Circuit Switched Data

Circuit Switched Data

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). 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.

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.

GSM data transmission has advanced since the introduction of CSD:


The T-Mobile system is area/city specific. It works in Denver, Colorado, Savannah, Georgia, Washington, DC, and Miami, FL and 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 the 4th May 2010.[1]

In the UK CSD is available with Vodafone, but requires activation by Vodafone customer services.


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Look at other dictionaries:

  • Circuit Switched Data — (CSD) es la forma original de transmisión de datos desarrollada para los sistemas de telefonía móvil basados en el acceso múltiple por división de tiempo (TDMA) como el GSM. CSD usa un intervalo de tiempo (time slot) de radio individual para… …   Wikipedia Español

  • Circuit Switched Data — (CSD)  технология передачи данных, разработанная для мобильных телефонов стандарта GSM. CSD использует один временной интервал для передачи данных на скорости 9,6 кбит/с в подсистему сети и коммутации (Network and Switching Subsystem NSS),… …   Википедия

  • Circuit Switched Data — ist ein Übertragungsverfahren beim Mobilfunk, bei dem eine Datenverbindung vom Mobilfunktelefon zu einer (beliebigen) Gegenstelle hergestellt wird. Diese Verbindung ist mit einem einfachen Telefongespräch vergleichbar. Im Unterschied dazu werden… …   Deutsch Wikipedia

  • Circuit Switched Data — Pour les articles homonymes, voir CSD. Le Circuit Switched Data (CSD) est la forme originale de transfert de données développée pour les systèmes de téléphone mobiles basés en technologie TDMA comme le GSM. Il a un fonctionnement similaire à… …   Wikipédia en Français

  • circuit switched data —    A method for keeping the circuit open between users for the duration of the connection …   IT glossary of terms, acronyms and abbreviations

  • High-Speed Circuit-Switched Data — (HSCSD), is an enhancement to Circuit Switched Data, the original data transmission mechanism of the GSM mobile phone system, four times faster than GSM, with data rates up to 38.4 kbit/s.As with CSD, channel allocation is done in circuit… …   Wikipedia

  • High-Speed Circuit-Switched Data — (HSCSD), es una mejora al mecanismo de transmisión de datos de GSM o circuit switched data (CSD). Fue aprobado por la ETSI en 1997 y fue desplegado por varios operadores de GSM en el mundo. HSCSD introduce dos modificaciones tecnológicas que… …   Wikipedia Español

  • High Speed Circuit Switched Data — (HSCSD) est une technologie dont le but est de fournir un débit plus élevé pour les applications nécessitant des transferts de données. Le GSM utilise le TDMA, c est à dire que le temps est divisé en slots (période donnée). En GSM, un mobile… …   Wikipédia en Français

  • High Speed Circuit Switched Data — (HSCSD), deutsch etwa schnelle leitungsvermittelte Datenübertragung, ist eine Erweiterung des GSM Mobilfunk Standards CSD um schnellere Datenübertragung zu erreichen. Durch Bündelung mehrerer Datenkanäle können theoretisch Datenübertragungsraten… …   Deutsch Wikipedia

  • High Speed Circuit Switched Data — High Speed Circuit Switched Data,   HSCSD …   Universal-Lexikon

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