Research On Relay Selection Of D2D Communications Under Cellular Networks

Due to the rapid growth number of mobile communication devices,it poses a huge challenge to the traditional cellular network.The cell system capacity and coverage can be improved and increased the cell system capacity and coverage by using the D2 D relay technology in the future network.In order to increase the coverage of the D2 D communication,the relay technology can be introduced in the D2 D communication.Due to the co-existence interference between the traditional cellular communication and the D2 D relay communication,it is necessary to design a reasonable relay selection and resource optimization scheme to reduce the mutual interference between D2 D users and cellular users.In view of the above problems,this thesis proposes two schemes of D2 D communication relay selection based on different scenarios and optimization objectives.The main contents are stated as follows:Firstly,this thesis studies the D2 D relay selection problem,which aims at improving the reach ability rate of edge user links and reducing the co-channel interference between cellular links and D2 D links.As the cell edge users are affected by channel fading,the quality of service(QoS)of the user is poor.In order to guarantee the edge user's channel quality,the D2 D assisted relay technology can help the edge user to communicate with the base station,but the D2 D link multiplexing cellular resources can generate frequency interference.Aiming at the problem of co-channel interference,this thesis studies a relay selection scheme aiming at maximizing the channel capacity of edge users and cellular users.The algorithm performs resource pre-allocation for each relay node,and then combines the resource allocation results to perform relay selection for the purpose of maximizing edge user and cellular user channel capacity.This scheme considers the QoS of edge users and the co-channel interference on the cellular link at the same time.Simulations present that the algorithm not only effectively improves the reach ability rate of edge users' links,but also guarantees the QoS of cellular users.Secondly,this thesis studies a D2 D relay selection scheme aiming at maximizing the energy efficiency of D2 D links.The scheme considers the issue of co-channel interference between traditional cellular communications and D2 D relay communications.At the same time,it considers the energy efficiency of D2 D relay users while ensuring the capacity requirements of cellular users.This thesis studies a D2 D relay selection algorithm based on resource allocation and power control.The algorithm uses the equivalent link to pre-allocate resources.It can reduce the number of resource allocations.Then the algorithm uses power control to ensure the interference to the cellular link is minimal.Finally,the D2 D link and the relay node are performed optimal matching with the energy efficiency value as the weight.Simulation proves that this algorithm can improve the energy efficiency value of the D2 D relay link effectively and ensure the spectrum efficiency of the entire system.