Wireless Access Point Temporary IP Assignment for Handoff Latency
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Solution Overview
Problem
Network layer handoff in wireless local area networks (WLANs) experiences high latency due to the time-consuming process of acquiring a new IP address from a DHCP server, which is unacceptable for voice communication applications, often resulting in voice quality degradation or call drops.
Innovation Solution
A method where a wireless access point maintains an available IP address pool and assigns a temporary IP address to a mobile node upon detection of its movement, allowing for immediate communication until a formal IP address is obtained from the DHCP server, thereby reducing handoff latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mobile node acquires a new IP address from a DHCP server through the standard DHCP process, then the mobile node obtains a valid IP address for communication in the new subnet, but the handoff latency becomes excessively long (on the order of seconds)
Solution Approach 1:
The access point pre-allocates IP addresses from the available IP address pool before the mobile node actually needs them for communication. When the mobile node moves to a new subnet, the access point can immediately assign a pre-prepared IP address, eliminating the time-consuming DHCP discovery and offer process. This preliminary preparation of IP addresses resolves the contradiction by ensuring valid IP address availability while minimizing handoff latency.
2Reliability
If the mobile node performs duplicate address detection by sending multiple ARP requests before obtaining a formal IP address, then the mobile node ensures it uses a valid unused IP address, but the latency increases by more than 100 ms
Solution Approach 1:
The access point acts as an intermediary between the mobile node and the IP address allocation process. Instead of the mobile node performing time-consuming ARP requests for duplicate address detection, the access point uses its movement detection capability to identify when a mobile node has moved to its coverage area and directly assigns an available IP address from its pool. This intermediary role eliminates the need for multiple ARP requests while ensuring IP address validity, thus resolving the contradiction between reliability and latency.
Data Source
AI summary
A method and a wireless access point device for a network layer handoff of a wireless mobile node over a wireless local area network. The method includes detecting a wireless mobile node that has moved into the coverage area of the wireless access point device; maintaining an available IP address pool; selecting a temporary IP address from the IP access pool in response to the detection of the mobile node moving into the coverage area; and assigning a temporary IP address to the mobile node for use by the node during an interim period. The method produces a network layer handoff of a wireless mobile node over a local area network. Also provided is a computer readable article of manufacture tangibly embodying computer readable instructions for executing the steps of the method.