Parallel Detection of Groupwise Space–Time Codes by Predictive Soft Interference Cancellation

Multiple-input multiple-output (MIMO) techniques promise huge capacity increase in fading channels. Groupwise space–time coding is a tradeoff between complexity and performance. In this letter, the structure of particular component space–time code trellises is exploited, using partial information from a Viterbi decoder of the simultaneously decoded interfering component codes. We have shown that by calculating the a posteriori probabilities of different states of the encoder at each time, and predicting the conditional mean and covariance of interference for the next time index, the system performance can be improved by soft interference cancellation. The word-error rate performance improvement for a system with four transmit and four receive antennas is 1.7 and 1.5 dB for two space–time codes with 8 and 16 states, respectively. In addition, the parallel structure does not have a decoding delay, as in successive interference cancellation, and is highly modular for very-large-scale integration implementation.