Research On Communication Performance Analysis In 5G Terminal Coordinated Scenario

In recent years,with the continuous development of mobile wireless communication,more emerging mobile services have been implemented.Therefore,there are new requirements for network performances,such as transmission rate,delay,and throughput.The 5th generation mobile communication system comes into being,which brings great opportunities to mobile communications.However,how to improve the user experience,reduce the power consumption,and lighten the network load have become an urgent problem for the future network.Device-to-Device(D2D),which supports direct communication between user equipments(UEs)within a certain distance instead of through the base station(BS).D2D has broad application prospects in extending network coverage,improving system throughput,and reducing user power consumption.D2D assisted relay communication technology can utilize UE with better link quality as a relay to assist other UE-UE and UE-BS communication,which can improve the system performance effectively.UE-to-Network Relay is a promising method to solve the aforementioned problems.By using the proximity communication,a specific user can act as a relay to assist the transmission between the UE and the BS,so that the cell edge user can obtain a better connection experience.The above technologies constitute part of 5G terminal coordinated scenario.In this thesis,we do research on the application of UE-to-Network Relay in the uplink cellular network.We consider that UEs can communicate with BSs in the direct mode or in the UE-to-Network Relay mode.In order to analyze network performance,we leverage stochastic geometry to model the network.We also propose a tractable analytical framework for UE-to-Network Relay enabled uplink cellular network and investigate a flexible mode selection scheme.We derive expressions of transmission power consumption,relay probability,and outage probability.Simulation results show the accuracy of our theoretical analysis and demonstrate that the proposed framework can reduce the outage probability and the transmission power simultaneously.As a result,this thesis provides guidelines for UE-to-Network Relay enabled networks.UE-to-Network Relay achieves remarkable effects in extending network coverage and improving the user experiences.However,it also imposes a significant challenge on backhaul pressure.Caching is considered as an efficient way to reduce data traffic and alleviate the burden of the backhaul networks.In this thesis,we jointly consider UE-to-Network Relay and caching.We propose a tractable analytical framework to model caching enabled UE-to-Network Relay in cellular networks.Besides,we employ a four-level hierarchical mode selection scheme,where a request is satisfied with priority order by:(1)self-request mode,(2)device request mode,(3)UE-to-Network Relay mode,and(4)cellular request mode.Based on the system model,we derive tractable expressions for performance metrics,such as cache hit probability,successful transmission probability,and cache-aided throughput by using the stochastic geometry.The accuracy of analytical results is validated by simulations.The results also show that the distance threshold should be set carefully to satisfy user communication requirements.Moreover,we find that the UE intensity and content popularity jointly have significant impacts on caching policy choices.In summary,this thesis analyzes the communication performance in 5G terminal coordinated network considering UE-to-Network Relay and caching respectively.At the end of the thesis,the research is summarized and the future research direction is discussed.