A comparative study on MIMO MLSE turbo equalizer on frequency selective channels

In this paper, we propose an LDPC (Low Density Parity Check) coded MLSE turbo equalizer for the spatially multiplexed transmission on MIMO (Multiple Input Multiple Output) frequency selective channels. When the Channel State Information (CSI) is available at the receiver, Maximum Likelihood Sequence Estimation (MLSE) using Viterbi algorithm is effective to compensate the Inter Symbol Interference (ISI) and Inter Antenna Interference (IAI) on MIMO frequency selective channels [1]. We consider here the LDPC coded case where the reliable decoder output from LDPC decoder is fed back to the MLSE equalizer to enhance the ability of MLSE for compensating the ISI and IAI. The output from the MLSE equalizer is then LDPC decoded and its output is again fed back to the MLSE decoder. This feedback is repeated several times. We compared the proposing LDPC coded MIMO MLSE turbo equalizer with the conventional LDPC coded MIMO SC/MMSE (Soft Canceller with MMSE filter) turbo equalizer [2], [3] and compared their BER characteristics.