Redundant Residue Number System Based Multicarrier DS-CDMA for Dynamic Multiple-Access in Cognitive Radios

Redundant residue number system (RRNS)-based multicarrier DS-CDMA (MC/DS-CDMA) is proposed for dynamic multiple-access (DMA) in cognitive radios (CRs). The proposed RRNS-based MC/DS-CDMA DMA has the merits of low-complexity for implementation, high-flexibility for reconfiguration and spectrum handoff, robustness to spectrum varying, and fault-tolerance to errors. Specifically, in our RRNS-based MC/DS-CDMA DMA system, RRNS-based orthogonal modulation aided by MC/DS-CDMA is employed for information transmission. At the receiver, signals are detected subcarrier-by-subcarrier independently based on suboptimum MMSE interference cancellation (SMMSE-IC). In performance study, we model the arrival process of primary users (PUs) in primary radios (PRs) as a Poisson process. Both the bit error rate (BER) performance and throughput performance are investigated. Our studies and performance results show that the RRNS-based MC/DS-CDMA constitutes one of the highly promising DMA schemes for application in CRs. It is capable of achieving a substantial throughput with required quality for the CR systems, while without degrading the quality-of-services (QoS) of the PR systems.