Research On Energy Saving Schemes Optimization With Quality Of Service Provisioning In Heterogeneous Network

With the development of mobile communications technologies and the mobile Internet, the mobile traffic has been experiencing explosive growth.The heterogeneous network (HetNet), which is composed of macrocell base stations (MBSs) and low-power smallcell base stations (SBSs),becomes one of the effective approaches for the operator to deal with the large mobile traffic challenge. However, with the number of the BSs in the networks becoming ever-increasing, the huge energy consumption of the overall wireless network becomes an inevitable problem. On the other side,due to the slow advance of the energy storage technologies, the limited battery duration becomes one of the main concerns affecting users' quality of the experience. In general, energy saving in wireless communication systems would not only reduce the operation expense of the operator, but also improve users' quality of the experience, and contribute to the sustainable development of economy as well. As the radio resources allocation has an impact on the energy consumption of the wireless communications system, the optimization of radio resources allocation schemes becomes one of the most important energy-saving technologies,and has caused much concern in the wireless communication community.The radio resource allocation would make an impact on the networks'performance and networks' capability of guaranteeing the quality of the service (QoS). Besides, all kinds of the network performance metrics always have a tradeoff relationship. Taking into considerations the tradeoff relationship between energy saving and QoS provisioning, this dissertation investigates the energy-saving radio resources allocation problem in the HetNet scenarios. Specifically, considering the deficiencies of the existing energy-saving radio resources allocation schemes in the aspects of spectral efficiency optimization, the QoS provisioning, and the fairness guarantee,this dissertation proposes novel power and subchannel allocation algorithms, which can not only reduce the energy consumption of the networks, but also provide effective guarantee for spectral efficiency, dalay,and the fairness among individual users. The main contributions of this dissertation can be summaried as follows.1) The joint optimization of the energy efficiency and spectral efficiency in green wireless communications networksIn order to deal with the tradeoff relationship between the energy efficiency and spectral efficiency in the wireless communication networks,we design a radio resources allocation scheme, which can make a joint optimization of the two conflicting metrics. Firstly, we propose a novel energy efficiency and spectral efficiency tradeoff utility function, which can characterize these two metrics in a unified manner. Based on the novel utility function, we propose a radio resources allocation problem that aims to optimize the energy efficiency and spectral efficiency jointly. The problem is a mixed integer non-convex optimization problem, which is difficult to be solved. In order to reduce the computation complexity, we seperate the original optimizataion problem into a subchannel allocation sub-probelm and a power allocation sub-problem, and design a subchannel allocation algorithm and a power allocation algorithm, respectively. The subchannel allocation algorithm and a power allocation algorithm would be implemented in an iterative manner and converge to the fixed point. The simulation results demonstrate that the proposed algorithm has a fast convergence speed. Besiedes, the proposed algorithm could make the tradeoff between the energy efficiency and spectral efficiency flexibly, and has a great advantage in optimizing the energy efficiency and spectral efficiency simultaneously.2) The delay provisioning in energy-saving radio resource allocation schemesWith new kinds of wireless services and applications rushing out, the delay provisioning plays an ever-increasing important role for QoS guarantee in wireless communication networks. However, the existing radio resources allocation mechanisms are not suitable for the delay provisioning in HetNet scenarios. By introducing the effective capcacity,we devise novel energy-saving radio resources allocation schemes, which can provide statistical delay guarantee in HetNet scenarios. Specifically,based on differences in the density of the smallcells and the inter-tier spectrum assignment, we formulate and solve the energy-saving raido resources allocation problem corresponding to two specific HetNet scenarios, respectively.Firstly, we focus on the dense HetNet scenario, where the smallcell and macrocell occupy different frequency spectrums. Because of co-tier interference, the performance of the neighbouring smallcells have coupled relationship. Hence, we introduce the supermodule game model, and formulate an energy-efficient power control game and propose a corresponding distributed power control algorithm. Secondly, we focus on the sparse co-channel HetNet scenario. Specifically, we formulate a minimization problem of the overall downlink transmit power in smallcells,and propose a heuristic subchannel allocation algorithm and an optimal power allocation algorithm, respectively. The simulation results verify the energy saving performance of the proposed algorithms, as well as the flexibility to guarantee the delay of the services.3) The energy-efficent radio resources allocation scheme with proportional-fair energy efficiency guaranteeThe exisiting energy-efficient radio resources allocation algrothms lacks of the capablitlity to guarantee the fairness in terms of energy efficiency. In this regard, we design an energy-efficient radio resources allocation algorithm, which can provide the energy efficiency based proportional fairness guarantee among individual users. Firstly, we formulate the proportional fair energy efficiency optimization problem.Then, based on the transformation and simplification, we transform the orignial optimization problem into a weighted sum maximization problem of individual's energy efficiency. We design a heuristic subchannel allocoation algorithm and an efficient optimal power allocation algorithm,respectively. The simulation results demonstrate that, the proposed algorithms can not only improve the energy efficiency performance of users',but also have a great advantage in guaranteeng users' fairness in terms of energy efficiency.