Research On Power Control And Adaptive Modulation Technology Of Wireless Communication Systems With Energy Harvesting

With the development of communication technology and the expansion of communication network,the energy consumption of communication system and network has gradually become the focus of academic and industrial circles.Harvesting the energy in the environment for communication equipment is one of the effective ways to reduce the traditional energy consumption.Due to the random fluctuation of harvested energy and the random change of wireless channel fading,the power control and transmission rate adaptation in energy harvesting wireless communication system are important problems that affect the transmission performance of the system.In this paper,the transmission power control and rate adaptation online strategy aiming at maximizing the long-term average transmission rate of energy harvesting wireless communication system are studied.Considering the actual transmission performance,the transmission power,modulation and coding rate are optimized.Compared with the optimization algorithm aiming at maximizing the channel capacity,the proposed algorithm can obtain higher actual transmission rate.The proposed algorithm in this paper has higher practicability.The main contents are as follows:1.Aiming at the point-to-point energy harvesting wireless communication system with energy harvesting device at the source node,the joint optimization of transmission power and modulation mode is carried out to maximize the actual achievable transmission rate.Due to the random characteristics of energy arrival and channel fading,it is a stochastic optimization problem.Firstly,a long-term time optimization problem with energy consumption and battery operation constraints is constructed.Then,the optimization problem is transformed into a joint optimization problem of transmission power,modulation mode and data frame length with the goal of minimizing the "drift plus penalty" of energy virtual queue per slot by using Lyapunov optimization framework.The optimization problem is solved by combining analytical and numerical methods.The simulation results show that the proposed algorithm can achieve higher actual achievable transmission rate than the comparison algorithm aiming at optimizing channel capacity.2.For the energy harvesting wireless communication system using rateless error correction coding,the transmission power,modulation mode and code length are jointly optimized to maximize the actual achievable transmission rate.Firstly,the relationship between the decoding error probability of Raptor code and the received signal-to-noise ratio(SNR)and the length of code word is deduced by mutual information analysis.Then,the joint optimization problem of transmission power,modulation mode and codeword length is constructed with the objective of maximizing the long-term average achievable transmission rate under the constraints of available energy.Further,the optimization problem is transformed into a single slot optimization problem with the minimization of "drift plus penalty" by using the Lyapunov optimization framework.Finally,a low complexity solution method is given.The simulation results show that the use of rateless error correction coding can significantly improve the actual achievable transmission rate of the system,narrow the gap with the channel capacity,and is superior to the optimization algorithm aiming at maximizing the channel capacity.