Content Dissemination Optimization And Relaying Access Performance Analysis For User Relaying Cellular Networks

The evolution of 5G/B5 G in terms of network architectures includes relaying,D2 D communication,user self-organization,heterogeneous networks,etc.,which offers possibilities for selecting mobile users as relays to assist base stations for content dissemination and the edge mobile users for network access.Therefore,it is of important theoretical significance and application value to study the downlink file distribution scheme of the user relay cellular system and to analyze the improvement of the uplink access performance of the user relaying cellular system.We focus on the downlink content dissemination scheme of user relaying cellular system and the improvement of the uplink access performance with the assistance of using mobile user relays.The main work and innovations are listed as follows:Firstly,the optimization of the group pushing probability for D2 D assisted offloading gain maximization.The main contributions include 1)With the consideration of content preference and sharing willingness of human users,the optimal content pushing strategy is investigated by formulating an optimization problem to maximize the offloading gain measured by the offloaded traffic.Users are placed into groups according to their content preferences and share content with intergroup and intragroup users at different sharing probabilities.2)Although the optimization problem is nonconvex,the closed-form optimal solution is obtained for a special case,when the sharing probabilities for intergroup and intragroup users are the same.Furthermore,an alternative group optimization(AGO)algorithm is proposed to solve the general case of the optimization problem.3)Finally,simulation results are provided to demonstrate the offloading performance achieved by the optimal pushing strategy for the special case and AGO algorithm.An interesting conclusion drawn is that the group with the largest number of interested users is not necessarily given the highest pushing probability.It is more important to give high pushing probability to users with high sharing willingness.Furthermore,the optimization of the group pushing probability to maximize the successful offloading user density.The main contributions include 1)With the joint impact of human's social characteristics and the physical transmission conditions on the D2 D assisted offloading performance.We first study the D2 D successful transmission probability,where the interference from both simultaneously D2 D transmitters and underlaid cellular downlinks are all considered.2)The caching strategy is optimized to maximize the offloading gain,which is defined as the successful reception of contents via D2 D communications.The optimal caching strategy of the special unbiased case is first derived in a closed form.To solve the nonconvex offloading gain maximization problem for the general case,we propose a numerical algorithm to obtain the globally optimal solution.To reduce complexity,we first use the asymptotic approximation to simplify the objective function and then provide a low-complexity iterative algorithm to obtain the caching strategy satisfying Karush-Kuhn-Tucker(KKT)conditions.3)The simulation results verify the accuracy of derived analytical results,and it is shown that the proposed algorithm outperforms the existing schemes in terms of offloading gain.Additionally,the performance analysis of access rate improvement and SNR Threshold Optimization for D2 D Relaying Access network.The main contributions include 1)we characterize the D2D-assisted relay performance in the context of a cellular uplink scenario,where the UTs close to BS can act as the full-duplex relays.2)To obtain the system performance metric defined as the network access probability,the expressions of the coverage probability for D2D-assisted relay mode and outage probability for direct access mode are derived,respectively.3)The simulations have shown that the derived analytical results are well matched with the simulated ones.It is observed that D2D-assisted relay mode can provide a better connection service than the direct access mode when the received SINR requirement is high and the transmission distance of the cell edge user is long.Finally,the performance analysis of power saving improvement of uplink user relaying access.The main contributions include: 1)A power efficient relay selection criterion is proposed to guarantee that the power saved by D2 D relaying access exceeds a given threshold.2)Then,the relay selection criterion is equivalently transformed into a region constraint,based on which the outage probability of D2 D relaying access is derived.3)Furthermore,the power consumption of D2 D relaying access is analyzed in two stages: the stage from the remote UE to the relaying UE and the stage from the relaying UE to the base station.The calculation of the average power consumption requires a double integral over the plane,and the closed-form expression is derived by applying the Green's theorem and proper variable substitutions.4)simulation results validate the analytical derivations and present the impacts of system parameters on the performance of D2 D relaying access in terms of outage probability and power consumption.