Date of Award
Santa Clara : Santa Clara University, 2020.
Master of Science (MS)
Computer Science and Engineering
While the cellular technology has been evolving continuously in recent years and client handoffs remain unnoticed, the 802.11 networks still impose an enormous latency issue once the client device decides to roam between the Access Point (AP). This latency is caused by many factors reckoning on scanning the channels and searching for APs with better signal strength. Once data from all the nearby APs has been collected, the client picks the most suitable AP and tries to connect with it. The AP verifies if it has enough capability to serve the client. It also ensures that the client has the required parameters and supported rates to match with the AP. The AP then processes this request, generates a new Association ID and sends it back to the client, thereby granting access to connect. Throughout this re-association process, the client fails to receive or send any data frames and experiences a lag between leaving the old and associating with a new AP. Originally, 802.11 authentication frames were designed for Wired Equivalent Privacy protocol, but later it was found to be insecure and thus got depreciated. Keeping these security aspects concerning shared key authentication in mind, few additional drafts were introduced by IEEE that concerned many key exchanges between the devices.
IEEE 802.11r was introduced in 2008 that permits wireless clients to perform faster handoff along with additional data security standards. The key exchange method was redefined and also the new security negotiation protocol started serving wireless devices with a better approach. This enables a client to set up the Quality of Service state and security on an alternative AP before making a transition which ends up in minimal connectivity losses. Although this was an excellent step towards minimizing the service disruption and channel scanning, failure to remain connected with consecutive suitable APs within the minimum time continued to be a challenge. Different manufacturers use their custom-built methodology of handling a client handoff and hence the latency costs differ based on the type of handoff scheme deployed on the device.
This thesis focuses on the foremost economical researches throughout recent years which targets minimizing the delays involved with channel scanning and AP selection. A wide sort of enhancements, whether it is on a client device or the AP, has been discussed and compared. Some modifications are associated with enhancing channel scan period or using beacons, and probe requests/responses in an efficient manner. Others concentrate on modifying the device hardware configuration and switching between Network Interfaces. Central controllers are a solution to handoff delays that may track the status of each device within the network and guide them to provide the appropriate Quality of Service to the end-users.
Singh, Dhananjay, "Channel Scanning and Access Point Selection Mechanisms for 802.11 Handoff: A Survey" (2020). Computer Science and Engineering Master's Theses. 15.