Repurposing Protocol Messages for Wireless Handoff Preparation
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Solution Overview
Problem
In wireless communication systems, especially those employing IEEE 802.11 standards, the lack of probe requests from mobile stations to access points during handoffs complicates the preparation and transfer of services, leading to potential service disruptions and inefficiencies in handoff processes.
Innovation Solution
The control element identifies impending handoffs by repurposing messages, such as IEEE 802.11k requests for neighbor lists, to proactively prepare destination access points for seamless service transfer without requiring explicit probe messages from mobile stations, ensuring that both the control element and destination access points are ready to receive and service the mobile station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the mobile station uses 802.11k to request a neighbor list and connects to a new access point without probe requests, then the handoff speed is improved, but the control element cannot know ahead of time which destination access point the mobile station will transfer to, causing the destination access point to be unprepared for service transfer
Solution Approach 1:
The control element performs preliminary actions by monitoring messages from the mobile station (such as 802.11k neighbor list requests or 802.11r fast handoff messages) to identify impending handoffs before they occur. This allows the control element to proactively prepare the destination access point by transferring the BSSID associated with the mobile station in advance, ensuring the destination access point is ready to service the mobile station immediately upon connection without requiring probe requests.
Solution Approach 2:
The system implements feedback by having the control element monitor and analyze messages exchanged between the mobile station and access points (such as 802.11k or 802.11r messages). These messages provide feedback information that allows the control element to detect the mobile station's intent to handoff and respond by preparing the destination access point accordingly, thus maintaining awareness of handoff events even when traditional probe requests are eliminated.
2Productivity
If the mobile station conducts fast handoff using 802.11r without sending probe requests, then the handoff efficiency is improved, but the destination access point may not have prepared to transfer the BSSID or service the mobile station
Solution Approach 1:
The control element performs preliminary preparation of the destination access point by monitoring 802.11r fast handoff messages from the mobile station. Upon detecting such messages, the control element proactively transfers the BSSID associated with the mobile station to the destination access point before the mobile station actually connects. This preliminary action ensures that when the mobile station performs fast handoff, the destination access point is already configured and ready to provide continuous service without interruption.
3Reliability
If traditional probe requests are used for handoff, then the control element can identify impending handoffs and prepare destination access points, but the handoff process becomes slower and less efficient
Solution Approach 1:
The patent makes existing protocol messages (802.11k neighbor list requests and 802.11r fast handoff messages) serve dual functions: their original purpose for the mobile station to obtain neighbor information or perform fast handoff, and an additional function as indicators to the control element of impending handoffs. This multi-functionality allows the control element to identify handoff events and prepare destination access points without requiring separate probe requests, thus eliminating the time loss while maintaining reliable service preparation.
Data Source
AI summary
A control element identifies the possibility that a station will transfer to a destination AP, and prepares that destination for a handoff. The control element repurposes messages from the station which indicate a possible near-term handoff, to prepare access points to receive that handoff. The control element treats a neighbor list request as a trigger to select which AP's to identify, to restrict the neighbor list to selected AP's, and to prepare each selected AP for a handoff. In selecting a destination AP, the control element also selects a particular set of related features for the combination of that AP and BSS. When an AP receives a repurposed message, it informs the control element, which selects destination AP's for transfer. The control element treats the repurposed message like a probe request. The control element prepares more than one AP for transfer if handoff is possible to more than one AP.