Nonlinear optimization and experimental design of reconfigurable intelligent surface-assisted communication systems
[Objective]The reconfigurable intelligent surface(RIS)is a key technology for 6G(the sixth generation)because it can achieve a programmable propagation environment with high energy efficiency and low hardware cost.To change an electromagnetic wave propagation environment,improve signal transmission efficiency,and reduce power consumption,an intelligent,reflective surface switch selection and power allocation design method are investigated for a RIS-assisted communication system.[Methods]A multidimensional variable joint nonlinear optimization problem is established to maximize the energy efficiency of the system and ensure that the data rate at the receiving end reaches a certain threshold and other constraints.The optimization variables involved include intelligent,reflective surface switch selection parameters and power allocation.In switch selection,a greedy algorithm selects the components playing the main role and turns off the intelligent,reflective surface playing a secondary role.In power distribution,the closed-form solution of power distribution is obtained by solving the convex optimization problem.Finally,an iterative optimization algorithm with a high transmission rate and low power consumption is designed.Meanwhile,we designed simulation experiments and verified that the proposed joint optimization algorithm can effectively improve the signal transmission data rate and energy efficiency by changing the electromagnetic wave propagation environment using MATLAB.[Results]The simulation results show that 1)the proposed distributed RIS optimization algorithm is superior to the other two comparison algorithms.Compared with the method of selecting one optimal RIS,the optimized RIS selection algorithm improved energy efficiency by 111.00%,87.31%,70.96%,63.00%,62.58%,64.09%,and 63.97%.Moreover,the energy efficiency of the system increases and stabilizes with increasing transmission power.This behavior is observed because the data rate cannot keep up with the increase in transmission power.As the maximum transmit power increases,the rate also increases.Compared with a single centralized arrangement,a distributed scheme with multiple RIS deployments in the network can provide multiple receiving signal paths and increase the data rate.2)With increasing minimum speed requirement,the energy efficiency is initially stable and later decreases,and the proposed algorithm outperforms other algorithms.This result is observed because when the rate threshold is small,it does not affect the energy efficiency.The transmission power of the base station increases with the threshold value,so the energy efficiency decreases.In addition,the power consumption of the two distributed RIS deployments is much lower than the transmit power of the centralized RIS,therefore,the energy efficiency of the distributed RIS system is much higher than that of the centralized RIS scheme.3)As the distance between RIS and users increases,energy efficiency first decreases and then increases.The RIS position must be reasonably set to maximize energy efficiency.[Conclusions]To meet the demands of high-speed and high-coverage multimedia services for future communication systems,we discuss a modeling and experimental design method for a RIS-assisted communication system.Considering the performance optimization and experimental design of this system,this paper also analyzes the mechanism behind the algorithm performance variation in the experiment.The application of this method in teaching helps improve students'abilities in scientific research innovation and engineering practice.
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