Research On Wireless Resource Allocation Algorithm Of Visible Light Communication System

Visible light communication has recently received extensive attention from academia because of its advantagers such as not requiring spectrum planning,good confidentiality,no electromagnetic pollution and so on.This paper focuses on the wireless resource allocation algorithm of the visible light communication indoor coverage system,and studies the mobile user's access LED selection scheme,time slot and power allocation scheme,and NOMA downlink power allocation scheme.The specific contents are as follows:(1)For the VLC indoor coverage scenario where the number of LEDs is greater than the number of users,under the condition that a user can select multiple LEDs as access points,the corresponding optimization problem of user access point selection is constructed based on the VLC system minimum rate maximization criterion.First,the optimization problem is converted into an optimization problem with a SINR threshold as large as possible equivalently.To solve the optimization problem,three algorithms are proposed,and three LED access point selection schemes are obtained according to the results of the algorithm;the ideas of the three algorithms are as follows respectively : 1)The user selects the optional LEDs with the largest channel gain in order according to a fixed sequence;2)The user selects the optional LEDs with the largest SINR according to the order of SINR from small to large;3)Increase the minimum SINR of the system gradually based on the second algorithm.Simulation shows that the performance of the third algorithm is better than that of the second algorithm which is better than that of the first algorithm.(2)For multi-LED and multi-user scenarios,under the condition that all LED lights are fully reused and users allocate channel resources through TDMA,based on the principle that the total power transmitted by all LEDs is minimum,the optimization problem of time slots and power allocation is constructed.First,it proves that the optimal time slot allocation must be proportional to the rate requirement through the counter-proof method,and then turns the optimization problem into a pure power allocation problem,and proposes two power allocation algorithms.The idea of the first algorithm is to always find a feasible point along the direction of the total power reduction.The idea of the second algorithm is to transform the constraints into linear constraints through Taylor expansion,and then use linear programming to solve them.Simulation shows that the performance of the first algorithm is better.(3)First,the QoS constraints are converted into power linear constraints,and the following conclusions are proved: the QoS constraints are convex constraints,and the expression of the solution when the constraint takes the equal sign is obtained;when the power value is greater than this expression,the QoS constraints must be satisfied.The algorithm of the first optimization problem is given according to the following steps: 1)Convert the problem to an optimization problem with the maximum user rate threshold.The user rate threshold is equivalent to a QoS constraint,that is,a linear constraint;2)Separate power variables and use the dichotomy method to find the maximum rate threshold;3)Substitute the obtained rate threshold into the expression of the final solution to obtain the numerical solution of the user power.The algorithm of the second optimization problem is given in the following steps: 1)After the QoS constraints are transformed into linear constraints,the problem is converted into a joint optimization problem of three variables.Both of them have the same optimal solution.2)Iterative algorithm is used to solve the problem and the numerical solution of the problem is obtained.The simulation verifies the system performance.