The Design Mechanism And Performance Optimization Of Multi-User Cluster-Based Cooperative Communication Based On Wireless Power Transfer With Radio Frequency

In recent years,with the development of high performance broadband communication system,energy-consumption problem of wireless communication equipment is becoming more and more prominent.The conventional method of manually replacing batteries/charging has many fundamental technical bottlenecks,such as high manpower cost,high cost and high communication outage rate,which is difficult to be widely used in large-scale wireless networks,especially in the future Internet of things system.The emerging radio frequency charging technology recently has provided a simple and efficient method of energy supply.By using radio frequency wireless charging devices,a large number of wireless devices can be supplied with non-invasive continuous power over a long distance.This innovative energy supply technology has also given birth to an important research direction in the field of communications,namely wireless powered communication network(WPCN).Although WPCN has got rid of the dilemma of limited battery power,it is also facing many technical challenges,such as the "doubly-near-far" problem,that is,the wireless energy harvested by the wireless devices far away from hybrid access point(HAP)in the downlink(DL)is less than that collected by the wireless devices(users)near the HAP.On the other hand,due to the nonrenewable and scarce spectrum resources,cognitive radio is introduced into the WPCN to share spectrum with traditional wireless communication network,where spectrum utilization is improved,however,it is inevitable that there will be interference with each other.Therefore,how to design the scheme of efficient wireless powered cooperative communication has become one of the hot topics of many scholars at home and abroad.This thesis focuses on the urgent needs of the modern wireless communication system,takes the WPCN as the research subject,and focuses on two research hot issues closely related to the WPCN.First,WPCN suffers from the problems of severe “doubly-near-far” user unfairness,and sum throughput-spectrum efficiency.Second,interference from WPCN coexisting with a primary network and throughput fairness of secondary network.This paper focuses on the shortcomings of current research.On the one hand,the results improve and promote the related research of WPCN,and on the other hand,provide theoretical reference and practical guidance for the practical application of multi-user cluster-based cooperative communication technology based on wireless power transmission with radio frequency in WPCN.The main research works and innovations of this thesis are as follows:1.A novel cluster-based cooperation protocol is proposed for improving the throughput performance in WPCN.The WPCN consists of one HAP equipped with multiple antennas and a series of distributed low-power single antenna wireless devices,where the HAP broadcasts DL wireless energy and receives wireless information transmission(WIT)from the wireless devices in the uplink(UL).To enhance the throughput performance of some far-away wireless devices,this thesis puts forward a multi-user cluster-based cooperation protocol,i.e.,one of the wireless devices is acted as the cluster head(CH)that helps relay the information transmitted by the other cluster members(CMs),which can effectively enhance the throughput performance of some far-away wireless devices.However,its performance is also limited by the high energy consumption of the CH.To tackle this energy imbalance issue,this thesis proposes to exploit the capability of multi-antenna energy beamforming(EB)technique at the HAP,which focuses more transferred power to the CH to balance the energy consumption of all the wireless devices.Meanwhile,this paper proposes to jointly optimize the EB design,the transmit time allocation among the HAP and the wireless devices,and the transmit power allocation of the CH to maximize the minimum data rate achievable among all the wireless devices for improved throughput fairness among the wireless devices,thus effectively solving the “doubly-near-far” problem.An efficient optimal algorithm is proposed to solve the joint optimization problem.Moreover,simulate under practical network setups and show that the proposed multi-antenna enabled cluster-based cooperation can effectively improve the throughput fairness of the WPCN.2.A secondary WPCN underlaid to a primary point-to-point communication link is proposed.The wireless devices in the WPCN use a multi-user cluster-based cooperation to transmit to the HAP.The primary communication link is active,and channel state information of the primary system is unknown by the WPCN.The multiantenna cluster-based cooperation protocol is applied to balance the dissimilar energy consumption of the wireless devices to further improve the throughput fairness of the WPCN,thus effectively solving the “doubly-near-far” problem.However,the use of EB and cluster-based cooperative communication may introduce more severe interference to the primary system than the wireless devices transmit independently.To tackle this problem,cognitive radio technology is introduced to the WPCN,i.e.,cognitive WPCN(CWPCN).To guarantee the performance of primary system,an interference temperature constraint(ITC)to the primary system is considered and the throughput performance of each wireless device under the peak ITC is derived.To achieve maximum throughput fairness,jointly optimize the energy beamforming design,the transmit time allocation among the HAP and the wireless devices,and the transmit power allocation of each wireless device to maximize the minimum data rate achievable among the wireless devices.The non-convex joint optimization problem can be transformed to a convex one and then be efficiently solved using off-the-shelf convex algorithms.Moreover,simulate under practical network setups and show that the proposed method can effectively improve the throughput fairness of the secondary WPCN,meanwhile guaranteeing the communication quality of the primary network.3.A secondary WPCN overlaid to a primary point-to-point communication link is proposed.The primary communication link is active,and channel state information of the primary system is known by the WPCN.The wireless devices in the WPCN adopts the multi-user cluster-based cooperation to transmit information to the HAP,while the HAP can cooperatively transmit primary transmitter(PT)'s information.In order to improve the DL energy transmission efficiency and the UL WIT spectral efficiency,EB technology is exploited at the HAP.However,as CWPCN becomes closer to the PT,the interference to the cluster head becomes greater.To tackle this issue,an effective primary rate constraint(PRC)thanks to the additional channel knowledge on the primary link is considered,where the achievable rate of the primary transmission is guaranteed to be no smaller than a predefined target,and derive the throughput performance of each wireless device under the PRC.Accordingly,jointly optimize the cooperative time between the HAP and the primary transmitter,the EB design,the transmit time allocation among the HAP and the wireless devices,and the transmit power allocation of each wireless device to maximize the minimum data rate achievable among the wireless devices.An efficient optimal algorithm is proposed to solve the joint optimization problem.Moreover,simulate under practical network setups and show that the proposed method can effectively improve the throughput fairness of the secondary WPCN under the PRC.