The Key Technology Research Of Energy Efficiency In Distributed Antenna System For Mobile Communications With D2D Communication

In the development of mobile wireless communication systems,the spectrum efficiency(SE)and energy efficiency(EE)have always been the most important factors of the performance of wireless communication systems.With the development of science and technology,the mobile business demands also come out explosive growth,which bring more challenge of higher SE of mobile wireless communication systems.With the rapid development of human society,the global environment becomes worse than before and the energy consumption keeps growth unceasingly at the same time.In order to guarantee the sustainable development of human society,how to improve the EE has become a top priority in a wide range of industries around the world.Due to the special structure of distributed antenna system(DAS),it has natural advantages of improving the system SE,customer service quality and enlarging the overage of communication.So it has caused more and more attention and research and has become an important technology of the next generation wireless communication systems.But there are some very complicated problems of DAS at the same time such as DAS still exists marginal users which has poor quality of service(Qo S)and difficult to suppress serious problems of interference in the system.Another key technology in the future mobile communication is device to device(D2D)communication,which can effectively improve the quality of edge of customer service,reduce the interference existing in DAS in some extent.D2 D communication means that two suitable user equipments can directly communicate with each other through the indirect regulation of Remote Access Unit(RAU).It can effectively improve customer service quality of marginal users and reduce the burden and the processing energy consumption of Central Processing Base Station(CPBS).So based on the defects of DAS,this dissertation combines the DAS and the D2 D communication technologies to improve the overall performance of the communication systems.The full text of the research work is as follows:(1)According to the serious interference in DAS,the virtual cells are constructed to improve spectrum efficiency and energy efficiency of the system.Because of user service in DAS is provided by all the RAU,this will bring great interference among users.The virtual cells theory can effectively improve the quality of customer service and reduce the interference in the communication system at the same time.The first part of this chapter analysis building virtual cells in unidirectional DAS.Through virtual cells construction algorithm,we form reasonable virtual cells in unidirectional DAS.And then we analyze the maximizing SE and EE optimization problems of the system.By relevant theories such as fractional programming theory and D.C.programming,the optimization problems of maximizing SE and EE of system are transformed into equivalent solvable convex optimization problems.The simulation results demonstrate that building virtual cells through proposed alogorithm in unidirectional DAS can effectively improve the SE and EE of the system.Based on the conclusion of adding virtual cells into unidirectional DAS,we expand the conclusion to bidirectional DAS in the second part of this chapter.Because in the actual situation,communication system will always exist uplink and downlink users.So consider bidirectional DAS is more reasonable.After considering the characteristics of bidirectional DAS,we propose the virtual cells construction algorithm of bidirectional DAS to build virtual cells in bidirectional DAS.Similarly,maximizing the SE and EE optimization problems of the system are analyzed.Through the transformation,the non-convex non-linear constrained optimization problems are transformed into solvable equivalent optimization problems.And then using the Concave Convex Procedure(CCCP)algorithm and interior point method to obtain the power allocations of maximizing SE and EE of the system,respectively.Simulation experimental results show that building virtual cells in bidirectional DAS can greatly improve the system SE and EE,which is more obvious when the user number is large.(2)For the poor customer service quality of centralized antenna systems(CAS),we exploit D2 D communication technology to improve the energy efficiency of the system.Through summarizing the existing related work about D2 D communication technology,most of the research work about constructing system model stiffly add D2 D pairs in communication systems but never consider the formation of the D2 D pair.So in this chapter,after analysing the characteristics of the D2 D communication,we reasonably join the D2 D communication in CAS according to the proposed D2 D pair selection algorithm.The composite fading channel model contains large scale and small scale fading,which is used in this chapter.The total power consumption model of system consists of transmitter power consumption,chip power consumption and power consumption of optical fiber communication.After adding the D2 D communication technology into CAS,maximizing system EE optimization problem is discussed.Through the sub-gradient iteration algorithm to obtain the power allocation of maximizing the system EE.The simulation experimental results show that when CAS adding the D2 D communication,the EE of communication system has a great improvement.(3)Aiming at the poor quality of service of those UEs that are located out the effective service area of BS in DAS,we use the D2 D communication to improve the spectrum efficiency and energy efficiency of those UEs.The first part first of this chapter analyzes the SE and EE of the single user and single D2 D pair DAS.We can find that maximizing the SE and EE ptimization problems of single user and single D2 D pair in DAS can not be directly solved because they are non-convex non-linear optimization problems with constraints.But by exploiting fractional programming and related theories,the original problem are transformed into D.C.structure.And then,we can obtain the power allocations of maximizing SE and EE of system through traditional convex optimization mehtods such as interior point method and CCCP algorithm.According to the analysis of the first part of the chapter,the second part of this chapter considers reasonably adding D2 D communication technologies in multi-user DAS.After analyzing multi-user DAS,we put forward the D2 D selection algorithm in multi-user DAS.Through the selection algorithm,we pick suitble users to form D2 D pairs according to those users are at the edge of the coverage of RAU in multi-user DAS.Then we analyze the optimization problems of maiximizing SE and EE of multi-user DAS with D2 D communication.Similar to the first part of this chapter,we convert these two optimization problems that can't directly solve by traditional convex methods into solvable equivalent optimization problems.Then we can obtain the power allocations of maximizing SE and EE of system.The simulation results show that the SE and EE of multi-user DAS with D2 D communication are reatly improved when compared with same situation of single DAS.