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 lTD is working to develop a family of standards for the next-generation
wireless devices. The new standards will use higher frequencies to increase capacity.
The new 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 (IMT2000).
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.
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