An Uplink SCMA Codebook Design Combining Probabilistic Shaping and Geometric Shaping

Jiang, Chengxin; Wang, Yafeng

doi:10.1109/access.2020.2989448

Cited by 8 publications

(3 citation statements)

References 26 publications

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“…Mapping matrices V 1 , V 2 , V 3 in ( 7) are chosen and this choice makes sure the number of collisions is as small as 2 [11]. Algorithm 1 is applied to solve Problem (20) with the initial point X 2 = xx H where all elements of x (i.e., all entries of {C j } 3 j=1 ) are independently generated by a random variable uniformly distributed between 0 and 1. In this relatively simple case, Algorithm 1 is found to be converging and leading to an optimal codebook collection whose optimal value coincides with that of the dual problem (24).…”

Section: Simulation Resultsmentioning

confidence: 99%

Downlink SCMA Codebook Design with Low Error Rate by Maximizing Minimum Euclidean Distance of Superimposed Codewords

Huang,

Su,

Lin

et al. 2021

Preprint

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Sparse code multiple access (SCMA), as a codebookbased non-orthogonal multiple access (NOMA) technique, has received research attention in recent years. The codebook design problem for SCMA has also been studied to some extent since codebook choices are highly related to the system's error rate performance. In this paper, we approach the downlink SCMA codebook design problem by formulating an optimization problem to maximize the minimum Euclidean distance (MED) of superimposed codewords under power constraints. While SCMA codebooks with a larger minimum Euclidean distance (MED) are expected to obtain a better BER performance, no optimal SCMA codebook in terms of MED maximization, to the authors' best knowledge, has been reported in the SCMA literature yet. In this paper, a new iterative algorithm based on alternating maximization with exact penalty is proposed for the MED maximization problem. The proposed algorithm, when supplied with appropriate initial points and parameters, achieves a set of codebooks of all users whose MED is larger than any previously reported results. A Lagrange dual problem is derived which provides an upper bound of MED of any set of codebooks. Even though there is still a nonzero gap between the achieved MED and the upper bound given by the dual problem, simulation results demonstrate clear advantages in error rate performances of the proposed set of codebooks over all existing ones. The correctness and accuracy of error curves in the simulation results are further confirmed by the coincidences with the theoretical upper bounds of error rates derived for any given set of codebooks.

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Section: Simulation Resultsmentioning

confidence: 99%

Downlink SCMA Codebook Design with Low Error Rate by Maximizing Minimum Euclidean Distance of Superimposed Codewords

Huang,

Su,

Lin

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Accordingly, the constellations for modulation of the GS scheme are organized as a non-evenly spaced topology with a uniform distribution [50], while those of the PS are based on an evenly-spaced topology following a nonuniform distribution [51][52][53]. The combination of the GS and PS schemes was recently considered in [54].…”

Section: Spectral and Energy Efficiencies For Scma-based Systemsmentioning

confidence: 99%

A Survey on Non-Orthogonal Multiple Access: From the Perspective of Spectral Efficiency and Energy Efficiency

et al. 2020

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Non-orthogonal multiple access (NOMA) is a promising technology for next-generation wireless networks with emerging demands on low latency, high throughput, and massive connectivity. Unlike orthogonal multiple access, NOMA allows multiple users to share the same radio resources, which significantly improves spectral efficiency (SE). To achieve green wireless communications for numerous networked devices, NOMA helps reduce energy consumption while satisfying rate fairness and quality-of-experience requirements. The goal of this paper is to introduce the innovative approaches for NOMA in terms of the SE and energy efficiency, and discuss emerging technologies involved with NOMA. Further, its challenges and future research directions are highlighted.

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“…In [6], [7], the authors focus on optimization of the mother constellation by maximizing important figures of merit, such as minimum Euclidean distance and minimum product distance. By combining probabilistic shaping and geometric shaping in uplink SCMA codebook design, [8] shows superiority of the designed codebooks in terms of block error rate (BLER) performance and average mutual information.…”

Section: Introductionmentioning

confidence: 99%

A Simplified Sphere Decoding-Based Detector for Generalized SCMA Codebooks

Ruyet

Silva³

et al. 2022

IEEE Access

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Sparse code multiple access (SCMA) is one of the promising schemes to meet high connectivity and spectral efficiency in the future wireless networks. The iterative detectors, for example message passing algorithm (MPA), can provide near optimal multiuser detection (MUD) performance but becomes infeasible when the codebook size is large or the overloading factor is high. Recently, sphere decoding (SD) has been considered in the MUD of SCMA by rewriting the generalized transmission into a linear system. In this work, we first review the state-of-the-art SD-based detectors for SCMA: sphere decoding for SCMA (SD-SCMA) and generalized SD-SCMA (GSD-SCMA). We not only explain the state-of-the-art in a comprehensive way, but also exploit the sorted QR decomposition and Schnorr-Euchner enumeration to accelerate the tree search. Although GSD-SCMA overcomes the codebook constraint of SD-SCMA, its computational complexity is extremely sensitive to the overloading factor. To satisfy the tradeoff between complexity and MUD performance, we propose two pruning algorithms, PRUN1 and PRUN2, and introduce the simplified GSD-SCMA (SGSD-SCMA). In the paper, error probabilities of the proposed pruning algorithms are derived. Simulation results show that the proposed detector outperforms the iterative detectors and SD-based state-of-the-art when the overloading factor is moderate and the codebook size is large.

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An Uplink SCMA Codebook Design Combining Probabilistic Shaping and Geometric Shaping

Cited by 8 publications

References 26 publications

Downlink SCMA Codebook Design with Low Error Rate by Maximizing Minimum Euclidean Distance of Superimposed Codewords

Downlink SCMA Codebook Design with Low Error Rate by Maximizing Minimum Euclidean Distance of Superimposed Codewords

A Survey on Non-Orthogonal Multiple Access: From the Perspective of Spectral Efficiency and Energy Efficiency

A Simplified Sphere Decoding-Based Detector for Generalized SCMA Codebooks

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