In time-varying frequency-selective fading channel

a time-frequency chip-level differential detection (TF-CLDD) in two-dimension spread spectrum is proposed.The bit error rate (BER) performance of TF-CLDD is analyzed

and the theoretical results are evaluated by simulation.The results of research indicate that TF-CLDD exhibits a performance to make the system resistant to both frequency-selective and time-selective fading

and it exhibits a better performance in selective fading channels than that in flat fading channels.We compare the performance of TF-CLDD with that of multicarrier spread spectrum chip-level differential detection (MC-SS-CLDD)

and the TF-CLDD effectively reduces the effect of intercarrier interference on the system.