| With the rapid development of the mobile communication networks,mobile data flow and intelligent terminal equipment show a blowout growth trend,which leads to the rising energy consumption cost of wireless communication system and aggravates the deterioration of ecological environment.Therefore,the green communication technology has become an important research direction for the future communication system.As an important index to measure the energy consumption performance of the wireless communication system,energy efficiency is widely concerned.In the 5th Generation Mobile System(5G),the design concept of environmental friendly communication system with high capacity and low energy consumption has been constantly emphasized.Non-Orthogonal Multiple Access(NOMA)technology is a new type of multiple access scheme that makes full use of multiple resource dimensions,and it has become one of the most important candidate technologies in 5G.Through joint superposition coding technology at the transmitter and successive interference cancellation technology at the receiver,NOMA can enable multiple users to reuse the same resource block,thereby significantly improving the system capacity and spectrum efficiency.With the increase of terminal density and the development of digital signal processing,the circuit power approaches or even exceeds the transmission power,and it increases with transmission rate.Obviously,it is unreasonable to ignore the circuit power,which files to meet the actual requirements of the short-distance transmission scenario.Moreover,it is imperfect to optimize the energy efficiency in a single resource dimension(such as the power resource),and it is more efficient to improve the system EE by considering not only power resource allocation but also channel resource allocation.Therefore,this paper mainly studies the energy-efficient transmission scheme in the NOMA system under the rate-dependent circuit power model.The main contributions of this paper are as follows:1.For the multi-user downlink NOMA system,considering the most general rate-dependent circuit power consumption model,based on GPE(Goodbit-Per-Energy)and TBPUE(Transmitted Bits Per Unit Energy)metrics respectively,we propose the energy-efficient transmission strategy while satisfying the total transmission power at the base station and transmission rate requirements of users.Firstly,considering the rate-dependent circuit power model in a convex function form,the optimization problem that maximizes the energy efficiency is formulated.Then,according to the nonlinear fractional programming theory,Dinkelbach's algorithm and convex optimization method,the optimal transmission power allocation algorithm is obtained.At last,the closed-form solution of the optimal power allocation is provided under the linear function circuit power model.2.For the multi-carrier downlink NOMA system,considering the most general rate-dependent circuit power consumption model,based on GPE energy efficiency metric,we propose the energy-efficient resource allocation strategy while satisfying the total transmission power at the base station and transmission rate requirements of users.Firstly,a low-complexity subchannel allocation scheme based on the greedy algorithm is proposed.Then,the optional subchannel power allocation algorithm and the power allocation strategy between multiplexed users are proposed.At last,the closed-form solution of the optional power allocation coefficients among subchannel multiplexed users are provided.The simulation results verify the energy-efficient resource allocation scheme in this paper,and study the influence of factors such as total power constraints,communication distance and spectrum efficiency,which is significant for the practical communication system design.In addition,compared with the traditional power allocation schemes in the NOMA system(such as fixed power allocation scheme,fractional power allocation scheme,etc.),the proposed scheme can achieve higher energy efficiency performance. |
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