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准正交空时分组编码(QOSTBC)是一种正交空时编码的变换编码结构,将时间分集和空间分集相结合,具有高效的分集利用率和编码效率。QOSTBC是解决大气湍流对光通信影响的有效手段之一。在研究了大气信道特性的基础上,提出一种基于QOSTBC结构和空间分集光通信系统的信道模型;介绍了QOSTBC原理,分析了系统的信道容量和误码率(BER);利用蒙特卡罗仿真比较了采用空时分集编码与未使用分集编码系统的容量及BER的情况。结果表明,使用QOSTBC系统的信道容量随发射天线数增加而递增,误码性能得到有效改善。QOSTBC与Alamouti编码系统相比系统信噪比节省约9dB,说明该系统具有编码所提供的良好信道容量和误码性能,能够有效地抑制大气湍流对光通信所产生的光强起伏影响。
Quasi-orthogonal space-time block coding (QOSTBC) is a transform coding structure of orthogonal space-time coding, combining time diversity and space diversity, with efficient diversity utilization and coding efficiency. QOSTBC is one of the effective methods to solve the influence of atmospheric turbulence on optical communication. Based on the study of atmospheric channel characteristics, a channel model based on QOSTBC structure and space diversity optical communication system is proposed. The principle of QOSTBC is introduced, and the channel capacity and bit error rate (BER) of the system are analyzed. By using Monte Carlo simulation The capacity and BER of space-time coded and unused diversity coded systems are compared. The results show that the channel capacity of QOSTBC system increases with the number of transmitting antennas, and the error performance is effectively improved. Compared with the Alamouti coding system, QOSTBC can save about 9dB signal-to-noise ratio, which shows that the system has the good channel capacity and error performance provided by coding and can effectively suppress the fluctuation of atmospheric light caused by atmospheric turbulence.