Efficient Receiver Design for Uplink NOMA-based ISaC Systems with Interference Cancellation

This paper investigates various receiver architectures for uplink non-orthogonal multiple access (NOMA)-based integrated sensing and communication (ISaC) systems. Specifi-cally, a novel signaling approach is considered whereby mutual interference between the radar and communication signals is canceled by alternately reversing the radar symbols and phase-rotating the transmitted data symbols in consecutive periods. While such a signaling approach eliminates both detection ambiguity and radar interference at the receiver, this requires the receiver to detect the targets and data over two symbol periods at a time. To this end, in this paper, we adapt various well-known receivers, such as the maximum ratio combining (MRC), zero forcing (ZF), successive interference cancellation (SIC) and max-imum likelihood (ML) receivers, and compare their performance under a variety of conditions. When evaluating the bit error rate (BER), the achievable sum rate (ASR), and the radar channel estimation (RCE) accuracy, it is found that the proposed ISaC system exhibits remarkable performance regardless of the radar signal's power compared to other ISaC signaling approaches. It is also found that the MRC receiver suffers from error floors when the system loading is relatively high, while ZF and ML provide comparable and superior performances regardless of the system load.