基于二维格星座对SCMA码本的一种设计方法

A design method on the SCMA codebook based on two-dimensional lattice constellation

现有的SCMA(稀疏码分多址)码本采用高维复数星座和映射矩阵相结合的设计方法,存在高维复数星座设计过程复杂,且任意时频资源星座图星座点间的最小欧式距离难以控制的问题。针对上述问题提出了一种基于时频资源星座的码本设计方法。首先设计一个二维格星座,然后通过星座优化和扩频得到特定用户的码本。所提方法不仅可以获得最大成形增益和最大最小欧式距离的合成星座图,还能使SCMA系统性能随着码本维度的增加而提升。仿真结果表明:在高斯信道下,提出的码本较现有的码本有效提升了系统性能。

The existing SCMA(sparse code division multiple access)code design uses the combined design method of high-dimensional complex constellation and mapping matrix,but the design process of high-dimensional complex constellation is overly complicated,and the minimum Euclidean distance between constellation points on any time-frequency resource constellation is difficult to control.Regarding the above problems,a codebook design method based on time-frequency resource constellation is proposed.First,a two-dimensional lattice constellation is designed,and then the user-specific codebook is obtained through constellation optimization and spread spectrum.The proposed method can not only obtain the superimposed constellation of maximum shaping gain and maximum minimum Euclidean distance,but also improve the performance of SCMA system with the increase of codebook dimension.The simulation results show that the proposed codebook effectively improves the system performance compared with existing codebooks in the Gaussian channel.