A Nonbinary LDPC-Coded SCMA System with Optimized Codebook Design

He, Qingli; Bai, Baoming; Feng, Dan; Xu, Hengzhou; Zhu, Min

doi:10.1109/vtcfall.2017.8288397

Cited by 12 publications

(11 citation statements)

References 18 publications

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“…In [51], an M-point constellation with low number of projections is proposed for non-binary low density parity check (LDPC) coded SCMA that aims to maximize the minimum Euclidian distance, d E, min , between the constellation points. As mentioned in Section IV-B, maximizing d E, min is not a KPI in fading scenarios with independent fading over the d v REs.…”

Section: ) M-baomentioning

confidence: 99%

Multidimensional Constellations for Uplink SCMA Systems—A Comparative Study

Vameghestahbanati

Marsland

Gohary

et al. 2019

IEEE Commun. Surv. Tutorials

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Sparse code multiple access (SCMA) is a class of non-orthogonal multiple access (NOMA) that is proposed to support uplink machine-type communication services. In an SCMA system, designing multidimensional constellation plays an important role in the performance of the system. Since the behavior of multidimensional constellations highly depends on the type of the channel, it is crucial to employ a constellation that is suitable for a certain application. In this paper, we first highlight and review the key performance indicators (KPIs) of multidimensional constellations that should be considered in their design process for various channel scenarios. We then provide a survey on the known multidimensional constellations in the context of SCMA systems with their design criteria. The performance of some of those constellations are evaluated for uncoded, high-rate, and low-rate LTE turbo-coded SCMA systems under different channel conditions through extensive simulations. All turbo-coded comparisons are performed for bit-interleaved coded modulation, with a concatenated detection and decoding scheme. Simulation results confirm that multidimensional constellations that satisfy KPIs of a certain channel scenario outperform others. Moreover, the bit error rate performance of uncoded systems, and the performance of the coded systems are coupled to their bit-labeling. The performance of the systems also remarkably depends on the behavior of the multi-user detector at different signal-to-noise ratio regions.Index Terms-Non-orthogonal multiple access (NOMA), Sparse code multiple access (SCMA), low density spreading (LDS), multidimensional constellation, SCMA codebook, fading channels, message passing algorithm (MPA), bit-interleaved coded modulation (BICM), key performance indicators (KPIs).

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Section: ) M-baomentioning

confidence: 99%

Multidimensional Constellations for Uplink SCMA Systems—A Comparative Study

Vameghestahbanati

Marsland

Gohary

et al. 2019

IEEE Commun. Surv. Tutorials

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“…Although many papers [1,3,5] present benchmarks with very small and dense resource allocation matrices, the sparse structure initially proposed for SCMA, similar to Low-Density Parity Check (LDPC) codes, suggests that the MPA receiver works better in larger dimensions. Recent works such as [6,7] proposed designing the SCMA resource allocation matrices using design methods of LDPC codes, achieving better performance with larger dimension (less dense matrices) systems.…”

Section: Introductionmentioning

confidence: 99%

A Multistage Method for SCMA Codebook Design Based on MDS Codes

Silva

Uchôa-Filho

et al. 2019

IEEE Wireless Commun. Lett.

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Sparse Code Multiple Access (SCMA) has been recently proposed for the future generation of wireless communication standards. SCMA system design involves specifying several parameters. In order to simplify the procedure, most works consider a multistage design approach. Two main stages are usually emphasized in these methods: sparse signatures design (equivalently, resource allocation) and codebook design. In this paper, we present a novel SCMA codebook design method. The proposed method considers SCMA codebooks structured with an underlying vector space obtained from classical block codes. In particular, when using maximum distance separable (MDS) codes, our proposed design provides maximum signalspace diversity with a relatively small alphabet. The use of small alphabets also helps to maintain desired properties in the codebooks, such as low peak-to-average power ratio and lowcomplexity detection.

