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Code division multiple access (CDMA) is a channel access method utilized by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne and CDMA2000 (which are often referred to as simply "CDMA"), that use CDMA as their underlying channel access methods.

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Wikipedia about CDMA

Code division multiple access (CDMA) is a channel access method utilized by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne and CDMA2000 (which are often referred to as simply "CDMA"), that use CDMA as their underlying channel access methods.

One of the basic concepts in data communication is the idea of allowing several transmitters to send information simultaneously over a single communication channel. This allows several users to share a bandwidth of frequencies. This concept is called multiplexing. CDMA employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel. By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a form of "spread-spectrum" signaling, since the modulated coded signal has a much higher data bandwidth than the data being communicated.

An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can understand each other.

Uses

  • One of the early applications for code division multiplexing—predating, and distinct from cdmaOne—is in GPS.
  • The Qualcomm standard IS-2000, known as CDMA2000. This standard is used by several mobile phone companies, including the Globalstar satellite phone network.
  • CDMA has been used in the OmniTRACS satellite system for transportation logistics.

Technical details

CDMA is a spread spectrum multiple access technique. In CDMA a locally generated code runs at a much higher rate than the data to be transmitted. Data for transmission is simply logically XOR (exclusive OR) added with the faster code. The figure shows how spread spectrum signal is generated. The data signal with pulse duration of Tb is XOR added with the code signal with pulse duration of Tc. (Note: bandwidth is proportional to 1/T where T = bit time) Therefore, the bandwidth of the data signal is 1/Tb and the bandwidth of the spread spectrum signal is 1/Tc. Since Tc is much smaller than Tb, the bandwidth of the spread spectrum signal is much larger than the bandwidth of the original signal.

Search results for CDMA

W-CDMA: Information from Answers.com

WCDMA is short for: Meaning Category Wideband Code Division Multiple Access ... Qualcomm created an experimental wideband CDMA system called CDMA2000 3x which ...www.answers.com/topic/w-cdma

What is the Difference Between GSM and CDMA?

Brief and Straightforward Guide: What is the Difference Between GSM and CDMA? ... CDMA, a proprietary standard designed by Qualcomm in the United States, has been ...www.wisegeek.com/what-is-the-difference-between-gsm-and-cdma...

Nokia APAC - CDMA - All terms - Glossary

CDMA is a ... The CDMA air interface is used in both 2G and 3G networks. 2G CDMA standards are generally called cdmaOne and include IS-95A and IS-95B, ...asia.nokia.com/A4183247

What is CDMA? - A Word Definition From the Webopedia Computer Dictionary

This page describes the term CDMA and lists other pages on the Web where you can find additional information. ... CDMA consistently provides better capacity ...www.webopedia.com/TERM/C/CDMA.html

CDMA Cell Phones - Yahoo! Shopping

Find the best price for CDMA Cell Phones at Yahoo! Shopping. Compare prices, read reviews and ratings for CDMA Cell Phonesshopping.yahoo.com/s:Cell%20Phones:137621-Cell%20Network%20T...

Images found for CDMA

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News about CDMA

Sistema: Shyam Telelink Launches CDMA Mobile Network in the State of Rajasthan

Business Wire via Yahoo! Finance MOSCOW----Sistema , the largest public diversified corporation in Russia and the CIS, which manages fast growing companies operating in the consumer services sector, today announced that Shyam Telelink Ltd. , a subsidiary of Sistema, has launched a CDMA 800 MHz mobile network under the brand name "Rainbow" in the state of Rajasthan.http://biz.yahoo.com/bw/080930/20080930005667.html?.v=1

Verizon getting a CDMA iPhone that runs Windows Mobile, clears acne

Engadget Filed under: Cellphones , Handhelds Rumors are coming fast and furious today citing unnamed tipsters that Apple is hard at work hammering out a CDMA iPhone for its friends at Verizon to be announced and released next year, the carrier it had initially approached about carrying the device back in 2005. Way we see it, though, 2009 ain't 2005; Apple's wielding boatloads more power in ....http://www.engadget.com/2008/09/29/verizon-getting-a-cdma-ip...

