NOMA-Aided Aggregated Coded Caching

We propose a new class of coded caching schemes for wireless networks, which we term as non-orthogonal multiple access (NOMA) aided aggregated coded caching (NACC), which manages to alleviate both the uneven channel bottleneck as well as the shared-cache limitation. In particular, NACC uses an aggregation principle to efficiently serve users with unequal channel strengths, as well as uses for the first time the NOMA principle to simultaneously transmit to multiple users that share the same exact cache state. This transmission strategy represents an efficient utilization of NOMA within the coded caching framework. We analyze the high-SNR transmission performance of the proposed scheme and derive analytical expressions for the achievable rate and the effective gain, providing a qualitative understanding of its spectral efficiency. Our numerical results for urban Micro-cell environments abiding by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5\mathrm{G}$</tex> standards, demonstrate that NACC achieves - with a single transmit antenna - the same spectral efficiency as a multi-user (MU) multicasting system with 32 transmit antennas, while it also matches the spectral efficiency of traditional MU unicasting system with 8 transmit antennas.