Analysis And Research On Switching Performance Of VoIP In Wireless Local Area Network

The VoIP terminal switching process based on wireless local area network is consisted of scanning, authentication and reconnected. Because of the scanning phase delay time is more than 90% of the switching delay time. Therefore, it is important to reduce the detection delay time. Based on the analysis of detection phase delay, in order to reduce the number of scanning AP, the mainly is reducing the number channel which have to be scanned and decreased the time of the detection and scanning in each channel. The neighbor graph is modified and in the same time three parameters is introduced: load ratio, residual bandwidth and number of access users, then this three parameters are calculated by using switching weighting formula, and select the maximum weight target AP which will be certificated and reconnected. It not only can reduce mobile terminal in the channel scan detection stage residence time, but also can reduce the number of channel scanning. Finally, the three parameters are simulated and analyzed in fuzzy hierarchy by using MATLAB. The conclusion can be reached that if there is more powerful signal intensity of target AP and more residual bandwidth and less number of users, the switching probability of the target AP value can be greater, The main research content and innovation in this article are summarized as follows.Firstly, a brief introduction for the theory of the VoWLAN is given, then the handoff delay process in the existing research results of the VoIP based on the wireless local area network is analyzed, which explain the main reason for the delay and provide some measures.Secondly, the neighbor graph is improved with the existing research results, the bandwidth utilization, load ratio and the number of access users are added in the neighbor list. According to the obtained parameters, the sAP switching weights can be obtained and then the AP is authenticated and reconnected.Next, in order to prevent the imbalance of the load, in the past, it is assumed that the maximum bandwidth provided by AP(maximum data rate) is the same. However in many cases the bandwidth of the AP is different, so it is required that it should be estimated that whether the residual bandwidth of target AP meet the need of the VoIP bandwidth before the active scan. If not, the AP number waiting for be scanned should be reduced by deleting some AP directly from the cache list.Finally, the switching strategy of VoWLAN is investigated in the paper. The factors of switching weight’s proportion are calculated during an analytic hierarchy process, and then the target switching value is calculated with the three parameters, i.e., the signal intensity, the residual bandwidth and number of access users in the fuzzy hierarchy, then the simulation is made in the MATLAB environment.