SIP Server Signaling for Seamless Voice Call Handoff in WLAN
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Solution Overview
Problem
Current wireless communication systems experience interruptions or call drops when a user roams between access points in a wireless local area network (WLAN) during voice calls, due to non-seamless WLAN coverage.
Innovation Solution
A method and system that utilize a Session Initiation Protocol (SIP) server to monitor signal characteristics and send messages indicative of pending transfers between access points, allowing for proactive management of voice calls, such as placing them on hold or transferring them to another network, to ensure seamless connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wireless device transfers between access points during a voice call, then the user can maintain mobility and continue using the WLAN network, but the voice call may be interrupted or dropped due to non-seamless WLAN coverage
Solution Approach 1:
The system performs preliminary actions by detecting when a wireless device is approaching the edge of an access point's coverage area and proactively initiating a handoff procedure before the device actually loses connection. This includes notifying the call server of the pending transfer and preparing the target access point in advance, ensuring seamless voice call continuity during the transition.
2Reliability
If the WLAN coverage is not seamless, then the wireless device will experience periods without connection during roaming, but implementing proactive handoff signaling requires additional system complexity
Solution Approach 1:
The patent introduces a call server as an intermediary component that coordinates the handoff process between access points. The call server receives notifications from access points about pending transfers and manages the reconnection process, distributing the complexity across multiple system components rather than requiring complex logic in each access point or wireless device.
3Reliability
If the wireless device monitors signal characteristics to determine when to transfer, then the transfer can be optimized for quality, but the device consumes additional energy and processing resources
Solution Approach 1:
The system implements feedback mechanisms where access points monitor signal characteristics and automatically notify the call server when a wireless device approaches the coverage boundary. This feedback loop enables optimized transfer decisions based on real-time signal quality without requiring continuous active monitoring and processing at the wireless device itself, reducing its energy consumption.
Data Source
AI summary
A method for signaling a transfer of a voice call communicated between a wireless device and a second device from a first access point to a second access point in a wireless network, the second device coupled to the first and second access points through a server, the method comprising: receiving at the server from the wireless device a message indicative of a pending transfer between the first and second access points, wherein the wireless device determines whether to send the message by monitoring a characteristic of signals received from each of the first and second access points; and, sending from the server to the second device a message indicative of the pending transfer to thereby prepare the second device for a possible interruption of the voice call.