A Joint Mechanism for Fog-Relay Networks Based on NOMA and Network Coding

Mobile edge computing (MEC) and fog computing are considered to be a promising technique for the fifth generation (5G) networks. The main features of them are to push computing tasks to network edges. Meanwhile, to achieve low latency and high access speed, it is necessary to adopt an advanced transmission mechanism at network edges. Considering the advantages of large rate and high reliability provided by non-orthogonal multiple access (NOMA) and network coding, in this paper we propose a hybrid round-trip transmission mechanism at network edges. Specifically, we consider a fog node as a relay; and utilize a hybrid concept to design a NOMA-NC method which combines uplink NOMA and downlink network coding. Theoretical derivation and numerical results demonstrate that the proposed method distinctly outperforms both (i) traditional orthogonal multiple access (OMA) method combining OMA and network coding (namely OMA-NC); and (ii) NOMA-based round-trip transmission method (namely NOMA-NOMA).