Reconfigurable Intelligent Surfaces(RIS),as a promising new technology,may bring about a new paradigm shift in wireless communication to meet new challenges in mobile communication.At present,the passive RIS auxiliary system in mainstream research will produce double fading phenomenon during transmission.In order to obtain good results,passive RIS needs a large reflection area.Active RIS can effectively overcome such drawbacks and has the advantages of no complex radio frequency chain,but it has the defect of limited energy.Therefore,this paper combines active RIS and energy harvesting(EH)technology to explore system performance and optimize energy storage.First,this paper proposes an active RIS-assisted system supported by EH technology,in which each reflective element is assisted by an active load,which can reflect and amplify the incident signal,instead of only reflecting the signal with adjustable phase shift like passive RIS.In this paper,the EH technology is used to supply energy to the active RIS,and the performance of the system to assist wireless communication under the photovoltaic power generation technology and the simultaneous wireless information and power transfer(SWIPT)technology is analyzed.The outage probability in the system performance index is analyzed in detail and the closed expression is given.In addition,the delay interruption rate of RIS in realizing ultra-reliable low-latency transmission and the signalto-noise ratio(SNR)gain probability of RIS in direct link transmission are analyzed.The simulation results show that the relevant parameters of EH,including solar irradiance of photovoltaic power generation,ambient temperature and time parameters of SWIPT,conversion efficiency,etc.,will affect the efficiency of active RIS to reduce the interruption probability,increase the SNR gain,and reduce the link delay.Second,this paper applies active RIS to cognitive radio networks,and explores the energy storage problem of RIS nodes based on the underlying setup of the coexistence of primary and secondary networks.The secondary network uses an active RIS to assist communication between the secondary transmitter and receiver in the presence of primary jammers,where the SWIPT-assisted active RIS can harvest energy from the secondary transmitter and the primary jammer.In order to find out the maximum value of RIS storage energy,an optimization problem model is established,and the constraints are the quality-of-service(QoS)requirements of the primary and secondary network.At the same time,the maximum stored energy of the photovoltaic power generation technologyassisted active RIS is analyzed.In this paper,extensive mathematical analysis is carried out to address the theoretical modeling problem and further simulation results are provided to demonstrate the effectiveness of the proposed energy storage scheme. |