Research On QoS Performance Of Wireless LAN Based On EDCA Mechanism

As wireless communication technology is widely used in life,wireless local area network has become one of the mainstream network access methods in today's society.IEEE802.11 is the most widely used standard of wireless local area network,and the core of its media access control(MAC)protocol is distributed coordination function(DCF).The performance of the MAC protocol of WLAN greatly affects the quality of service of the network.In recent years,the types of services carried by the network have gradually increased,and DCF can't guarantee the Quality of Service(QoS)of some services.Therefore,IEEE proposes enhanced distributed coordination mechanism(EDCA)to provide quality of service differentiation for data frames at the MAC layer.This paper takes the EDCA mechanism as the research point,and conducts research from two aspects: performance analysis and performance optimization.In the section of performance analysis,based on the two-dimensional Markov model,this paper models a single priority business within the station.A one-dimensional Markov model is used to describe the service differentiation brought by AIFS.In addition,this paper considered the service differentiation brought by virtual collision mechanism and contention window,and the throughput model of EDCA in the saturated state is obtained.Based on the saturation model,this paper introduces an idle state,describes the situation of waiting when no packet arrives under unsaturated traffic.Combining the post-backoff process under unsaturated conditions,a new unsaturated performance model is proposed.Using the M/M/1/K queuing model,the one-step transition probability of the unsaturated model can be obtained,and then the unsaturated performance model can be solved.In order to verify the correctness and accuracy of the model proposed in this paper,this paper compares the results calculated by the model with EXata simulation results.The results show that the model proposed in this paper can be consistent with network simulation and has higher accuracy than traditional model.Based on performance analysis,this paper proposes two EDCA optimization methods.The first method uses the saturated throughput model to obtain the mapping between the number of active stations and the optimal minimum contention window.The station in the network estimate the number of active stations in the WLAN by receiving the MAC data frames,so as to dynamically configure the value of minimum contention window.The second method is the improvement of GDCF,which adjusts the contention window in an adaptive way of slowly decreasing the contention window to reduce network collision.Simulations in EXata show that the two methods can greatly improve the performance of the network.