World Library  
Flag as Inappropriate
Email this Article

Circuit Switched Data

Article Id: WHEBN0000959943
Reproduction Date:

Title: Circuit Switched Data  
Author: World Heritage Encyclopedia
Language: English
Subject: High-Speed Circuit-Switched Data, List of mobile phone standards, Sony Ericsson K800i, Personal Digital Cellular, Mobile broadband
Collection: Gsm Standard
Publisher: World Heritage Encyclopedia

Circuit Switched Data

In communications, Circuit Switched Data (CSD) is the original form of data transmission developed for the time division multiple access (TDMA)-based mobile phone systems like Global System for Mobile Communications (GSM). As of 2010, many telecommunication carriers are dropping support for CSD, and CSD has been superseded by GPRS and EDGE (E-GPRS).


  • Technical 1
  • Availability 2
  • Related 3
  • See also 4
  • References 5


CSD uses a single radio time slot to deliver 9.6 kbit/s data transmission to the GSM Network and Switching Subsystem where it could be connected through the equivalent of a normal modem to the Public Switched Telephone Network (PSTN) allowing direct calls to any dial-up service. For backwards compatibility the IS-95 standard also supports CDMA Circuit Switched Data however unlike TDMA there are no time slots, all CDMA radios can be active all the time to deliver up to 14.4 kbit/s data transmission speeds. With the evolution of CDMA to CDMA2000 and 1xRTT the use of IS-95 CDMA Circuit Switched Data declined in favour of the faster data transmission speeds available with the newer technologies.

Prior to CSD, data transmission over mobile phone systems was done by using a modem, either built into the phone or attached to it. Such systems were limited by the quality of the audio signal to 2.4 kbit/s or less. With the introduction of digital transmission in TDMA-based systems like GSM, CSD provided almost direct access to the underlying digital signal, allowing for higher speeds. At the same time, the speech oriented audio compression used in GSM actually meant that data rates using a traditional modem connected to the phone would have been even lower than with older analog systems.

A CSD call functions in a very similar way to a normal voice call in a GSM network. A single dedicated radio time slot is allocated between the phone and the base station. A dedicated "sub-time slot" (16 kbit/s) is allocated from the base station to the transcoder, and finally another time slot (64 kbit/s) is allocated from the transcoder to the Mobile Switching Centre (MSC).

At the MSC, it is possible to use a modem to convert to an "analog" signal, though this will typically actually be encoded as a digital pulse-code modulation (PCM) signal when sent from the MSC. It is also possible to directly use the digital signal as an Integrated Services Digital Network (ISDN) data signal and feed it into the equivalent of a remote access server.


The T-Mobile system is area/city specific. It works in Las Vegas into SoCal roaming onto Cingular.

There is no service in Sarasota, Florida or anywhere in Texas. Fax services required a second number for an additional $10/mo.

The AT&T Mobility GSM EDGE network supports CSD in legacy Cingular and AT&T Wireless footprint areas. It is not generally available but can be provisioned for selected customers with specific needs requiring the service.

Currently in Australia, CSD is only available on Mobile Plans with Vodafone, Optus and Telstra, however Telstra is in the process of shutting down their CSD network as of 4 May 2010.[1]

In the UK CSD is available with all of the mobile networks but may require activation by the networks customer service team. CSD is commonly used in the UK for early smart metering deployments and as such there are no real plans to decommission or remove access to this part of the 2G network.


GSM data transmission has advanced since the introduction of CSD:

See also


  1. ^ "Telstra ending CSD calls". Retrieved 5 July 2011. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.