Research On Key Techniques Of Wireless LAN Deployment On The Alike Frequency

Wireless network relative to the wired network has the characteristic such as free to move, easy deployment, and mobile communication network cannot satisfy the user demand for high speed data business, then, based on the IEEE802.11 protocol of WLAN get rapid development. How the roaming scenarios, however, to provide users with quality and reliable wireless services, is still a problem that has not been efficient solution. WLAN deployment mode, which is different from traditional frequency with WLAN deployment plan with simple, AP plug and play, layered with frequency deployment can increase the access of users, the advantages of the support work 40 Mhz bandwidth, thus worthy of promotion.This topic according to frequency mass with WLAN deployment problem, two sets of AP in the practical test of small coverage area biggest communication capabilities,covering performance, roaming performance, through the analysis of a large number of test samples, it is concluded that the AP with frequency deployment of basic data, draw a loose deployment, close to deploy two kinds of deployment scenarios, the same frequency will bring advantages and disadvantages. Loose deployment scenarios, the communication performance is good, the disadvantage is that the wireless terminal roaming in the area of the two AP coverage overlap when switching, and throughput is reduced, switching speed slower. Tight deployment scenarios, multiple AP only communication performance is equivalent to one AP communication performance, do not have advantage, but when roaming throughput drop is not obvious, only individual samples will appear in the table tennis phenomenon, namely the AP access is not stable.In the wireless network environment, and the cable is different, every client can choose according to their own environment of different transmission speed. So is multi-rate wireless network environment, fair is not suitable for wireless network throughput. In the wireless network is analyzed, relative to the throughput time of fair management fair management advantage. In order to eliminate the frequency deployment of wireless client communication signal overlapping coverage area signal interference, when a system time-division duplex algorithm is put forward. Of interference in the region where the wireless client communication, only access AP it works, other AP does not work. But after analysis, the algorithm performance is better than to make all wireless clients receive the same transmission time performance is good.Based on the above analysis, in order to solve the loose deployment scenarios, the wireless terminal roaming in the area of the AP coverage overlap, the throughput will decline, switch slower this phenomenon. Presents a TARED algorithm, time allocation algorithm. The core idea of the algorithm is that the flow in the AP buffer queue length,actually decided the send the probability of each flow, send probability, a high throughput is high. The areas covered by the signal overlapping wireless client transfer rate on the weighted coefficient, according to the purpose of each flow wireless location of the client and the transmission rate to calculate the reasonable target queue length. By packet loss, make the current queue length of each flow stability in the target queue length. To ensure that each single flow reasonable take wireless channel transmission time, avoid systems congestion at the same time, in order to improve the networkoverall performance.Also, based on the results of the practical test analysis, in order to solve the tight deployment scenarios, the AP will phenomenon of table tennis, is put forward based on the AP selection access mechanism of SDN. Selection of wireless access to the client receives the signal strength, has the number of wireless terminal AP rate, the bandwidth of the AP, AP communication of the four parameters of the transmission error rate.According to the several parameters set a metric weights, wireless terminals will be according to the measurement function to choose the appropriate access to the AP, and the current client for the metric function value difference between two AP that does not exceed a certain threshold, the AP cannot switch, as far as possible in order to achieve the AP access stability, avoiding the phenomenon of table tennis.