Optimal Power Allocation in Uplink NOMA with Simultaneous Cache-Enabled D2D Communications
Aditya Powari, Daniel K. C. So
TL;DR
The paper addresses boosting uplink NOMA performance by integrating cache-enabled D2D communications within an underlay FD-D2D framework. It proposes a two-user uplink NOMA system where each UE transmits both its uplink file and a cache file, with CIC at the BS to mitigate cache interference and SIC to preserve decoding order, and derives closed-form power-allocation expressions. The authors prove concavity of the sum-rate with respect to the power-split variables, obtaining a closed-form optimal $\\alpha_1^*$ and, via a stationary point $\\hat{\\alpha_2}$, an optimal $\\alpha_2^*$ under QoS constraints $R_{min-j}$. Numerical results show the proposed scheme significantly outperforms phased and slotted baselines in total throughput and D2D/uplink rates, demonstrating the practical benefits of integrating cache-enabled D2D with uplink NOMA for future wireless networks.
Abstract
Non-orthogonal multiple access (NOMA) is widely viewed as a potential candidate for providing enhanced multiple access in future mobile networks by eliminating the orthogonal distribution of radio resources amongst the users. Nevertheless, the performance of NOMA can be significantly improved by combining it with other sophisticated technologies such as wireless data caching and device-to-device (D2D) communications. In this letter, we propose a novel cellular system model which integrates uplink NOMA with cache based device-to-device (D2D) communications. The proposed system would enable a cellular user to upload data file to base station while simultaneously exchanging useful cache content with another nearby user. We maximize the system sum rate by deriving closed form solutions for optimal power allocation. Simulation results demonstrate the superior performance of our proposed model over other potential combinations of uplink NOMA and D2D communications.