Design And Optimization Of D2D Discovery Schemes In LTE-A Networks

As an important research issue in future 5G networks,Device-to-Device(D2D)communication has drawn adequate attention in recent years.D2D discovery and D2D communication are two key technical procedures in realizing proximity-based services.D2D discovery involves nearby user equipments(UEs)to sense and recognize their potential proximal neighbors while D2D communication includes the establishment and utilization of a physical link between D2D UEs to transfer data to each other.Among the above key technical functions,D2D discovery is the first and necessary procedure for D2D UEs to realize the direct exchange of local data.However,the existing D2D device discovery mechanisms have many problems such as low discovery probability and large discovery delay,etc.In order to solve the problems mentioned,research has been done from the following three aspects:Firstly,a contention-based D2D autonomous discovery mechanism is proposed based on random access techniques adopted in LTE-A networks.The proposed scheme utilizes the random backoff strategy to reduce collision and increase successful discovery probability.Moreover,the adaptive congestion control strategy based on access class barring is utilized to further alleviate the collision of D2D discovery.Simulation results have testified that our proposal can improve the number of discovered D2D UEs and resource efficiency,reduce average discovery delay.Secondly,referring to the recent progress of third generation partnership project standardization,the priority-based hybrid D2D discovery mechanism is proposed regarding the scenario which includes both the public safety service and the normal commercial service.The base station assisted resource scheduling mechanism is proposed for D2D UEs with public safety service while the combination of the competition-based discovery mechanism and the dynamic resource scheduling mechanism is used by D2D UEs with normal commercial service.Simulation results have testified that the proposed hybrid D2D discovery scheme can reduce average energy consumption and increase the number of discovered D2D UEs.Lastly,the effects of inband emission interference(IEI)and co-channel interference on the performance of D2D discovery in multi-cell networks is studied.The analytical model of signal to interference and noise ratio and successful discovery probability is derived based on stochastic geometry theory.Simulation results show that IEI increases with the decrease of the distance between discovery resource and cellular resource,thus leading to the reduction of discovery probability.Moreover,a distance-based power control scheme is proposed to alleviate the interference suffered by D2D UEs in discovery procedure.Simulation results demonstrate the effectiveness of the proposed scheme.