Design of Power-Imbalanced SCMA Codebook

Abstract

Sparse code multiple access (SCMA) is a promising multiuser communication technique for the enabling of future massive machine-type networks. Unlike existing codebook design schemes assuming uniform power allocation, we present a novel class of SCMA codebooks which display power imbalance among different users for downlink transmission. Based on the Star-QAM mother constellation structure and with the aid of genetic algorithm, we optimize the minimum Euclidean distance (MED) and the minimum product distance (MPD) of the proposed codebooks. Numerical simulation results show that our proposed codebooks lead to significantly improved error rate performances over Gaussian channels and Rayleigh fading channels.

A Novel Non-Coherent SCMA With Massive MIMO

“…, s J K×J , where s j K×J = V j Λ j I K . In this paper, the following signature matrix is employed [15]:…”

A Design of Low-Projection SCMA Codebooks for Downlink Satellite Internet of Things

“…Then, based on ( 17) and ( 23), we know that the ABER is dominated by the MED between w and ŵ in Φ M J , which corresponding to the multiple error events that all the errors occurred with multiple layers. Therefore, an important codebook design criteria in this case is to maximize the MED of the superimposed codewords, which has been widely employed for SCMA systems operating in the AWGN channel [27], [29], [33]. Similarly, the MED can also obtained by letting κ → ∞ in (24).…”

“…After the design of the C M C , phase rotations are applied to generate multiple sparse codebooks. In addition, aiming at increasing the power diversity between users and improving the minimum distance properties of the superimposed codewords, we introduce energy scaling to each codebook dimension [29]. Specifically, the jth user's codebook with non-zero elements is generated by C j = E j R j C M C , where R j and E j denote the phase rotation matrix and power scaling matrix for the jth user, respectively.…”

“…Therefore, d f distinct rotation angles and scaling factors of each dimension should be optimized to distinguish the superimposed codewords. Different from the Latin rectangular construction, we consider the signature matrix Z K×J for (4 × 6) and (5 × 10) SCMA systems [29] as follows:…”

“…In addition, a uniquely decomposable constellation group based codebook design approach was proposed in [28] by maximizing the MED at each resource node. A novel class of powerimbalanced SCMA codebooks has been developed in [29] by maximizing the MED of the superimposed codewords whilst maintaining a large MPD of the MC. Downlink quaternary sparse codebooks with large MED were obtained in [33] by solving a non-convex optimization problem.…”