Nortel Fleshes Out WiMax Strategy

Unstrung.comCHICAGO -- WiMax World 2008 -- More details of Nortel Networks Ltd. (NYSE/Toronto: NT - message board )'s WiMax strategy are emerging, and the plan appears to be very similar to the re-badging approach the vendor took with its 3G CDMA offerings.http://www.unstrung.com/document.asp?doc_id=165090

Apple Rumoured to Be Working on CDMA iPhone

Cellular-News.comAn Apple rumour website has reported that the company is working on a CDMA based iPhone, with a launch expected early next year. Citing an unnamed Verizon source, 9to5Mac noted that the company has been recruiting CDMA EVDO engineers for some months, lending credence to the report.http://www.cellular-news.com/story/33876.php

CDMA Apple iPhone with High-Speed EVDO in the Works?

MobileMagGenerally speaking, CDMA versions of cell phones can come months, even years after their GSM counterparts have hit the market. That's what happened with the Motorola RAZR when it was first introduced and it's what happens with a lot of BlackBerry models as well.http://www.mobilemag.com/content/100/340/C16272/

News about Cdma

TRADE NEWS: Agilent Technologies to Present at LTE & HSPA Evolution ...

MSN MoneyCentralHe contributed significantly to the development of the W-CDMA air interface and corresponding conformance tests that have now evolved to incorporate HSDPA, HSUPA and LTE. His earlier work involved the standardization of the GSM ... http://news.moneycentral.msn.com/provider/providerarticle.as...

How the BlackBerry Storm Became the Storm

BusinessWeekThere’s been a lot of confusion about the name of the new BlackBerry Storm. During development, it was known by the two code names, Storm and Thunder. This led to speculation that there were actually two separate products, the Storm, based on CDMA ... http://www.businessweek.com/the_thread/techbeat/archives/200...

Bell teams with Telus to overhaul wireless network

Globe and MailBell and Telus announced plans Friday to overlay their current 3G code division multiple access (CDMA) networks with a new global system for mobile communications standard known as high speed data packet access. Bell and Telus both currently operate ... http://www.theglobeandmail.com/servlet/story/RTGAM.20081010....

HTC readying full touch phone with WiMAX?

MacNN ... T8290 and when is unknown, though the handset appears tapped for Russia's WiMAX provider Yota and supports the same 2.5GHz band used by Sprint's just-launched Xohm network . The carrier is already using HTC's related Touch Diamond but runs on a CDMA ... http://www.macnn.com/print/58088

BlackBerry Storm non-exclusive at Telus in Canada

MacNNQuickly following the American launch, Telus on Wednesday also said it would be one of the first to carry the BlackBerry Storm in Canada. Its version is an exact match for the Verizon model and includes both CDMA plus EVDO Revision A for Telus' own ... http://www.macnn.com/print/57989

Search results for Cdma

Nortel: Solutions : CDMA Networks: Overview

Code Division Multiple Access (CDMA) technology is a driving force behind wireless networks around the globe. Our innovative CDMA portfolio of core and access products allows ... http://www.nortel.com/cdma

CDMA definition of CDMA in the Free Online Encyclopedia.

C ode D ivision M ultiple A ccess) A method for transmitting simultaneous signals over a shared portion of the spectrum. The foremost application of CDMA is the digital cellular ... http://encyclopedia2.thefreedictionary.com/CDMA

What is CDMA? - a definition from Whatis.com - see also: code ...

The term CDMA refers to any of several protocols used in 2G (second-generation) and 3G (third-generation) wireless communications. As the term implies, CDMA is a form of ... http://searchtelecom.techtarget.com/sDefinition/0,,sid103_gc...

CDMA Explained

One of the Worlds most popular mobile portals.Over 1 million global visitors per month ... Jun-02: 13,370,000: Jun-03: 54,885,000: Jun-04: 112,600,000: Sep-01: 1,634,000: Sep-02 ... http://cellular.co.za/cdma.htm

EETimes Encyclopedia

EE Times is the online source of global news for the creators of technology. Encyclopedia: Results found for: CDMA : CDMA (C ode D ivision M ultiple A ccess) A method for ... http://www.eetimes.com/encyclopedia/defineterm.jhtml?term=CD...
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Videos found for CDMA

Interference Management for CDMA Wi...

