Research On Coexistence Mechanism Between LTE-U And WiFi Networks And Traffic Balancing Technology

In recent years,with the rapid development of intelligent equipment and internet application,The requirements for speed,delay,reliability and other network performance are increasing,which brought tremendous pressure to the existing network.Given the high-value licensed spectrum in low frequency has been exhausted already,the industry has proposed an idea which extended LTE to the unlicensed spectrum,that is,LTE in unlicensed(LTE-U).The LTE-U technology aggregates the unlicensed spectrum with the licensed spectrum leveraging the existing CA technology,it is deployed in Small Cell and transmits in unlicensed spectrum using LTE air interface protocol to offload the mobile service data traffic for the licensed spectrum.LTE-U's main research focused on 5GHz unlicensed band.The 5GHz band allows any wireless access technology to use,which may cause coexistence problem between different systems.If LTE-U is deployed directly and occupies the unlicensed spectrum resources without any change,it will not only be unfair to other technologies deployed already,but also disobey the decree requirements of the unlicensed spectrum.Thus,a multi-channel LTE-U coexistence mechanism based on Q learning is proposed in this paper,which consider the idea of carrying out LTE-U and WiFi rotation in the form of duty cycle.This algorithm takes system performance and fairness factors into accounts,and calculate the optimal duty cycle to optimize the system utility function.Besides,in order to further improve the spectral efficiency,this paper also proposed a frequency reuse algorithm,which allows LTE-U multiplex transmission under the premise of ensuring WiFi's transmission without interference.The simulation results show that the Q-learning coexistence algorithm proposed can improve the system throughput while ensuring the fairness,and the frequency reuse algorithm can utilize the channel information to further improve the system performance.In the complex heterogeneous networks where LTE,LTE-U and WiFi coexist,there is a trade-off problem between the use of unlicensed spectrum to offload traffics and the LTE QoS guarantee in unlicensed spectrum.In this paper,a multi-channel optimal traffic balancing algorithm for LTE-U is proposed.The algorithm takes the real-time channel interference and traffic in the licensed and unlicensed spectrum into account.The heterogeneous network is modeled as a mathematical problem and the system utility function is designed.Water-filling algorithm and convex optimization algorithm are used to solve the optimal problem through calculating the optimal system parameters.It's been verified in the simulation results that the system parameters can be calculated quickly through the traffic balancing algorithm proposed and the system utility value can be improved obviously.In the further work,the improvement of action granularity and the convergence speed of Q learning algorithm for coexistence can be considered.Besides,the complexity of heterogeneous network and the real-time optimization will be further studied.