IPFax T0 Timer Accuracy via SIP Response Feedback

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Solution Overview

Problem

In IPFAX communication, the timing of dialing completion is not accurately measured due to the difference between AT commands and SIP commands, leading to inaccurate T0 timer measurements and improper timing for sending T.38 CNG commands.

Innovation Solution

A communication apparatus and method that converts AT dial requests into SIP session-establishment requests, starting the T0 timer upon receiving a provisional or session-establishment response, ensuring accurate measurement of the time period T0 for line connection and optimizing the timing of sending T.38 CNG commands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the T0 timer is started with end of a command, then the command execution timing is simple to track, but the measurement by the T0 timer cannot be accurate

Engineering Contradiction:

ImproveT0 timer measurement accuracyVSAvoidcontrol complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses feedback from SIP response messages (provisional responses or session-establishment responses) to determine when to start the T0 timer. The control unit monitors the response from the opposing machine and triggers the timer start based on this feedback, ensuring accurate measurement of the line connection time period T0 while maintaining clear control logic.

Inventive Principle:

Principle #23Feedback

2Reliability

If a T.38 CNG command is sent out before a SIP session is established, then the command can be sent immediately, but it is useless and wastes resources

Engineering Contradiction:

ImproveT.38 CNG command effectivenessVSAvoiddelay in sending CNG command

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary actions by first establishing the SIP session and receiving the session-establishment response before sending the T.38 CNG command. The control unit is configured to send the CNG command only after confirming that the SIP session is established, ensuring the command is effective while minimizing delay through efficient session establishment procedures.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If the timing of dialing completion cannot be accurately controlled, then the AT command processing is simple, but the FAX application cannot exactly know the timing with which dialing is completed

Engineering Contradiction:

Improvedialing completion timing accuracyVSAvoidFAX application control simplicity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The control unit acts as an intermediary between the AT command processing and the FAX application. It receives the SIP response indicating dialing completion, processes this information, and then provides accurate timing information to the FAX application. This intermediary role ensures precise timing measurement while keeping the FAX application's control logic simple and unchanged.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9578138B2Sip session management for fax communication

Publication Date: 2017.02.21 CANON KK

AI summary

A communication apparatus that accurately measure a time period T0 required for line connection in IPFAX, and optimizes the timing with which a T.38 CNG command is sent out. An AT command that is a dial request is converted into a SIP command that is a session-establishment request, and the SIP command is sent. When there is a provisional response or a session-establishment response to the sent SIP command, a T0 timer which clocks the time period T0 is caused to start counting.