Enabling Technologies Of LTE And WiFi Coexistence Networks

In recent years,with the rapid development of smart mobile devices and explosive growth of mobile data services demand,the existing cellular network is facing more and more serious challenges.At present,the research on wireless physical layer technology has been mature,so the new type of media access mechanism,new network technology and multi-network coexistence technology has attracted great attention and has been studied in depth.New media access mechanism and network technology can effectively alleviate the current scarcity of spectrum resources of the cellular network and improve the overall performance of the system,which is of great significance to realize the future multi-network integration.In this paper,we focus on the new media access mechanism and resource allocation scheme of LTE and WiFi coexistence network,and solve the problem of mutual interference and the fairness of resource allocation between LTE and WiFi coexistence network.1.This paper introduced the basic concept and development of LTE and WiFi network,expatiates the research progress and meaning of LTE and WiFi coexistence network.At the same time,this paper explains the basic theoretical knowledge of LTE and WiFi media access mechanism,the basic operation of WiFi channel access mechanism Distributed Coordination Function(DCF),Point Coordination Function(PCF)and so on.Meanwhile,we focus on the key technologies and challenges of LTE and WiFi coexistence network,which lays the foundation for the following study of novel coexistence and media access mechanism.2.A novel mechanism of Carrier Sense Multiple Access with Collision Avoidance based on the indication information to solve the problem of hidden nodes was studied,which was divided into three improved modes according to both the basic mode and RTS/CTS mode of DCF.The mechanism indicates that WiFi Access Point(WiFi AP)will broadcast indication information frame(IND)when collision occurs,then node with higher quality of service(QoS)will be selected to access the channel.The simulation results of NS2 show that Carrier Sense Multiple Access with Collision Avoidance based on the indication information has better system performance compared with the conventional DCF mechanism.3.A novel DBF unlicensed channel access mechanism and the corresponding joint licensed and unli-censed spectrum resource allocation scheme was proposed.The novel mechanism achieves that when DBF and WiFi AP are invisible mutually,DBF could exploit extra transmission opportunities in the unlicensed band as WiFi AP is communicating with users outside the overlapping area.Thus,spatial reuse is fully used and the spectrum utilization is improved.Numerical results show that if DBF and WiFi AP are invisible mu-tually,the proposed scheme outperforms the existing scheme in terms of sum utility and throughput because of extra fraction of unlicensed channel time for DBF.Otherwise the performance is the same as the existing scheme.That is DBF and WiFi AP use the unlicensed band alternately.4.An optimization scheme about joint user association and spectrum resource allocation was studied.Simultaneously,three algorithms of maximizing the performance gain of the WiFi system,maximizing the performance gain of the LTE system and balancing the performance gain of the LTE and WiFi system and the optimal number of offloading WiFi users and assigned unlicensed slots for DBF were discussed.The simulation results show that the algorithm of balancing the performance gain of the LTE and WiFi system can improve the overall system performance regardless of the state about LTE and WiFi.