Research On Power Allocation Algorithms In Energy Harvesting Wireless Communication Systems

With the development of wireless communication technology,environmental protection and energy consumption issues have attracted widespread attention.The technology of green development and energy saving has become the mainstream technology of wireless communication development.Energy harvesting is a method of resource regeneration in wireless communication,which can realize the efficient use of renewable resources.In a scenario that the system has energy-harvesting transmitters,energy harvesters can harvest energy from the natural environment(such as wind energy,solar energy,tidal energy,etc.).Since the amount of harvested energy is limited and has large randomness,it is important to decide how to allocate the energy to transmit data.In this thesis,the power allocation policies of the energy harvesting wireless communication network are studied.The power allocation problems of the point-to-point communication system with energy consumption and the relay communication system with energy cooperation are discussed,and the corresponding algorithms are proposed.The main contents of this thesis are as follows:(1)An optimal off-line power allocation algorithm with three-threshold structure is proposed in point-to-point communication networks with two energy losses.In the three-threshold algorithm,two thresholds can be achieved by using a linear search method while the third threshold is calculated according to the channel state information and energy losses;then,the offline power allocation is based on the three thresholds and energy arrivals.Furthermore,inspired by the optimal offline algorithm,a low-complexity online algorithm with adaptive thresholds is derived.Finally,the simulation results show that the offline power allocation algorithms proposed in this paper are better than other algorithms,the performance of the online algorithm proposed is close to the offline one,and these algorithms can help improve the average throughput of the system.(2)An off-line optimal power allocation algorithm for wireless relay systems with bidirectional energy cooperation in off-line scenario is proposed.The system model was firstly established and convex optimization knowledge was used to obtain the optimal solution expression assumption.Ideal power allocation scheme was firstly proposed when assuming that there is no consumption in energy transfer process.Based on the scheme,the transmit power and the energy transferred were optimized again under the causality constraints on both energy and data.The simulation results show that the power allocation algorithm proposed in this paper is superior to other power allocation algorithms and can effectively improve the system throughput.(3)Several online power allocation algorithms are proposed for wireless relay systems with bidirectional energy cooperation in online scenario.In this system,the power allocation in online scenarios is mainly studied.Firstly,the optimal online allocation strategy is proposed by using dynamic programming method.Then,a sub-optimal algorithm is proposed in which Lagrange parameters are first calculatesd offline and then online power allocation is proposed.Furthermore,a simple online algorithm called non-storage strategy is described.Finally,several online algorithms and the offline algorithm in Chapter 4 are simulated and compared.The simulation results show that the performance of proposed online power allocation algorithm is close to that of the offline algorithm.