Time-Division Long-Term Evolution (TD-LTE), also referred to as Long-Term Evolution Time-Division Duplex (LTE TDD), is a 4-G mobile-telecommunications technology and standard co-developed, since late 2007, by Datang Telecom, China Mobile, Huawei, ZTE, Nokia Siemens Networks, Alcatel Shanghai Bell, Qualcomm, ST-Ericsson, Leadcore, etc. It is one of two variants of the 3GPP Long Term Evolution (LTE) technology, the other being Frequency-Division Long-Term Evolution (FD-LTE or LTE FDD). Likewise, TD-LTE-Advanced is an LTE Advanced time-division variant, an evolutionary upgrade version of TD-LTE.
Deployments and coverages
- In early 2011, China Mobile invested CNY 1.5 billion on the '6+1 Scheme', in which large-scale TD-LTE field trial was conducted in 6 cities including Shanghai, Guangzhou, Shenzhen, Hangzhou, Nanjing, and Xiamen. Each of the cities deployed around 500 TD-LTE femtocell base-stations. A demonstration network was set up in Beijing. Outside the mainland, China Mobile built a TD-LTE network in Taipei, for testing purposes for the local GSM operator Far EasTone, .
- As of September 2011, China Mobile has sealed agreements with 32 international telecom carriers, for launching 27 TD-LTE trial networks.
- On 10 April 2012, Airtel launched 4G services using TD-LTE technology in Kolkata, becoming the first company in India to offer 4G services. Since the initial launch, Airtel also launched 4G in Bangalore and Pune.
- On 30th December 2012, Dialog Axiata launched Fixed 4G services using TD-LTE technology in Sri Lanka. Sri Lanka's first & only Fixed 4G LTE Broadband operator is Dialog.
TD-LTE offers asymmetric use of unpaired spectrum.. In "unpaired spectrum" transmissions travel in both directions on the same frequency band. It is distinct from "paired spectrum," where two frequencies are allocated, one for the transmit channel and the other for the receive channel (hence "Frequency Division.") "Time Division" means the receive channel and the transmit channel take turns (i.e. divide the time between them) on the same frequency band. In this instance, "asymmetric" means that more time-slots are allocated to data going down to the phone than coming back up from the phone. The usage patterns of the future (fewer phone calls, more Internet) are asymmetric.
The frequency bands used by TD-LTE are 3.4–3.6 GHz in Australia and UK, 2.57−2.62 GHz in the US and China, 2.545-2.575 GHz in Japan, and 2.3–2.4 GHz in India and Australia. The technology supports scalable channel bandwidth, between 1.4 and 20 MHz. A typical range is up to 200 metres (660 ft) indoors on a 2.57–2.62 GHz radio frequency link.
Vendors that announced end-user support include Nokia and ZTE. Nokia announced a TD-LTE/FD-LTE/HSPA+/TD-SCDMA/EDGE multi-mode netbook based on the ST-Ericsson M7400 MPSoC. ZTE announced V2, a TD-LTE/TD-SCDMA/GSM multi-mode dual-standby smartphone.
Apart from the ST-Ericsson M7400 MPSoC mentioned above, other vendors which announced chipset support include Innofidei, which together with the Hong Kong Applied Science and Technology Research Institute announced the Warp drive 5000, a TD-LTE/FD-LTE dual-mode baseband processor and Sequans Communications which announced the SQN3010, a similar chip.
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