![](https://csdnimg.cn/release/download_crawler_static/4779678/bg10.jpg)
P1: OTA/XYZ P2: ABC
c01 JWBK249/Myung August 27, 2008 19:29 Printer Name: Yet to Come
2 Single Carrier FDMA
speech transmission. Second generation technology, deployed in the 1990s,
transmits speech in digital format. Equally important, second generation
systems introduced advanced security and networking technologies that
make it possible for a subscriber to initiate and receive phone calls through-
out the world.
Even before the earliest second generation systems arrived on the mar-
ket, the cellular community turned its attention to third generation (3G)
technology with the focus on higher bit rates, greater spectrum efficiency,
and information services in addition to voice telephony. In 1985, the Inter-
national Telecommunication Union (ITU) initiated studies of Future Public
Land Telecommunication Systems [1]. Fifteen years later, under the head-
ing IMT-2000 (International Mobile Telecommunications-2000), the ITU
issued a set of recommendations, endorsing five technologies as the basis of
3G mobile communications systems. In 2008, cellular operating companies
are deploying two of these technologies, referred to as WCDMA (wideband
code division multiple access) and CDMA2000, where and when they are
justified by commercial considerations. Meanwhile, the industry is looking
beyond 3G and considering SC-FDMA as a leading candidate for the “long
term evolution” (LTE) of radio transmissions from cellular phones to base
stations. It is anticipated that LTE technology will be deployed commer-
cially around 2010 [2].
With respect to radio technology, successive cellular generations have
migrated to signals transmitted in wider and wider radio frequency bands.
The radio signals of first generation systems occupied bandwidths of
25 and 30 kHz, using a variety of incompatible frequency modulation for-
mats. Although some second generation systems occupied equally narrow
bands, the two that are most widely deployed, GSM and CDMA, occupy
bandwidths of 200 kHz and 1.25 MHz, respectively. The third generation
WCDMA system transmits signals in a 5 MHz band. This is the approxi-
mate bandwidth of the version of CDMA2000 referred as 3X-RTT (radio
transmission technology at three times the bandwidth of the second genera-
tion CDMA system). The version of CDMA2000 with a large commercial
market is 1X-RTT. Its signals occupy the same 1.25 MHz bandwidth as
second generation CDMA, and in fact it represents a graceful upgrade of
the original CDMA technology. For this reason, some observers refer to
1X-RTT as a 2.5G technology [3]. Planners anticipate even wider signal
bands for the long term evolution of cellular systems. Orthogonal Fre-
quency Division Multiplexing (OFDM) and SC-FDMA are attractive tech-
nologies for the 20 MHz signal bands under consideration for the next gen-
eration of cellular systems.