A Novel HARQ Scheme for SCMA Systems

Long, Yu; Chen, Zhi; Guo, Zhiwu; Fang, Jun

doi:10.1109/lwc.2016.2585110

Cited by 15 publications

(13 citation statements)

References 6 publications

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“…It can be shown that the proposed RSCMA outperform all other schemes in low-SNR region (below SNR = 9dB) and high SNR region (above SNR = 25dB). Specifically, in low-SNR region it can achieve 10.5%, 30.5%, and 220% higher throughput than RMA, LT coded SCMA and HARQ-SCMA [9] schemes, respectively, while in high-SNR region it achieves 17%, 63.22%, and 11 times higher throughput than LT-coded SCMA, RMA, and HARQ-SCMA schemes, respectively. The reason for the poor throughput performance of the HARQ-SCMA is that if any errors happen in decoding process a frame of the information bits need to be totally retransmitted [9] while only several extra symbols or coded bits need to be transmitted in other schemes.…”

Section: Simulation Resultsmentioning

confidence: 95%

“…Apart from rateless codes, hybrid automatic repeat request (HARQ) can also be used to cope with the dynamical channel states. In [9], the authors proposed an HARQ scheme for SCMA system. In this scheme, users whose transmitted data packets are correctly decoded in the BS would retransmit the data packets to assist the BS to decode the messages of other users.…”

Section: Introductionmentioning

confidence: 99%

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Grant-Free Rateless SCMA for Cellular Internet of Things Networks

et al. 2019

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For supporting the massive connectivities and better adapting the high dynamical channel states of the cellular Internet of things networks, in this paper we proposed a new grant-free rateless sparse code multiple access (RSCMA) protocol. In the proposed grant-free RSCMA, users switch from the inactive mode to the active mode as soon as they receive data packages, and start to transmit the data without the request-grant process between the base station (BS) and users. In each transmission, the active users firstly choose a certain number of the modulated SCMA symbols according to the pre-assigned access control function (ACF), and then transmit the linearly superimposed SCMA symbols to the BS over the available resource elements. At the BS, owing to the sparsity of RSCMA, message passing algorithm which allows multi-user detection with near-optimal performance can be utilized to decode the messages. The transmission will continue until the user successfully receives an ACK signal sent back from the BS. Theoretical analysis in terms of achievable constellation constrained throughput is provided to show the maximal sum rate of RSCMA and to optimize the ACF design under the trade-off between the complexity and throughput performance. Both theoretical and simulation results show that the RSCMA can achieve higher throughput than the existing rateless multiple access schemes, such as hybrid automatic repeat request SCMA, LT code coded SCMA, and rateless multiple access.

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Section: Simulation Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Grant-Free Rateless SCMA for Cellular Internet of Things Networks

et al. 2019

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“…where s th0 =ŝ 0 (i, j; k), s th1 , s th2 , s th3 are given in (34), (35), (36) and A, B are given below.…”

Section: A First Round: M =mentioning

confidence: 99%

“…Indeed, the transmitter can enforce blanking, i.e., transmitting no information for the users that have successfully decoded their own packets, in order to decrease the interference on weak users [33]. Such blanking-based HARQ protocols have also been used in the context of SCMA systems in [35] to improve the overall throughput of the system. Other works have recently studied the performance of single-packet HARQ protocols in NOMA systems [21], [22].…”

Section: Introductionmentioning

confidence: 99%

On the Performance of HARQ Protocols With Blanking in NOMA Systems

Mheich

Xiao

et al. 2020

IEEE Trans. Wireless Commun.

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In this paper, we investigate the throughput performance of single-packet and multi-packet hybrid-automatic repeat request (HARQ) with blanking for downlink non-orthogonal multiple access (NOMA) systems. While conventional singlepacket HARQ achieves high throughput at the expense of high latency, multi-packet HARQ, where several data packets are sent in the same channel block, can achieve high throughput with low latency. Previous works have shown that multi-packet HARQ outperforms single-packet HARQ in orthogonal multiple access (OMA) systems, especially in the moderate to high signal-tonoise ratio regime. This work amalgamates multi-packet HARQ with NOMA to achieve higher throughput than the conventional single-packet HARQ and OMA, which has been adopted in the legacy mobile networks. We conduct theoretical analysis for the throughput per user and also investigate the optimization of the power and rate allocations of the packets, in order to maximize the weighted-sum throughput. It is demonstrated that the gain of multi-packet HARQ over the single-packet HARQ in NOMA systems is reduced compared to that obtained in OMA systems due to inter-user interference. It is also shown that NOMA-HARQ cannot achieve any throughput gain with respect to OMA-HARQ when the error propagation rate of the NOMA detector is above a certain threshold.

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“…In [30], the authors introduce a low-complexity SCMA receiver based on MPA. In [31], the authors propose a new hybrid automatic repeat request (HARQ) combined with SCMA. Finally, in [32], the authors present a real-time SCMA transceiver prototype that can provide up to 300% overloading in field tests.…”

Section: Introductionmentioning

confidence: 99%

Sparse code multiple access on the generalized frequency division multiplexing

Aquino

Mendes

2020

J Wireless Com Network

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Recent advances in the communication systems culminated in a new class of multiple access schemes, named non-orthogonal multiple access (NOMA), where the main goal is to increase the spectrum efficiency by overlapping data from different users in a single time-frequency resource used by the physical layer. NOMA receivers can resolve the interference among data symbols from different users, increasing the overall system spectrum efficiency without introducing symbol error rate (SER) performance loss, which makes this class of multiple access techniques interesting for future mobile communication systems. This paper analyzes one promising NOMA technique, called sparse code multiple access (SCMA), where C users can share U<C time-frequency resources from the physical layer. Initially, the SCMA and orthogonal frequency division multiplexing (OFDM) integration is considered, defining a benchmark for the overall SER performance for the multiple access technique. Furthermore, this paper proposes the SCMA and generalized frequency division multiplexing (GFDM) integration. Since GFDM is a highly flexible non-orthogonal waveform that can mimic several other waveforms as corner cases, it is an interesting candidate for future wireless communication systems. This paper proposes two approaches for combining SCMA and GFDM. The first one combines a soft equalizer, called block expectation propagation (BEP), and a multi-user detection (MUD) scheme based on the sum-product algorithm (SPA). This approach achieves the best SER performance, but with the significant increment of the complexity at the receiver. In the second approach, BEP is integrated with a simplified MUD, which is an original contribution of this paper, aiming for reducing the receiver’s complexity at the cost of SER performance loss. The solutions proposed in this paper show that SCMA-GFDM can be an interesting solution for future mobile networks.

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A Novel HARQ Scheme for SCMA Systems

Cited by 15 publications

References 6 publications

Grant-Free Rateless SCMA for Cellular Internet of Things Networks

Grant-Free Rateless SCMA for Cellular Internet of Things Networks

On the Performance of HARQ Protocols With Blanking in NOMA Systems

Sparse code multiple access on the generalized frequency division multiplexing

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