Research On Resource Optimization And Transmission Mechanism Of Non-Orthogonal Multiple Access Technique

With the requirements establishment and research advancement of the fifth generation(5G)mobile communication system,non-orthogonal multiple access(NOMA)technology has become one of the key technical directions.Multiple access technology has always been one of the most basic technology drivers in mobile communication systems.Due to the limited granularity of resource allocation,traditional orthogonal multiple access technology is difficult to support a larger number of access devices and achieve higher spectral efficiency.In addition,the signaling overhead in the scheduling-based transmission scheme is too large to apply in the low activation rate and small packet transmission scenarios such as 5G mMTC and Internet of Things.The grant-free NOMA is a promising solution.The main work of the paper is as follows:Firstly,a practical channel estimation scheme for non-orthogonal coded access(NOCA)is designed.The existing research of code domain based non-orthogonal multiple access is mostly based on the assumption of ideal channel estimation.In this paper,the Zadoff-Chu sequence is used as the uplink pilot reference signal for the NOCA system.Two different pilot patterns and corresponding receiver estimation algorithms are designed.It is compared with the ideal channel estimate in the simulation to verify the performance.In addition,a suitable spreading codebook for data is given in the case of different overload rates.Secondly,a joint coding scheme and a new power allocation algorithm for power domain based NOMA are proposed.It is difficult to achieve good decoding performance when the channel condition of near-user with lower power is not good enough in conventional NOMA.Therefore,this paper proposed a multi-slot joint coding method and designed the offset resource configuration schemes of different frame structures for the near and far users.The receiver adopts the zigzag SIC algorithm to obtain effective performance gain.In addition,a new power allocation scheme is designed based on the back propagation algorithm,which effectively improves the average user throughput compared with the fractional transmit po-wer allocation scheme.Thirdly,the small packet transmission under the grant-free NOMA is studied.From scheduling-based transmission to grant-free transmission,header overhead control,access capacity and collision rate analysis,resource configuration require precise design.In this paper,the LTE RLC UM mode is reused,and the corresponding layer 2 header structure is designed.The theoretical derivation of collision-free probability is obtained under ideal conditions for the lognormal distribution traffic model.Different impact factors for the network throughput performance are evaluated through simulation analysis,including the different traffic patterns,network load and retransmission mechanisms.The effective resource allocation can improve the throughput and provide reference for the design of the RLC layer.In addition,the statistical distribution of actual intelligent terminals multi-application traffic in recent years provided by Nokia Siemens is simulated to obtain optimal resource allocation and verify the corresponding conclusions obtained above.