Abstract: In satellite-ground communications system, the channel bit error rate directly affects the communication performance of system. According to the characteristics of satellite-ground communications, the design method of satellite-ground channel monitoring sequence length is proposed. This method considers the requirements for acquisition probability and acquisition time of monitoring sequence by the receiver, avoiding the impact of low acquisition or long time-delay on channel real-time monitoring. In communication system, different Signal Noise Ratio（SNR） will affect acquisition probability and acquisition time of monitoring sequence, therefore, according to characteristics of satellite-ground communications, design of monitoring sequence length is mainly considered in low SNR, and simulation verification?analysis is implemented. Simulation results show that, in order to ensure monitoring sequence acquisition time can compare with transmission time, the monitoring sequence length is at least 8 485 bit to guarantee the acquisition probability is 1.

Key words: satellite-ground communications, Signal Noise Ratio（SNR）, monitoring sequence, acquisition probability, acquisition time

摘要： 星地通信系统中，信道误码率直接影响系统的通信性能。针对星地通信特点，提出了星地信道监测序列长度设计方法，考虑了接收端对监测序列的捕获概率和捕获时间要求，避免了低捕获或长时延对信道实时监测的影响。通信系统中，信噪比不同将影响监测序列的捕获概率和捕获时间，因此，针对星地通信的特点，重点考虑了低信噪比下监测序列的长度设计，并进行了仿真验证分析。仿真结果表明，在保证监测序列捕获时间可以和传输时间相比拟的前提下，监测序列长度至少取8 485 bit才能保证捕获概率为1。

关键词: 星地通信, 信噪比, 监测序列, 捕获概率, 捕获时间