Time- and frequency-domain hybrid detection scheme for OFDM-CDMA systems

An efficient receiver structure for OFDM-CDMA, or MC-CDMA, systems is developed by combining the frequency- and the time-domain detection methods. The frequency-domain detection method uses the transformed signal, thus is efficient for large parallel data transmission, such as in typical OFDM systems, while the time-domain detection method does not transform the signal and uses a correlator receiver, which is efficient for single data transmission with a large processing gain. The developed method generates the decimated-in-frequency (DIF) signal using the small size of the DFT or FFT operations, so that each DIF time-domain signal contains only one data symbol, and uses a correlator receiver for detecting each data symbol. This scheme requires less or an equal number of computations than both methods in any variations of the system parameters, such as the processing gain, the number of parallel data, and the OFDM block size.