Research On Energy-Efficient Transmission Of Energy Harvesting Non-Orthogonal Multiple Access Communication In Cellular Networks

Non-orthogonal multiple access(NOMA)is an essential enabling technology for the fifth generation(5G)wireless networks to meet the homogeneous cellular network's demands on massive Machine Type Connection(mMTC).The key idea behind NOMA communication technology is to serve multiple users simultaneously by power domain multiplexing or sparse coding,and exploit Successive Interference Cancellation(SIC)at the receivers to perform signal demodulation.This paper aims at the average system energy efficiency of users on the power domain NOMA for uplink transmission in the single-tier-multi-cell Homogeneous Cellular Networks(HCNs).Since users are often only powered by the battery they carry,users are usually energy limited when performing uplink NOMA transmissions.Therefore,this paper considers combining RF energy harvesting technology with NOMA communication technology to enhance the average system energy efficiency of uplink NOMA users.During to the lack of initial energy,this paper takes “harvest-then-transmit” scheme into account so as to achieve the effective transmission of uplink NOMA users.The system transmission time is divided into two phases: downlink power transmission and uplink information transmission.In the downlink(DL)power transmission,energy-constrained user harvests energy from all BSs which is randomly distributed in the surrounded,and storage the harvested energy for the uplink information transmission.Users locate in the typical cell are divided into two clusters according to their distance to their severing base station before their information transmission.Then,in the uplink(UL)information transmission,the typical users located in different group are randomly paired to perform uplink NOMA.Based on the system model mentioned above,we first derive the expression of the average interference power of typical users in different group according to the probability density function of the interference distance.Secondly,the expression of the success probability of SIC for NOMA users in the typical cluster is derived.Finally,we not only obtain the expression of the average energy efficiency of the typical users in a closed-form but make a comparison between the NOMA scenario and the Orthogonal Multiple Access(OMA)scenario.Simulation results for different parameters validate the analytical results and suggest there exists an optimal suitable time allocation factor and inner-circle radius for achieving maximal effective average UL NOMA energy efficiency in HCNs.The comparison reveals that the average effective uplink energy efficiency of NOMA information transmission outperforms OMA scheme due to the double near-far effect.