NOMURA: A Spectrally Efficient Non-orthogonal 5G Multiple Access Downlink Scheme for Cognitive Radio

Orthogonal Frequency Division Multiple Access (OFDMA) is now becoming an impeding rather than a sustainable technology for realizing the vision of 5G due to its tight synchronization, orthogonality constraints, and significant bandwidth wastage due to Cyclic Prefix. To overcome this limitation, several non-orthogonal schemes have been introduced as candidates for upcoming 5G technology for providing flexible, reliable, fair and high-speed multiple access to users and/or devices. A combination of Non-Orthogonal Multiple Access (NOMA) and Universal Filtered Multi-Carrier (UFMC) is found suitable for downlink scenario. We propose NOMA-UFMC-based Radio Access (NOMURA) scheme, which is asynchronous, bandwidth efficient and provides higher throughput. The proposed scheme is non-orthogonal in two aspects: (1) NOMA provides resources to different users via power scaling while utilizing same frequency resources, and (2) UFMC allows for a slight delay in synchronization, hence not strictly compliant with orthogonality requirements. The components of the proposed scheme, namely NOMA and UFMC, are backward compatible with OFDMA ensuring trivial application of Multiple Input Multiple Output and other performance enhancement measures already developed for OFDMA. We provide simulation results benchmarked against OFDMA and Filter Bank Multi-Carrier-Filtered Multi-Tone and show that NOMURA is more apt for flexible bandwidth allocations, active cancellation, higher throughput and provides equivalent Bit Error Rate performance under AWGN and Rayleigh fading conditions.