Research On Optimal Coexistence Of WIFi And LTE In Unlicensed Band

With the development of mobile communication technology,the global mobile data traffic is growing exponentially.But the radio frequency spectrum can be used for wireless communications is finite and extremely valuable.At the same time,there is large amount of unlicensd spectrum available.So how to get a harmonious coexistence of WiFi and LTE in unlicensed spectrum has attracted many researchers' attention.This paper mainly studied the new coexistence methods between WiFi network and LTE network in unlicensed spectrum.The main work of this thesis is as follows:First,to achieve the fairness between uplink and downlink in WiFi-LTE coexistence network,we propose a model that in coexistence network the uplink and downlink are decoupling,combining the SVM algorithm and fair utility function,and construct the mixed integer nonlinear programming model problem.The optimization problem is divided into two steps: firstly,the methods which are piece-wise linearization technique and RLT are applied to linearize the nonlinear optimization problems.Then,it is proved that this method is feasible,and the optimal value of fair utility function with different values of each parameter is obtained through simulation.By comparing the simulation results of the uplink-downlink coupled coexistence network,it is improved the uplink and uplink decoupling can effectively improve the network throughput and realize the load balancing between the uplink and uplink.Secondly,to maximize the QoE in WiFi-LTE coexistence network,we consider mobile data offloading from LTE to WiFi.In order to determine how many LTE users need to be offloaded to WiFi network,we propose a QoE-based approach for traffic offloading from LTE to WiFi combining with channel conditions and the limitation of the number of users.Then,we use the physical significance of traffic offloading to transform the original problem into a linearly solvable optimization problem,and prove that such transformation does not change the optimal solution of the original problem.MATLAB is used to solve the optimal solution of the reconstructed problem.Finally,it can be concluded that the satisfaction of LTE users in the coexistence system can be effectively improved through mobile data offloading.