A novel multi-dimensional constellation design method based on lattices for sparse code multiple access

Abstract

Sparse Code Multiple Access (SCMA), as a new non-orthogonal multiple access scheme, achieves the good performance to access to massive information. Shaping gain of a multi-dimensional constellation is the main source of the performance improvement. However, when the number of constellation points is large, the process of the constellation design is too complex. In this paper, a novel multidimensional constellation design method based on lattices is proposed. The constellation with spherical boundary, which has the largest shaping gain, is designed and correspondingly a simplified optimization algorithm is proposed. We present the capacity of the constrained constellation on the AWGN channel. Experimental results show that the proposed constellation design method reduces the average transmit power. In addition, compared to orthogonal frequency division multiple access (OFDMA), the performance of the system is improved.