Research On Simultaneous Wireless Information And Power Transfer Theory And Method In Edge Radio Access Networks

To cope with the explosive increase of the mobile data services,edge radio access networks have been proposed.The core idea is to make use of the communication and caching abilities at the edge devices,such as the wireless relays and the user equipments(UEs),to improve the network capacity and reduce transmission delay.A key challenge for the edge radio access networks is to reduce the power consumptions at the edge devices,while utilizing them in information forwarding or processing,and improve the network performances.As a result,introducing the simultaneous wireless information and power trans-fer(SWIPT)techniques into the edge radio access networks has become an appealing approach,which compensates the power consumption at the edge devices while improves the wireless information transmission rate.However,the corresponding theoretical and technical solutions are still missing,and need to be researched urgently.Focusing on the wireless relay and the device-to-device communication scenarios in the edge radio access networks,this dissertation constructs the corresponding theoretical analysis models for the SWIPT,deduces the theoretical performances,proposes advanced algorithms and provides the corresponding optimized performances.The main contributions of this dissertation can be summarized as follows:1.Multiple antenna selection based SWITP method for the wireless relaysWith the cost of the increased energy consumptions at the wireless relays,the network capacity of the edge radio access networks can be enhanced.To this end,the base station transmits information and power simultaneously via the SWIPT techniques,and the wireless relays forward the received information using the received power.The traditional SWIPT techniques divide the received signals at the wireless relays into two parts for information and power receiving separately through one of the time domain,the power domain and the space domain.To further improve the transmission efficiency,the joint splitting through both the power domain and the space domain is considered in this dissertation,and a "joint power splitting and antenna selection strategy" is pro-posed.Moreover,the wireless information transmission rate of the proposed strategy is deduced and optimized.However,the binary variables introduced by the multiple antenna selection make the feasible region of the optimization problem non-convex.To solve this intractable problem,a "layered optimization algorithm with the greedy searching" is proposed.Simulation results show that the wireless information transmission rate of the proposed SWIPT strategy out-performs the traditional ones.Moreover,different from the traditional relays,the wireless relays in the edge radio access networks with the SWIPT should be located closer to the base station.2.Dynamic power management based SWITP method for the wireless relaysThe traditional SWIPT strategies for the wireless relays adopt a "harvest-and-use"operation,which uses up the received power at each time slot.To realize a more effective usage of the received power,a "joint power splitting and dynamic power management strategy" is proposed in this dissertation,wherein a part of the received power can be stored for future usages via the dynamic power management operation.To improve the wireless information transmission rate,the dynamic characteristics of the power receiving and power consumption should be matched.As a result,the SWIPT designs at different time slots are coupled together,which makes it difficult to analyze the performances of the proposed strategy.To handle this problem,a "layered optimization algorithm with the backward induction" is proposed,which obtains the theoretical optimal solution with the non-causal channel state information(CSI).Then,the proposed strategy and the optimization algorithm are extended to the cases with the causal CSI and the statistical information of the CSI.Simulation results reveal that,the proposed SWIPT strategy achieves a better information transmission rate than the traditional ones with the "harvest-and-use" operation,but its performances are determined by the acquisition of the CSI.In particular,when only causal CSI is available,the performances of the proposed strategy is equivalent to the traditional ones;when the statistical information of the CSI is available,the proposed strategy outperforms the traditional ones;and when the non-causal CSI is available,the theoretical optimal solution can be reached.3.SWIPT method for the device-to-device communicationsWith the cost of the increased energy consumptions at the UEs,the network capacity of the edge radio access networks can be enhanced.To this end,the remote radio heads in the cloud radio access networks can transmit information and power simultaneously via the SWIPT techniques,and the UEs partici-pate in device-to-device(D2D)communications using the received power.The traditional SWIPT strategies adopt a "best effort" operation,and encourage the UEs to participate in D2D communications as much as possible,which results in a heavy burden on the power consumption,and impairs the tradeoff between the wireless information transfer and the wireless power transfer.To handle this problem,a "joint data-energy beamforming and traffic offloading strategy" is designed and optimized in this dissertation,wherein only a part of the UEs are selected for the D2D communications.However,the binary variables introduced by the offloading decision and the constraints on the data-energy beamforming make the optimization problem non-convex,thus a "layered optimization algorithm with the ellipsoid method" is proposed to solve this intractable problem.Furthermore,a "separated data-energy beamforming based algorithm"is proposed to lower the computational complexity.Simulation results reveal that the proposed SWIPT strategy outperforms the traditional ones with the "best effort" operation in the wireless information transmission rate.Moreover,compared with the traditional cases,more UEs can be encouraged to participate in D2D communications with the SWIPT,because the power constrains at the UEs can be alleviated.