Fast Roaming Scheme Design And Implementation Based On IEEE802.11

With the development of mobile Internet,new Internet applications are increasingly demanding mobile networks.As the most popular Internet access method in the past decade,Wi-Fi is widely used due to the advantages of easy to use,high speed,low latency,low cost,and etc.However,in the scenario of STA mobile,the current Wi-Fi service capability still has room for optimization.The essential reason of restricting the quality of the Wi-Fi service in the users' mobile scenario is that the STA needs to perform time-consuming roaming operations between multiple APs.Moreover,since the roaming process is driven by the STA,the main steps needs to be performed on the basis of disconnecting with the previous AP,thus the network quality of the applications on application layer is greatly affected.Original Wi-Fi roaming needs to be completed through the procedures of authentication,re-association,and four-way handshake to exchange keys,which inevitably results in a loss of Wi-Fi during the roaming process for a long time.A common optimization idea for this problem is to complete time-consuming operations such as key exchange before the association,thereby speeding up the roaming process,but since the roaming process is still driven by the STA,the step of disconnecting and reconnecting the Wi-Fi still exists,resulting in Wi-Fi loss with time getting shorter.In order to solve this problem,the main optimization idea of this thesis is to make AP drive Wi-Fi roaming to avoid the disconnection and reconnection process between STA and Wi-Fi,and make the roaming process completed without sensing on the device side.Therefore,it has advantages of high roaming efficiency,high resource utilization,good roaming user experience and so on.Aiming at the problem of roaming speed and service quality of Wi-Fi,this thesis designs and implements a Wi-Fi fast roaming scheme working on the 802.11 protocol family.The fast roaming scheme works through the cooperation between APs in the same BSS,which uses the STA signal strength perceived by APs as the reference,the AP as the roaming drive point,the fast roaming protocol as the control mode,and the means of resource reservation,pre-authentication and pre-association,to complete high-quality collaborative services of multiple APs to STAs.The protocol is more sensitive to the device connection network status,and can complete the background Wi-Fi roaming on the basis of the STA maintaining the continuous network online,which brings a great improvement to the STA's online experience.Moreover,the Wi-Fi fast roaming scheme in this thesis proposes a master-slave structure with roaming process controller and a distributed structure without roaming process controller,which is suitable for different application scenarios and has high application value.