Method and apparatus for adjusting power control setpoint in a wireless communication system

Abstract

Techniques to adjust the setpoint of a power control loop in a wireless communication system. The setpoint may be adjusted based on frame status indicative of erased/good decoded frames, one or more (typically soft) metrics indicative of the confidence in the decoded results, power surplus/deficit indicative of the difference between the received signal quality and the setpoint, setpoint surplus/deficit indicative of the difference between the setpoint and a threshold E b /N t needed for the desired level of performance, or a combination thereof. The metrics may include re-encoded symbol error rate, re-encoded power metric, modified Yamamoto metric, minimum or average LLR among decoded bits, number of decoding iterations, and possibly others. The setpoint may be adjusted in different manners and/or by different amounts depending on the above-noted factors. The techniques may be employed for forward and/or reverse links in CDMA systems.

1 . A method of adjusting power control setpoint, the method comprising:
 decoding one or more received frames of a signal to provide one or more decoded frames;   obtaining one or more soft metrics based on the one or more decoded frames;   determining a setpoint step size based on the one or more soft metrics; and   adjusting a power control setpoint based on the setpoint step size.   
   
   
       2 . The method of  claim 1 , wherein decoding the one or more received frames comprises decoding one or more received forward link frames in a wireless communication system. 
   
   
       3 . The method of  claim 1 , wherein decoding the one or more received frames comprises decoding one or more received convolutional encoded frames. 
   
   
       4 . The method of  claim 1 , wherein decoding the one or more received frames comprises decoding one or more received turbo encoded frames. 
   
   
       5 . The method of  claim 1 , wherein decoding the one or more received frames comprises decoding one or more received block code encoded frames. 
   
   
       6 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a frame error rate based on the one or more decoded frames. 
   
   
       7 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a re-encoded symbol error rate based on the one or more decoded frames. 
   
   
       8 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a re-encoded symbol error rate based on the one or more decoded frames. 
   
   
       9 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a modified Yamamoto metric based on the one or more decoded frames. 
   
   
       10 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a re-encoded power metric based on the one or more decoded frames. 
   
   
       11 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a log likelihood ratio based on bits in the one or more decoded frames. 
   
   
       12 . The method of  claim 11 , wherein the log likelihood ratio comprises a minimum log likelihood ratio. 
   
   
       13 . The method of  claim 11 , wherein the log likelihood ratio comprises an average log likelihood ratio. 
   
   
       14 . The method of  claim 1 , wherein obtaining one or more soft metrics comprises obtaining a number of iterations before declaring a decoded frame for the one or more decoded frames. 
   
   
       15 . The method of  claim 1 , further comprising:
 determining a signal quality based on the one or more received frames of the signal; and   comparing the signal quality to a target signal quality to obtain a power surplus value, and   wherein determining the setpoint step size is based in part on the power surplus value.   
   
   
       16 . The method of  claim 1 , further comprising:
 determining a setpoint surplus value, and   wherein determining the setpoint step size is based in part on the setpoint surplus value.   
   
   
       17 . The method of  claim 1 , wherein determining the setpoint step size comprises scaling a setpoint step size based on the one or more soft metrics. 
   
   
       18 . The method of  claim 1 , wherein adjusting the power control setpoint comprises adjusting the power control setpoint of a first traffic channel of the signal. 
   
   
       19 . The method of  claim 18 , further comprising adjusting a power control setpoint of a second traffic channel of the signal based on the power control setpoint of the first traffic channel. 
   
   
       20 . The method of  claim 1 , wherein decoding one or more received frames of the signal comprises decoding at least one virtual frame received over a time interval that is equal to a time interval for a traffic channel frame. 
   
   
       21 . A power control apparatus, the apparatus comprising:
 a demodulator configured to demodulate received signal and recover symbols;   a decoder coupled to the demodulator and configured to decode at least one frame of symbols from the received signal;   a receive data processor coupled to the decoder and configured to determine a soft metric from the at least one frame of symbols; and   a power control processor coupled to the receive data processor and configured to determine a setpoint step size based at least in part on the soft metric, and adjust a power control setpoint based on the setpoint step size.   
   
   
       22 . The apparatus of  claim 21 , wherein the demodulator is configured to demodulate a received Code Division Multiple Access (CDMA) signal. 
   
   
       23 . The apparatus of  claim 21 , wherein the demodulator is configured to demodulate a received Wideband Code Division Multiple Access (W-CDMA) signal. 
   
   
       24 . The apparatus of  claim 21 , wherein the decoder is configured to decode a convolutionally encoded signal. 
   
   
       25 . The apparatus of  claim 21 , wherein the decoder is configured to decode a turbo encoded signal. 
   
   
       26 . The apparatus of  claim 21 , wherein the decoder is configured to decode a block encoded signal. 
   
   
       27 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a frame error rate. 
   
   
       28 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a re-encoded symbol error rate. 
   
   
       29 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a modified Yamamoto metric. 
   
   
       30 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a re-encoded power metric. 
   
   
       31 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a log likelihood ratio among bits in a decoded frame. 
   
   
       32 . The apparatus of  claim 21 , wherein the receive data processor is configured to determine the soft metric based on a number of iterations before declaring a decoded frame. 
   
   
       33 . The apparatus of  claim 21 , further comprising a receive signal quality measurement module coupled to the demodulator and configured to determine a performance of a inner power control loop, and
 wherein the power control processor is coupled to the receive signal quality measurement module and is configured to determine the setpoint step size based at least in part on the performance of the inner power control loop.   
   
   
       34 . The apparatus of  claim 33 , wherein the receive signal quality measurement module is configured to determine one of a power surplus or a power deficit relative to a target signal quality level. 
   
   
       35 . The apparatus of  claim 33 , wherein the receive signal quality measurement module is configured to determine one of a setpoint surplus or a setpoint deficit relative to a target signal quality level. 
   
   
       36 . A power control apparatus, the apparatus comprising:
 means for decoding one or more received frames of a signal to provide one or more decoded frames;   means for obtaining one or more soft metrics based on the one or more decoded frames;   means for determining a setpoint step size based on the one or more soft metrics; and   means for adjusting a power control setpoint based on the setpoint step size.   
   
   
       37 . A memory unit having stored thereon software code, when executed by a processor, performing the functions:
 decoding one or more received frames of a signal to provide one or more decoded frames;   obtaining one or more soft metrics based on the one or more decoded frames;   determining a setpoint step size based on the one or more soft metrics; and   adjusting a power control setpoint based on the setpoint step size.