Research On Wireless Frequency Selection Algorithm In A Dense WLAN Environment

With the continuous development and improvement of 802.11 protocol series, wireless LAN technology has been increasingly used by the majority of users. At the same time due to the widespread use of wireless devices and only three non-overlapping channels in the 2.4GHz band where bandwidth resources are very limited, it is prone to lead to channel contention between devices, resulting in large interference in a network topology. So how to assign limited channels to the large number of wireless devices and make the network to minimize interference has become an important research direction.DFS is a technology that reduces the interference caused by overlapping channels by changing the channel assignment scheme. DFS’s key is the interference model and the way interference is modeled differs from one algorithm to another. Currently most of the current common interference models are related to the overlapping channel, the physical distance between the AP and AP’s traffic demand and ignore the importance of BSS. However if there has to be channel contention in WLAN, we hope that the channel assignment scheme can ensure that the important service has the less interference. We will discuss the interference model from the perspective of BSS in detail in this dissertation. Our main work and contributions include:① Proposing a new concept of priority. The priority in this article is different from the priority in other DFS algorithm. The priority includes static priority and dynamic priority in this article. The static priority represents the importance of BSS. The higher the priority, the more important the BSS. The dynamic priority represents AP’s traffic demand and is obtained by calculating the number of STA. If an AP has more STAs, it has more traffic demand and its dynamic priority is bigger. In order to use the priority in the interference model, we define the unified priority that unify static priority and dynamic priority according to the mapping formula.② Proposing the interference model based on the priority and the overlapping channel interference factor. This paper changes the thing that the previous model is only related to the channel and the distance between APs by using the priority in interference model. AP interference is calculated from the three aspects in the proposed interference model: the degree of channel overlap, the distance between APs and the priority. The assignment scheme got by the proposed DFS can not only make the minimum interference in the network, but also assign the good channel to the high priority AP. After that we have a detail analysis on the result impact and the algorithm parameters generated.