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28th Asia-Pacific Conference on Communications (APCC)

作者： Han, Minsig Demissu, Metasebia G. Abebet, Ameha T. Kang, Chung G. Korea Univ Sch Elect Engn Seoul South Korea Samsung Res Seoul South Korea

ISBN: (纸本)9798350382617

In grant-free sparse code multiple access (SCMA) systems, SCMA codebooks (CBs) are used for efficient grant-free random access. However, CB collisions can occur when multiple active users select the same CB, degrading the performance of multi-user detection (MUD) at the base station (BS). The existing methods modify the factor graph on the message-passing algorithm (MPA) for each CB collision scenario, resulting in high computational complexity. In this paper, we aim to confirm that even in the presence of CB collisions, MUD performance can be ensured through a deep learning (DL)-based receiver and explore its limitations. We propose a single DL architecture for collision-aware MUD (CA-MUD) that can tolerate CB collisions, without resorting to the distinct MUD processes associated with individual collision scenarios. To facilitate the generation of training data for CA-MUD that comprehensively represents the grant-free SCMA scenario, we introduce a transceiver model that regulates the number of active CBs and sets the maximum tolerable CB collisions. Simulation results demonstrate that our proposed approach allows a single CA-MUD network to handle various CB collision scenarios, including 2-fold CB collision subject to a limited number of active users.

关键词： Grant-free random access sparse code multiple access multi-user detection deep learning codebook collision

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Grant-Free Uplink Transmission With Multi-codebook-Based sparse code multiple access (MC-SCMA)

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IEEE access 2019年 7卷 169853-169864页

作者： Abebe, Ameha Tsegaye Kang, Chung G. Korea Univ Dept Elect Engn Seoul 02841 South Korea

In sparse code multiple access (SCMA)-based grant-free (GF) access, both users channel and the selected SCMA codebook (CB) are considered as a transmission signature for multi-user detection (MUD). In conventional SCMA-based grant-free (GF) access where a single codebook (CB) is employed per a users random access transmission, however, random selection of CBs and random fading channel reduce the minimum Euclidean distance among overloaded layers (signatures). This significantly degrades the performance. Furthermore, it is also challenging to reduce the collision rate in the course of selecting random access resources while maintaining low preamble overhead. In this paper, we consider a new approach that maps users consecutive symbols to codewords from the different SCMA CBs in a round-robin manner. It is shown that a combinatorial nature of multiple CBs and the inherent code diversity therein allow to simultaneously reduce collision probability while providing sufficient separation among transmissions, consequently decreasing users activity misdetection rate. It is also shown that the proposed multi-codebook SCMA (MC-SCMA)-based GF access scheme outperforms the conventional single CB-based SCMA version by overloading of more users (almost up to 200) as it allows a large number of highly non-orthogonal preambles to be employed while keeping the same preamble length (overhead). Finally, we conclude that the proposed joint design of non-orthogonal preambles and data transmission based on multiple CBs provides a significant performance improvement for the grant-free access system. It can also readily be extended to other code-based non-orthogonal multiple access (NOMA) schemes.

关键词： NOMA Multiuser detection Channel estimation Time-frequency analysis OFDM Euclidean distance Data communication sparse code multiple access grant-free access random access compressed sensing preamble transmission channel estimation multi-user detection activity detection

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FH-SCMA: Frequency-hopping based sparse code multiple access for Next Generation Internet of Things

FH-SCMA: Frequency-hopping based Sparse Code Multiple Access...

