摘要(英) |
The conventional Sparse Code Multiple Access (SCMA) receiver employs codewords with complex dimensions to transmit user information and improve resource utilization. However, the complexity of the message propagation algorithm increases exponentially with the size of the codebook and the number of antennas, making hardware implementation a significant challenge. Therefore, based on expectation propagation algorithm (EPA), we propose group-approximate EPA (GA-EPA) for complexity reduction. The approximate calculations in the logarithmic domain by maximum value selection is used. This reduces approximately 30% of multiplications and about 60% of divisions. However, since 16-point codebook is adopted, a probability grouping method is proposed, where codewords are grouped to generate the associated probability. This approach not only achieves performance similar to using the top-four maximum values but also reduces the computation complexity. Finally, QR decomposition is employed to eliminate a half of transmitted information, and the computational load on variable nodes and resource nodes is also reduced by about 1/2. We then design the SCMA hardware detector for an uplink system having a total of 6 users, 4 resource elements, and 4 receive antennas, with a 16-point codebook for 4 recursive decoding passes. Besides the probability grouping and QR decomposition for complexity reduction and throughput enhancement, and we also utilize customized floating-point datapath to decrease hardware area by approximately 17% and take advantage of exponential operation to split a large table into two small tables. From synthesis results in 40nm CMOS technology, our design can generate soft decision and achieves a throughput of 363.64Mbps at a maximum operating frequency of 166.67MHz. Compared to conventional design supporting only 4-point codebook, our design has smaller gate count, 13x improvement in normalized throughput and better normalized hardware efficiency. |
參考文獻 |
[1] 林日揚, "基於收斂偵知期望值傳播演算法於稀疏碼多工接收器之設計與實作", 碩士論文, 國立中央大學, 民國109年6月。
[2] C. Yan, G. Kang and N. Zhang, "A Dimension Distance-Based SCMA Codebook Design," in IEEE Access, vol. 5, pp. 5471-5479, 2017, doi: 10.1109/ACCESS.2017.2685618.
[3] M. Taherzadeh, H. Nikopour, A. Bayesteh and H. Baligh, "SCMA Codebook Design," 2014 IEEE 80th Vehicular Technology Conference (VTC2014-Fall), Vancouver, BC, Canada, 2014, pp. 1-5, doi: 10.1109/VTCFall.2014.6966170.
[4] X. Meng, Y. Wu, Y. Chen and M. Cheng, "Low Complexity Receiver for Uplink SCMA System via Expectation Propagation," 2017 IEEE Wireless Communications and Networking Conference (WCNC), San Francisco, CA, USA, 2017, pp. 1-5, doi: 10.1109/WCNC.2017.7925590.
[5] J. Xiao, J. Hu and K. Han, "Low Complexity Expectation Propagation Detection for SCMA Using Approximate Computing," 2019 IEEE Global Communications Conference (GLOBECOM), Waikoloa, HI, USA, 2019, pp. 1-6, doi: 10.1109/GLOBECOM38437.2019.9013512.
[6] P. Wang, L. Liu, S. Zhou, G. Peng, S. Yin and S. Wei, "Near-Optimal MIMO-SCMA Uplink Detection With Low-Complexity Expectation Propagation," in IEEE Transactions on Wireless Communications, vol. 19, no. 2, pp. 1025-1037, Feb. 2020, doi: 10.1109/TWC.2019.2950314.
[7] J. -Y. Lin and P. -Y. Tsai, "Design of A Convergence-Aware Based Expectation Propagation Algorithm for Uplink Mimo Scma Systems," ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Barcelona, Spain, 2020, pp. 1698-1702, doi: 10.1109/ICASSP40776.2020.9053809.
[8] P. C. Bao, D. Van Xuan Huong, D. N. M. Dang, Q. L. Trung and L. D. Khai, "High Throughput and Low Complexity Implementation for Uplink Scheme of 5G Technology," 2019 26th International Conference on Telecommunications (ICT), 2019, pp. 304 308.
[9] A. Ghaffari, M. Léonardon, A. Cassagne, C. Leroux and Y. Savaria, "Toward High Performance Implementation of 5G SCMA Algorithms," in IEEE Access, vol. 7, pp. 10402 10414, 2019.
[10] X. Pang, W. Song, Y. Shen, X. You and C. Zhang, "Efficient Row-Layered Decoder for Sparse Code Multiple Access," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 68, no. 8, pp. 3495-3507, Aug. 2021, doi: 10.1109/TCSI.2021.3084634. |