Application of the short time DFT correlator to the RAKE receiver for DS/SS communication system and its BER improvement effect

In a spread spectrum communication system, the process gain increases the robustness during multipath fading propagation by spreading the power spectrum to remove interference from the degraded signals. By means of diminishing the undesired signal in the received signal through detecting the delay difference of each propagated signal at the prepositioned correlator, and by identifying the propagation profile to compensate for the distortions on the transmission channels, the RAKE receiver achieves time diversity reception to improve the robustness. This means that the correlator is significant in the RAKE receiver function. However, unfortunately the sounder is intermittently interposed in the conventional system used to measure the channel profile and loses such high compliancy as tracing the rapid fading process. It is proposed that the instantaneous cross correlation function, which is derived from the short time DFT (ST DFT), is effective in describing such rapid fading process and that the instantaneous correlator based on the instantaneous cross correlation function provides a satisfactory solution for avoiding such redundancy as interposing sounder signals.