Improved joint subcarrier and power allocation to enhance the throughputs and user fairness in indoor OFDM-NOMA VLC systems.
Improved joint subcarrier and power allocation to enhance the throughputs and user fairness in indoor OFDM-NOMA VLC systems.
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DOI：
10.1364/oe.440735
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发表时间：
2021-08
期刊：
影响因子：
3.8
通讯作者：
Geyang Wang;Yingjie Shao;Lian-Kuan Chen;Jian Zhao
中科院分区：
文献类型：
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作者：
Geyang Wang;Yingjie Shao;Lian-Kuan Chen;Jian Zhao
正交频分复用非正交多址接入（OFDM-NOMA）是室内可见光通信（VLC）系统中一种很有前途的多用户接入方案。在本文中，我们提出了三个新的联合子载波和功率分配算法在OFDM-NOMA-VLC，以提高吞吐量和/或用户公平性。这三种算法分别满足公平吞吐量平衡（FTB）、公平优先（FF）和吞吐量优先（TF）场景的要求。这些算法改进了以往联合分配算法中的目标函数，从用户的整体吞吐量而不是每个子载波上的吞吐量来保证用户的公平性。使用所提出的算法的设计也表现出降低的峰均功率比（PAPR），因此，当系统受到信号峰值功率的限制时，可以更好地使用平均信号功率来进一步提高吞吐量。仿真结果表明，该算法上级传统的子载波功率联合分配算法以及传统的固定功率分配（FPA）和增益比功率分配（GRPA）算法。所提出的算法的性能改善尤其是更大的每个子载波的复用用户的数量或OFDM子载波的数量较大，在此情况下，使用传统算法的设计的PAPR较高。当总用户数、每子载波复用用户数和子载波数分别为5、2和16时，三种算法的吞吐量分别比传统联合分配算法提高了62.17%、53.35%和67.25%，而用户公平性分别提高了4.64%、7.87%和7.87%。降解率为20.71%。因此，所提出的三种算法可以分别满足FTB、FF和TF场景的要求。
Orthogonal frequency division multiplexing non-orthogonal multiple access (OFDM-NOMA) is a promising multi-user access scheme in indoor visible light communication (VLC) systems. In this paper, we propose three novel joint subcarrier and power allocation algorithms in OFDM-NOMA-VLC to improve the throughputs and/or user fairness. These three proposed algorithms address the requirements in fairness-throughput-balanced (FTB), fairness-first (FF), and throughput-first (TF) scenarios, respectively. All of them improve the objective function in the previous joint allocation algorithm and ensure the fairness of users in terms of their overall throughput, rather than that in every subcarrier that is tight and redundant. The designs using the proposed algorithms also exhibit reduced peak-to-average power ratios (PAPRs) and so the average signal power can be better used to further enhance the throughput when the system is limited by the signal peak power. Simulations verify that the proposed algorithms are superior to the previous joint subcarrier and power allocation algorithm as well as the conventional fixed power allocation (FPA) and gain ratio power allocation (GRPA) algorithms. The performance improvement of the proposed algorithms is particularly greater for a larger number of multiplexed users per subcarrier or a larger number of OFDM subcarriers, under which the PAPRs of designs using conventional algorithms are higher. When the total user number, the number of the multiplexed users per subcarrier, and the number of subcarriers are 5, 2, and 16, respectively, the throughputs of the three proposed algorithms are 62.17%, 53.35%, and 67.25% higher than the conventional joint allocation algorithm, while the user fairness is improved by 4.64%, 7.87%, and degraded by 20.71%, respectively. Therefore, the three proposed algorithms can address the requirements in FTB, FF, and TF scenarios, respectively.