An OFDM-CDMA scheme using orthogonal code multiplexing and its parallel interference cancellation receiver

We propose a novel orthogonal frequency division multiplexing - code division multiple access (OFDM-CDMA) scheme that can support effectively multiple users with variable transmission rates over frequency-selective fading channels. It uses orthogonal code multiplexing (OCM) for supporting variable rate transmission and pseudo-noise (PN) code scrambling for user separation. In this scheme, each modulation symbol is spread over the whole effective subcarriers using a distinct orthogonal multiplexing code to fully exploit frequency diversity. In multiple access environments, the use or interference suppressing techniques is strongly required to maximize the resource utilization. Hence, we use the parallel interference cancellation (PIC) receiver in terms of its complexity and performance. In addition, we set the reference value for the signal-to-interference-plus-noise (SINR), which can give the maximum channel capacity through the use or the PIC receiver. Through simulation results in both additive white Gaussian noise (AWGN) and multipath fading channels, we analyze the performance and capacity of the proposed system according to channel environments.