Sparse Codes Allocation In D2d Communications Underlaying Cellular Network

Sparse code multiple access (SCMA) is a new modulation and non-orthogonal multiple access scheme for 5G systems, in which the coded bits are mapped to multidimensional sparse codewords, and the message passing algorithm (MPA) is employed to detect multi-user signals. Device-to-Device communications underlaying cellular network is also a key technique in 5G networks; hence the sparse codes allocation between D2D users and cellular users is a new issue to be studied. Based on the short-range characteristics of D2D communications, this paper proposes a sparse codes allocation scheme between D2D users and cellular users. The proposed scheme allocates orthogonal resource blocks to the cellular users, whereas the D2D links reuse resources with cellular users in a non-orthogonal mode. By limiting the distance from the D2D transmitter to the base station, the proposed scheme enlarges the power diversity of the interfering symbols, which makes the interfering symbols at a resource block more easily separated. Simulation results show that, compared to the allocation scheme without distance limitation, the proposed scheme performs better in BER performance and the convergence behavior.