Iterative detection and decoding for a mimo-ofdm system

Abstract

Techniques to iteratively detect and decode data transmitted in a wireless (e.g., MIMO-OFDM) communication system. The iterative detection and decoding is performed by iteratively passing soft (multi-bit) “a priori” information between a detector and a decoder. The detector receives modulation symbols, performs a detection function that is complementary to the symbol mapping performed at the transmitter, and provides soft-decision symbols for transmitted coded bits. “Extrinsic information” in the soft-decision symbols is then decoded by the decoder to provide its extrinsic information, which comprises the a priori information used by the detector in the detection process. The detection and decoding may be iterated a number of times. The soft-decision symbols and the a priori information may be represented using log-likelihood ratios (LLRs). Techniques are provided to reduce the computational complexity associated with deriving the LLRs, including interference nulling to isolate each transmitted signal and “dual-maxima” approximation.

1 . A method for transmitting data in a wireless communication system, comprising:
 receiving channel state information (CSI) indicative of one or more characteristics of a communication channel used for data transmission, wherein the CSI is derived at one or more receivers based on iterative detection and decoding of a plurality of modulated signals as received at the one or more receivers, iterative detection and decoding comprises:   deriving first a priori information for the coded data based on the received modulation signals and second a priori information for the coded data; and   decoding the first a priori information to derive the second a priori information, the second a priori information comprises decoded information for the coded data subtracted by the first a priori information.   
     
     
         2 . The method of  claim 1 , further comprising:
 interleaving the coded data based on one or more interleaving schemes, and wherein the interleaved data is modulated.   
     
     
         3 . A transmitter in a wireless communication system, comprising:
 a TX data processor that processes data based on one or more coding schemes to provide coded data, wherein the coding scheme is selected based on channel state information (CSI) derived at a receiver via iterative detection and decoding of a plurality of received modulated signals, iterative detection and decoding comprising:   deriving first a priori information for the coded data based on the received modulation signals and second a priori information for the coded data; and   decoding the first a priori information to derive the second a priori information, the second a priori information comprises decoded information for the coded data subtracted by the first a priori information.   
     
     
         4 . The transmitter of  claim 3 , wherein the TX data processor interleaves the coded data based on one or more interleaving schemes, and wherein the interleaved data is modulated by a modulator to provide a plurality of modulation symbol streams. 
     
     
         5 . The transmitter of  claim 4 , wherein one interleaving scheme is used for each modulation symbol stream. 
     
     
         6 . The transmitter of  claim 4 , wherein one interleaving scheme is used for each group of one or more modulation symbol streams. 
     
     
         7 . The transmitter of  claim 4 , wherein the coded data is interleaved over time and space. 
     
     
         8 . The transmitter of  claim 4 , wherein the coded data is interleaved over time, frequency, and space. 
     
     
         11 . The transmitter of  claim 3 , further comprising:
 a controller that receives the CSI and selects the coding and modulation schemes based on the received CSI.   
     
     
         10 . The transmitter of  claim 4 , further comprising:
 a controller receives the CSI and selects the coding, interleaving, and modulation schemes based on the received CSI.   
     
     
         11 . The transmitter of  claim 3 , wherein the one or more coding schemes comprise a parallel concatenated convolutional code. 
     
     
         12 . The transmitter of  claim 3 , wherein the one or more coding schemes comprise a serial concatenated convolutional code. 
     
     
         13 . The transmitter of  claim 3 , wherein the one or more coding schemes comprise a convolutional code. 
     
     
         14 . The transmitter of  claim 3 , wherein the one or more coding schemes comprise a block code. 
     
     
         15 . The transmitter of  claim 3 , wherein the one or more modulation schemes are non-Gray modulation schemes. 
     
     
         16 . The transmitter of  claim 3 , wherein the one or more modulation schemes are anti-Gray modulation schemes. 
     
     
         17 . The transmitter of  claim 3 , wherein a separate coding scheme and a separate modulation scheme are used for each of the plurality of modulated signals. 
     
     
         18 . The transmitter of  claim 4 , wherein a separate coding scheme, a separate interleaving scheme, and a separate modulation scheme are used for each of the plurality of modulated signals. 
     
     
         19 . The transmitter of  claim 3 , wherein a common coding scheme and a common modulation scheme are used for the plurality of modulated signals. 
     
     
         20 . The transmitter of  claim 4 , wherein a common coding scheme, a common interleaving scheme, and a common modulation scheme are used for the plurality of modulated signals. 
     
     
         21 . A transmitter apparatus in a wireless communication system, comprising:
 means for processing data based on one or more coding schemes to provide coded data;   means for selecting the coding scheme based on channel state information (CSI) derived at a receiver via iterative detection and decoding of a plurality of received modulated signals, iterative detection and decoding comprising:   means for deriving first a priori information for the coded data based on the received modulation signals and second a priori information for the coded data; and   means for decoding the first a priori information to derive the second a priori information, the second a priori information comprises decoded information for the coded data subtracted by the first a priori information.   
     
     
         22 . The transmitter apparatus of  claim 21 , further comprising:
 means for interleaving the coded data based on one or more interleaving schemes to provide a plurality of coded and interleaved data streams, and wherein the interleaved data is modulated.