Research On Radio Resource Allocation Scheme For SCMA Uplink Based On Massive Capacity

In order to meet the demand of next-generation wireless communication network,such as ultra-large capacity,massive connectivity and ultra-low latency access,multiple access technology as the key technology of wireless communication network air interface technology is facing enormous challenges.Compared with the traditional OMA technology,the NOMA technology can support more users to achieve effective access on the same time-frequency resources and further effectively solve the large-scale access of users.Therefore,the NOMA has received wide attention from researchers.The Sparse Code Multiple Access technology is a powerful candidate in NOMA.Firstly,in this thesis,the relevant principles of SCMA is introduced;including SCMA modulation spread spectrum principle,SCMA encoder principle,SCMA codebook design principle,Multi-user detection principle based on MPA.In addition,the SCMA system model is analyzed and the transmitter and receiver models are given.The SCMA uplink model is further given and the overload characteristics of SCMA are analyzed.The simulation results show that the overload factor has a great impact on the system BER performance.Secondly,the radio resource allocation scheme of single cell SCMA system uplink in mMTC scenario is studied.The mMTC application scenario can solve the problem of a large number of user accesses by using SCMA technology.Due to the massive connection characteristics of the mMTC system,multiuser clustering technique can be used to construct a hierarchical network in a single cell in a future 5G network.Combined with the characteristics of the hierarchical network,a multi-level resource allocation framework is further proposed.When the number of active users in the MTC user cluster is much larger than the number of basic transmission unit in the SCMA system,user group matching of the SCMA uplink system becomes extremely important.Corresponding to the multi-level resource allocation framework,for the SCMA system user group matching in a single MTC user cluster,the optimization problem based on the maximum system sum rate is constructed.User group matching scheme based on channel information and sub-carrier granularity is proposed to optimize the system capacity.As the overload factor increases and the subcarrier granularity decreases,the number of users that the mMTC system can access is greatly improved.Finally,for the SCMA system in a single user group,combined with the relationship between the SCMA codebook and the time-frequency resource,the wireless resource allocation optimization problem based on system sum rate maximization is constructed according to the SCMA uplink characteristics.Firstly,the codebook allocation is optimized based on the power sharing scheme by constructing the system user interference model.Secondly,based on the codebook allocation scheme,the sum rate optimization problem is simplified to the convex optimization problem,and the power allocation scheme is solved.The resource allocation joint iterative optimization algorithm is proposed to perform joint iterative optimization to further improve the system capacity.