基于空时分组编码的水声MIMO通信系统仿真研究

为了提高水声信道的信道容量,将多输入多输出（MIMO）技术用于水声信道,提出一种基于空时分组编码（STBC）的MIMO通信系统。为了抵抗水声多径传播造成的频率选择性衰落,接收机采用MIMO判决反馈均衡器,结合二阶锁相环路补偿载波相位偏移,将水声信道转换为频率非选择性信道。通过计算机仿真证明了该方法的有效性,并与单输入单输出（SISO）系统以及采用空时网格编码（STTC）的MIMO系统进行了性能对比,结果表明STBC和STTC可以获得两倍于SISO的频带利用率和较低的误码率,STBC系统的误码率性能比STTC略差,但编译码计算量远低于STTC系统,更适于实际应用。

Space-time Block Coding MIMO System for Underwater Acoustic Communications

To improve the channel capacity, a new Alamouti space-time block coding (STBC) multiple-input multiple-output (MIMO) system was employed for underwater communications. To cope with frequency selective fading caused by intersymbol interference(ISI), a MIMO decision feedback equalizer (DFE) was used to change the channel into a freqency non-selective one, which was jointly optimized with a second order phase-locked loop(PLL) to compensate the carrier phase shift. Then maximum likelihood decoding can be implemented to decouple the signal transmitted from different antennas. Simulation results show that the proposed system is effective. Comparations with single-input single-output (SISO) system and space-time trellis codes(STTC) MIMO system show that both MIMO systems have twice fold spectral efficiency and lower bit error rate than SISO. The bit error rate performance of STBC is worse than STTC but the computational complexity of STBC is much lower than STTC.