Research On Non-Orthogonal Multiple Access Technology Based On Two-Way Relay And Network Coding

With the in-depth development of science and technology,wireless communication networks are increasingly developing in the direction of intelligence and diversification.The fifth generation mobile communication technology 5th generation(5G)has become a global research hotspot.At present,it has entered the era of big data and artificial intelligence.With the increasing popularity of various intelligent terminals,data traffic has also increased explosively,making spectrum resources more scarce.Among many technologies to improve spectrum efficiency,non-orthogonal multiple access(NOMA)has the potential to enhance user fairness,improve spectrum efficiency,reduce access delay and promote diversified quality of service(Qo S),which has attracted great attention of many scholars and experts at home and abroad.Different from the traditional orthogonal multiple access(OMA)technology,the basic idea of NOMA is to let users share the same resources to transmit information,and then use the Successive Interference Cancellation(SIC)technology to decode the superimposed signal step by step at the receiver.Two-way relay(TWR)technology has become a hot research field because of its ability to expand the communication range of wireless network,save time slot resources and improve system throughput and reliability.At the same time,network coding(NC)extends the traditional communication node’s function of merely forwarding information to the integration of computing and forwarding,which greatly improves the network capacity.Therefore,the combination of NOMA,two-way relay technology and network coding technology can give full play to the advantages of these three technologies in communication networks,which is of great research significance.This paper mainly studies the non orthogonal multiple access communication system model based on the combination of two-way relay and network coding technology.The main work and innovation of this paper are summarized as follows:(1)Aiming at the communication system with uplink and downlink two-way transmission tasks in the actual scene,a two-way relay non-orthogonal multiple access(TWRN)access transmission scheme with two time slots is proposed.The uplink and downlink two-way NOMA transmission technology of signals is studied based on the decoding and forwarding protocol,and the two-way information exchange between base stations and users is realized in two time slots by using the principle of network coding.Further considering the imperfect channel state information condition,the transmission performance of the system is analyzed,and the expressions of system outage probability,ergodic and rate closure are derived.The correctness and effectiveness of the theoretical results are verified by simulation experiments.The simulation results show that under the conditions of perfect channel state information(CSI)and imperfect CSI,compared with the schemes proposed in the existing literature,unidirectional relay NOMA and OMA networks,the scheme proposed in this paper effectively reduces the transmission outage probability of the system.It improves the traversal speed and throughput of the system.In addition,the influence of the power allocation factor of the transmitter on the system is analyzed.Finally,the influence of the setting of different target rates on the interrupt performance of the system is analyzed.(2)For the amplification and forwarding two-way relay NOMA communication system,the existing scheme has the problem of poor transmission performance of uplink signals under imperfect CSI conditions.This paper improves the system model and signal transmission mode,uses three time slots to complete the mutual exchange of signals between base stations and users,and studies the uplink and downlink NOMA two-way transmission technology of signals based on amplification and forwarding protocol.Based on the different transmission tasks of the second and third time slots,the improved scheme in this paper has two working modes.This paper studies the interrupt performance of uplink and downlink signals under imperfect channel state information.Simulation results show that the traditional scheme has the limitations of uplink signal interruption performance in the case of imperfect CSI.The scheme proposed in this paper not only ensures the transmission quality of downlink signal,but also effectively reduces the interruption probability of uplink signal and improves the robustness of the system.Finally,the influence of the power allocation factor of the transmitter on the interrupt performance of the system is analyzed.