Research On Energy Efficient Power Control And Access Control In Heterogeneous Cellular Networks

With the rapid development of mobile Internet, the data service of mobile cellular networks is also explosively growing. To cope with the problems brought by limited spectrum resources and spurt growth of mobile data traffic, overlay heterogeneous networks(HetNet) has been proposed as a promising solution. This network architecture can effectively solve the coverage and capacity problem of today’s mobile cellular networks. The emerging of a variety of small base stations in HetNet is to provide a low-cost, scalable and profitable wireless mobile cellular network for operators. Small base stations, including micro, pico and femto base stations, refer to a class of base stations with small volume and light weight, low power transmitter. The femto base station(FBS), also known as home base station, used in the third generation mobile systems to meet the high traffic demand in indoor communication, has been widely studied by researchers.Currently, its application is not only limited to providing indoor coverage as hot spots, but also extended to provide access to corporate customers and improve throughput of urban networks. However, due to spectrum sharing between femto base stations and macro base stations, there are still many technical problems influencing stability and reliability of the network, such as interference, switching and maintenance problems. Femto base stations aredeployed randomly and are usually used for covering hotspots and blind spots. If femto base stations are deployed in large-scale, maintenance of sites and equipmentis challenging due to the random sites deployment. Thus, it is imperative to investigate interference coordination and power control problems in macro-femto networks.On the other hand, along with the growing business of mobile cellular communications, the cost of high energy consumption and high carbon dioxide emission also puts pressure on the development of mobile cellular systems. Nowadays, green communication has drawn intensive attention by academic community and industrial. Energy efficiency has become a benchmark for evaluating future green communications. In a typical cellular network, the energy consumption on base station side occupies 60%-80% of the total energy consumption of the entire network. Thus, it is important to improve energy efficiency of base stations.This thesis is dedicated to addressing energy efficiency optimization problems for HetNets. Considering the energy efficiency and the signal quality of users simultaneously, one way to improve system energy efficiency is to adjust the transmit power of the base station, the other is to adjust user’s access in the case of fixed total system power. Based on the above considerations, the main work and achievements of the thesis are as follows:1) According to the characteristics of the femto networks, we propose a distributed power control method based on the interaction of distributed gradient of power. The method can effectively track the variation of power efficiency with little information interaction, effectively increasing the energy efficiency of the system. Our proposed algorithm provides an effective solutionfor improving energy efficiency in HetNets by power control.2) We propose a distributed power control method based on non-cooperative game theory. Macro and femto base station selfishly solve their own optimal energy efficiency problems, by regarding the interference from other base stations as noise injection. Each base station uses an improved energy-efficient water filling algorithm to find the most favorable power allocation strategy. Each base station updates its own power configuration iteratively in order to achieve the balance of power game. Simulation results show that the algorithm not only improves system throughput but also improves the system energy efficiency.3) Based on package auction model, we propose a user access mechanism for macor-femto network. We use a forward multi-object auction with package bidding to determine the access point of macro users. The wireless service provider(WSP) sells packages of macro users to the femtocell owners which are preferred by macro users. Compared with the single object auction, multi-object auction is more favorable by WSP, because the multi-object auction can encourage more femto owners to participate in auction process, thus, the final auction price is more conducive for WSP.All in all, by using convex optimization theory, game theory and auction theory, we effectively build the system energy efficiency model and solve the optimization problem. Our researches provide some new ideas and new methods to the energy efficiency problem in macro-femto network...