Soft Information Combining for Turbo-MIMO Packet Retransmission

We studied three types of retransmission scheme for turbo-MIMO packet: Chase combining, incremental redundancy, and soft information combining, these three schemes are suitable for different situations. The MIMO channel in each retransmission is correlated in temporal dimension, and a standard method is utilized to simulate the retransmission channel model. Interleaving can shuffle the MIMO channel artificially, so the outage capacity of channel with interleaving is much better than the capacity without interleaving. If using different interleaver in retransmission, the receiver can only combine the retransmitted data after MIMO symbol demapping, we call it “soft information combing”. We find soft information combing is much useful in the true environment, we also find coding gain of incremental redundancy over Chase combining in most cases.