Multi-channels turbo equalization for M-ary orthogonal modulation signal

M-ary orthogonal modulation is widely used in wireless communication systems as a frequency spread method. To improve the demodulation performance of this signal with low signal to noise ratio (SNR) in severe intersymbol interference (ISI) channel, a multi-channels turbo equalization algorithm is proposed. In this algorithm, a new soft demapping and mapping method is presented and the extrinsic information is exchanged between the multi-channels equalizer and the decoder. Simulation indicates gains of up to 4.5 dB relative to the hard symbol decision algorithm and 3.5dB relative to the single-channel turbo equalization algorithm can be achieved after two iterations.