Research On Interference Management In D2D-Enabled Cellular Networks Based On Stochastic Geometry

With the popularity of smart phones,customers' demands for multimedia services are growing.Massive amount of data and all kinds of applications have caused an increase in the traffic loads of base station(BS),which in turn leads to BS' inability to satisfy the clients' demands eventually.In order to meet the requirements of growing business without increasing the number of BSs,the Device-to-Device(D2D)communication has been introduced into the cellular networks.The D2 D communication reduces the traffic loads of BSs,decreases the transmission delay of communications,increases the communication capacity and improves the energy efficiency of the system.Therefore,the D2 D communication is widely accepted as one of the key technologies in the 5th generation mobile networks(5G).In D2D-enabled cellular networks,nearby users can communicate with each other by establishing a direct link(without directing all communications through the BSs).Because the communication data does not relay via the BS,D2 D communications can reduce the traffic loads of BSs and decrease the transmission delay of communications significantly.Considering that the communication distance is short and the path-loss between nearby users is small,the D2 D communication can obtain the channel gain,hop gain and reuse gain,which increases the energy efficiency and spectrum efficiency.However,despite the many advantages mentioned above,the D2 D users may cause interferences to cellular users using the same frequency band,thus degrading the communication quality and the performance of the devices.Therefore,the interference management of D2 D communications is crucial for the D2D-enabled cellular networks.There has been extensive research on the real-time Channel State Information(CSI)based interference management to mitigate the interference caused by D2 D communications.It takes a lot of time and signaling overheads to obtain the real-time CSI between users,thus increasing the burden of BSs and decreasing the transmission capacity.In order to avoid the huge overheads,we propose the stochastic geometry based interference management methods in this dissertation.The dissertation includes the following parts:(1)the analysis and management of the D2 D interference with co-channel mode into single cell environment;(2)the analysis and management of the D2 D interference with general mode(co-channel mode and orthogonal-channel mode)into multiple cells environment;(3)the D2 D success probability-aware power control method.The first part of the dissertation studies the statistical characteristics of the interference from D2 D communications to cellular communications and finds out the maximum D2 D users density for a given cellular services' access failure probabilities with co-channel mode into single cell environment.Based on the stochastic geometry and stochastic process,a random network model is built to determine the influence of D2 D communications on cellular services' access failure probability.In the random network model,we derive the expression of the cellular services' access failure probabilities based on the probability distribution function of the users' location and channel fading.Given the cellular services' access failure probability requirement,we can calculate the maximum D2 D user density and the maximum D2 D transmit power based on the expression.The maximum D2 D user density can guide the call admission control for D2 D communications.This enables BSs to limit the density of D2 D users accessing the cell to satisfy the requirement of cellular services' access failure probability.The simulation results verify the accuracy of the estimated cellular services' access failure probability and show that BSs can guarantee the cellular services' access failure probability by limiting the D2 D user density.The second part of the dissertation explores the statistical characteristics of the interference from D2 D communications to cellular communications in co-channel and orthogonalchannel mode into multiple cells environment.We evaluate the maximum D2 D user density in co-channel mode and the maximum fraction of resource allocated to D2 D communications in orthogonal-channel mode respectively.Compared with the single cell environment,cellular services are interfered by D2 D users and other-cell BSs in multiple cells environment.Based on the stochastic geometry and stochastic process,we derive the expression of the cellular services' access failure probabilities to determine the influence from D2 D communications and other-cell BSs on cellular services' access failure probability.Given the cellular services' access failure probability requirement,we can calculate the maximum D2 D user density in co-channel mode and the maximum fraction of resource allocated to D2 D communications in orthogonal-channel mode from the expression.Therefore,BSs can realize the call admission control for D2 D communications and meanwhile guarantee the cellular services' access failure probability.The simulation results verify that the proposed call admission control method can decrease the interference caused by D2 D communications and satisfy the requirement of cellular services' access failure probability.The third part of the dissertation probes the power control for D2 D communications.We propose a D2 D success probability-aware power control method.The proposed method significantly reduces the interference from D2 D communications to cellular communications by minimizing the D2 D transmit power while satisfying the D2 D success probability requirements.We derive the expression of the D2 D success probability based on the statistical characteristics of the interference from cellular communications to D2 D communications and the statistical characteristics of the interference between D2 D users.By the expression we can determine the minimum transmit power for D2 D users and guarantee the D2 D success probability.Compared with the real-time CSI based power control method,the proposed method can yield higher reliability,smaller feedback overhead and lower complexity in high mobility networks due to the consideration of the probability distribution function of the user's location and channel fading.The simulation results show that the proposed method can increase both the cellular communication success probability and the energy efficiency of cellular communications.