Achievable Sum Rate Analysis for Moving Relay Assisted Cooperative NOMA System Over Rician Fading Channels

The number of mobile users on onboard vehicles is increasing continuously. Vehicular users suffer from vehicle penetration loss, fast variation of channel conditions, and signal strengths. These challenges are made even worse by a growing need for high data rates and high quality of service requirements in vehicular scenarios, which cause frequent handovers, call drops, and complete outages. The achievable rate supports adapting techniques for communication to dynamically changing conditions, ensuring reliable and efficient transmission of information despite variations. Moving relay (MR) has been proven to be one of the most promising techniques for handling such scenarios over Rayleigh fading channels. However, the performance of MR for non-vehicular users needs to be analyzed over Rician fading channel in terms of achievable rate. This paper proposes a cooperative non-orthogonal multiple access (NOMA) based system over Rician fading for non-vehicular users with half duplex decode and forward protocol-based MRs in downlink communication. We derive the achievable sum rate of the proposed system for non-vehicular users and analyze its performance in terms of power allocation coefficient, transmit signal-to-noise ratio (SNR), and Rician factor. Also, a comparison of the proposed system with a conventional orthogonal multiple access (OMA) system is provided. The simulation results show that the proposed cooperative NOMA system achieves 11.96 % higher achievable sum rate at 5 dB SNR and 14.88% higher achievable sum rate at 25 dB SNR compared to conventional OMA system. The analytical results are verified through Monte Carlo simulations. The proposed system may be useful for designing high-speed vehicular scenarios in 5G and beyond communication.