Research On The Friendly Coexistence Of QoE-aware D2D Communication And WiFi In Unlicensed Spectrum

The fifth generation(5G)wireless network raises two most obvious requirements which are user-centric and higher network capacity.For 5G network,the operation and optimization of operators inevitably migrate from network-centric to user-centric.The conventional quality of service(QoS)is from the perspective of the service provider to ensure the user's service quality,while quality of experience(QoE)is defined basically as a subjective measurement of end-to-end service from the viewpoint of users.The user will be lost if the service can not guarantee a certain QoE,therefore,the research based on the user experience has great significance.Meanwhile,5G network needs to boost the capacity significantly to accommodate the mobile traffic surge.As a key candidate technology for 5G,Device-to-Device(D2D)communication can provide several advantages such as low power consumption,low latency,efficient frequency and high bit rates.Compared with the limited and costly licensed spectrum,the adequate and free unlicensed bands are more attractive for operators to deploy D2D.Nowadays,Device-to-Device communication in Unlicensed Spectrum(D2D-U)communication has become one of the hotspots of 5G.However,since WiFi and D2D are two independent systems,the system performance will be significantly decreased without effective coexistence mechanism,therefore,the main target is to guarantee the fair and friendly coexistence of D2D and WiFi for extending D2D to the unlicensed frequency band.Friendly coexistence mechanisms of QoE-aware D2D communication and WiFi in unlicensed spectrum are studied in this thesis.The main contents and innovations are as follows.Firstly,in order to guarantee the fairness of WiFi system while maximizing the total throughput of D2D-U system and WiFi system,this thesis proposed a fair Duty-Cycle Algorithm(F-DCA)which allocates the appropriate time proportion to D2D-U system adaptively according to the load of WiFi networks.Secondly,multiple D2D-U users communicate simultaneously during the time when the D2D-U system occupies the channel.In order to control co-channel interference and improve user satisfaction,a QoE-based power control algorithm is designed to maximize the D2D-U system throughput with high user satisfaction,a D.C.algorithm is adopted to solve this problem which has the low complexity.Thirdly,an enhanced listen before talk(ELBT)mechanism is proposed.Specifically,a dynamic channel switching technology is introduced on the basis of the LBT mechanism,which can effectively avoid the interference caused by the long-term useage of the same channel to the WiFi system and improve resource utilization.Fourthly,a matching algorithm is adopted for resource allocation.The D2D-U user reuses the uplink of the LTE-U(LTE in Unlicensed Spectrum)user for communication.In order to control co-channel interference,a one-to-one stable matching algorithm based on user experience is adopted to allocation the appropriate channel resources for D2D-U users.The objective function is to maximize the total satisfaction of D2D-U and LTE-U.At the last,the correctness of the theoretical research is verified by Matlab simulations.