Linux Unwired [Electronic resources] نسخه متنی

1.5 Cellular Data

With the rise of digital cellular phone networks, it
became possible to use these networks to transfer data rather than
just voice. There are several differing and competing technologies
available.

Cellular Digital Packet Data
(CDPD) was one of the first data networking technologies available
for mobile phones. CDPD utilizes unused bandwidth in the 800-900 MHz
range normally used by mobile phones. Data transfer rates max out at
a theoretical 19.2 kbps. Today, CDPD is obsolete, and cellular
carriers are actively trying to phase it out.

General Packet Radio
Service (GPRS) is an add-on technology to existing
Time Division Multiple
Access (TDMA)-based GSM mobile phone networks. Timeslots in the GSM
network are normally allocated to create a circuit-switched voice
connection. With a GPRS-enabled network, the timeslots are used for
packet data as needed. This by design creates a very slow data
network with high latency and, theoretically, the speed of a 56 kbps
modem. AT&T Wireless,
T-Mobile, and
Cingular
Wireless use this technology. In 2003, an enhancement to GPRS,
Enhanced Data
Rates for Global Evolution (EDGE), was partially rolled out in the
United States by AT&T Wireless and Cingular. In theory, EDGE can
triple the data rate of GPRS, but you need an EDGE-capable handset,
such as the Nokia 6200, to use it.

1xRTT stands for
Single Carrier Radio Transmission
Technology and is part of the CDMA2000 family of protocols, which
includes successors to 1xRTT such as Single Carrier Evolution Data
Only (1xEV-DO). It is built on top of the CDMA-based mobile phone
networks and allows for ISDN-like data transfer speeds up to 144 kbps
(1xEV-DO is capable of much higher speeds).
Sprint's PCS Vision and
Verizon's Express
Network use this technology. As of this writing, Verizon Wireless is
experimenting with 1xEV-DO in two U.S. markets, with testers
obtaining data rates between 500 and 800 kbps.