基于公平性最大化的可见光多用户预编码器设计  

Fairness-Maximizing Precoder Design for Multi-User Visible-Light Communication Systems

作　　者：李飞[1] 高向川[1] Li Fei;Gao Xiangchuan(School of Electrical and Information Engineering,Zhengzhou University,Zhengzhou 450001,Henan,China)

机构地区：[1]郑州大学电气与信息工程学院,河南郑州450001

出　　处：《光学学报》2024年第22期79-88,共10页Acta Optica Sinica

基　　金：国家自然科学基金(61640003);河南省重点研发专项(231111212400);河南省科技攻关项目(232102211067);河南省可见光通信重点实验室开放课题(HKLVLC2023-B06)。

摘　　要：近年来,可见光通信因其高速率、低成本等优势被认为是未来6G的关键技术之一。在可见光多用户MIMO(Multiple input multiple output)下行系统中,光信道的高相关性会导致传统块对角预编码算法存在子信道增益差异大的问题,严重影响系统误码率性能。基于此,提出了一种基于公平性最大化的预编码算法。该方案在发送光信号非负和总功率约束下,以最大化最小用户子信道增益为目标,并将该非凸难问题分解为用户内信道均衡和用户间功率分配两个独立子问题进行求解。在子问题一中,首先对预编码矩阵使用参数化表示,推导了其最佳结构,对非凸约束进行分支定界,把子问题转化为混合整数约束凸规划问题,对全局最优解进行了有效求解。在子问题二中,进一步给出了最佳的用户功率分配闭式解,实现了最小子信道增益最大化。实验结果表明,所提方案的误码率性能相较基准方案,获得了2 dB~12 dB增益。Objective Visible light communication(VLC)leverages the visible light spectrum to offer significantly greater bandwidth than radio frequency(RF)communication,addressing RF spectrum congestion and meeting the demands of the Internet of Things(IoT)and future 6G technologies.Typically,multiple light-emitting diodes(LEDs)are installed to meet lighting requirements.By employing multiple input multiple output(MIMO)technology,high data rates and reliability are achieved without additional time and spectrum resources.However,the use of MIMO technology causes overlapping optical signals,resulting in severe multi-user interference(MUI).Transmitter precoding techniques,such as block diagonal(BD)precoding,have been extensively studied as key methods to mitigate MUI.However,due to the high correlation in optical channels,BD precoding suffers from significant disparities in subchannel gains,leading to poor overall bit error rate(BER)performance.Addressing this subchannel gain disparity and mitigating MUI is essential for achieving high-speed,reliable communication.Methods To address these challenges,we propose an improved multi-user precoding scheme based on fairness maximization in BD precoding.Building upon the BD precoding’s ability to eliminate MUI and considering VLC’s unique characteristics,we formulate an optimization problem aimed at maximizing the minimum subchannel gain under the constraints of non-negative transmitted optical signals and total transmission power.Due to the non-convex nature of the problem,solving it directly is difficult.To overcome this,we decompose the problem into two independent subproblems:intra-user channel equalization and inter-user power allocation.In the first subproblem,we parameterize the precoding matrix and derive its optimal structure.Then,we use a branch-and-bound algorithm to manage the non-convex constraints,transforming the problem into a mixed-integer constrained convex programming problem.This approach effectively solves the optimal precoding matrix parameters,ensuring that

关 键 词：可见光通信 多用户 预编码 混合整数凸规划 系统误码率 

分 类 号：TN929.1[电子电信—通信与信息系统]