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IEEE Wireless Communications and Networking Conference (WCNC)

作者： Bai, Zhicheng Li, Bo Yang, Mao Yan, Zhongjiang Zuo, Xiaoya Zhang, Yongping Northwestern Polytech Univ Sch Elect & Informat Xian Peoples R China

ISBN: (纸本)9781509041831

The next generation Internet of Things (IoT) is expected to support extremely diverse applications and terminals, which requires the massive connectivity. Unfortunately, current mobile communication systems with orthogonal multiple access technique can hardly satisfy this demand. On the other hand, the narrow band property has become the trend of the next generation IoT, however, the problem of interference alleviation in the narrow band system is difficult to be resolved. Recently, the sparse code multiple access (SCMA), a non-orthogonal multiple access technique for 5G, shows the obvious improvement in user connectivity and system capacity. After carrier aggregation brought into the future network, The IoT could offer the frequency hopping mechanism larger bandwidth resources. In this paper, by introducing frequency hopping mechanism to the SCMA, a frequency-hopping based sparse code multiple access (FH-SCMA) multiple access technique is proposed to meet the demand of both massive connectivity and the improvement in the interference alleviation. Simulation results show that the FH-SCMA obtains a spectrum efficiency gain of almost 300% compared with the frequency division multiple access (FDMA) based IoT system with frequency-hopping, and the performance of interference alleviation can also be significantly improved by about 2 to 5 times over the FDMA with frequency hopping.

关键词： Internet of Things sparse code multiple access frequency-hopping NB-IoT

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Space-Time coded Generalized Spatial Modulation for sparse code Division multiple access

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2021年第8期20卷 5359-5372页

作者： Liu, Yusha Xiang, Luping Yang, Lie-Liang Hanzo, Lajos Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

Space-time coded generalized spatial modulation-aided sparse code division multiple access (STC/GSM-SCDMA) is proposed, which exploits the two-dimensional transmit diversity potential of both the spatial and of the frequency domain. Hence, it constitutes a promising solution for the pervasive connectivity of devices in next-generation nonorthogonal multiple access (NOMA) systems. More explicitly, our STC/GSM scheme achieves diversity in the spatial-domain, while the sparse signal-spreading action of SCDMA results in frequency-domain (FD) diversity. A single-user bit error rate (BER) bound is derived as the benchmark of the BER performance of our STC/GSM-SCDMA system. Furthermore, a pair of novel detectors, namely a bespoke message passing aided (MPA) detector and a tailor-made approximate message passing (AMP) detector are conceived by designing a new factor graphs for our proposed STC/GSM-SCDMA system. The performance of these detectors is characterized in terms of their BER vs. complexity. Our simulation results show that the proposed AMP detector is capable of operating within 2 dB of the MPA detector's signal-to-noise ratio (SNR) requirement, while supporting a normalized user load of 150%, despite its appealing low complexity, which is about 1000 times lower than the MPA detector.

关键词： Wireless communication NOMA Message passing Frequency-domain analysis Bit error rate Detectors Complexity theory Space-time coding generalized spatial modulation sparse code multiple access nonorthogonal multiple access

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Design and Analysis of Irregular sparse code multiple access

Design and Analysis of Irregular Sparse Code Multiple Access

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International Conference on Wireless Communications and Signal Processing

作者： Shutian Zhang Baicen Xiao Kexin Xiao Zhiyong Chen Bin Xia Dept. of Electron. Eng. Shanghai Jiao Tong Univ. Shanghai China

ISBN: (纸本)9781467376884

sparse code multiple access (SCMA) is an excellent approach to support massive connections and short time-delay, which are the two key requirements in the future fifth generation (5G) communication system. Due to the drawback that traditional SCMA can't serve users with different business needs in the same scenario, we propose an irregular sparse code multiple access (SCMA) in this paper. In contrast with the traditional SCMA system based on the regular structure, the irregular SCMA can handle massive connections and short time delay in the same system simultaneously by assigning different codebooks with various dimensions for different users who demand for divers performance needs. Simulation results illustrate that irregular SCMA can achieve about 0.7 dB gain over regular SCMA in terms of the same bit error rate (BER) condition.

