Research On Power Control Algorithms In Heterogeneous Macro-femto Cellular Networks

Green mobile communication technology is the key to the sustainable development of next generation cellular mobile communication systems.Since femtocell base stations have low transmission power and high spectral efficiency,support for high-speed mobile user access and provide higher quality of service,deploying femtocell base stations in the area of macrocell base station has become a core technology of mobile communication networks,and being used widely.Therefore,the mobile communication system inevitably adopts a dense heterogeneous Macro-femto cellular network structure.At present,researches on energy efficiency optimization of heterogeneous Macro-femto cellular networks have made some achievements at home and abroad,including power control,adaptive sleep,base station deployment,and user association strategies and so on.Due to the denseness of base stations,the resource management of wireless networks is very complicated.In order to improve the energy efficiency of Macro-femto cellular network,the power control algorithm in the cellular system is studied in this thesis.First of all,the data transmission delay between base stations and users in a heterogeneous Macro-femto cellular networks,as well as the energy efficiency of the entire networks,is considered.In this thesis,the Lyapunov optimization theory is used to solve the problem with transforming the user data delay into the stability of data queues.Based on the knowledge of queuing theory,the constraint relationship of time delay and energy efficiency is analyzed.Power control parameter and user scheduling parameter are set to improve energy efficiency and reduce user data delay respectively.Therefore,a Power Control Algorithm for Energy Efficiency and Delay Trade-off(PCA-ED)is proposed.By selecting the appropriate trade-off parameter,a compromise between energy efficiency and time delay can be obtained.Simulation shows that PCA-ED algorithm can maximize the system energy efficiency while guaranteeing the stability of the system.Secondly,we regard the wireless communication channel as a frequency-selective and time-varying channel,it is difficult to select a resource block with high energy efficiency to users according to the current channel quality,this thesis uses the Dinkelbach method and the Lagrange duality method to perform a series of conversions on the energy efficiency function,and solves the relevant parameters finally.Therefore,a Power Control Algorithm based on Resources blocks Allocation(PCA-RA)is proposed,each base station performs multiple iterations to update the power level to achieve maximum energy efficiency after the resource block allocation via a polling manner is finished.Simulation results show that the algorithm can effectively improve the system energy efficiency.