Cooperative VLC User Access and Dynamic Power Adjustment in Indoor Cell-free VLC Network
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摘要: 针对室内自由小区VLC网络照明和吞吐量联合优化困难的问题,该文提出VLC协作用户接入和功率动态调整(VCUA-DPA)方法。在用户接入阶段,设计考虑网络的负载均衡、用户速率需求和协作小区数目限制的用户和VLC协作的用户接入算法;在功率分配阶段,设计联合优化照明均匀度和系统吞吐量的功率动态调整分配算法。仿真结果表明,所提VCUA-DPA在明显提升系统吞吐量的同时能优化室内照明均匀度。
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关键词:
- 室内自由小区 VLC网络 /
- 用户接入 /
- 功率分配 /
- 系统吞吐量 /
- 照明均匀度
Abstract: Focusing on the difficulty of jointly optimizing lighting and throughput in indoor cell-free Visible Light Communication (VLC) network, a method of VLC Cooperative User Access and Dynamic Power Adjustment (VCUA-DPA) is proposed. In the user access stage, by considering the network load balance, user rate demands and the limitation of the number of cooperative cells, a user access algorithm through user and VLC cooperating is designed in this paper. In the power allocation stage, a dynamic power adjustment algorithm is designed to optimize jointly illumination uniformity and system throughput. Simulation results show that the proposed VCUA-DPA can significantly improve the system throughput and optimize the indoor illumination uniformity. -
算法1 基于用户需求的VLC协作用户接入(VCUA) 算法 输入:NA, MU, B,用户的信道增益矩阵$ {\boldsymbol{H}} = {[{h_{i,j}}]_{M \times N}} $、初始发射功率$ {{\boldsymbol{P}}^{(0)}} $、用户满意度阈值$ {\rho _{{\text{th}}}} $; 输出:用户和AP接入矩阵$ {\boldsymbol{A}} = {[{a_{i,j}}]_{M \times N}} $; (1) 根据式(2),计算用户和候选AP的信道增益值,分别建立用户i关联AP的关联集合,各AP j关联用户的AP关联集合,i∈MU, j∈NA; (2) 所有用户i从候选AP集中选择信道增益值最大的AP,记为AP j*,令${a_{i,j^*} } = 1$,并删除AP j*的关联集合; (3) repeat (4) 选择剩余带宽最大的AP j*为本轮迭代的提供者,则AP j*的候选用户为本轮迭代的需求者; (5) 由式(9)和式(10),分别计算用户i的需求权重因子和AP j的供应权重因子,i∈MU, j∈NA; (6) 由式(11),计算各候选AP j的用户接入优先级,j∈NA; (7) 从用户的关联集合中,选择用户接入优先级最高的候选AP j,分别记为用户i*和AP j*,令${a_{i^*,j^*} } = 1$; (8) 计算AP j*的剩余带宽,计算用户i*的需求权重因子; (9) 若$B_{j^*}^R \le 0$,删除AP j*的关联集合; (10) 若${\rho _{i^*} } \le {\rho _{ {\text{th} } } }$,则删除用户i*的关联集合; (11) until 所有用户确定关联的协作VLC AP. 算法2 联合优化照明和吞吐量的动态功率调整 (DPA) 算法 输入:N,M,B,μmin,接收点的信道增益矩阵$ {{\boldsymbol{H}}_s} = {[{h_{s,j}}]_{S \times N}} $、AP j的服务用户集合Aj、AP j的干扰用户集合Qj、用户i的服务VLC
AP集合Ci、迭代次数t=1、最大迭代次数$ {T_{{\text{max}}}} $、最小和最大照明强度$ {E_{{\text{min}}}} $和$ {E_{{\text{max}}}} $、基准发射功率增量$ \Delta P $、基准发射功率增量最
