Relay Area For D2D Pair In Relay-assisted D2D Communication

In recent years,Device to Device(D2D)technology has attracted widespread attention in the academic community.D2 D communication allows two cellular network terminal devices that are close to each other to perform direct information exchange without being forwarded by the base station,which greatly improves information transmission efficiency and reduces transmission delay.D2 D links can also reuse cellular network spectrum resources and coexist with cellular communication links in an underlay manner to increase network capacity.Therefore,D2 D has become a key technology for 5G mobile communication networks.At present,D2 D communication can be divided into two types: direct D2 D and relay-assisted D2 D.The former is the direct communication between two short-range devices under the authorization of the base station,while the latter allows the terminal to maintain direct communication between the devices by means of a relay after the distance exceeds the direct D2 D communication range.Relay-assisted D2 D communication extends the reach of the device,reduces the switching probability between direct D2 D and cellular communication,and further improves network capacity and spectrum utilization.However,when the terminal moves,the D2 D relay area will change accordingly.How to find the optimal D2 D relay area becomes a problem.This dissertation studies this problem,and the specific research contents and results are as follows:1)Research and derive the direct D2 D communication area of the device.Limited by the receiving sensitivity of the terminal equipment,it is only suitable to establish direct D2 D communication when the equipment meets certain conditions.In view of this,by comparing the signal strength received from the base station with the signal strength received from other devices,this paper derives a closed expression suitable for establishing a direct D2 D communication area,marking the area as a D-D2 D communication boundary circle.2)Research and establish closed expressions of switching probability between direct D2 D communication and other communication modes.It is considered that the devices of the direct D2 D pair are in motion.After the motion,the devices may no longer meet the direct D2 D communication conditions and need to switch modes.Based on the definition of the mode switching probability,this paper deduces the corresponding mode switching probability for the two cases of direct D2 D communication switching to cellular communication and direct D2 D communication switching to relay D2 D communication,and verifies them through simulation.3)Research and locate the optimal relay area that can minimize the D2 D mode switching probability.Considering the motion of a device in a direct D2 D pair,the device location area that may provide a relay for it was proved from a geometric point of view,and it was proved to be a circular area;taking the principle of minimizing the mode switching probability of D2 D communication to cellular communication as a criterion,The radius and position of the optimal relay circle are deduced,and the effect of the device moving distance on the mode switching probability is studied through simulation.The research in this paper shows that the relay can effectively reduce the mode switching probability between direct D2 D and cellular communication,and the estimation of the relay position can provide technical support for the implementation of relay-assisted D2 D communication.