SCMA Codebook Design Based on Decomposition of the Superposed Constellation for AWGN Channel

Abstract

In this study, we propose a method named decomposition of the superposed constellation (DCSC) to design sparse code multiple access (SCMA) codebooks for the additive white Gaussian noise (AWGN) channel. We prove that the power of the user symbols (USs) is accurately determined by the power of the superposed constellation (SC). Thus, we select quadrature amplitude modulation (QAM) constellations as the SC and decompose the SC into several groups of USs with power diversity. The minimum Euclidean distance (MED) between superposed symbols (SS-MED) in the receiver is determined by the selected QAM and MED between the multi-dimensional codewords (CW-MED) is optimized by matching the symbols on different dimensions. We propose a simplified DCSC (S-DCSC) by modifying the factor graph and avoiding the transmission of USs with low power, which greatly reduces the complexity of the message passing algorithm (MPA). The simulations show that the SS-MEDs of DCSC and S-DCSC are larger than those in previous papers and the BER performance of the proposed codebooks is better than others.

A Novel Image-Classification-Based Decoding Strategy for Downlink Sparse Code Multiple Access Systems

“…Ref. [6] proposed a method named simplified decomposition of the superposed constellation (S-DCSC), which gained lager superposed symbols in the receiver than other codebook design schemes. The codebook design techniques are continually evolving to facilitate a more effective SCMA system.…”

SCMA Codebook Design Based on a 16 Star-QAM with MED Maximization

“…The best sets achieving the largest MED are to be taking in consideration to form our desired codebook. The codebook of the six users is represented in Table . 1. with DCSC-SCMA [8], authors took the codebook design under power constraints, such as balancing the MC power, in addition to the maximization of both MEDs. Also, with SVD-SCMA [7] authors first construct the MC based on singular value decomposition (SVD) to guarantee a higher MED, then applying a rotatiRQ RSHUDWRU WR JHQHUDWH GLIIHUHQW XVHU ¶V FRGHERRNV in which MED of the different users are equal.…”

“…Instead of optimizing the Euclidean Distance between the point-to-point within the same dimension of each codebook, the studies are FRQGXFWHG RQ WKH XVHU ¶V FRGHZRUGV RYHUODSSLQJ RQ WKH same subcarrier to establish a larger MED. While most recent studies as [7], [8], investigated maximization of the two different MEDs, simultaneously. As well as, in this paper we optimize the codebook design using the MED maximization criterion under the point-to-point of same codebook along with superimposed codewords.…”

Equivalent MIMO Channel Matrix Sparsification for Enhancement of Sensor Capabilities

“…One of the effective approaches of signal detection is based on iterative methods, such as low-density signature (LDS) [20] or sparse code multiple access (SCMA) [3,[20][21][22][23][24][25][26][27]. A necessary condition for their use is the ability to represent the channel model in the form of a sparse matrix, as a result of which an individual observation is not a superposition of all symbols at once but only a subset of the symbols.…”