MIMO系统中的低复杂度迭代树搜索算法

Low complexity iterative tree search detection for MIMO systems

提出了应用于Turbo-MIMO系统的基于比特的迭代树搜索检测算法．利用自然二进制映射和扩展信道矩阵的OR分解，使迭代树搜索算法（ITS）中的度量计算转换为逐比特进行，这样大大减小了树中每层需要进行的度量更新和排序的运算量．在此基础上，再利用先验信息进一步减小度量更新的计算量．由于扩展信道矩阵的秩等于发射天线数，该算法对信道缺秩的情况不敏感．仿真结果表明：在误码率性能上，该算法略次于使用自然二进制映射的基于符号的ITS算法，与使用格雷映射的基于符号的ITS算法只有1dB左右的差距；而该算法的计算量在高信噪比时只相当于基于符号的ITS算法的6％～40％．

This paper presents a low complexity bit-level iterative tree search （ITS） detector for Turbo- MIMO wireless communication systems. When combining natural binary bit mapping and QR decomposition on the augmented channel matrix with the symbol-level ITS, we get a bit-level ITS algorithm. In this algorithm the metric is computed in a bit-by-bit fashion, In this way the computational complexity of metric updating and sorting can be greatly reduced. Based on the bit-level ITS, the complexity can be further reduced using the a priori information from the decoder. Because the rank of the augmented channel matrix is always equal to the number of transmitting antennas, the algorithm can work well in an ill-conditioned channel. Simulation shows that the proposed algorithm can achieve similar performance to that of the ITS using natural binary bit mapping and has about 1 dB gap with the ITS using Gray bit mapping. In the high SNR region, the complexity of the proposed bit-level ITS is about 6%-10% of the symbol-level ITS.