Research On Multi-user Access Technology Based On Wireless Power Transfer

With the rapid deployment of 5G wireless communication systems and the Internet of Things,massive terminals flood into the network resulting in the increased complexity of communication network architecture and the rapid growth of data traffic.The larger and larger network scale brings more overheads of network deployment and terminals maintenance.Meanwhile,the energy demand is different from the past and the green and low-carbon concept promotes the development of the current network towards the direction of low cost and high energy utilization.Therefore,the data and energy integrated networks was born to solve the problems of the current network.In DEIN,the terminal is a battery-less device without battery and the energy is collected from space to drive the device to run.In order to ensure the reliability and stability of energy acquisition of terminals.The energy node or hybrid access point transmits radio frequency signals to the terminals for wireless power transfer as the main energy source of terminals.Reasonable and effective terminal access scheme based on the data and energy integration can improve the energy utilization efficiency from the angle of time,frequency and others,and further improve the performance of communication network.Therefore,in order to solve the problems of low energy utilization rate and throughput of the data and energy integrated networks,it is necessary to take full advantage of the new energy characteristics and apply the protocols and solutions of classical network into DEIN to realize the combination of the data and energy integrated networks and traditional networks.In this thesis,we design an multi-user access scheme based on wireless energy transfer and study the interference coordination technology between multiple HAP regions under the background of the data and energy integrated networks.Firstly,based on the WPT,a battery-less devices access framework of coordinated time-sharing access is proposed.The battery-less devices transmit data in the slot HAP allocated and collects energy from the RF signal HAP transmitted.In the case of no extra data overhead,the system allocates slots to battery-less devices in region in an alternate allocation way.In this thesis,a coordinated battery-less time-sharing access scheme is designed and a Markov model is constructed to analyze data distribution.In order to further improve system throughput and device access quantity,data tables which are the HAP and battery-less devices need to maintenance are designed to realize interaction between HAP and battery-less devices with a few of data overheads,and a coordinated battery-less time-sharing access scheme with energy state prediction is proposed.Part of idle time slots are released to battery-less devices which need to transmit data.Markov model and simulation are constructed to verify the scheme,and the results show that this algorithm can effectively improve system throughput and device access quantity.Then,in the initial access stage of battery-less devices,different devices are divided into different HAP regions according to the characteristics of battery-less devices.In this thesis,based on the K-AP clustering algorithm,WPT-K-AP region division algorithm for WPT system is designed,which is based on the energy harvest capability and LOS probability as the similarity measurement between battery-less device and HAP,to obtain multiple non-overlapping regions by taking HAP as region center.The battery-less device collects energy from RF signals of multiple HAP and communicates only with the HAP in the same region.Finally,considering the sporadic traffic characteristic of battery-less devices,the same frequency band is separately used for energy and data transmission in each region to improve spectrum utilization.The fractional frequency reuse framework of sparse code multiple access is used to coordinate the co-frequency interference between regions.The sparse codebook is obtained by SCMA with low density spread spectrum and high dimensional modulation.Based on FFR,the codebook is allocated to the center nodes and edge nodes in different regions with the help of coloring theory and the inter-region interference coordination algorithm is designed.The performance of region division algorithm and inter-region interference coordination algorithm is verified by simulation.