produce a final gain level for transmission of the communication channel to the receiver if the rate of change of C/I is positive;

wherein the adjusting comprises: adding a gain margin to the gain stage of the communication channel to produce a final gain stage for transmission of the communication channel to the receiver if the rate of change of C/I is negative, wherein the magnitude of the gain margin is proportional to the magnitude of the rate of change of C/I.

39. The method of claim 38, further comprising transmitting the communication channel to the receiver at the final gain level.