Design of Power-Imbalanced SCMA Codebook

The synergistic amalgamation of sparse code multiple access (SCMA) and multiple-input multiple-output (MIMO) technologies can be exploited for improving spectral efficiency and providing enhanced wireless services to massive users. In this case, however, channel estimation is a burning issue with the increasing number of users and/or antennas. To tackle this problem, we propose a novel non-coherent transmission scheme for SCMA, referred to as NC-SCMA. In the proposed NC-SCMA, each user first maps its binary data to sparse codewords, and then perform differential modulation on the nonzero dimensions. Upon receiving all users' signals, we leverage the channel hardening effect to carry out differential demodulation and multi-user detection without any instantaneous channel state information. In addition, the design of the sparse codebooks in the NC-SCMA system is investigated with the aid of the pair-wise probability. Numerical results demonstrate the superiority of the proposed technique over the benchmark scheme in terms of bit error rate performance.

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“…, 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]:…”

Section: B Proposed Codebook Design For Nc-scmamentioning

confidence: 99%

A Novel Non-Coherent SCMA With Massive MIMO

Luo

Wen

Chen

et al. 2022

IEEE Wireless Commun. Lett.

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“…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).…”

Section: B Design Criteria Of Multi-dimensional Codebookmentioning

confidence: 99%

“…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.…”

Section: Sparse Codebook Constructionmentioning

confidence: 99%

“…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:…”

Section: Sparse Codebook Constructionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Luo¹,

Liu²,

Chen³

et al. 2022

Preprint

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This paper presents a systematic investigation on codebook design of sparse code multiple access (SCMA) communication in downlink satellite Internet-of-Things (S-IoT) systems that are generally characterized by Rician fading channels. To serve a huge number of low-end IoT sensors, we aim to develop enhanced SCMA codebooks which enable ultra-low decoding complexity, while achieving good error performance. By analysing the pair-wise probability in Rician fading channels, we deduce the design metrics for multi-dimensional constellation construction and sparse codebook optimization. To reduce the decoding complexity, we advocate the key idea of projecting the multi-dimensional constellation elements to a few overlapped complex numbers in each dimension, called low projection (LP). We consider golden angle modulation (GAM), thus the resultant multi-dimensional constellation is called LPGAM. With the proposed design metrics and based on LPGAM, we propose an efficient approach of multi-stage optimization of sparse codebooks. Numerical and simulation results show the superiority of the proposed LP codebooks (LPCBs) in terms of decoding complexity and error rate performance. In particular, some of the proposed LPCBs can reduce the decoding complexity by 97% compared to the conventional codebooks, and own the largest minimum Euclidean distance among existing codebooks. The proposed LPCBs are available at https://github.com/ethanlq/SCMA-codebook.

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A Novel Scheme for the Construction of the SCMA Codebook

Lei

Cheng

et al. 2022

IEEE Access

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As a code-domain non-orthogonal multiple access technique, sparse code multiple access (SCMA) is considered as a promising technique for future wireless Internet of Things (IoT) networks. The minimum Euclidean distance (MED) and minimum product distance (MPD) have been highlighted as the key performance indicators of the codebook in additive gaussian white noise (AWGN) and downlink Rayleigh channels respectively. In this paper, based on the mother codebook, a novel codebook design scheme is proposed to achieve better error performance in both AWGN and downlink Rayleigh channels. The problem of constructing the mother codebook is considered as the quadratic assignment problem (QAP), where the Tabu searching algorithm is employed to reduce the complexity of searching for the best permutation result. Then, the rotation matrix is adopted to find the best degrees for the generation of the constellation group, and two algorithms are proposed to assign the obtained constellation in factor graph matrix. Taking the degree optimization and the constellation assignments into joint consideration, an improved unified optimization is further explored to maximize the MED of each user. Besides, a novel polarized modulation scheme is proposed, which places the symbols in the three dimensional (3D) stokes parameters to improve the performance of the system. Finally, simulation results are provided to show the performance of the proposed codebooks, and the comparisons of symbol error performance (SER) in different codebooks are also discussed in detail.INDEX TERMS Sparse code multiple access (SCMA), codebook design, minimum Euclidean distance, minimum product distance, three dimensional SCMA codebooks

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Design of Power-Imbalanced SCMA Codebook

Cited by 21 publications

References 19 publications

A Novel Non-Coherent SCMA With Massive MIMO

A Novel Non-Coherent SCMA With Massive MIMO

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

A Novel Scheme for the Construction of the SCMA Codebook

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