Transmission Scheme Design For Optimizing Latency And Energy Consumption In Heterogeneous Wireless Networks

The rapid development of mobile communication technology leads to the rapid growth of communication demand,which brings higher requirements on data rate and time delay of communication.Meanwhile,the rapid increase of energy consumption of communication equipment also brings the urgent need of green communication.In order to support the growing prosperity of mobile communication applications and realize the sustainable development of wireless communication systems,the design of effective transmission schemes with low latency and low energy consumption has become a hot research issue in the industry and academia.From the perspective of low latency and low energy consumption,aiming at common Network scenarios in wireless communication,this dissertation studies the low latency cooperative transmission scheme design for Cloud Radio Access Network(CRAN)with full duplex relay and low energy consumption transmission scheme design for Backscatter Communication assisted Device-to-Device communications(D2D),respectively.The main contents and innovation points are as follows:(1)To reduce the latency of downlink CRAN content distribution,a cooperative transmission scheme based on full duplex amplification and forwarding relay is proposed.By deploying full duplex capability at the RRH(Remote Radio Head)node and making it work in amplification and forwarding mode,transmission latency and information processing latency can be reduced.The objective of minimizing the maximum transmission delay was achieved by jointly optimizing the transmitting and receiving beamforming vectors of each node.A mathematical model was established for the problem,and a two-step optimization algorithm was proposed to solve the problem.Firstly,the orthogonal space of self-interference and RRH interference is obtained by singular value decomposition and forced zero beam assignment,and the receiving beam assignment vector of RRH is designed as a linear combination of vectors in the orthogonal space,so as to eliminate the self-interference and RRH interference.Then,an alternating iterative optimization algorithm based on continuous convex approximation is proposed to optimize the sending and receiving beam shaping vectors alternately.Finally,the effectiveness of the proposed scheme and algorithm is verified by simulation experiments.Experimental results show that the cooperative transmission scheme based on full duplex amplification and forwarding can effectively reduce the transmission latency of downlink CRAN.(2)To realize the low energy communication in D2 D network,a two-stage D2 D transmission scheme combining backscatter communication and wireless energy carrying communication is proposed.Firstly,the D2 D transmitter modulates the desired information and backscattering it to the receiver on the radio frequency signals emitted by the base station.At the same time,the transmitter also needs to absorb energy from the radio frequency signals for storage.Secondly,D2 D transmitters can use the stored energy for active RF communication to further improve communication throughput.A mathematical problem is established to jointly optimize D2 D power allocation,backscattering coefficient,time allocation coefficient and energy allocation coefficient to maximize system throughput.In order to solve this problem,a centralized resource management scheme and a distributed resource management scheme with low interaction are proposed respectively.First of all,the centralized resource management scheme mainly divides the optimization variables based on the block gradient descent algorithm,and turns them into convex optimization problems,and then alternately iterates optimization.Secondly,the distributed resource management scheme is mainly based on the alternating direction multiplier algorithm to divide the original optimization problem into several sub-problems for distributed solution.Simulation results show that the proposed two-stage transmission scheme can enable D2 D users to realize communication with almost no energy consumption,and its throughput is higher than that of the existing research schemes.