Key Technologies Design For Relay-aided Simultaneous Wireless Information And Power Transfer

In research on beyond B5 G and 6G wireless communications techniques,how to use energy efficiently for improving the transmission performance has gained a lot of attentions recently.For providing energy to massive nodes of Internet of Things,simultaneous wireless information and power transfer(SWIPT)techniques have gained spotlight in point-to-point and point-to-multi-point networks.In the energy-constrained relay networks,SWIPT can be applied for powering the relay and the relay will forward the source signal using the energy harvested from the RF signal.Currently,there are two basic SWIPT receiver structures,i.e.,time-switching receiver and power-splitting receiver.Accordingly,there are two basic relaying protocols for SWIPT relaying networks,i.e.,time-switching relaying(TSR)and power-splitting relaying(PSR).In this thesis,research work is conducted on two key technologies for SWIPT relaying systems,including the in-block time-switching for dual-hop SWIPT relaying systems and SWIPT relaying for cooperative non-orthogonal multiple access(NOMA)systems.The main contributions of this thesis are summarized as follows:First,this thesis investigates an optimized relaying protocol for a dual-hop relaying system.Employing re-chargeable battery at the relay node,the relay node can realize accumulation and scheduling of the harvested energy.Then,this thesis proposes the inblock time-switching mode,which realizes the SWIPT relaying in each transmission block.For verifying the system performance of the proposed in-block time-switching mode,Monte Carlo simulations are conducted.The simulation results show that the proposed in-block switching mode significantly improves the outage performance and successful rate for the considered system.For a cooperative NOMA system with direct links,this thesis investigates the SWIPT employing both the direct and relay links and proposes a coordinated direct and relay transmission(CDRT)SWIPT scheme.In the CDRT-SWIPT scheme,the direct links from the source to both two users are utilized.Through rotation of the signals of the direct and relay links,an orthogonal structure is formulated the received signal at each user,so that each receiver can recover the desired signal by using a simple linear operation.Considering that the cooperative NOMA system works under independent but not identically distributed Nakagami-m fading channels,this thesis presents the analytical expressions for the outage probabilities of both two users.In addition,this thesis analyzes the diversity gain of the CDRT-SWIPT scheme.The analytical results show that the diversity gain is determined by the shape factor of Nakagami-m fading.The simulation results show that the proposed CDRT-SWIPT scheme achieves an enhanced outage performance over that of the SWIPT without employing the direct links.