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ITU-T Study Group 16 (Study Period 2005-2008) |
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Question 11/16 - Voiceband Modems and Protocols: Specification and Performance Evaluation |
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(Continuation of Questions 11, 12 and 13/16)
- Motivation
During previous study periods, activity related to voiceband modems has been high. Of particular interest is the use of voiceband modems for network access, which has become by far the dominant application. Today, people use modems to access the Internet, an online service or a corporate network. In the predominant case the network connection consists of a central-site modem directly connected to the digital backbone of the PSTN and a remote user's modem connected via an analogue local loop to the PSTN.
With the evolution of Packet based Networks and specifically voice over packet, the PSTN is expanding to include the advantages of these network types. The need to ensure the best performance transmission of voiceband modems over these networks is a necessary requirement. This also includes supporting the ability of end-point modems to interoperate with the same performance as expected from circuit switched networks.
There is a need for the continued study of DTE-DCE and DCE-DCE interfaces and protocols to keep pace with changing modem and DTE technologies and applications remains of high importance. This includes work on HDLC-based protocols for both modem-based communication, e.g. V.42 and V.75, and ISDN-based communication, e.g. V.120. Additionally, data compression on top of these protocols is addressed.
Although digital networks are rapidly being deployed around the world, analogue access will remain the only choice in many locations. Users in these locations will continue to have the need to access and exchange electronic information. Therefore, the continued study of modem technology is required to supply these users with the best standardized tools to meet their needs.
This question is responsible for all aspects of PSTN modem standardization.
- Study Items
- Techniques to support the transmission of voice band data over IP networks, such as signal discrimination techniques for IP gateways.
- Modulation techniques for high-speed voiceband modems connected to either an analogue local loop or directly to a circuit-switched digital network.
- Optimised techniques for high-speed voiceband modems connected via a packet switched digital network.
- Modulation techniques compatible with an optional linear coding mode in PSTN network.
- Procedures for initial training, retraining, rate re-negotiation (including seamless), determination of a given connection's ability to support a particular modulation mode, fallback to other modulation modes, etc.
- Procedures for the exchange of capabilities and selection of operating mode, such as enhancements to Recommendation V.8 and V.8 bis, as well as procedures for switching between operating modes.
- Compatibility with network equipment, such as CME and echo control devices.
- Interworking issues arising from the use of modems on various multimedia platforms.
- Means for evaluating voiceband modem performance, including the specification of network models and test procedures.
- DTE-DCE interchange circuits including functional and electrical characteristics.
- Protocols to be used by the DTE to transfer information over the DTE-DCE interface for the purposes of:
- dialling; and
- configuration and control of the local DCE by the DTE.
- The extension of DTE-DCE protocols to the remote DCE (DTE), to be considered in conjunction with Question 14/16.
- Terminal adapters (TAs) for devices having V-series interfaces for use on ISDN bearer services. This will include their use on:
- multi-use bearer service; and
- other bearer services.
- Protocols between DCEs for applications such as:
- half-duplex operation;
- statistical multiplexing;
- secure access and privacy of data;
- compression of synchronous data;
- improved data compression algorithms;
- management of remote DCEs.
- Procedures to ensure reliable interworking between DTEs on the PSTN using modems and:
- DTEs on non-ISDN digital networks;
- DTEs on ISDNs using terminal adapters (TAs) with modems on 3.1 kHz audio bearers, TAs for adaptation to digital bearers, and TAs for use on multi-use bearer services.
- Maintenance of existing modem, TA and related Recommendations.
- Tasks
Tasks include, but are not limited to:
- Development of enhancements to Recommendation V.150.x (2005) series.
- Development of a Text-over-IP Protocol Recommendation (V.ToIP).
- Development of Voice Band Data Protocol Recommendation (V.152).
- Coordinate the application and integration of V.150.1, V.152 and V.ToIP with other relevant Recommendations.
- Development of new DTE-DCE interface-related Recommendations as well as the revision of existing ones. Develop new control Recommendations as well as the update of Recommendations V.25X-series and V.80.
- The development of new and improved data compression techniques.
- Maintenance of related Recommendations: V.8, V.8bis, V.17, V.21, V.22, V.22 bis, V.24, V.27, V.27 bis, V.27 ter, V.29, V.32, V.32 bis, V.34, V.42, V.42 bis, V.43, V.44, V.56 bis, V.56 ter, V.59, V.61, V.70, V.75, V.76, V.80, V.90, V.91, V.92, V.110, V.120, V.130, V.150.0, V.150.1, V.250, V.251, V.252, and V.253.
An up-to-date status of work under this Question is contained in the
SG 16 Work Programme.
- Relationships
Recommendations:
- G.711, G.799.1, G.769, H.323, I.366.2, T.30, T.38 and V.18
Questions:
- Questions 2/16 and 3/16 on gateway access to IP networks.
- Question 14/16 on fax and audiographics conferencing.
- Questions 15/16 to 18/16 on network signal processing.
Study Groups:
- ITU-T Study Group 2 on services.
- ITU-T Study Group 11 on network signalling systems.
- ITU-T Study Group 13 on ISDN, voiceband and text telephone modems over AAL2.
- ITU-T Study Group 17 on DTE-DCE interface issues.
Other bodies:
- ISO/IEC JTC 1/SC 6 on DTE-DCE interface issues HDLC and data compression.
- Other organizations using "AT" commands, e.g. ETSI, 3GPP, 3GPP2.
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