Optimization Design Of SCMA Transceiver Schemes

With the increasing amount of mobile terminal equipment and the rapid growth of the application of Internet of Things, the existing frequency resources become more and more insufficient, which brings a serious challenge to the traditional communication system. In recent research, non orthogonal multiple access schemes provide reliable communication services while effectively improve the communication system resource utilization, support more users at the same time. Sparse code multiple access, as the representative of the non orthogonal multiple access schemes,is expected to be a multiple access scheme for the next generation mobile communication system. In this paper, the implementation of sparse code multiple access is studied, and the reasonable optimization scheme is put forward dealing with the existing problems, and the performance comparison of the corresponding optimization schemes is given by the simulation.For SCMA transmitter, a codebood design scheme is put forward,which is the key to the sparse code multiple access system. Based on grid theory, a top level constellation with better power efficiency is constructed followed by optimization of the distance spectrum characteristics of each user. This scheme can reduce the signal peak to average power ratio significantly without the performance loss, which is more feasible.On the other hand, the performance and computational complexity of the receiver are optimized respectively. The iterative detection and decoding receiver is introduced where confidence information is exchanged iteratively between message passing receiver and decoder. This iterative receiver scheme leads to higher likelihood of bit soft information and thus effectively improves the system performance, supporting high overload rate and worse channel conditions. In addition, in order to reduce the computational complexity of the receiver, based on the traditional message receiver, this paper proposes an adaptive scheme combining interference cancellation receiver with the message passing algorithm. The receiver strategy is determined through the received signal power ratio threshold. Due to the low computational complexity of successive interference cancellation, the system can achieve a good tradeoff between performance and computation complexity.