A Joint Decoding Scheme for Turbo Codes in Overloaded MIMO-OFDM Systems

摘要

In a MIMO system, significant performance degradation occurs when the number of transmit antennas is larger than that of receive antennas. In order to encounter this problem, joint decoding which conduct cooperative decoding for all of streams can be employed to minimize the performance degradation. In this report, a joint decoding scheme for turbo codes so called joint turbo decoding has been proposed. In joint turbo decoding, the calculations of soft information are conducted for each bit combinations from all of streams instead of conducted separately for each stream. In addition, to combine the trellis diagram from all of streams, a super-trellis diagram is employed. Numerical results obtained through computer simulation show that compared to the conventional scheme, the proposed scheme achieves better performance by 2.0dB in the BER of 10~(-5) for the case of 4 transmit and 2 receive antennas in the typical urban (TU) channel. Moreover, the proposed scheme also achieves throughput improvement with the throughput/(SNR/QPSK-stream) ratio close to the theoretical overloaded MIMO capacity.