Research On Random Non-orthogonal Multiple Access Technology And Protocol

With the commercialization and large-scale popularization of the 5th Generation Mobile Communication System(5G),the Internet of Things(Io T)has been widely used in people's lives.Due to the particularity of Io T communication,higher requirements and greater challenges will be put forward for wireless communication technology.Specifically,devices in the Io T send packets at unpredictable times,and their packets are usually short.Therefore,the allocation-based access mode will no longer be applicable.In order to solve this problem,random access(RA)technology is studied in this article,in which the device randomly occupies communication resources.Compared with other random access protocols,ALOHA and its derivatives protocol can reduce collisions while maintaining a lower complexity.Therefore,the irregular repetition slotted ALOHA(IRSA)protocol is introduced in this article.At the sending end,each user randomly selects slots to send copies of packets,each copy has the location information of the other copies.At the receiving end,packets in non-conflicted slots are decoded first,and then the interference cancellation process is carried out until it cannot be iterated.The bipartite graph is used in this article to represent the IRSA iterative decoding process.The simulation results show that compared to the slotted ALOHA system throughput is only 1/ e,the theoretical throughput of IRSA with a maximum packet repetition number of 16 can reach 0.965.In the actual simulation,its throughput also can reach more than 0.8.With the increase of slot number and iterations,the performance of IRSA is closer to the theoretical value.Multi-packet reception(MPR)is a concept that the receiver can decode multiple data packets at the same time to improve channel utilization.In order to further improve throughput performance,the concept of MPR is introduced into the IRSA protocol.An IRSA protocol with MPR capability is introduced in this article,represented as K-IRSA.The throughput and packet loss rate of the scheme are deduced by using the theoretical analysis method,and the algorithm flow of the scheme is summarized.In the performance simulation,the impact of packet error rate(PER)on the system performance is innovatively considered.Simulation results show that the normalization throughput performance of K-IRSA scheme is the best when K =2,but its performance decreases when K(29)2.Non-orthogonal Multiple Access(NOMA)technique is considered in the IRSA protocol in this article,based on the study of K-IRSA.Firstly,a power domain NOMA technology is introduced,and the access scheme combining with IRSA is given,which is represented as IRSA-NOMA.A power level is selected for each packet in turn,to ensure that the selected power level of each packet is different.Then each packet randomly selects a time slot to be sent.The expressions of the throughput and packet loss rate of the proposed scheme are obtained by using the method based on node degree variation.Finally,the performance of the proposed scheme is simulated and compared with the existing scheme.The simulation results show that the proposed IRSA-NOMA scheme can provide higher throughput and lower packet loss rate than the existing schemes.