Wireless LAN Handover Latency Reduction via Selective Channel Scanning
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Solution Overview
Problem
Conventional wireless LAN handover methods based on the IEEE 802.11 standard suffer from high latency due to the need for scanning all channels to detect new access points, especially in crowded environments, leading to inefficient handover processes and network load concentration on the strongest signal access points.
Innovation Solution
A method and apparatus that selectively scan channels based on estimated access points in the communication area, using an extended reassociation request frame and neighbor access point table to update information and compute network load values, allowing for informed handover decisions to minimize latency and distribute network load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mobile station scans all channels to detect new access points, then the detection coverage is complete, but the handover latency increases
Solution Approach 1:
The access point maintains a neighbor access point table in advance, containing information about neighboring access points including their channel numbers. When handover is needed, the mobile station receives this pre-prepared information and only scans the specific channels of neighboring access points, rather than scanning all channels. This preliminary preparation of neighbor information significantly reduces handover latency while maintaining reliable detection coverage.
2Ease of operation
If the mobile station performs passive scanning to detect access points, then the scanning process is simple, but the handover must be delayed until beacon frame reception
Solution Approach 1:
The access point proactively provides neighbor access point information to the mobile station through extended beacon frames or probe response frames, so the mobile station doesn't need to wait for beacon frames during passive scanning. The mobile station can immediately perform handover using the pre-provided neighbor information, eliminating the delay while keeping the passive scanning approach simple.
3Device complexity
If the mobile station determines handover based only on signal strength, then the decision process is simple, but the network load concentrates on the strongest signal access point
Solution Approach 1:
The handover decision criteria are extended beyond just signal strength to include additional parameters such as network load information. The access point includes load information in the neighbor access point table, and the mobile station uses both signal strength and load information to make handover decisions. This allows the system to balance load across access points while maintaining a relatively simple decision process.
Data Source
AI summary
A handover method and apparatus at a link layer of a wireless LAN according to the IEEE 802.11 standard are provided to minimize a handover latency. The handover method is performed in a mobile station moving from one subnet to another subnet, each subnet being managed by one of a plurality of access points. Channels available to the mobile station are selectively scanned based on information regarding one and more access points which are estimated to be present in a communication area of the mobile station, and a handover is performed to one of the access points based on the scanning result.