关键词： 5G mobile communication codes error statistics multi-access systems synchronisation 5G communication system BER bit error rate codebooks fifth generation communication system irregular SCMA sparse code multiple access time-delay Business Complexity theory Receivers Time-frequency analysis Uplink

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SCMA-Q-learning with overload control for random access in LEO satellite mMTC networks

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PHYSICAL COMMUNICATION 2025年 69卷

作者： Wu, Zeyu Jing, Guoliang Ding, Jie Zhao, Xu Jiangsu Univ Sci & Technol Sch Comp Zhenjiang 212100 Jiangsu Peoples R China Guilin Univ Elect Technol Guangxi Key Lab Trusted Software Guilin 541004 Peoples R China Beijing SmartChip Microelect Technol Co Ltd Beijing 10000 Peoples R China

With the continuous advancement of 5G and beyond wireless networks, the exponential increase in Machine- Type Communication (MTC) devices presents substantial challenges, particularly in deal with Random access Channel (RACH) congestion in massive MTC (mMTC) networks. Low Earth Orbit (LEO) satellite communication networks are increasingly valued for their global coverage and low-latency benefits. This paper deals with the RACH congestion problem in LEO satellite networks by proposing an innovative method that combines sparse code multiple access (SCMA), Q-learning, and access Class Barring (ACB) technology. The proposed approach allows MTC devices to dynamically optimize resource allocation by selecting the most appropriate codebooks and time-slot groups in response to environmental changes. Additionally, ACB is employed to control system overload by adjusting the access probability of devices based on network conditions. Simulation results show that the proposed SCMA-QL-ACB method significantly improves system throughput and reduces collisions compared to existing techniques.

关键词： Random access Machine-type communications Q-learning sparse code multiple access access class barring

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Low Complexity Message Passing Receiver Design for SCMA-GFDM System

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2024年第12期73卷 18755-18768页

作者： Cheng, Hao Zhang, Min Zhang, Chuan Zhang, Haiyang Huang, Yongming Wang, Baoyun Nanjing Univ Posts & Telecommun Sch Internet Things Nanjing 210003 Peoples R China Southeast Univ Sch Informat Sci & Engn Nanjing 210096 Peoples R China Purple Mt Labs Nanjing 211111 Peoples R China Nanjing Univ Posts & Telecommun Sch Commun & Informat Engn Nanjing 210003 Peoples R China

sparse code multiple access (SCMA) and generalized frequency-division multiplexing (GFDM) are two promising techniques that can effectively handle massive connectivity and enhance spectrum efficiency in the sixth generation wireless communication systems. Unfortunately, the high computational cost of the SCMA-GFDM receiver limits its practical application. To this end, by virtue of the frequency domain implementation of the GFDM transmission, we apply the discrete fourier transform (DFT) operation on the received symbols, which in return diagonalizes the channel matrix. Next, this efficient received signal after DFT is put into the zero-forcing (ZF) equalizer of GFDM, and subsequently, fed into the message passing algorithm (MPA) receiver of SCMA, which establishes a low complexity multiuser detection for the SCMA-GFDM system. For rigor, the closed form average bit error ratio (BER) bound for this SCMA-GFDM system is also derived by computing the effective noise power. Finally, simulation results illustrate the robustness of the designed low complexity DFT-MPA detector in terms of BER performance, and also demonstrate the validity of the analytical BER bound.

关键词： Receivers NOMA Information filters Symbols Interference Complexity theory codes sparse code multiple access generalized frequency-division multiplexing DFT-MPA closed form bit error ratio

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Uplink SCMA System With multiple Antennas

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2017年第8期66卷 6982-6992页

作者： Lim, Seung-Chan Kim, Namshik Park, Hyuncheol Korea Adv Inst Sci & Technol Sch Elect Engn Daejeon 34141 South Korea ReCoLab Inc Suwon 17104 South Korea

sparse code multiple access (SCMA) is a codebook-based nonorthogonal multiple access that exploits the coding gain of designed codebooks and the near-optimum performance of belief-propagation (BP) detection. In this paper, we study an uplink SCMA system equipped with multiple receive antennas utilized to get a diversity gain. Assuming that the maximum likelihood detection is applied to the system, we derive the upper bound on the average bit error rate (ABER) and analyze the diversity order which is shown to be the product of the number of receive antennas and the spreading gain. Exploiting the multiple received signals, we also propose a simplified detection method called Gaussian approximation based BP (GA-BP) detection with linear prefiltering. As the first step of the proposed detection, a conventional linear filter is applied to mitigate the multiuser interferences. Then, the GA-BP iteratively removes the residual interferences which may be approximated to a Gaussian random variable for the massive number of user equipments. Numerical results show that for moderate and high signal to noise ratio region the analyzed upper bounds on ABER of SCMA system tightly coincide with the simulation results. Also, for the moderate numbers of antennas, the ABER of GA-BP with matched filter closely approaches to that of the conventional BP detection with much lower computational costs.