小值$ \Delta {P_{\min }} $、发射功率增量的调整系数ε,0 < ε < 1;输出:联合优化照明和吞吐量的各AP发射功率$ {P^*} = [{P_1},{\text{ }}{P_2},{\text{ }} \cdots ,{\text{ }}{P_N}] $; (1) 根据式(15),执行Dinkelbach单纯形法[6]求解优化目标O3'的各VLC AP发射功率Pl; (2) for $ j = 1,2, \cdots ,N $ do (3) 由式(17)计算AP j的基准发射功率增加$ \Delta P $时吞吐量增益$G_j^{ {{\rm{in}}} }$,由式(18)计算AP j的基准发射功率减少$ \Delta P $时吞吐量增益$G_j^{{\rm{de}}}$; (4) 若$G_j^{ {{\rm{in}}} } > G_j^{{\rm{de}}}$,则AP的编号j加入Vin集合;否则,AP的编号j加入Vde集合; (5) end for (6) while $ t < {T_{{\text{max}}}} $ do (7) for $j \in {V_{ {\rm{in} } } }$ do (8) 由式(17)计算AP j的基准发射功率增加$ \Delta P$时的吞吐量增益$G_j^{ {{\rm{in}}} }$,若$G_j^{ {{\rm{in}}} } > 0$且$({P_{\max } } - P_j^l) \ge \Delta P$,进一步判断AP j的所有干扰用户
是否都能满足用户速率需求,若是,则AP j加入G集合;(9) end for (10) for $j \in {V_{{\rm{de}}} }$ do (11) 由式(18)计算AP j的基准发射功率减少$\Delta P $时的吞吐量增益$G_j^{ {{\rm{de}}} }$,若$G_j^{ {{\rm{de}}} } > 0$且$({P_{\max } } - P_j^l) \ge \Delta P$,进一步判断AP j的所有服务用户
是否都能满足用户速率需求,若是,则AP j加入G集合;(12) end for (13) 若G集合为空集,则转步骤(18);否则,转步骤(14); (14) 按照吞吐量增益值大小对G集合中的AP进行降序排序; (15) 记G集合中第一个AP为 j*,若AP j*为Vin集合中的AP,则转步骤(16);否则,转步骤(17); (16) 由式(5)和式(6)分别计算AP j*的基准发射功率为$P_{j^*}^l + \Delta P$时各接收点的Es和$\mu^*$,若${E_{\min } } \le {E_s} \le {E_{\max } },\forall s$且$\mu^* \ge {\mu _{\min } }$,则AP j*
的发射功率调整为$ P_j^l = P_j^l + \Delta P $,令t = t+1,转步骤(6);否则,从G集合中删除AP j*,转步骤(13);(17) 由式(5)和式(6)分别计算AP j*的基准发射功率为$ P_{j*}^l - \Delta P $时各接收点的Es和$\mu^*$,若${E_{\min } } \le {E_s} \le {E_{\max } },\forall s$且$\mu^* \ge {\mu _{\min } }$,则AP j*
的发射功率调整为$ P_j^l = P_j^l - \Delta P $,令t = t+1,转步骤(6);否则,从G集合中删除AP j*,转步骤(13);(18) 令$\Delta P$=$\varDelta$×ε,若$\varDelta$>$\Delta P_{\min} $,则转步骤(7);否则,转步骤(20); (19) end while (20) 令P*=Pl,输出联合优化照明和吞吐量的各AP发射功率P*。 表 1 仿真参数
参数 含义 数值 参数 含义 数值 h PD的高度 0.85 m $ {\mu _{\min }} $ 最小照明均匀度 0.7 $ {P_{{\text{min}}}} $ VLC AP的最小发射功率 3 W $ {E_{\min }} $ 最小照明强度 300 lx $ {P_{\max }} $ VLC AP的最大发射功率 10 W $ {E_{\max }} $ 最大照明强度 1500 lx B VLC系统带宽 40 MHz $ \Delta P $ 基准发射功率的增量 1.5 W $ {\phi _{1/2}} $ 发射机的半功率角 60° $ \Delta {P_{\min }} $ 基准发射功率增量最小值 0.3 W $ {\psi _c} $ 接收机视场角 60° $ \varepsilon $ 基准发射功率增量调整系数 0.8 $ {A_{{\text{PD}}}} $ PD的接收面积 1 cm2 $ {T_{\max }} $ 功率调整的最大迭代次数 20 $ \gamma $ 光电转换系数 0.53 A/W $ \delta $ LED发射光功率和光通量的转换系数 2.1 mW/lm -
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