Wide Area Wireless Data Services

Wide Area Wireless Data Services

Wide area wireless data services provide wireless data to high-mobility users over a very large coverage
area. In these systems a given geographical region is serviced by base stations mounted on towers,
rooftops, or mountains. The base stations can be connected to a backbone wired network or form a
multihop ad hoc network.
Initial wide area wireless data services has very low data rates, below 10 Kbps, which gradually
increased to 20 Kbps. There were two main players providing this service: Motient and Bell South Mobile
Data (formerly RAM Mobile Data). Metricom provided a similar service with a network architecture
consisting of a large network of small inexpensive base stations with small coverage areas. The increased
efficiency of the small coverage areas allowed for higher data rates in Metricom, 76 Kbps, than in the
other wide-area wireless data systems. However, the high infrastructure cost for Metricom eventually
forced it into bankruptcy, and the system was shut down. Some of the infrastructure was bought and is
operating in a few araas as Ricochet.
The cellular digital packet data (CDPD) system is a wide area wireless data service overlayed on
the analog cellular telephone network. CDPD shares the FDMA voice channels of the analog systems,
since many of these channels are idle due to the growth of digital cellular. The CDPD service provides
packet data transmission at rates of 19.2 Kbps, and is available throughout the U.S. However, since newer
generations of cellular systems also provide data services, CDPD is mostly being replaced by these newer
services.
All of these wireless data services have failed to grow as rapidly or to attract as many subscribers as
initially predicted, especially in comparison with the rousing success of wireless voice systems and wireless LANs. However, this might change with the rollout of the widely anticipated Wi-Max systems. Wi-Max
is based on the IEEE 802.16 standard. The core 802.16 specification is a standard for broadband wireless
access systems operating at radio frequencies between 10 GHz and 66 GHz with a target average data
rate of 70 Mb/s and peak rates of up to 268 Mb/s. The core standard has evolved in the 802.16a standard
to specify multiple physical layer specifications and an enhanced multiple access specification. Products
compatible with the Wi-Max standard should be available over the next few years. The proliferation of
laptop and palmtop computers and the explosive demand for constant Internet access and email exchange
indicates a possibly bright future for Wi-Max, but how Wi-Max ultimately plays out will depend on its
adoption by equipment vendors, pricing, and competition from other wireless services.