Energy Efficiency Analysis And Optimization In Cooperative Communication Systems

Due to the limitation of the wireless spectrum resources and the explosive growth of users demand for capacity, the aim of the traditional wireless network is high spectral efficiency(SE). However, the high SE of network is often obtained at the expense of energy consumption, which not only brings the high growth of energy consumption, but also a huge waste of energy resources. With the increasing awareness of resource conservation and environmental protection, how to obtain higher energy efficiency(EE) has become an important and difficult issue in the wireless communication field. Therefore, the EE in the cooperative communication system is studied in this paper.Firstly, the EEs of direct transmission, one-way relay transmission and two-way relay transmission under the decode-and-forward protocol are studied. Considering the impacts of the fading channel condition, the transmitted bit numbers, the relay position and the circuit power consumption on EE, the close form of EE in the Rayleigh fading channel is derived and then the EE is maximized by using the convex optimization algorithm. Finally, the analysis of theory is verified by simulation.Based on this study, combined with OFDM technology, the EE of OFDM bidirectional cooperative network is studied, and a resource allocation algorithm based on optimal EE is proposed. According to the EE model, the fractional programming of EE is firstly transformed into the subtrahend form of linear programming by using the parametric convex function method, and then the optimal power allocation is derived by using the Lagrange dual and the sub-gradient method, further the optimal subcarriers are obtained by combining with the channel matrix, after that the value of optimal power allocation and sub-carrier allocation are obtained by using Dinkelbach iterative algorithm. Lastly, the algorithm is verified by simulation.