The "Second Generation" truly
arrived with the implementation of digital cellular systems in the early 1990s. The first
digital standards to be implemented commercially were based on TDMA (Time Division
Multiple Access). These standards are US-TDMA, GSM (Global System for Mobile
Communications) and PDC (Personal Digital Cellular). Over the last two years, cdmaOne,
which is based on IS-95 CDMA (Code Division Multiple Access) and the ANSI-41 (formerly
IS-41) networking standard, has joined GSM and PDC as one of the three most rapidly
growing digital cellular standards worldwide. To date, these standards have reduced
equipment costs, offered operators improvements in system capacity, and have increased the
levels of call quality and services available to subscribers.
Traditionally, it has been the need for increased system
capacity, advanced features, and improved networking which has driven the evolution of
cellular standards. More recently, though, it has been the expanding interest in wireless
data services that has been driving such developrnent. This interest in wireless data
services is largely due to the expected convergence of a number of major trends. These
trends include increased personal mobility, the increased use of portable computing, and
the explosion in data communications that is expected to result from the growth of the
Internet and the demand for multi-media applications.
These factors have driven vendors, operators, and the
standards bodies towards the near-term development of specifications for "Generation
2.5" or "2.5G" functionality. 2.5G will primarily involve the enhancement
of circuit-switched data specifications for speeds of up to about 64 kbps (as opposed to
about 14.4 kbps for 2G systems), as well as the addition of advanced packet-switched
functionality. In the OSM environment, these capabilities are reflected in the "High
Speed Circuit Switched Data" and OPRS (Generalized Packet Radio Service)
specifications. Similarly, the CDG (CDMA Development Group) has introduced specifications
for 64 kbps data to the Telecommunications Industry Association (TIA).Initial commercial
implementation of 2.50 capabilities is expected during 1998-1999.
The functions provided by 2.5G falls far short of
the capablities that will be required to support the industry's vision of the future. A
rapidly growing body of effort is working on development of the "Third
Generation", or "3G".