Energy-efficient Relay Station Deployment Algorithms In Cellular Networks

The application of relay technology makes cellular network performance has been greatly improved, especially with the emergence of the heterogeneous network, how to design the energy-saving relay cellular network architecture has been widespread concern and research by scholars. This paper regards decode-and-forward relay technology as research object, and the goal of this paper is to optimize the system energy efficiency(EE) and investigate the tradeoff of spectral efficiency(SE) and energy efficiency by combining green cellular networks idea and deploying low power consumption and low cost relay station in the cellular network.This paper studies the problem of fixed relay station deployment and mobile relay station deployment. The main research results of this paper are summarized as follows:For the optimization problem of fixed relay stations deployment, this paper firstly proposes a uniform symmetric deployment system model. By optimizing the base station coverage parameters, the position parameters of the relay station and the number of the relay stations, maximizing the EE under the constraint of the SE. A metric defined as the ratio of average area throughput to average area power consumption is used to measure the average EE and its analytical expression is derived. The tradeoff between the average EE and the average SE is formulated as an optimization problem to which the closed-form solution is difficult to obtain. Therefore, through the analysis of the deployment parameters, the optimization function problem can be transformed into finding out the solution in the feasible region, the optimal numerical solution can be obtained through repeated one-dimensional exhaustive search method, as well as the optimal fixed relay station deployment strategy. Simulation results show that the number and position of relay station has a great impact on the system performance, and there exists an optimal number of relay stations for maximizing the average EE while satisfying the SE constraint under certain parameter settings.Because of the limited capacity of the base station and the fixed relay station, the user traffic has the characteristics of time and space, and the fixed relay station will be overloaded. Therefore, we study the problem of mobile relay station to unload small base station traffic. We first analyze the interference between relay stations and determine the minimum interference distance, and then put forward the mobile relay station deployment scheme, by optimizing the relay station location, maximizing the EE of every observation time under the constraints of SE and coverage. Through the analysis, it is found that the objective function optimization problem can be transformed into the optimal allocation problem, which the object is to minimize the total distance, and then the optimal solution is obtained by extending Hungarian algorithm. In addition, in order to highlight the superiority of the extended Hungarian algorithm, we also use a heuristic greedy deployment algorithm and a static deployment algorithm to compare. Finally, considering the user’s mobility, we also analyze the impact of the user’s mobile speed on the relay handover rate and relay service time. Simulation results demonstrate that the extended Hungarian deployment algorithm can considerably improve system EE compared to the other two algorithms. Moreover, relay switching occurs more frequently and average relay service time reduces with the increase of the speed of mobile users.The research results of this paper have practical reference value for the design of energy saving cellular relay network, and it also has significance reference value for the deployment of other sites in the heterogeneous network.