GSM, TDMA, CDMA, & GPRS… what is it?

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By Miro Stoichev

People are often confused about some of the many acronyms and communication technologies that exist. A reader asked WDN to explain several of the common technologies that we hear about every day. Here’s our reply. If you have information that you’d like to provide regarding GSM, TDMA, CDMA, GPRS, or others, please feel free to send your info to the WDN.

GSM – Global System for Mobile Communication

GSM (introduced in 1991) service as of reoughly 1997 was available in more than 100 countries and has become the de facto standard in Europe and Asia. GSM is used on the 900 MHz and 1800 MHz frequencies in Europe, Asia and Australia, and the MHz 1900 frequency in North America and Latin America. GSM allows eight simultaneous calls on the same radio frequency and uses narrowband TDMA.

TDMA – Time Division Multiple Access

The technology is used for digital trasmissions such as moving a signal between a mobile phone and a base station. With TDMA, a frequency band is chopped into several channels or time slots which are then stacked into shorter time units, facilitating the sharing of a single channel by several calls. GSM actually uses narrowband TDMA, enabling eight simultaneous calls on the same radio frequency. Most recently, the numbers of TDMA users world-wide was estimated at 82 million as of November 2001 – more than 50% increase in one year.

CDMA – Code Division Multiple Access

A wireless transmission method in which signals are encoded using a random sequence, or code, to define a channel. Experts believe that CDMA offers improved spectral efficiency over analog transmission in that it allows for greater frequency reuse. Characteristics of CDMA systems include reduce dropped calls, increase battery life and offer more security. CDMA was originally a military technology first used during World War II. Because Qualcomm Inc. created communications chips for CDMA technology, it was privy to the classified information which later became public. Qualcomm has since claimed patents on the technology and was the first to commercialize it. See Qualcomm for more on this. From qualcomm… “CDMA works by converting speech into digital information, which is then transmitted as a radio signal over a wireless network. Using a unique code to distinguish each different call, CDMA enables many more people to share the airwaves at the same time – without static, cross-talk or interference.”

GPRS – General Packet Radio Service

A packet-linked technology that enables high-speed wireless Internet and other communications over a GSM network. GPRS is well suited for sending and receiving small bursts of data. Rest assured that GPRS is NOT related to GPS (Global Positioning System), a technology frequently referred to in mobile communications, particularly location-sensitive technologies (LBS & GIS). GPRS enables information to be sent or received immediately and users are considered to be “always connected” as no dial-up modem connection is required. Benefits include: Faster data speeds and “always on” mobility; Almost instantaneous connection set-up; Connection to an abundance of data sources around the world, through support for multiple protocols, including IP; and A step towards full 3G services. GPRS provides users with fast file download, and effective Internet searching, while GPRS subscribers are charged only for data sent and received and not for time online.

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