Code-division multiple access: Difference between revisions

Revision as of 07:25, 15 August 2024

Revision as of 20:54, 27 October 2024

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CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range.

It is used as the access method in many [[mobile phone standards]]. [[cdmaOne|IS-95]], also called "cdmaOne", and its [[3G]] evolution [[CDMA2000]], are often simply referred to as "CDMA", but [[UMTS]], the 3G standard used by [[GSM]] carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. Many carriers (such as [[AT&T Corporation|AT&T]], [[United StatesU.S. Cellular Corporation|UScellular]] and [[Verizon (mobile network)|Verizon]]) shut down 3G CDMA-based networks in 2022 and 2024, rendering handsets supporting only those protocols unusable for calls, even to [[9-1-1|911]].<ref>{{cite web|url=https://www.cnn.com/2022/02/22/tech/att-3g-network-shutdown/index.html|title=AT&T is shutting down its 3G network. Here's how it could impact you|first=Samantha Murphy|last=Kelly|date=February 22, 2022|website=[[CNN]]}}</ref><ref>{{Cite web|last=Johnson|first=Allison|date=2021-03-30|title=Verizon will shutter its 3G CDMA by the end of 2022|url=https://www.theverge.com/2021/3/30/22358628/verizon-3g-cdma-shutdown-date-2022|access-date=2021-10-09|website=The Verge|language=en}}</ref>

It can be also used as a channel or medium access technology, like [[ALOHA]] for example or as a permanent pilot/signalling channel to allow users to synchronize their local oscillators to a common system frequency, thereby also estimating the channel parameters permanently.