针对高空平台不稳定性以及大气湍流对平台光通信性能的影响，提出利用空间分集技术改善高空平台光通信链路性能。在系统采用开关键控(OOK)调制条件下，利用矩母函数特性分别得到采用协作分集技术和多输入多输出(MIMO)技术的高空平台光链路误码率表达式，并求解协作通信系统中继平台的最优位置。仿真结果表明：协作分集技术与光MIMO技术对高空平台光链路性能的改善效果受到跟瞄误差的限制。采用发射选择分集的光MIMO技术对光链路的误码率性能最好。与采用重复码的MIMO方法相比，协作分集技术更适用于跟瞄误差大的通信系统。中继平台的最优位置与中继策略以及跟瞄误差无关。在中继平台最优位置附近，采用协作分集的光链路性能优于采用重复码MIMO光通信链路。

Because of the position instability and atmospheric turbulence are two of the major influences on high altitude platforms (HAPs) optical links, the method to improve the performance of HAPs optical links using spatial diversity is presented. The expressions of HAPs optical links bit error rates (BER) for multiple-input multiple-output (MIMO) scheme and cooperative diversity scheme are obtained with on off keying (OOK) modulation system. And the optimum place for the relay platform is shown. The simulation results show that the improvement of cooperative diversity and optical MIMO on HAPs optical communications may be restricted by tracking error. The BER performance of MIMO optical links based on transmit laser selection is the best. Compared with MIMO optical links based on repetition coding, cooperative diversity is suited to optical communication links with bigger pointing error. The optimum place of the relay platform for HAPs optical links with cooperative diversity is independent on relay strategy and pointing error. The cooperative diversity scheme is superior to the HAPs MIMO optical links with repetition coding when the place of the relay platform is optimum.