Sub-Graph Based Joint Sparse Graph for Sparse Code Multiple Access Systems

Lai, Ke; Wen, Li; Lei, Jing; Xiao, Pei; Maaref, Amine; Imran, Muhammad Ali

doi:10.1109/access.2018.2828126

Cited by 16 publications

(14 citation statements)

References 40 publications

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“…In general, the LDPC code, the mapper and the protection levels of the UEP SCMA codebook could be optimized jointly using EXIT charts. The sparse graphs of LDPC code and SCMA could also be combined into one joint sparse graph which improves the overall performance of the system [12]. However, in practice, it is desirable to design an LDPC code which can support multiple rates and multiple codebook/constellation sizes within the context of bit-interleaved coded systems [13] instead of optimizing the LDPC code for each codebook/constellation size.…”

Section: Resultsmentioning

confidence: 99%

Unequal Error Protection SCMA Codebooks

Mheich

Wen

Xiao

et al. 2019

IEEE Trans. Veh. Technol.

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This paper investigates the design of unequal error protection (UEP) codebooks for sparse code multiple access (SCMA) systems. We propose a joint LDPC code and SCMA codebook design approach by incorporating cloud-partitioning of codewords in the design of SCMA codebooks with different protection levels. The protection levels of the SCMA codebooks could be optimized based on the existing error correction code. Simulation results show that significant gains could be obtained using code-aware UEP SCMA codebooks compared to codebooks designed independently of the channel code. Index Terms-NOMA, SCMA, UEP, codebook design, channel coding. I. INTRODUCTION Non-orthogonal multiple access (NOMA) techniques support massive connectivity and improve the spectral efficiency of wireless radio access by enabling overloading (i.e., the number of multiplexed users can be larger than the number of resources). Low-density signature (LDS) is a code-domain NOMA where the constellation symbol is expanded to a sequence of complex symbols by using a specific signature [1]. The low-density characteristic of LDS signatures allows to use message passing algorithm for multiuser detection with lower complexity than maximum-likelihood decoding. SCMA is a generalization of LDS, where the procedure of bit to modulation mapping and spreading are combined together such that coded bits are directly mapped to multi-dimensional sparse codewords selected from user-specific SCMA codebooks [2]. By using multi-dimensional codebooks, SCMA can benefit from shaping gains of multi-dimensional constellations. There are many SCMA codebook design methods in literature. Nikopour et al. are the first to propose a multi-stage suboptimal method for the design of multiuser SCMA codebooks [3]. Following this direction, other sub-optimal design methods are proposed e.g. in [4], [5], [6], [7], [8] to improve the performance or to lower the complexity of multiuser detection or codebook design. Most these works assess the performance of codebooks in uncoded systems or do not take into account the error-correction code in their codebook design. In a real communication system, an error-correction code is used and

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Section: Resultsmentioning

confidence: 99%

Unequal Error Protection SCMA Codebooks

Mheich

Wen

Xiao

et al. 2019

IEEE Trans. Veh. Technol.

Self Cite

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“…SCMA detectors which include the error-correction codes structure into their design began to gain more attention. For instance, the LDPC code was employed as the channel coding scheme for the SCMA system in [155], [156] while a polar-coded SCMA was studied in [157]- [159].…”

Section: E Detectors For Channel-coded Scmamentioning

confidence: 99%

“…In [155], the sparse factor graphs of LDPC coding and SCMA are combined into a joint sparse graph in order to jointly perform the decoding and the detection on one graph. Then, MPA was simplified by using partial message passing based on a joint trellis representation.…”

Section: E Detectors For Channel-coded Scmamentioning

confidence: 99%

Sparse Code Multiple Access: Potentials and Challenges

Rebhi

Hassan

Raoof

et al. 2021

IEEE Open J. Commun. Soc.

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The massive connectivity is among other unprecedented requirements which are expected to be satisfied in order to follow the perpetual increase of connected devices in the era of internet of things. In contrast to the family of conventional orthogonal multiple access schemes, the key distinguishing feature of non-orthogonal multiple access (NOMA) is its capacity to support the massive connectivity. Sparse code multiple access (SCMA) is one of the powerful schemes of code-domain NOMA (CD-NOMA) and is among the promising candidates of multiple access techniques to be employed in future generations of wireless communication systems thanks to the sparsity pattern of its codebooks. This technique has been actively investigated in recent years. In this paper, we provide a comprehensive survey of the state-of-the-art of SCMA. First, we will pinpoint SCMA place in the NOMA landscape including power-domain NOMA and CD-NOMA with the aim of justifying why SCMA is prominent. Then, its system architecture is highlighted and its basic principles are presented, afterwards a review of exiting codebook designs and available SCMA detectors is provided, before showing how resources are expected to be assigned, and how SCMA can be combined with other existing and emerging technologies. Finally, we present a range of future research trends and challenging open issues that should be addressed to optimize SCMA performance.

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“…In [38], the authors ensured ideal system error performance by minimizing the upper limit of the worst performance threshold for decoding. The authors of [39] proposed a joint sparse graph based on the subgraph of the LDPC-SCMA system, and performed joint detection and decoding through message passing between the subsparse graph and LDPC sparse graph.…”

Section: Related Workmentioning

confidence: 99%

A Joint Detection and Decoding Scheme for PC-SCMA System Based on Pruning Iteration

Zhang

et al. 2020

Symmetry

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Polar coding and sparse code multiple access (SCMA) are key technologies for 5G mobile communication, the joint design of them has a great significance to improve the overall performance of the transmitter-receiver symmetric wireless communication system. In this paper, we firstly propose a pruning iterative joint detection and decoding algorithm (PI-JDD) based on the confidence stability of resource nodes. Branches to be updated are dynamically pruned to avoid redundant iterative, which is able to reduce 24~50% complexity while achieving the approximate error performance of traditional serial joint iterative detection and decoding algorithm S-JIDD. Then, to further reduce the bit error rate (BER) of the receiver, a cyclic redundancy check (CRC) termination mechanism is added at the end of each joint iteration to avoid the convergence error caused by decoding deviation. Simulation results show that the addition of an early stopping criterion can achieve a remarkable performance gain compared with the S-JIDD algorithm. More importantly, the combined algorithm of the two proposed schemes can reduce the computational complexity while achieving better error performance.

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Sub-Graph Based Joint Sparse Graph for Sparse Code Multiple Access Systems

Cited by 16 publications

References 40 publications

Unequal Error Protection SCMA Codebooks

Unequal Error Protection SCMA Codebooks

Sparse Code Multiple Access: Potentials and Challenges

A Joint Detection and Decoding Scheme for PC-SCMA System Based on Pruning Iteration

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