Research On Key Techniques Of Indoor Simultaneous Wireless Information And Power Transfer Based On Asynchronous Focusing Time Reversal

With the incoming of the 5G era,intelligent manufacturing and smart home based on the Internet of Things have gained rapid development.As the key components of smart factories and smart homes,wireless sensors play a very important role in the intelligence realization and the guarantee of secure,stable,and reliable operation of smart factories and smart homes.However,the difference from other applications is that the wireless sensors oriented for intelligent factories and smart homes not only are massive but also have a small volume.Generally,it is quite difficult to deploy a battery of high capacity and large size for these wireless sensors.Therefore,it raises a challenging technical difficulty in power supply to ensure the continuous,long-term,and uninterrupted operation of wireless sensors for applications in smart factories and smart homes.At the same time,smart factories and smart homes are very complicated in structure and various blocking effects exist inside the rooms,which makes the propagation environment of electromagnetic waves quite complex.It is another challenging difficulty to ensure the secure,stable,and reliable data interaction and wireless propagation of the wireless sensor data.Facing to the above difficulties,the time reversal simultaneous wireless information and power transfer(TR-SWIPT)technology provides a new approach to the large capacity of wireless communications and long-term power supply of indoor wireless sensors.TR-SWIPT is based on the time reversal theory,which is capable of not only making full use of the multipath effects,focusing efficiently the energy of multipath components,making remarkable signal-to-noise ratio improvement of the receiver and the capacity of wireless communication system,but also capable of wirelessly transferring the power with high efficiency.However,when multiple focal spots are used for simultaneous wireless information and power transfer(SWIPT),the interference between these focal spots due to the sidelobes from the adjacent focal spots will be harmful to the performance of the communication and the accurate allocation of the power.In order to solve the interference between these focal spots,this thesis proposes an asynchronous focusing time reversal simultaneous wireless information and power transfer technology(AFTRSWIPT).The underlying mechanism of the proposed method is that multiple focal spots focus their energy at different times so that the accumulated value of their sidelobes have less effect on their main lobes after the optimized design of the focusing time,eventually improving the whole performance of the SWIPT.The following includes the main contents and novel contributions of this thesis.Firstly,based on the asynchronous focusing mechanism of multiple focal spots,an AFTR-SWIPT technique with multiple parallelly-transmitted focusing spots is proposed,which employs a part of focusing spots to transmit the information and some ones to transmit the power wirelessly.The information and the power are simultaneously transmitted so that the wireless communication link can gather a long-term and noninterrupted power supply with enough energy.In order to achieve optimal power efficiency,an AFTR-SWIPT method is developed with the optimal power transfer efficiency under the requirement of a certain communication capacity.The conditions and scenarios for possible applications for the AFTR-SWIPT with multiple parallellytransmitted focusing spots are assessed.Secondly,a method of improving communication capacity based on AFTR-SWIPT is proposed.The channel capacity of AFTR communication in the case of strong multipath is analyzed.A scheme of information transfer by using the focusing field is proposed.By using the diffraction limit characteristic of TR,it is verified that the asynchronous focusing wireless communication by TR can greatly improve the spectrum utilization efficiency,thus increasing the channel capacity of the wireless communication system.Then,a method to improve the power transfer efficiency in AFTR-SWIPT is proposed.The power transfer efficiency under different energy users in AFTR-SWIPT is measured and compared.The phase of the received signal is optimized by genetic algorithm,and the wireless power transfer simulation model of AFTR-SWIPT is established.This model incorporates the receive phase as well as the spatial channel response.The validity of the model is verified by a variety of simulation comparisons.The model can be used to evaluate the performance of asynchronous focused timereversal wireless power transfer systems.In order to explore the influence of different receiving phases on the wireless power transfer efficiency of AFTR,a vector network analyzer was used to measure the channel,and the efficiency changes before and after receiving phase optimization were compared.Finally,in view of the high cost and complexity of TR at the radio frequency,an AFTR-SWIPT at baseband based on software defined radio is proposed.The AFTRSWIPT system is verified through the software defined radio platform,and the AFTRSWIPT based on the software defined radio platform is realized via the baseband signal processing.Through video transmission and powering the selected light emitting diodes at a certain distance,the feasibility of AFTR-SWIPT at baseband is proved.It makes AFTR-SWIPT quite promising to emerge into 5G,Wi Fi and 6G in the future.