CDMA2000
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Template:Table Mobile phone standards CDMA2000 is a 3G mobile telecommunications standard that uses CDMA, a modulation scheme for digital radio, to send voice, data and signaling data (such as a dialed telephone number) between mobile telephones and cell sites.
CDMA or "code division multiple access" is a digital radio system that transmits streams of bits. CDMA permits several radios to share the same frequencies. Unlike TDMA "time division multiple access" a competing system used in GSM and PCS, 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 multiplexing.
CDMA-2000 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.
CDMA2000 is an incompatible competitor of the other major 3G standard W-CDMA (UMTS). Since CDMA-2000 is based on older standards, many authorities speculate that the incompatible CDMA standards exist so that European and other countries might assure a domestic market and patent protections for their mobile phone providers.
CDMA-2000 is one of the approved radio interfaces for the ITU's IMT-2000 standard and a successor to 2G CDMA (IS-95, branded cdmaOne). The underlying signaling standard (used to transmit "hookstatus", "busy", "dialtone" "ring" and phone numbers) is known as IS-2000.
CDMA2000 is a registered trademark of the Telecommunications Industry Association (TIA-USA) in the United States, not a generic term like CDMA. TIA has branded their 2G CDMA standard (aka IS-95) as cdmaOne.
There are many different types of CDMA2000. In order of increasing complexity:
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IS-2000
IS-2000 is the second generation of CDMA digital cellular, an extension of IS-95. It is an early form of CDMA2000.
The main differences between IS-95 and IS-2000 signalling are: the use of a pilot signal on the IS-2000 reverse link to permit the use of coherent modulation, and 64 more traffic channels on the forward link that are orthogonal to the original set. Some changes were also made to the 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 link layer basically consisted of a "Best effort delivery" RLP - this arrangement is still used for voice.
In the United States, U.S. Cellular, Verizon Wireless and Sprint PCS use IS-2000.
CDMA2000 1x
CDMA2000 1x, also known as 3G1X or sometimes 1xRTT, is the core 3G CDMA2000 technology. The designation 1x is used to identify the version of CDMA2000 radio technology that operates in one pair of 1.25 MHz radio channels.
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.
CDMA2000 1xRTT
CDMA2000 1xRTT (Radio Transmission Technology) is the basic layer of CDMA2000, which supports up to 144 kbit/s packet data speeds. 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. 1xRTT doubles voice capacity over IS-95 networks. While capable of higher data rates, most deployments have limited the data rate to around 150 kbit/s.
CDMA2000 1xEV
CDMA2000 1xEV (Evolution) is CDMA2000 1x with High Data Rate (HDR) capability added. 1xEV is commonly separated into two phases:
Phase 1 of CDMA2000 1xEV, CDMA2000 01xEV-DO (Evolution-Data Optimized) supports downlink (Forward Link) data rates up to 3.1 Mbit/s and Up Link (Reverse Link) rates up to 1.8 Mbit/s in a radio channel dedicated to carrying high speed packet data.
Phase 2 of CDMA2000 1xEV, CDMA2000 1xEV-DV (Evolution-Data and Voice), supports downlink (Forward Link) data rates up to 3.1 Mbit/s and Up Link (Reverse Link) rates of up to 1.8 Mbit/s. 1xEV-DV can also support concurrent operation of legacy 1x voice users, 1xRTT data users, and high speed 1xEV-DV data users within the same radio channel.
Verizon Wireless in North America has begun nationwide deployment of 1xEV-DO, and Alaska Communications Systems, or ACS, has begun deployment of 1xEV-DO in the main population centers of Alaska. Sprint PCS, also in North America, has announced its intention to deploy 1xEV-DO nationally.
As of July 2004, there are no commercial deployments of 1xEV-DV. American carrier Sprint PCS had announced plans to deploy a 1xEV-DV network on top of their existing CDMA network. However, due to delays in the availability of 1xEV-DV equipment and competitive pressures from other American networks deploying 3G networks, Sprint announced, in June 2004, its intention to broadly deploy 1xEV-DO.
Qualcomm has recently put the development of EV-DV on an indefinite halt, due to lack of carrier interest, mostly because both Sprint and Verizon are using EV-DO.
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.
External links
- Radio-Electronics.Com (http://www.radio-electronics.com/info/cellulartelecomms/evdo/ev-do.php)Article on CDMA20001xEV-DO
- TIA CDMA2000 (http://www.tiaonline.org/standards/sfg/imt2k/cdma2000/cdma2000table.cfm)Standards documentation