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Long-Term Evolution Time-Division Duplex
Long-Term Evolution Time-Division Duplex (LTE-TDD), also referred to as Time-division Long-Term Evolution (TD-LTE), is a 4G telecommunications technology and standard co-developed by an international coalition of companies, including China Mobile, Datang Telecom, Huawei, Nokia Solutions and Networks, Qualcomm, Samsung, and ST-Ericsson. It is one of two variants of the Long Term Evolution (LTE) technology standard, the other being Frequency-Division Long-Term Evolution (LTE-FDD).
==Overview of technology==
Time-Division Duplex LTE, abbreviated as TD-LTE, TDD LTE, or LTE-TDD is one of the two mobile data transmission technologies that fall under the international standard of LTE, the other being Frequency-Division Duplex (LTE-FDD). LTE-TDD was developed specifically with idea of migration to 4G from the third generation 3G TD-SCDMA networks in mind.
There are two major differences between LTE-TDD and LTE-FDD: how data is uploaded and downloaded, and what frequency spectra the networks are deployed in. While LTE-FDD uses paired frequencies to upload and download data, LTE-TDD uses a single frequency, alternating between uploading and downloading data through time. The ratio between uploads and downloads on a LTE-TDD network can be changed dynamically, depending on whether more data needs to be sent or received. LTE-TDD and LTE-FDD also operate on different frequency bands, with LTE-TDD working better at higher frequencies, and LTE-FDD working better at lower frequencies. Frequencies used for LTE-TDD range from 1850 MHz to 3800 MHz, with several different bands being used. The LTE-TDD spectrum is generally cheaper to access, and has less traffic.〔 Further, the bands for LTE-TDD overlap with those used for WiMAX, which can easily be upgraded to support LTE-TDD.〔
Despite the differences in how the two types of LTE handle data transmission, LTE-TDD and LTE-FDD share 90 percent of their core technology, making it possible for the same chipsets and networks to use both versions of LTE.〔 A number of companies produce dual-mode chips or mobile devices, including Samsung and Qualcomm, while operators China Mobile Hong Kong Company Limited and Hi3G Access have developed dual-mode networks in China and Sweden, respectively.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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