Performance Analysis Of SWIPT Assisted NOMA In Coordinated Direct And Relay Transmission

With the advantages of low latency and wide connectivity,non-orthogonal multiple access(NOMA)has become one of the most promising radio access in 5G.In cooperative NOMA which is an important research branch of NOMA,relay is usually powered by battery with limited capacity.In some energy-constrained scenarios,the difficulty replacement of battery often results in severe constraints on communication and equipment life.Based on the energy-constrained cooperative NOMA transmission,this paper carries out the cooperative transmission research with simultaneous wireless information and power transfer(SWIPT).Considering the different locations of relay will lead to change of energy and information process,we focus on the performance analysis of the SWIPT-based cooperative NOMA transmission under two typical relay locations.The major contributions of this work are summarized as follows:In a remote relay transmission(the relay is farther away from the base station than the near user),this paper derives the outage probability and ergodic capacity for each user under perfect successive interference cancellation with the help of the mathematical tools,such as Puxi function and Lech function.The upper limit of the reachable rate with a certain outage probability is given.The numerical results verify the correctness of the derivations.The Monte Carlo simulation results show that compared with the SWIPT-based cooperative orthogonal multiple access transmission,the remote relay transmission can effectively improve the performance.In order to verify the diversity gain of each user,the approximate expressions of outage probability in high signal-to-noise ratio(SNR)regime are given and the achievable diversity orders for each user are same.In addition,considering the imperfect successive interference cancellation of NOMA,theoretical analysis with influence factor is given and the lower limit of outage probability and upper limit of ergodic capacity are obtained.In a near relay transmission(the relay is closer to the base station than the near user),under perfect and imperfect successive interference cancellation,the outage probability and ergodic capacity for each user are derived with Gauss-Chebyshev quadrature formula and exponential integral function.The approximate expressions of outage probability in high SNR regime examine the diversity orders of each user.The numerical results verify the correctness of the derivations.The simulation results show that the performance of the near relay transmission is better than SWIPT-based cooperative orthogonal multiple access.It also points out that the performance of imperfect and perfect successive interference cancellation is close at low SNR.In addition,the performance comparison between remote relay and near relay transmission shows that the near relay transmission has better performance of the outage probability,and the remote relay transmission has better performance of ergodic capacity.Simulation results show that SWIPT-based cooperative NOMA can obtain great performance and is suitable for 5G scenarios with low power,massive connection and wide coverage.