Time-Division Long-Term Evolution (TD-LTE), also referred to as Long-Term Evolution Time-Division Duplex (LTE TDD),[1] is China's home-grown 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.
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The TD-LTE project was approved on 26 December 2007, at the state council executive meeting of the New Generation Broadband Wireless Mobile Communication Networks, along with TD-SCDMA.[2]
In early 2011, China Mobile has invested CNY 1.5 billion on the '6+1 Scheme', in which large-scale TD-LTE field trial has been conducted in 6 cities including Shanghai, Guangzhou, Shenzhen, Hangzhou, Nanjing, and Xiamen.[3] Each of the cities has been deployed with around 500 TD-LTE femtocell base-stations. Besides, a demonstration network has been set up in Beijing. Outside the mainland, China Mobile has also built a TD-LTE network in Taipei, for the local Far EasTone, for testing purposes.[4] As of September 2011[update], China Mobile has sealed agreements with 32 international telecom carriers, for enabling the launch of 27 TD-LTE trial networks.[5]
TD-LTE offers asymmetric use of unpaired spectrum. It allocates separate channels for outward and return signals, emulating full-duplex transmission over a half-duplex communication link.
The frequency bands used by TD-LTE are 3.4–3.6GHz in Australia,[6] 2.57−2.62GHz in the US[7] and China,[8] and 2.3–2.4GHz in India[9] and Australia.[6] The technology supports scalable channel bandwidth, between 1.4 and 20MHz.[10] A typical range is up to 200 metres (660 ft) indoors on a 2.57–2.62GHz radio frequency link.[11]
Vendors which announced end-user support include Nokia which announced a TD-LTE/FD-LTE/HSPA+/TD-SCDMA/EDGE multi-mode netbook based on the ST-Ericsson M7400 MPSoC[12] and ZTE which announced V2, a TD-LTE/TD-SCDMA/GSM multi-mode dual-standby smartphone.[13]
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[14] and Sequans which announced the SQN3010, a similar chip.[15]
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