| The wireless sensor network refers to a freely distributed and dedicated sensor network capable of information interaction through wireless communication technology,in which sensor nodes can sense environmental information,process data and transmit data wirelessly.The wireless sensor network is the mapping interface for the physical to the digital world,as well as an important foundation to promote the third wave of global informatization.With the advancement of ultra-high-speed,low-latency,high-reliability 5G(fifth-generation)communication and the proposal of the concept of high real-time,fidelity,and interactive DT(digital twins),the infrastructure conditions for wireless sensor networks are becoming perfect.Perception scenes and objects are constantly expanding,even covering the entire physical world.The tiny and lightweight sensors promote the development of wireless sensor networks,but the drawbacks of the limited energy are also increasingly prominent.How to extend the lifetime,realize continuous energy supply,and reduce maintenance cost under the condition of limited size and weight has become the key problem in this field.In order to break through the bottleneck,electric energy conversion and storage schemes based on environmental energy such as solar,thermal,mechanical and chemical energy have attracted widespread attention.However,their hardware cost is high,and it is difficult to meet the multi-scenario requirements of the wireless sensor network.In contrast,WPT(wireless power transfer)technology is regarded as the most effective solution to prolong the lifetime of wireless sensor network because of its low cost,high stability,and ultra-controllability.On the one hand,the WPT uses RF(radio frequency)signals as the carrier,its technical principle,hardware equipment are similar and compatible with wireless data communication,which makes it possible to realize energy and information transmission simultaneously.On the other hand,RF signals are stable,continuous and controllable.By adjusting parameters such as RF signal transmission power,waveform,duty cycle,etc.,the power transfer process can be controlled efficiently and reliably.Therefore,how to design a reasonable transmission strategy to optimize the performance is the focus of research in this field.In wireless sensor networks,the effectiveness of sensing information usually decreases sharply over time.Most of the current research is limited to the throughput performance of the network and ignores the timeliness of the information.In addition,with the large-scale and dense deployment of Io T devices,there must be overlapping among multiple networks,which brings additional energy sources to wirelessly powered sensors and also leads to serious internetwork interference.In response to the above problems,this paper first introduces the concepts of age of information and information freshness to measure the timeliness of information,and proposes a method of minimizing age of information based on random access probability in a single network scenario.Under the condition of the known channel model,the method can realize high-freshness data transmission in a long transmission period with a small amount of calculation.Secondly,according to the characteristics of multi-network scenarios,a dense multi-network system architecture and transmission strategy based on energy recovery are designed to maximize the throughput.In this system,the sensor uses the RF energy that escapes when the HAP(hybrid access point)communicates with the remote MAP(master access point)for energy harvesting,avoiding the use of dedicated power transfer signals.The MAP performs functions such as data fusion,calculation and control with the information aggregated by HAPs.This protocol combines the advantages of WPCN(wireless powered communication network)and SWIPT(simultaneous wireless information and power transfer),and is more suitable for multiple networks with low-power devices.The main contributions of this paper can be summarized as follows:1.Aiming at the problem of information timeliness of wireless sensor network,a singlenetwork multi-sensor access model based on age of information is designed,and combined with wireless energy transmission technology,the resource allocation of three basic tasks of downlink energy,control command and uplink data transmission is realized,a long-term mean age of information minimization algorithm is proposed2.For the multi-network coexistence scenario,the problem of extra energy and internetwork interference,which is rarely studied at present,is considered.A time-division based transmission protocol is designed to enable the HAP to power the sensor while communicating with the remote MAP,improving energy efficiency and timeliness.A multi-variable joint optimization method for system-rated energy consumption,time switching factor,transmit power,energy allocation weight,and receive beamforming is proposed to improve network throughput performance.3.Aiming at the above transmission strategies,go through theoretical derivation and combine with Rayleigh quotient,Frobenius norm,convex optimization and alternate iteration methods,the optimal solution expression is given.The stability and effectiveness of the system models and protocols are proved.The above research contents provide new ideas and methods for improving the lifetime of wireless sensor networks and decreasing the age of information.At the same time,the performance optimization strategies for the coexistence scenarios of multiple wireless powered sensor networks in the future are explored.The innovative content is the expansion based on the existing research foundation and the exploration of future scenarios,which lays the foundation for subsequent research. |
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