Abstract: A new concatenated code structure is proposed which concatenates a space-time block codes with non binary low density parity check (LDPC) codes, which is high-level modulated without any parallel-to-serial conversion to lower the error and simplify the system structure. The performance of the new system in Bit error rate (BER) and complexity is evaluated, its comparisons are made with the binary LDPC concatenated codes OFDM system by simulation in AWGN channels and multiple Raleigh fading channels. Results show that the new system is superior to the old one. Compared with GF(2), a0.2dB and0.3dB increments are obtained by GF(4) and GF(16) respectively atBER=10^-6 in AWGN channels, an 1dB and 2dB increments are obtained by GF(4) and GF(16) respectively in multi-path Rayleigh fading channels. The performance improves as the field order is increased, but the computational complexity is increased also. The number of additions is increased 2 times and 10times by GF(4) and GF(16) respectively.

Key words: LDPC codes based on binary extension fields, space-time codes, multiple Rayleigh fading, OFDM