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“…where D is a design criterion. A sub-optimal multi-stage optimization approach is deployed in [30,[51][52][53][54][55][56][57][58][59][60][61][62][63][64] for uplink SCMA systems that involves finding S * first and then X * . Moreover, when the system is fully overloaded, there is a unique solution for S * .…”

Section: Scma Multidimensional Constellation Designmentioning

confidence: 99%

“…In [60], an M-point constellation with low number of projections is proposed for non-binary low density parity check (LDPC) coded SCMA that aims to maximize the minimum Euclidean distance, d E, min , between the constellation points. As mentioned in Section 3.3, maximizing d E, min is not a KPI in fading scenarios with independent fading over the d v REs.…”

Section: A Mn Dmentioning

confidence: 99%

“…In fact, it is a key feature that distinguishes SCMA from other NOMA techniques [38]. The design of multidimensional constellation has been studied for downlink SCMA systems in e.g., [42][43][44][45][46][47][48][49][50], and for uplink SCMA systems in e.g., [30,[51][52][53][54][55][56][57][58][59][60][61][62][63][64]. The objective of this work is to provide a thorough study on multidimensional constellations for uplink SCMA systems, and to highlight their design metrics under various channel scenarios.…”

Section: Introductionmentioning

confidence: 99%

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Designing Multidimensional Constellations and Efficient Detection Schemes for Sparse Code Multiple Access (SCMA) Systems

Vameghestahbanati¹

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Sparse code multiple access (SCMA) is a class of non-orthogonal multiple access that is proposed to support uplink machine-type communication services. In this thesis, we investigate the design of SCMA systems from two main aspects: multidimensional constellations (MdCs) and efficient detection schemes. In an SCMA system, designing MdCs plays an important role in the system performance. Since the behavior of multidimensional constellations highly depends on the type of the channel, it is crucial to employ a constellation that is suitable for a certain application. In the first part of this thesis, we highlight and review the key performance indicators (KPIs) of MdCs that should be considered in their design process for various channel scenarios. We also provide a survey on the known MdCs in the context of SCMA systems with their design criteria. The performance of some of those constellations are evaluated for uncoded and LTE turbo-coded SCMA systems under different channel conditions through extensive simulations. We then investigate the effect of the 5G low density parity check (LDPC) codes on determining KPIs in designing MdCs under various channel scenarios. Since the optimal maximum likelihood (ML) receiver for SCMA is too complex in most applications, one highly popular detection technique is the message passing algorithm (MPA), which exploits the sparsity structure of SCMA. MPA is a near-optimal technique, where its performance improves with increasing the signal-to-noise-ratio (SNR) and the number of iterations. We design novel SCMA SNR-adaptive MdCs which result in substantial performance gains (as much as 2 dB) in comparison to the best known SCMA MdCs in the literature, especially in low-to-medium SNR regions when the number of MPA iterations has to be low, and in the presence of 5G-compliant LDPC codes. Sphere decoding (SD) based detection schemes for SCMA have recently received attention due to their promising features. However, the existing SD-based schemes can only be applied to systems with constellations that possess a certain structure. In the second part of the thesis, we propose an SD-based detection scheme, namely improved SD (ISD), for SCMA that achieves the optimal ML detector for any arbitrary regular or irregular constellations. I would also like to mention the government of Ontario in acknowledgment of the Ontario Trillium scholarship which pledged a wide support to my Ph.D., Huawei Technologies research and development team, specially Dr.

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A Nonbinary LDPC-Coded SCMA System with Optimized Codebook Design

Cited by 12 publications

References 18 publications

Multidimensional Constellations for Uplink SCMA Systems—A Comparative Study

Multidimensional Constellations for Uplink SCMA Systems—A Comparative Study

A Multistage Method for SCMA Codebook Design Based on MDS Codes

Designing Multidimensional Constellations and Efficient Detection Schemes for Sparse Code Multiple Access (SCMA) Systems

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