Block iterative FDE for MIMO underwater acoustic communications

In this paper, we propose a low complexity iterative detection scheme for the uncoded zero padding (ZP) single carrier (SC) transmission in Multiple-input Multiple-output (MIMO) underwater acoustic (UWA) channels. Due to the long multipath in UWA channels, ZP SC-FDE has to use large block size to achieve low computational complexity and high data efficiency. But, the higher bandwidth efficiency results in more sever channel estimation error and performance degradation. To enhance the performance of the ZP SC systems with high data efficiency, we design a soft-decision block iterative frequency-domain equalization (BI-FDE) combined with iterative channel estimation. With increasing reliability as the the iteration proceeds, the soft decision symbols obtained at the previous iteration are used to re-estimate the channel, thus improving the overall system performance. Since both the feedfoward and feedback filters are designed in frequency domain without the aid of channel coding, the proposed SD BI-FDE scheme is affordable for real-time implementation. The performance enhancement of the proposed iterative receiver has been verified through a pool test.