| In a traditional wireless network with single-layer single-type base station,the base stations cover the service area with hexagons.With the continuous evolution of wireless networks,base station types,user equipment types and service requirements are rapidly growing.Irregular and multilayer heterogeneous dense wireless networking mode replaces the traditional wireless network.It has three problems.(1)The service range of base stations are uncertainty,and the dense deployment of small cell base stations are needed to reasonable manage based on the number of user equipment.The match between the user equipment and the network is also needed to study.(2)There are multiple accessible wireless networks or cell base stations around each user equipment.So the strategy which is gradually changing to the service-centric connection mode is needed to determine the final connection for the user equipment.(3)The service requirements of the user equipment are diverse and complex.The different requirements such as rate and time delay bring challenges to the resource allocation of the wireless network.After the user equipment connects to the base stations,how to allocate resources to meet the requirements of multiple and complex services for one user equipment is one of the research contents of this thesis.In the multilayer heterogeneous dense wireless networks,aiming at the above problems and challenges,at first,this thesis studies and analyzes the probability of user equipment connecting with base stations.The relationship between the coverages of base stations is discussed in terms of probability which are derived by the user equipment number.Cell zooming and sleeping management is performed according to user equipment conditions of base station.This process will result in cell reselection and traffic offloading.And then,in a multilayer heterogeneous dense base stations deployment scenario,there are multiple accessible candidate base stations when a user equipment wants to connect to a cell.The object of determining the user equipment best-matching base station is to improve system energy efficiency.This optimization process is limited by the user's service QoS.At last,after selecting the best-matching base station,a resource allocation strategy that satisfies multiple service requirements is studied according to the different awareness for the service time delays.The time delay tolerance is used as a one-dimensional wireless resource and assigned to different services.The main research results are as follows:(1)Adaptive cell zooming and sleeping technology for user and network matching.In heterogeneous dense wireless networks,the service coverage of macro cell base stations and small cell base stations is an irregular mode.The object is to optimize cell unit area power consumption during cell zooming and sleeping process.At first,the cell zooming factor is defined to indicate the degree of cell zooming.The deployment of base stations and user equipment adopts the distribution mode of the random poisson point process.The connection probability of user equipment accessing an arbitrary base station is derived.According to the random poisson point process theory,the average number of user equipment connecting with an arbitrary base station is obtained.Then,game theory is used as a mathematical tool to construct a target utility function to maximize the unit area energy efficiency.The Nash equilibrium is the relationship between the cell zooming factors of different base stations.The coverage of base station is adjusted by adjusting the cell zooming factor.The user equipment will connect with the best base station and adaptive cell zooming are optimized.The sleeping process of the small cell base station is further applied to turn off the small cell with light traffic to save the hardware and circuit power consumption.Each small cell base station has a sleeping opportunity.The number of user equipment served by the small cell base station decides whether the small cell needs to sleep.Sleeping thr-eshold of the small cell is set first,then the sleeping probability of the small cell is derived.Energy gains are obtained after sleeping.Since the user equipment will be offloaded to the macro cell base station after the small cell sleeping.The capacity of the macro cell base station limits the upper threshold of the small cell sleeping,which also limits the sleeping probability of the small cell.Simulation results show that reasonable cell zooming process saves 41%of the transmission power,while cell sleeping process can save more total power depending on different sleeping thresholds.(2)Active green offloading technology for user and network matching.It proposes a method for matching the service-centric connection with a base station in a multilayer heterogeneous dense wireless network.Heterogeneous dense wireless network is a two-layer heterogeneous network consisting of macro cell base stations and small cell base stations.There are three possible access network modes for user equipment,includ.ing connection with a macro cell base station,connection with a small cell base station,and multiple small cell base station cooperation provides services for user equipment.Under the premise that the user equipment connects with base station to meet the rate requirement,the final decision on which connection method the user equipment will choose is based on the system energy efficiency is improved during the connection process.The user equipment first randomly accesses the nearest base station.The user equipment may access the small cell base station or the macro cell base station.The multiple candidate base stations serve as bidders to satisfy the rate requirement as a constraint condition.The auction theory determines whether to offload and optimally offloading base stations.Considering user equipment that is offloaded to the edge of the small cell base station,the effective receiving power of cell edge user equipment is similar to the received interference power.The current serving base station is the main serving base station.And the base stations which transmit severe interference are transformed to coordinating base stations through coordinated multiple points transmission/reception(CoMP)technology.User equipment is provided services by multiple base stations.During the offloading process,the user's rate requirement is guaranteed.In CoMP process,the user receives more power,and the actual rate is far greater than the demand rate.This is unmatched with the purpose of energy,efficiency improvement.Therefore,increasing the energy efficiency of the user equipment which use the CoMP technology are further considered.The power control process under the premise of satisfying their rate requirements are performed.The interference to other user equipment using the same frequency is reduced through the power control process.Simulation results evaluate the three-stage improvements of system energy efficiency achieved by AGO,collaboration communications and power allocation separately,which proves the benefits of AGO in multilayer heterogeneous dense wireless network.(3)Multi-service delay-aware resource allocation scheme for service and resource matching.After a user equipment is connected to a base station by rate requirements,each user equipment can have multiple services.Based on the rate requirements of different services and different awareness of time delay,the time delay tolerance is used as one dimensional resources of the wireless network.Taking full advantage of the difference sensitivity of services to time delay,time and transmit power are allocated to different services at the same time.The relationship between time delay,service rate and service duration is established using effective capacity.And the minimum QoS index is also analyzed.The Cobb-Douglas production function is constructed during the resource allocation process to describe the balance between spectral efficiency and energy efficiency.The power consumption is limited by the total power of the channel.And the service time delay is limited by the maximum time delay of the service.The subgradient method is used to solve the problem to get the optimal solution.After resource allocation,the user satisfaction of the service is defined and analyzed.In addition,based on the Vickrey-Clarke-Grove(VCG)auction model,multi-service scheduling is designed from two different perspectives including network and service to ensure the benefits of different participants.Simulation results verify that the proposed strategy effectively contribute to the service data-rate increment and power consumption decrease,while the multi-service satisfactions are effected by data-rate and delay allowance. |
PDF Full Text Request