IP Phone Analog Line Sharing for PSTN Failover

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Solution Overview

Problem

Current methods for providing failover connections to the Public Switched Telephone Network (PSTN) for multiple IP phones in a subnet require a large number of analog line peripherals, which is impractical for subnets with over 100 IP phones.

Innovation Solution

A client/server network architecture where IP devices can access and share network capabilities, including analog line resources, among themselves when disconnected from the central server, using multicast Phone Capabilities messages and resource request/grant mechanisms to distribute the load and reduce the need for individual peripherals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If each IP phone is provided with an analog line peripheral for failover connections, then reliability is improved, but device complexity and cost increase significantly

Engineering Contradiction:

Improvefailover connection reliabilityVSAvoidnumber of analog line peripherals

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple IP phones share a single analog line peripheral through the central server's call management. When primary VoIP connections fail, the server redirects calls from multiple phones through the same physical analog line, combining multiple failover requirements into one shared resource. This reduces the total number of analog line peripherals needed while maintaining reliability for each phone.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The central server performs multiple functions: it manages normal VoIP routing, monitors connection status, and acts as a call gateway to analog lines. By making the server multi-functional, the system eliminates the need for each phone to have dedicated analog line peripherals, as the server universally handles failover for all connected IP phones.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Loss of substance

If analog line peripherals are reduced to降低成本, then cost is improved, but failover capability may be compromised

Engineering Contradiction:

Improvenumber of analog line peripheralsVSAvoidPSTN failover capability

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The central server acts as an intermediary between IP phones and the PSTN analog line. It receives VoIP calls, monitors their status, and automatically routes failed calls through available analog line peripherals to the PSTN. This intermediary approach allows efficient utilization of fewer analog line peripherals while maintaining reliable failover capability through intelligent call management.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements feedback mechanisms where the central server continuously monitors the status of VoIP connections and analog line availability. When primary connections fail, the server detects this through feedback signals and automatically activates failover routing through analog lines, ensuring reliability is maintained despite having fewer physical peripherals.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8681777B2Method for sharing resources over a network

Publication Date: 2014.03.25 MITEL CORP

AI summary

In a client/server network, each of a plurality of IP devices has access to a network capability, such as an analog line, when connected to a central server. At least one of the IP devices is in direct communication with a second analog line and grants other IP devices access to the second analog line when the other IP devices lose their connection to the central server.