[论文解读] Energy-Efficient Resource Allocation for Aggregated RF/VLC Systems

Sylvester Aboagye, Telex M. N. Ngatched+2 more|arXiv (Cornell University)|Jun 3, 2022

Optical Wireless Communication Technologies被引用 6

一句话总结

本文提出了一种用于聚合射频/可见光通信（RF/VLC）系统的联合节能资源分配框架，通过匹配理论与多目标优化方法，联合优化接入点（AP）分配、子信道分配（SA）和功率分配（PA）。与混合系统相比，该方案在能量效率、和速率及中断性能方面均取得显著增益，尤其在遮挡和干扰条件下表现更优。

ABSTRACT

Visible light communication (VLC) is envisioned as a core component of future wireless communication networks due to, among others, the huge unlicensed bandwidth it offers and the fact that it does not cause any interference to existing radio frequency (RF) communication systems. Most research on RF and VLC coexistence has focused on hybrid designs where data transmission to any user could originate from either an RF or a VLC access point (AP). However, hybrid RF/VLC systems fail to exploit the distinct transmission characteristics of RF and VLC systems to fully reap the benefits they can offer. Aggregated RF/VLC systems, in which any user can be served simultaneously by both RF and VLC APs, have recently emerged as a more promising and robust design for the coexistence of RF and VLC systems. To this end, this paper, for the first time, investigates AP assignment, subchannel allocation (SA), and transmit power allocation (PA) to optimize the energy efficiency (EE) of aggregated RF/VLC systems while considering the effects of interference and VLC line-of-sight link blockages. A novel and challenging EE optimization problem is formulated for which an efficient joint solution based on alternating optimization is developed. More particularly, an energy-efficient AP assignment algorithm based on matching theory is proposed. Then, a low-complexity SA scheme that allocates subchannels to users based on their channel conditions is developed. Finally, an effective PA algorithm is presented by utilizing the quadratic transform approach and a multi-objective optimization framework. Extensive simulation results reveal that: 1) the proposed joint AP assignment, SA, and PA solution obtains significant EE, sum-rate, and outage performance gains with low complexity, and 2) the aggregated RF/VLC system provides considerable performance improvement compared to hybrid RF/VLC systems.

研究动机与目标

• 为解决聚合RF/VLC系统中联合优化的不足，特别是针对干扰与遮挡条件下的能量效率（EE）问题。
• 为异构RF/VLC网络中的AP分配、子信道分配与功率分配，设计一种可扩展且低复杂度的解决方案。
• 利用RF（全覆盖）与VLC（高带宽、低干扰）的互补优势，提升系统性能。
• 评估电路功耗、服务质量（QoS）需求及LoS遮挡概率等关键系统参数对能量效率与中断性能的影响。

提出的方法

• 提出一种基于新型匹配理论的算法，实现节能的AP分配，综合考虑用户信道条件与AP异构性。
• 基于已分配AP的信道增益，设计一种低复杂度的子信道分配方案，以平衡公平性与频谱效率。
• 在多目标优化框架内，提出一种基于二次变换的功率分配算法，以平衡能量效率与速率需求。
• 将原始的混合整数非线性规划问题分解为三个子问题（AP分配、SA、PA），并通过交替优化求解。
• 通过交替优化迭代优化联合解，确保收敛性与低计算复杂度。
• 仿真模型引入了真实参数，包括LoS遮挡概率、电路功耗与QoS约束。

Figure 1 : Network model of a three–tier heterogeneous network.

实验结果

研究问题

• RQ1 在存在干扰与LoS遮挡的条件下，如何最大化聚合RF/VLC系统中的能量效率？
• RQ2 在能量效率、和速率与中断性能方面，聚合系统相比混合RF/VLC系统有何性能增益？
• RQ3 电路功耗与LoS可用性如何影响系统能量效率？
• RQ4 能否在异构RF/VLC网络中实现低复杂度的AP分配、子信道分配与功率分配联合优化？

主要发现

• 所提出的联合解决方案在能量效率、和速率与中断性能方面显著优于基准方案，在所有LoS概率场景下均实现最佳能量效率表现。
• 由于具备双链路分集增益与更高的可靠性，聚合系统在低LoS条件下显著优于混合系统。
• 即使在电路功耗增加的情况下，所提方案仍能保持较高的能量效率，但随着电路功耗上升，能量效率仍会下降，凸显低功耗硬件的重要性。
• 中断性能在聚合系统中显著提升，用户可同时通过RF与VLC链路通信，即使在信道条件较差时也能满足QoS要求。
• 基于匹配的AP分配算法能有效将用户分配至最优AP，避免因视场角（FoV）与遮挡效应导致的次优关联。
• 基于二次变换的PA算法可实现高效的功率分配，有效平衡能量效率与速率需求，优于忽略QoS约束的方案。

Figure 2 : Block diagram of data transmission in an aggregated RF/VLC system.