Log-domain iterative decoding combined USTM with codes over GF(2m) on flat Rayleigh fading channel

In this paper, a serial concatenated scheme combining USTM with LDPC codes over GF(2^m) is presented. A modulation technique of USTM, Unitary space-time modulation, can efficiently work on decoding when the channel state information is unknown at the receiver in multi-input multi output system over flat raleigh fading channel. The BER performance of USTM system in MIMO channel will largely be improved by serially concatenating a good achieving the shannon limit LDPC(low-density parity-check) codes as outer codes, which have attracted much more attention recently, defined by a sparse parity check matrix over GF(2^m) in our scheme. The well-known Sum-Product algorithm is also used as the iterative decoding of LDPC codes over GF(2^m) , but here the algorithm works in the log-domain other than probability-domain for some advantages, such as implementation, computational complexity and etc. Simulating results show that our scheme works very well and about 20dB coding gain is provided by LDPC codes as an outer codes at a BER of 10^-5 than USTM without channel coding. And further simulations assure that USTM concatenating with LDPC codes over GF(2^m) outperforms more 5-6dB coding gain that LDPC codes over GF(2).