Research On Energy Scheduling And Rate Optimization For Energy Harvesting Relay Systems

Relay technology is one of the important technologies in wireless communication systems.Relay transmission improves signal transmission quality,extends transmission distance,and expands coverage.Relay transmission is also the core technology for network connectivity in Ad-hoc networks.The location of the relay node has a large impact on the transmission performance and may need to be set where it cannot be powered by the conventional grid.The use of energy harvesting technology by relay nodes to harvest energy from the environment is an effective means of solving their power supply problems.This thesis studies energy scheduling and rate optimization for energy harvesting relay systems.The main contents are as follows:1.The antenna grouping and signal forwarding strategies of the relay node in simultaneous wireless information and power transfer relay systems are studied.The source node and the destination node equipped with a single antenna communicate through forwarding of the relay node equipped with multiple antennas.The relay harvests energy from the received RF signal by means of antenna selection to complete signal forwarding.The first hop is the simultaneous transmission of information and power.The antennas of the relay node are divided into two groups,and the signals received by the antennas in one group are subjected to maximum ratio combining processing;the signals received by the antennas in the other group are converted into energy.The relay adopts an amplifying and forwarding protocol,and in the second hop,the relay node uses all antennas to amplify and forward the combined signal,with adopting a maximum ratio transmission precoding method.In order to maximize the system transmission rate,the relay antenna grouping is optimized and a low complexity antenna grouping algorithm is proposed.2.The online power control strategy of a two-hop decoding and forwarding relay system powered by energy harvested from the environment is studied.The relay node harvests energy from the environment and is equipped with a rechargeable battery and data buffer with finite capacity to store the harvested energy and buffer the data received from the source node.Under the condition of only the current energy harvesting and channel state information,an online energy scheduling and power control algorithm is proposed to minimize the average transmission energy of the source node and maximize the average relay forwarding rate based on Lyapunov optimization framework.The Lyapunov optimization framework is used to transform the stochastic optimization problem into two performance optimization sub-problems which are solved under queue stability.The algorithm has lower computational complexity.The simulation results show that the proposed algorithm has a small difference in transmission rate and lower power consumption compared with the offline water filling algorithm.Compared with the greedy algorithm and the semi-greedy algorithm,the proposed algorithm has better transmission rate and power consumption.