CDMA2000
CDMA2000 is a family of third-generation
(3G) mobile telecommunications standards that use
CDMA, a multiple access scheme for digital radio,
to send voice, data, and signalling data (such as
a dialed telephone number) between mobile phones and
cell sites. It is the second generation of CDMA digital
cellular.
CDMA (code division multiple access) is a mobile digital
radio technology that transmits streams of bits and
whose channels are divided using codes (PN sequences).
CDMA permits many radios to share the same frequency
channel. Unlike TDMA (time division multiple access),
a different technique used in GSM and D-AMPS, all
radios can be active all the time, because network
capacity does not directly limit the number of active
radios. Since larger numbers of phones can be served
by smaller numbers of cell sites, CDMA-based standards
have a significant economic advantage over TDMA-based
standards, or the oldest cellular standards that used
frequency division multiple access (FDMA).
CDMA2000 has a relatively long technical history,
and remains compatible with the older CDMA telephony
methods (such as cdmaOne) first developed by Qualcomm,
a commercial company, and holder of several key international
patents on the technology.
The CDMA2000 standards CDMA2000 1x, CDMA2000 1xEV-DO,
and CDMA2000 1xEV-DV are approved radio interfaces
for the ITU's IMT-2000 standard and a direct successor
to 2G CDMA, IS-95 (cdmaOne). CDMA2000 is standardized
by 3GPP2.
CDMA2000 is a registered trademark of the Telecommunications
Industry Association (TIA-USA) in the United States,
not a generic term like CDMA. (This is similar to
how TIA has branded their 2G CDMA standard, IS-95,
as cdmaOne.)
CDMA2000 is an incompatible competitor of the other
major 3G standard UMTS. It is defined to operate at
400 MHz, 800 MHz, 900 MHz, 1700 MHz, 1800 MHz, 1900
MHz, and 2100 MHz.
Below are the different types of CDMA2000, in order
of increasing complexity:
CDMA2000 1x
CDMA2000 1x, the core CDMA2000 wireless air interface
standard, is known by many terms: 1x, 1xRTT, IS-2000,
CDMA2000 1X, 1X, and cdma2000 (lowercase). The designation
"1xRTT" (1 times Radio Transmission Technology)
is used to identify the version of CDMA2000 radio
technology that operates in a pair of 1.25-MHz radio
channels (one times 1.25 MHz, as opposed to three
times 1.25 MHz in 3xRTT). 1xRTT almost doubles voice
capacity over IS-95 networks. Although capable of
higher data rates, most deployments have limited the
peak data rate to 144 kbit/s. While 1xRTT officially
qualifies as 3G technology, 1xRTT is considered by
some to be a 2.5G (or sometimes 2.75G) technology.
This has allowed it to be deployed in 2G spectrum
in some countries which limit 3G systems to certain
bands.
The main differences between IS-95 and IS-2000 signaling
are: 64 more traffic channels on the forward link
that are orthogonal to the original set. Some changes
were also made to the data link layer to accommodate
the greater use of data services—IS-2000 has
media and link access control protocols and QoS control.
In IS-95, none of these were present, and the data
link layer basically consisted of a "best effort
delivery" RLP—this arrangement is still
used for voice.
In the United States, Verizon Wireless, Sprint PCS,
Alltel, and U.S. Cellular use 1x, also it is in use
in Canada by Bell Mobility and TELUS Mobility, and
in Mexico by Iusacell and Unefon.
In India, Reliance and Tata Teleservices are major
wireless services providers on CDMA 2000 1x.
CDMA2000 3x
CDMA2000 3x utilizes a pair of 3.75-MHz radio channels
(i.e., 3 X 1.25 MHz) to achieve higher data rates.
The 3x version of CDMA2000 is sometimes referred to
as Multi-Carrier or MC. The 3x version of CDMA2000
has not been deployed and is not under development
at present.
CDMA2000 1xEV-DO
CDMA2000 1xEV-DO (1x Evolution-Data Optimized, originally
1x Evolution-Data Only), also referred to as 1xEV-DO,
EV-DO, EVDO, or just DO, is an evolution of CDMA2000
1x with High Data Rate (HDR) capability added and
where the forward link is time-division multiplexed.
This 3G air interface standard is denoted as IS-856.
CDMA2000 1xEV-DO in its latest revision, Rev. A, supports
downlink (forward link) data rates up to 3.1 Mbit/s
and uplink (reverse link) data rates up to 1.8 Mbit/s
in a radio channel dedicated to carrying high-speed
packet data. 1xEV-DO Rev. A was first deployed in
Japan and will be deployed in North America in 2006.
The Rev. 0 that is currently deployed in North America
has a peak downlink data rate of 2.5 Mbit/s and a
peak uplink data rate of 154 kbit/s.
Verizon Wireless, Sprint Nextel Corporation, Bell
Canada, and TELUS are in the midst of nationwide deployment
of 1xEV-DO Rev. A in North America, and Alaska Communications
Systems (ACS) is deploying 1xEV-DO in the main population
centers of Alaska. Verizon Wireless currently uses
its 1xEV-DO Rev. 0 network for its VCAST services,
while Sprint Nextel Corporation currently uses its
1xEV-DO Rev. 0 network for its Power Vision services.
Japanese operator KDDI uses the brand "CDMA 1X
WIN" for their CDMA2000 1xEV-DO network, but
this is only in reference to its building on past
marketing promotions.
South Korean Operator SK Telecom currently uses its
1xEV-DO Rev.0 network for its "june" brand
, while KTF currently uses its 1xEV-DO Rev.0 network
for its "fimm" brand services.
CDMA2000 1xEV-DV
CDMA2000 1xEV-DV (1x Evolution-Data/Voice), supports
downlink (forward link) data rates up to 3.1 Mbit/s
and uplink (reverse link) data rates of up to 1.8
Mbit/s. 1xEV-DV can also support concurrent operation
of legacy 1x voice users, 1x data users, and high
speed 1xEV-DV data users within the same radio channel.
In 2005, Qualcomm put the development of EV-DV on
an indefinite halt, due to lack of carrier interest,
mostly because both Verizon Wireless and Sprint are
using EV-DO.
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