Research On User Demand Aware Content Delivery Mechanism In D2D Communications

In order to cope with the challenges brought by the rapid growth of data traffic and diverse application requirements,the Fifth Generation of Mobile Communication that integrates multiple wireless access technologies has become the focus of attention in recent years.As one of the key technologies in 5G communication,Device-to-Device communication is widely considered to have great potential to alleviate the shortage of spectrum resources,which can reduce the load of base stations and increase the capacity and transmission rate of communication networks.With consideration of the above advantages of D2 D communication,using D2 D communication for data distribution can greatly improve the communication quality of users and provide more diverse and high-quality localization services.This thesis first briefly introduces the characteristics and background of D2 D communication,and introduces the key issues and technologies in D2 D communication.Then,the application scenarios and research status of D2 D content distribution mechanism are introduced,and the advantages and disadvantages of existing mechanisms are analyzed separately.Finally,for the shortcomings of the existing content distribution mechanisms,the corresponding improvement mechanisms are proposed in this thesis:Firstly,in view of the low efficiency of distributing multimedia data in existing D2 D multicast communication systems,a user-information-aware D2 D multicast file distribution mechanism is proposed.Using D2 D multicast communication for content distribution can greatly reduce the transmission redundancy of multimedia data,but the existing schemes have not yet fully exploited the advantages of D2 D multicast communication.Considering that there are a large number of geographically adjacent users but the time of request service is very different,the willingness of potential requesters to accept the pushed video is estimated based on the users' interests,the popularity of the videos and the residual-energy of the users' devices.And then by combining with interference and social information,a clustering and cluster head selection algorithm is proposed.Lastly,the video is simultaneously sent to the requesters and the potential requesters who meets the condition of willingness.Numerical results show that the proposed mechanism further improves the efficiency of multimedia data distribution.Secondly,considering the huge impact of user's mobility and social relationship between users on D2 D relay communication,a social-aware relay selection mechanism for relay-based D2 D communications is proposed.This thesis first analyzes the transmission performance of D2 D relay communication in the half-duplex relay mode and the full-duplex relay mode,and then the social relationship strength between users and the law of user's mobility are analyzed through the user's location check-in record,and a relay communication gain metric is proposed to measure the extent of transmission performance improvement brought by D2 D relay communication.By combining the advantages of half-duplex relay and full-duplex relay,a relay node and relay mode selection algorithm with maximum relay communication gain is proposed.Numerical results show that the proposed mechanism improves the relay transmission rate and the stability of the transmission link.