Optimization And Design Of Communication Systems Based On Wireless Power Transfer

In recent years,the Internet of Things(Io T)has developed rapidly,and various types of low-power nodes have grown exponentially.However,these nodes are often powered by batteries,and the life of the entire network is limited by battery capacity.The emergence of wireless power transfer(WPT)technology has broken this bottleneck.WPT is a technology that uses radio frequency signals to wirelessly charge devices.Using this technology can continuously power low-power nodes and prevent nodes from failing due to energy-depleting equipment.Configuring WPT technology for the Io T can effectively extend the life cycle of the Io T and expand the scope of applications.In the process of integrating the Io T and WPT,the WPT system and the wireless communication system are essentially combined into one to form a communication system based on WPT.It is of great significance to optimize the design of a communication system based on WPT and maximize the role of WPT technology in enhancing the original communication system.This article is aimed at communication systems based on WPT,including simultaneous wireless information and power transfer(SWIPT),relay communication system based on SWIPT,and hybrid wireless powered communication networks(WPCN)to achieve the information boundary of rate-energy region.The goal is to improve system throughput and data processing rate,reduce data delay.Combining theories and methods such as optimization,optimal stopping and dynamic programming,and by means of model construction,parameter optimization,theoretical analysis,and simulation verification,the research on optimal design of communication system based on WPT is investigated.The contribution of the thesis mainly includes the following aspects:1)For a SWIPT system,considering the cost of channel measurement,the uncertaintyinterval of the probability density function is described under the limitation of limit-ed channel gain measurement samples,and the robust outage capacity is defined onthe uncertainty interval as a measure of information rate.Then,in the two commonworking modes of power splitting(PS)and time switching(TS),the PS ratio and TSratio are optimized respectively to achieve the outer boundary of the associated robustoutage capacity-energy region,the shape of the corresponding robust outage capac-ity-energy region are analyzed under PS mode and TS mode,and it is proved thatthe PS mode outperforms the TS mode.Finally,simulations verify the correctness ofthe analytical results and the validity of the designed schemes.2)For a relay communication system based on SWIPT,we first consider the non-linearity of the energy harvester at the relay node.In the TS mode and PS mode,the transmission power,the bandwidth of the communication link connecting eachrelay node,the PS ratio and TS ratio at each relay node are optimized to maximizethe end-to-end throughput.The original problem is non-convex,it is difficult to obtainthe optimal solution.By using convex optimization and bilevel optimization jointly,the original problem is transformed into a monotonic optimization problem to obtaina global optimal solution.Finally,the simulation verifies the validity of the designedscheme.3)For a relay communication system based on SWIPT,we next consider the case wherethe relay node is configured with a multi-antenna full-duplex digital transceiver.Sys-tem parameters under TS mode are optimized,in order to maximize the end-to-endthroughput.Although the problem studied is non-convex,the semi-definite relax-ation and successive convex approximation methods are proposed to solve the origi-nal problem,and it is proved that the designed solution can converge to a stationarypoint and reach a feasible solution at the same time.Finally,the simulation verifiesthe validity of the designed scheme.4)For a hybrid WPCN,the first design goal is to maximize the data processing rate.Inthe fading channel with multiple fading blocks,facing the uncertainty of the channelgain of multiple fading blocks in the future,based on the defined statistics,a one-steplook-ahead criterion for stopping energy harvesting is proposed,and the optimalityof the proposed method is proved.With a series of special properties proved,theboundedness of the optimal number of fading blocks for data offloading is derived.Finally,simulations verify the correctness of the analysis results and the validity ofthe designed scheme.5)For a hybrid WPCN,the second design goal is to minimize the delay measure duringthe multi-node information return process.By introducing a new delay metric called”information age”,the wireless energy harvesting time and the access bandwidth ofeach node are optimized.In order to solve the proposed problem,a combinationof bilevel optimization and convex optimization is used,and the interval convexity ofthe problem equivalent to the original problem is found to obtain the optimal solution.Finally,simulations verify the correctness of the analysis results and the validity of the designed scheme.