Energy Efficiency Of Full-Duplex Relay Channels

Nowadays,full-duplex(FD) transmission becomes a promising component of 5G communications.In FD systems,nodes are allowed to transmit and receive signals simultaneously at the same frequency band,which greatly improves the spectral efficiency(SE).In order to guarantee a good quality of service(QoS),as well as enhance the coverage of cellular systems,relaying techniques have been widely adopted in various wireless communications.On the other hand,with the depletion of energy resources and the emerge of green communication,energy efficiency(EE)has also attracted a lot of research interest.The limited battery capacity,short service life,and high cost of replacement become new challenges for wireless sensors and mobile phones,and thus how to maximize the system EE is significantly important in evaluating the corresponding system performance.In this thesis,we study the energy efficiency(EE)of a three-node Gaussian relay channel,which is composed of one source node,one destination node,and one relay node.The source transmits signals to the destination with the assistance of the relay,and the relay can operate in the silence,half-duplex(HD),or full-duplex(FD)relaying mode,depending on the channel conditions.Our main contributions are summarized as follows.First,the channel capacity for the FD and HD relay channels under the decode-andforward(DF)and amplify-and-forward(AF)schemes are investigated,respectively,and the energy consumption of the above two schemes are also analyzed.In particular,for the FD relaying mode,the residual self-interference(RSI)and the extra circuit power consumption introduced by the self-interference cancellation(SIC)at the relay are considered and modeled as linear functions over the relay transmission power.Then,considering the AF and DF schemes are adopted at the relay node,the EE maximization problems subject to the SE and transmission power constraints are studied.under the DF scheme,the EE maximization problems of the FD and HD relaying mode are both formulated as max-min problems,whose optimal power allocations and the corresponding maximized EE are derived by solving the corresponding max-min problems;under the AF scheme,the EE maximization problems of the FD and HD relaying mode are both formulated as fractional optimization problems,whose optimal power allocations and the corresponding maximized EE by adopting the fractional programming method.Furthermore,the EE for the direct transmission(DT)without relay,HD,and FD relaying modes with the DF and AF schemes are compared under different channel conditions.Finally,numerical results validate our analysis.The results of this thesis,which provides a clear guidance on power allocation,relaying mode switching,and relay selection,etc,can be used in various relay networks.