Method and apparatus for signal quality loss compensation in multiplexing transmission systems

Abstract

A wireless communication receiver receiving a multiplexed signal comprising two or more signal streams calculates a received signal quality for the multiplexed signal as a function of stream-specific received signal qualities, determines one or more loss parameters indicative of variations in the stream-specific received signal qualities, and generates quality feedback based on such information. In turn, a transmitter controls the selection of one or more transmission parameters of the multiplexed signal based on the quality feedback, such that its transmit link adaptations account for the losses in received signal quality at the receiver arising from the variations in the stream-specific received signal qualities. The quality feedback may include calculated loss values, or parameter/penalties that permit loss calculation, and the method applies to both code multiplexing and spatial multiplexing.

1 . A method of feeding back received signal quality information, the method comprising:
 receiving, at a receiver, a multiplexed signal including two or more signal streams;   calculating, at the receiver, a received signal quality for the multiplexed signal as a function of two or more different stream-specific received signal qualities determined for the multiplexed signal;   determining, at the receiver, a loss parameter that represents a loss in the received signal quality for the multiplexed signal arising from the two or more different stream-specific received signal qualities, wherein the determined loss parameter is useable to compensate the calculated received signal quality for the loss;   generating, at the receiver, received signal quality information including the calculated received signal quality, or a quantized version thereof, and the loss parameter; and   transmitting, from the receiver, the received signal quality information as feedback.   
     
     
         2 . The method of  claim 1 , wherein calculating the received signal quality comprises calculating a mode-specific received signal quality for each of one or more multiplexing modes defined for the multiplexed signal. 
     
     
         3 . The method of  claim 2 , wherein determining the loss parameter comprises, for each mode-specific received signal quality, determining one or more coding rate-dependent loss parameters. 
     
     
         4 . The method of  claim 1 , wherein calculating the received signal quality comprises calculating a Channel Quality Indicator (CQI) value for each of one or more multiplexing modes associated with the multiplexed signal, and wherein determining the loss parameter comprises determining one or more coding rate-dependent loss parameters for each CQI, such that the received signal quality information comprises mode-specific CQI values and corresponding coding rate-dependent loss parameters. 
     
     
         5 . The method of  claim 1 , wherein the multiplexed signal comprises a spatially multiplexed signal transmitted from a different number of transmit antennas in each of one or more spatial multiplexing modes, and wherein calculating the received signal quality comprises calculating a received signal quality for a best set of transmit antennas in each spatial multiplexing mode. 
     
     
         6 . The method of  claim 5 , wherein determining the loss parameter comprises, for each spatial multiplexing mode, determining one or more coding rate-dependent loss parameters. 
     
     
         7 . The method of  claim 1 , wherein calculating the received signal quality comprises calculating an average signal quality from the stream-specific received signal qualities. 
     
     
         8 . The method of  claim 7 , wherein determining the loss parameter comprises determining a maximum spread of the stream-specific signal qualities, such that the received signal quality information indicates the average received signal quality and the maximum spread. 
     
     
         9 . The method of  claim 7 , wherein determining the loss parameter comprises determining a variation statistic characterizing variations between the stream-specific signal qualities, such that the received signal quality information indicates the average received signal quality and the variation statistic. 
     
     
         10 . The method of  claim 9 , wherein the variation statistic comprises one or more of a variance of the stream-specific received signal qualities, a standard deviation of the stream-specific received signal qualities, and a maximum spread of the stream-specific received signal qualities. 
     
     
         11 . The method of  claim 1 , wherein determining the loss parameter comprises determining a loss value representing an effective reduction in the received signal quality arising from the two or more different stream-specific received signal qualities. 
     
     
         12 . The method of  claim 11 , wherein determining the loss value comprises determining the loss value from a loss equation or data table maintained at the receiver that models signal quality loss as one or more coding rate-dependent functions of the received signal quality of the multiplexed signal. 
     
     
         13 . The method of  claim 1 , wherein calculating the received signal quality comprises determining a set of best transmit antennas for each of one or more spatial multiplexing modes associated with the multiplexed signal, and calculating a channel quality indicator value for each spatial multiplexing mode based on the stream-specific received signal qualities of the multiplexed signal corresponding to the best set of transmit antennas. 
     
     
         14 . The method of  claim 13 , wherein determining the loss parameter comprises determining one or more loss parameters for each spatial multiplexing mode using the stream-specific received signal qualities corresponding to the best set of antennas for that spatial multiplexing mode, and wherein generating the received signal quality information comprises generating the received signal quality information as the channel quality indicators and corresponding loss parameters calculated for the spatial multiplexing modes. 
     
     
         15 . The method of  claim 1 , wherein the receiver comprises a Wideband Code Division Multiple Access (W-CDMA) receiver, and wherein the multiplexed signal comprises a spatially multiplexed High Speed Downlink Shared Channel (HS-DSCH) signal, and wherein the received signal quality information comprises a Channel Quality Indicator (CQI) value and one or more coding rate-dependent loss parameters, for each of one or more spatial multiplexing modes associated with the spatially multiplexed HS-DSCH signal. 
     
     
         16 . A method of compensating for losses in received signal quality experienced by a receiver, the method comprising:
 transmitting, from a transmitter, a multiplexed signal including two or more signal streams;   receiving, at the transmitter, received signal quality information as feedback from the receiver, the received signal quality information including a received signal quality for the multiplexed signal, or a quantized version thereof, and a loss parameter that represents a loss in the received signal quality for the multiplexed signal arising from two or more different stream-specific received signal qualities of the multiplexed signal, wherein the loss parameter is useable to compensate the received signal quality for the loss; and   controlling, at the transmitter, the selection of one or more transmission parameters of the multiplexed signal based on the received signal quality and the loss parameter.   
     
     
         17 . A wireless communication receiver comprising one or more processing circuits configured to:
 receive a multiplexed signal including two or more signal streams;   calculate a received signal quality for the multiplexed signal as a function of two or more stream-specific received signal qualities determined for the multiplexed signal;   determine a loss parameter that represents a loss in the received signal quality for the multiplexed signal arising from the two or more different stream-specific received signal qualities, wherein the determined loss parameter is useable to compensate the calculated received signal quality for the loss;   generate received signal quality information including the calculated received signal quality, or a quantized version thereof, and the loss parameter; and   transmit the received signal quality information as feedback.