Optimizing Cooperative Non-Orthogonal Multiple Access Schemes for Future Wireless Networks

The early generations of wireless networks were optimized for voice communications in 2G networks or voice plus some data applications in 3G and 4G networks for human-human communications. However, the emerging 5G networks and future beyond 5G (B5G) or 6G networks have new applications in wireless networks such as massive heterogeneous machine-to-machine (M2M)/internet of things (IoT) communications, industrial and tactile internet, and vehicle-to-everything (V2X), that subsumes vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) communications, applications. These new applications pose some stringent requirements on the achievable rate, spectral efficiency, user fairness, reliability, and latency. This has spurred the adoption of new and/or combinations of communications schemes that would meet these requirements. As an example, the orthogonal multiple access schemes (OMA), are not expected to meet the massive connectivity and fairness requirements in dense future networks. One of such candidate schemes are non-orthogonal multiple access (NOMA) schemes, where multiple users are allowed to simultaneously share the same time-frequency resource, which have attracted a large amount of research where they have the merits of higher spectral efficiency, guaranteed user fairness, lower latency, and improved cell-edge users rates as compared to the conventional OMA schemes. On the other hand, cooperative communications schemes, at the user-level or at the base station (BS)/access-point (AP) level (i.e., coordinated multipoint (CoMP) schemes), are envisioned to be one of the enablers of the different high-data-rate future wireless networks including radio frequency (RF), visible light communication (VLC) and RF/VLC physical layer (PHY) networks especially for the cell-edge users. The proposed project aims at the investigation of the optimal combinations of NOMA schemes and cooperative/collaborative communications schemes for future networks using spectral efficiency and achievable rates metrics. The results obtained from this project will shed new light on the design and the performance gains and trade-offs of these NOMA-based cooperative communication schemes in both RF and VLC networks for the single-cell and/or multi-cell scenarios. The tasks of this project will proceed in the following succession. Related literature reviews have already been conducted; however, they have to be updated to include the up-to-date work and to further focus on the optimal NOMA-based cooperative/collaborative schemes. This will enable the development of novel contexts for such schemes in future RF networks and then the analytical and/or numerical solutions of the resulting typically non-convex optimization using the candidate methods for such optimization problems. In the second phase, the optimal NOMA-based cooperative/collaborative schemes for VLC systems/networks, along with the additional signal design and illumination constraints in these networks, will be investigated and finally, the main conclusions for both RF and VLC networks will be stated.