The Global Cellular Network
Today there is no single cellular network. Devices support one or two of a myriad of technologies and generally work only within the confines of a single operator's network. To move beyond this model, more work must be done to define and implement standards.
The International Telecommunication Union (ITU) is working to develop a family of standards for next-generation wireless devices. The new standards will use higher frequencies to increase capacity. These standards will also help overcome the incompatibilities introduced as the different first- and second-generation networks were developed and deployed over the last decade.
The dominant first-generation digital wireless network in North America was the Advanced Mobile Phone System (AMPS). This network offers a data service using the Cellular Digital Packet Data (CDPD) overlay network, which provides a 19.2 Kbps data rate. The CPDP uses idle periods on regular voice channels to provide the data service.
The key second-generation wireless systems are the Global System for Mobile Communications (GSM), Personal Communications Service (PCS) IS-136, and PCS IS-95. The PCS standard IS-136 uses time-division multiple access (TDMA), while IS-95 uses code-division multiple access (CDMA). The GSM and PCS IS-136 use dedicated channels at 9.6 Kbps to deliver the data service.
The ITU is developing International Mobile Telecommunications-2000 (IMT-2000). This family of standards is intended to provide a seamless global network. The standards are being developed around the 2 GHz frequency band. The new standards and frequency band will provide data rates up to 2 Mbps.
In addition to defining frequency usage, encoding techniques, and transmission, standards also need to define how mobile devices will interact with the Internet. Several standards bodies and industry consortiums are working to that end. The Wireless Application Protocol (WAP) Forum is developing a common protocol that allows devices with limited display and input capabilities to access the Internet. The Internet Engineering Task Force (IETF) is developing a mobile IP standard that adapts the ubiquitous IP protocol to work within a mobile environment.