A pilot symbol assisted interference cancellation scheme for an asynchronous DS/CDMA system
Oliver Nesper, Paul K. M. Ho · 2002
We consider a single cell asynchronous BPSK DS/CDMA system with successive interference cancellation. The system operates in a Rayleigh flat fading channel and pilot symbols are inserted periodically to the transmitted data for the purpose of channel estimation. We introduced previously a pilot symbol assisted interference canceller that was made up of two parts-a decorrelating receiver for the faded pilot symbols, followed by a successive interference canceller (SIC) for the data symbols. The receiver could operate in small cells with a maximum round trip delay of a quarter of a symbol time and was able to provide a performance improvement over a pure SIC receiver for both the pilot and the data symbols. We introduce two fragile structures that allow the usage of the hybrid receiver in larger cells with a round trip delay of one symbol time. Furthermore, the complexity of the decorrelator is kept at a moderate level. The performance of the hybrid receiver operating on both frame structures is compared and a comparison is made with a pure SIC cancelling receiver. It was found that one of the investigated frame structures in conjunction with the hybrid receiver increased the system capacity as compared to a pure SIC receiver and offers moreover a comparable system complexity.