基于水声信道传播时延排序的分层空时信号检测

基于分层空时编码的多输入多输出技术是一种极具潜力的高速水声通信技术, 但要实现这种潜力需要复杂的空时信号处理方法, 以抵消来自水声信道的多径干扰和异步到达干扰, 以及叠加在接收端的各层信号之间的干扰. 对低复杂度的空时信号处理方案进行了研究, 提出了一种基于子信道传播时延排序的有序连续干扰抵消信号检测算法, 利用子信道间的传播时延差, 实现可使差错概率最小的最佳检测排序; 给出了利用信道估计, 以极低的计算量确定排序的方法, 从而可以大幅降低信号检测的计算复杂度. 采用低复杂度的单载波频域均衡来抵消水声信道中的码间干扰和异步到达干扰. 仿真结果表明, 基于时延排序的信号处理算法可以获得检测性能的改善, 而且性能增益在高数据率时更加显著. 研究结果表明, 采用有效的信号处理方法可使水声信道中造成信号检测干扰的传播时延成为改善系统性能的有利因素.

Ordered detection of layered space-time signals based on the propagation delays of underwater acoustic channels

The multiple-input multiple-output (MIMO) architecture with the layered space-time codes is a very promising solution for the high data rate underwater acoustic communications. The realization of this potential advantage, however, needs the essential layered space-time signal processing methods for canceling the interference resulting from the multipath propagation and the asynchronous arrivals of the sub-streams due to the different propagation delays, and the interference between the transmitted streams superposed in each receiving hydrophone. In this paper, the low-complex layered space-time signal detection scheme for the underwater acoustic communications is investigated. A propagation delay-based ordered successive interference cancellation (OSIC) algorithm is proposed at first. Sub-streams are sorted at the receiver according to the arrival orders resulting from the relative propagation delays inherent in the underwater acoustic channels from the transmitting transducers to the receiving hydrophones. The sub-stream with the first arrival is detected first. The proposed OSIC algorithm based on the "first-come first-go" principle has an advantage in the reduction of the interference from yet-to-be-detected sub-streams, therefore improving the detection performance at each step. The analysis manifests that the delay-based ordering is an optimal detection ordering to minimize the probability of overall block error for the asynchronous space multiplexing architectures. Then the ordering procedure is given which is performed by estimating the relative delays between the MIMO channels and requires only one ordering before the signal detection. This channel estimation-based method simplifies dramatically the ordering procedure and the calculations, therefore reducing substantially the calculation complexity of the layered signal detection. Finally, the single-carrier frequency domain equalization is employed to compensate for the multipath interference and the asynchronous arrival interference from the underwater acoustic propagation. Numerical results show that the performance gain can be obtained with the delay-based OSIC detection algorithm relative to the detection without ordering; moreover the gain increases substantially with the data rate. The investigation results demonstrates, on the other hand, that the inherent relative propagation delay in the underwater acoustic channels leading to asynchronous interference to the signal detection can be turned into an advantage to improve the performance with the efficient space-time signal processing algorithms.