Research On Device-to-device And Full Duplex Technologies For 5G

With the large-scale commercialization of fourth generation(4G)communication networks,key technologies research and standardized specifications of fifth generation(5G)communication networks targeting the various use scenarios in 2020 and beyond has put on the agenda.Spectrum efficiency and energy efficiency are still two important performance metrics for 5G communication systems.Device-to-Device(D2D)can reuse cellular network resources and take advantage of the users' near geographical locations to enhance the system spectrum efficiency.Besides,full-duplex technology allows full-duplex base station to receive and transmit signals simultaneously in the same time and same frequency band,which improves the system spectrum efficiency nearly 2-fold.What is more,the radio frequency(RF)energy harvesting makes low-power networks operate self-organizingly,which greatly enhance the system energy efficiency.Therefore,this thesis focuses on D2D communications and RF energy harvest based full-duplex communications.the main contents include:Firstly,we review the development of mobile communication networks from the first generation(1G)to the fifth generation(5G).Characteristics of 4G and the outlook of 5G are highly introduced.Then,we focus on the key technologies of 5G mobile communications,including the D2D technology,cooperative communication technology,full duplex technology and energy harvesting technology.Secondly,a power allocation scheme in the virtual multiple-input-multiple-output(MIMO)D2D communication networks is proposed to minimize the outage performance,satisfying the total power constraint on D2D terminals.Firstly,the channels response of the links between D2D transmitting thermals and D2D receiving thermals are modeled to be Rayleigh flat fading.Then,we derive the outage probability of virtual MIMO D2D communication networks.Furthermore,the optimal power allocation scheme is derived by using the first-order Taylor series approximation.Finally,numerical results show that the proposed power allocation scheme achieves a satisfying outage performance compared with the average power allocation scheme.Thirdly,for the RF energy harvest based full-duplex scenario,a novel communication protocol,which combines downlink simultaneous wireless information and power transfer(SWIPT)and uplink wireless information transfer(WIT)is designed.In addition,we also consider the downlink physical layer security issues,via adding artificial noise(AN)at the base station to prevent malicious users from eavesdropping data.Based on these above,an optimal time slot and power allocation algorithm is proposed to maximize the uplink sum rate under the minimum downlink rate requirements and the maximum downlink eavesdropping SNR.At last,our analysis is confirmed by simulation results.Finally,a summary of the full text is made and future research directions are discussed.