Network-coded MIMO-NOMA systems with FEC codes in two-way relay networks

This paper assumes two users and a two-way relay network with the combination of 2×2 multi-input multi-output (MIMO) and nonorthogonal multiple access (NOMA). To achieve network reliability without sacrificing network throughput, network-coded MIMO-NOMA schemes with convolutional, Reed-Solomon (RS), and turbo codes are applied. Messages from two users at the relay node are network-coded and combined in NOMA scheme. Interleaved differential encoding with redundancy (R-RIDE) scheme is proposed together with MIMO-NOMA system. Quadrature phase-shift keying (QPSK) modulation technique is used. Bit error rate (BER) versus signal-to-noise ratio (SNR) (dB) and average mutual information (AMI) (bps/Hz) versus SNR (dB) in NOMA and MIMO-NOMA schemes are evaluated and presented. From the simulated results, the combination of MIMO-NOMA system with the proposed R-RIDE-Turbo network-coded scheme in two-way relay networks has better BER and higher AMI performance than conventional coded NOMA system. Furthermore, R-RIDE-Turbo scheme in MIMO-NOMA system outperforms the other coded schemes in both MIMO-NOMA and NOMA systems.