Research On SWIPT-Based Cooperative Spectrum Sharing System And Energy-Aware Retransmission Scheme

With the rapid development of the Internet,mobile devices connected to the wireless network have grown exponentially.In order to cope with the explosive growth of data traffic and meet the needs of various emerging business scenarios in the Internet of Everything,the realization of high-speed,low-latency and low energy-consumption network interconnection and data transmission has become the key to the research of new generation mobile communication technology.Since the scarcity of wireless spectrum resources and the limited battery capacity of mobile devices,cognitive cooperative spectrum sharing and simultaneous wireless information and power transfer are recognized as the key technologies for effectively alleviating the bottleneck of spectrum and energy resources and building efficient Internet of Things.In the SWIPT-based cooperative spectrum sharing system considered in this paper,the unauthorized secondary user serves as a cognitive relay to assist the authorized primary transmission while harvesting energy,and shares the spectrum to send its own signal in return.In most existing studies,no matter how much energy collected by the relay is used for information transmission in the next time slot instantly.However,the energy harvested by the relay is severely limited due to the extremely low efficiency of wireless power transfer in practice,which causes the mismatch between the information to be delivered and the available energy,thus resulting in a high outage probability and unnecessary energy waste.In order to solve this problem,this paper studies an energy-aware retransmission scheme based on decode-and-forward relaying protocol firstly,where the primary transmitter retransmits the signal within the given threshold for the number of retransmissions,and the relay performs dynamic power splitting to ensure successful information decoding while collecting a certain amount of energy for subsequent signal transmission.Then considering the possible performance gain brought by the direct link,this paper further studies an energy-aware retransmission scheme based on amplify-and-forward relaying protocol with the existing direct link.To ensure a certain outage performance at the destination,an energy threshold and a threshold for the number of retransmissions are set for the system.The primary transmitter continuously retransmits the signal until the energy harvested by the relay reaches the energy threshold or the number of retransmissions reaches the retransmission threshold.Finally,the important performances of the system such as outage,throughput and energy efficiency are obtained by theoretical analysis.The simulation results show that with appropriate and matched retransmission threshold and energy threshold given according to the system parameters,compared with the traditional baseline scheme,the energy-aware retransmission scheme can obtain additional performance gains under unfavorable conditions of high rate,low power and weak channels.In this paper,simultaneous wireless information and power transfer is applied in the cooperative spectrum sharing communication system to effectively prolong the lifetime of energy-constrained network nodes.Meanwhile,different energy-aware retransmission schemes are proposed under different system models and relaying protocols to perfectly adapt the energy flow to the information flow,thus improving the spectrum utilization and energy efficiency of the system.