相对时延对ST-FSK系统性能的影响

空时频移键控(ST-FSK)结合了空时分组码和频移键控的优点，在瑞利衰落信道条件下无需信道信息，可采用非相干的最大似然(ML)检测器。该文推导了在接收端已知相对时延条件下的非相干ML判决度量，讨论了在接收端未知相对时延条件下信噪比与二进制、四进制ST-FSK系统误比特率性能的关系。理论和仿真结果都表明:(1)低信噪比弱化了相对时延对ST-FSK系统可靠性的影响，但在高信噪比条件下相对时延会严重制约系统性能；(2)相对时延对系统性能的影响与系统进制数的关系不大。

On the Performance of ST-FSK Systems in the Presence of Relative Delay

Combining the advantages of space-time block codes and frequency-shift keying, space-time frequency-shift keying (ST-FSK), which does not require any channel state information at the transmitter and the receiver, can adopt the noncoherent ML detector under the Rayleigh fading channels. The paper deduces the noncoherent ML decision metric at the receiver with the knowledge of relative delay, and for the different SNRs it discusses the performance of binary and quaternary ST-FSK systems in the presence of distinct relative delay. Both theoretical analysis and simulation results show that, (1) lower SNR lessens the relative delay sensitivity of ST-FSK systems, but the relative delay sensitivity limits the systems’ performance for higher SNR; (2) the sensitivity makes little difference between binary and quaternary ST-FSK systems.