论文标题
联合基站和IRS部署以增强网络覆盖范围：一种基于图的建模和优化方法
Joint Base Station and IRS Deployment for Enhancing Network Coverage: A Graph-Based Modeling and Optimization Approach
论文作者
论文摘要
智能反射表面（IRS）可以密集地部署在复杂的环境中，以通过可调的IRS反射在多个基站（BS）和用户之间创建层叠的视线（LOS）路径，从而显着提高了无线网络的覆盖范围。为了实现这一目标，至关重要的是优化无线网络中BS和IRS的部署位置，这在本文中进行了研究。具体而言，我们将网络的覆盖面积分为多个非重叠的单元，并决定是否在每个单元格中部署BS/IRS，给出了可用的BSS/IRSS总数。我们表明，为了确保网络覆盖/通信性能，即每个单元具有至少一个BS的直接/级联LOS路径，以及此类LOS路径的平均IRS反射次数低于给定阈值，因此部署成本或所需BSS/IRS的数量是一个基本的权衡。为了最佳地表征这一权衡，我们根据图理论制定了联合BS和IRS部署问题，但是由于涉及组合优化，很难最佳地解决。为了避免这一难度，我们首先考虑给定BS部署的简化问题，并通过应用分支机构和结合方法，并分别从候选地点删除IRSS，并提出最佳和有效的次优IRS部署解决方案。接下来，提出了一种有效的顺序更新算法来解决联合BS和IRS部署问题。提供了数值结果，以显示联合BS和IRS部署的拟议设计方法和优化算法的功效。网络覆盖范围性能与成本比率不同的部署BSS/IRS的数量之间的权衡也揭晓。
Intelligent reflecting surface (IRS) can be densely deployed in complex environment to create cascaded line-of-sight (LoS) paths between multiple base stations (BSs) and users via tunable IRS reflections, thereby significantly enhancing the coverage performance of wireless networks. To achieve this goal, it is vital to optimize the deployed locations of BSs and IRSs in the wireless network, which is investigated in this paper. Specifically, we divide the coverage area of the network into multiple non-overlapping cells and decide whether to deploy a BS/IRS in each cell given a total number of BSs/IRSs available. We show that to ensure the network coverage/communication performance, i.e., each cell has a direct/cascaded LoS path with at least one BS, as well as such LoS paths have the average number of IRS reflections less than a given threshold, there is a fundamental trade-off with the deployment cost or the number of BSs/IRSs needed. To optimally characterize this trade-off, we formulate a joint BS and IRS deployment problem based on graph theory, which, however, is difficult to be optimally solved due to the combinatorial optimization involved. To circumvent this difficulty, we first consider a simplified problem with given BS deployment and propose the optimal as well as an efficient suboptimal IRS deployment solution to it, by applying the branch-and-bound method and iteratively removing IRSs from the candidate locations, respectively. Next, an efficient sequential update algorithm is proposed for solving the joint BS and IRS deployment problem. Numerical results are provided to show the efficacy of the proposed design approach and optimization algorithms for the joint BS and IRS deployment. The trade-off between the network coverage performance and the number of deployed BSs/IRSs with different cost ratios is also unveiled.
