Wireless Primer-3G Technology
Vendors are just beginning to activate third-generation networks for commercial purposes. Many sources say that 3G will be the wireless-networking technology of the future, offering data rates high enough for mobile users to work with multimedia Web content, videoconferencing, and e-commerce. 3G is fast, in part, because it uses a 5-MHz-wide carrier signal, rather than the 200- KHz-wide carrier that narrowband CDMA uses.
Wideband code-division multiple access technology, an ITU standard derived
from CDMA, is also known as IMT-2000 direct spread.
This technology is a CDMA upgrade. CDMA2000 offers a migration path, beginning with CDMA2000 1X, which is considered by some sources to be a 2.5G technology because it offers maximum sub-3G data rates of 153.6 Kbits per second. During the next few years, users could move to 1xEV-DO (1x evolution, data only) and 1xEV-DV (1x evolution, data and voice), offering data rates up to 614 Kbits per second, and ﬁnally to 3x, which would provide the full 3G maximum throughput of 2.05 Mbits per second.
Time-division CDMA, developed and used primarily in China, combines timedivision multiplexing and CDMA techniques.