Editing UMTS (section)

==== TD-CDMA (UTRA-TDD 3.84 Mcps High Chip Rate (HCR)) ====
[[TD-CDMA]], an acronym for Time-Division-[[code-division multiple access|Code-Division Multiple Access]], is a channel-access method based on using [[spread spectrum|spread-spectrum]] multiple-access (CDMA) across multiple time slots ([[time-division multiplexing|TDMA]]). TD-CDMA is the channel access method for UTRA-TDD HCR, which is an acronym for UMTS Terrestrial Radio Access-Time Division Duplex High Chip Rate.<ref name="Forkel"/>

UMTS-TDD's air interfaces that use the TD-CDMA channel access technique are standardized as UTRA-TDD HCR, which uses increments of 5&nbsp;[[MHz]] of spectrum, each slice divided into 10&nbsp;ms frames containing fifteen time slots (1500 per second).<ref name="Forkel"/> The time slots (TS) are allocated in fixed percentage for downlink and uplink. TD-CDMA is used to multiplex streams from or to multiple transceivers. Unlike W-CDMA, it does not need separate frequency bands for up- and downstream, allowing deployment in tight [[frequency band]]s.<ref>{{cite web|title=UMTS World TD-CDMA information|url=http://www.umtsworld.com/technology/tdcdma.htm|publisher=umtsworld.com|access-date=2008-02-28}}</ref>

TD-CDMA is a part of IMT-2000, defined as IMT-TD Time-Division (IMT CDMA TDD), and is one of the three UMTS air interfaces (UTRAs), as standardized by the 3GPP in UTRA-TDD HCR. UTRA-TDD HCR is closely related to W-CDMA, and provides the same types of channels where possible. UMTS's HSDPA/HSUPA enhancements are also implemented under TD-CDMA.<ref>{{cite web|title=IPWireless Ships First Commercial 3GPP Chipset with Full HSDPA Implementation|url=http://www.ipwireless.com/news/press_020805.html|publisher=ipwireless.com|access-date=2008-02-28 |archive-url = https://web.archive.org/web/20070927010536/http://www.ipwireless.com/news/press_020805.html <!-- Bot retrieved archive --> |archive-date = 2007-09-27}}</ref>

In the United States, the technology has been used for public safety and government use in the [[New York City]] and a few other areas.{{needs update|date=October 2023}}<ref>{{cite web|url=http://www.fiercewireless.com/tech/ipwireless-introduces-td-cdma-network-a-box-targeting-rural-operators-public-safety|title=IPWireless introduces TD-CDMA Network in a Box targeting rural operators, public safety |website=Fiercewireless |date=2 May 2010 }}</ref> In Japan, IPMobile planned to provide TD-CDMA service in year 2006, but it was delayed, changed to TD-SCDMA, and bankrupt before the service officially started.