Interference Management for CDMA Wireless SystemsRoy Yates ----- Rutgers UniversityRealMedia - Video

Pioneer of CDMA

Pioneer of CDMAQualcomm, the pioneer and leader of Code Division Multiple Access digital wireless technology shares its technological insightsWindows Media - Video

CDG - CDMA Development Group

CDG - CDMA Development GroupPerry LaForge of CDG has a chat with Nicole Scott about the state and future of wireless broadband services.Flash - Video

BluePhoenix.TV -- CDMA/HSDPA/WiMax

BluePhoenix.TV -- CDMA/HSDPA/WiMaxWhat does the future hold for mobile phones? This is a short vid on my opinion! Visit me at http://live.bluephoenix.tvFlash - Video

Boston ESC 2007 - Measuring just 75...

Boston ESC 2007 - Measuring just 75mm x 45mm, the Mobile-ITX features all the silicon required to ru...Boston ESC 2007 - Measuring just 75mm x 45mm, the Mobile-ITX features all the silicon required to run full x86 applications, as well as CDMA silicon for 3G communications to...Flash - Video

Videos found for CDMA

CDMA.avi

CDMA.aviCDMA ('98 김범석 2월 15일) [ 동영상 ]avi: 63.0 MB w:720px - h:480px

M19U2: 1xEV-DO F-TCH ... Introducin...

M19U2: 1xEV-DO F-TCH ... Introducing the Ultimate CDMA Training...M19U2: 1xEV-DO F-TCH ... Introducing the Ultimate CDMA Training and resource site (CDMAinteractive.com)... coming up in Feb-2007 1 min 35 sec - Dec 24, 2006 Introducing the upcoming (Feb-2007) CDM...flash: 0 MB w:320px - h:240px

The Ultimate CDMA resource site ......

The Ultimate CDMA resource site ... coming up in Feb-2007The Ultimate CDMA resource site ... coming up in Feb-2007 1 min 36 sec - Dec 24, 2006 Introducing the upcoming (Feb-2007) CDMAinteractive.com website featuring over 500 technical training videos on ...flash: 0 MB w:320px - h:240px

M11U5: The R-TCH Channel ... Introd...

M11U5: The R-TCH Channel ... Introducing the Ultimate CDMA Training...M11U5: The R-TCH Channel ... Introducing the Ultimate CDMA Training and resource site (CDMAinteractive.com)... coming up in Feb-2007 1 min 5 sec - Dec 24, 2006 Introducing the upcoming (Feb-2007) ...flash: 0 MB w:320px - h:240px

M6U1: The Control Channel ... Intro...

M6U1: The Control Channel ... Introducing the Ultimate CDMA Training...M6U1: The Control Channel ... Introducing the Ultimate CDMA Training and resource site (CDMAinteractive.com)... coming up in Feb-2007 58 sec - Dec 24, 2006 Introducing the upcoming (Feb-2007) CDMA...flash: 0 MB w:320px - h:240px

Answers for CDMA

yodasminion

What's the difference between GSM and CDMA carriers?

yodasminionGSM means Global System for Mobile communications and CDMA is Code division multiple access, they are different technologies for cellular. GSM is the only one in the U.S. to use SIM cards. Veriz...
Adam

Can I use an older model sprint branded CDMA phone for sprint service?

AdamYes you can as long as it's not 2g....Sprint is doing away with the 2g network so you will not be able to utilize a 2g phone on the Sprint network anylonger. Keep in mind that most phones made before...
Fernando C

Will a Motorola Razr V3 work with Verizon wireless prepay even if it is a cdma phone?

Fernando CNope it has to be setup on the Verizon's CDMA network, as sprint and nextel uses CDMA also Their is a range of frequencys for each carrier ok Good Luck. if your looking for Verizon Phones, I a...
liipl 2

I want to purchase a cellphone (CDMA)on ebay.How do i get it programmed to work with my local carrier?

liipl 2you cant unlock a cdma phone, but if you take it to the carriers store and the carrier permits this they can reflash it with their operating system.
antplby

What are the top CDMA cell phones I can buy?

antplbyTop cdma LG phones are the LG enV 9900, LG Chocolate 8550, LG 8830 and 5400, LG 9400 TV phone, Samsung Juke, LG 8100, Motorola Razr and Razr 2, Samsung A870 (these are all for verizon). Sprint CDMA LG...

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