Media Gateway Handoff for Multi-Mode Mobile Stations
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Solution Overview
Problem
Multi-mode mobile stations face challenges in seamlessly transitioning between different wireless networks, such as WWANs and WLANs, leading to disruptions in communication sessions when moving out of coverage areas.
Innovation Solution
A method and system that utilize a media gateway and call control system to facilitate handoffs between WWANs and WLANs, allowing multi-mode mobile stations to maintain communication sessions by establishing and switching between call legs through different wireless networks, ensuring a 'soft' handoff process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a multi-mode mobile station uses diverse wireless access technologies (WWAN and WLAN) to extend coverage and improve transmission capabilities, then wireless coverage area and bandwidth are improved, but seamless handoff between networks cannot be achieved
Solution Approach 1:
The system establishes a second call leg through the target wireless network before dropping the first call leg. The mobile station receives media through the second interface and stores it, accumulating stored media, before the handoff is complete. This preliminary establishment of the second connection ensures seamless handoff while maintaining extended wireless coverage through multi-mode operation.
2Duration of action of moving object
If the mobile station switches networks quickly to maintain coverage, then service continuity is improved, but media transmission completeness is compromised
Solution Approach 1:
The mobile station begins receiving and storing media through the second interface before the handoff is complete, accumulating stored media in advance. This ensures that when the first call leg is dropped, no media is lost and service continuity is maintained without information loss.
Solution Approach 2:
The system maintains continuous media reception by having the mobile station receive media through both the first and second interfaces during the handoff transition. The stored media accumulates continuously, ensuring uninterrupted service and complete media transmission throughout the network switch.
3Reliability
If the system establishes a second call leg before dropping the first, then seamless handoff is achieved, but system complexity increases
Solution Approach 1:
The network infrastructure acts as an intermediary to manage the dual call leg state during handoff. The mobile station receives handoff instructions from the network and coordinates the establishment and dropping of call legs through controlled signaling. This intermediary management simplifies the complexity by centralizing control in the network rather than requiring complex mobile station logic.
Data Source
AI summary
A multi-mode mobile station includes a first interface for wireless communication with a wireless local area network (WLAN) and a second interface for wireless communication with a wireless wide area network (WWAN). A call control system routes all calls to and from the multi-mode mobile station through a media gateway that serves as an anchor point for handoffs between the WLAN and WWAN. For example, while involved in a call that has a WLAN call leg from the media gateway, the multi-mode mobile transmits a handoff request. The call control system then establishes a WWAN call leg from the media gateway, and the multi-mode mobile station stores in a buffer any media received via the WWAN call leg. The call control system subsequently transmits a handoff instruction to the multi-mode mobile station. In response, the multi-mode mobile station plays out the stored media and drops the WLAN call leg.