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 Today, CDPD is obsolete, and cellular carriers are actively trying to phase it out.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.