关键词： Belief-propagation gaussian approximation low-complexity detection multiple antennas sparse code multiple access

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Energy-Saving Resource Management for D2D and Cellular Coexisting Networks Enhanced by Hybrid multiple access Technologies

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第4期16卷 2678-2692页

作者： Zhai, Daosen Sheng, Min Wang, Xijun Sun, Zhisheng Xu, Chao Li, Jiandong Xidian Univ State Key Lab Integrated Serv Networks Xian 710071 Peoples R China

In this paper, we investigate the energy-saving resource management problem for a new device-to-device (D2D) and cellular coexisting network, where D2D users employ orthogonal frequency division multiple access (OFDMA) and cellular users employ sparse code multiple access (SCMA). This hybrid network can support massive connectivity by exploiting the degrees of freedom in code and space domains, however, the complicated spectrum sharing pattern also leads to serious interference, which further boosts the power consumption of mobile devices (MDs). To tackle this problem, we propose a unified resource management scheme to minimize the total transmit power of all MDs by jointly optimizing mode selection, resource allocation, and power control. First, we analytically get the optimal resource-sharing mode (dedicated mode or reuse mode) for cellular users and D2D users based on the mapping rule between SCMA codebooks and OFDMA resource blocks. For each resource-sharing mode, we reformulate the resource management problems as classical problems in graph theory, and then devise efficient algorithms leveraging the special structure of the constructed graphs. Finally, simulation studies indicate that the network capacity is upgraded with the hybrid multiple access technologies, and the energy efficiency performance is also enhanced through the unified resource management.

关键词： Resource management device-to-device sparse code multiple access graph theory

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Adaptive codebook Design and Assignment for Energy Saving in SCMA Networks

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IEEE access 2017年 5卷 23550-23562页

作者： Zhai, Daosen Northwestern Polytech Univ Sch Elect & Informat Xian 710072 Shaanxi Peoples R China

sparse code multiple access (SCMA) has been proposed as a candidate air interface ( AI) technique for 5G wireless networks. However, the existing resource management schemes with predesigned SCMA codebooks cannot fully exploit user diversities in the frequency domain, thus degrading the performance of SCMA systems. To fully exploit the potential of SCMA, in this paper, we design a more flexible and configurable SCMA through adaptively adjusting the codebook design and assignment according to the user's features. Specifically, for the uplink networks, first we formulate a detection complexity minimization problem by jointly considering the codebook design (i.e., mapping matrix and constellation graph design) and codebook assignment, which is an integer linear program and NP-hard in general. To tackle this hard problem effectively, first we borrow the idea of dual coordinate search to devise a suboptimal but computational efficient algorithm to determine the mapping matrix and codebook assignment. Based on the obtained mapping matrix, we use the multi-dimensional modulation characteristic of SCMA to carefully design the constellations for each codebook to further reduce the detection complexity. For the downlink networks, we formulate a total power consumption minimization problem by jointly considering the codebook design and assignment and power allocation. Exploiting the special structure of the problem, we employ the Lagrangian dual decomposition technique to propose a fast iterative algorithm, which can solve the problem optimally with low complexity. Finally, we present extensive simulations to exhibit the performance improvement against other algorithms in terms of detection complexity and power consumption. The modified SCMA in this paper can be intelligently optimized based on service and user awareness, which can provide some guidelines for the design of software-defined AI in future wireless networks.

关键词： sparse code multiple access codebook design resource management green communications

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