Ergodic capacity performance analysis of NOMA combined with AF relay downlink transmission

In this paper, we consider a typical downlink two-user transmission mode, in which the base station cannot transmit information directly to two users, mainly due to obstacles or shadow effects between links. Therefore, it is necessary to use relay node. In order to improve spectral efficiency by reducing transmission time slots, we use non-orthogonal superposition coding technology to construct superimposed signal at the base station. The base station sends superimposed information to the relay node, and in the next time slot, the relay node transmits the superimposed signal to the downlink two users through the amplify-and-forward protocol (AF) in a broadcast manner. In order to verify the advantages of the proposed transmission mode in ergodic capacity performance, we compare with the traditional orthogonal relay transmission modes, such as time division multiple access (TDMA) combined with AF transmission mode and TDMA combined with decode-and-forward (DF) transmission mode. Monte Carlo simulation confirm the advantages of the proposed transmission mode.