TD-SCDMA

TD-SCDMA (singketan tina kecap-kecap basa Inggris "Time Division-Synchronous Code Division Multiple Access") nyaéta salah sahiji standar télékomunikasi mobil 3G, anu keur digawékeun di Republik Rakyat Cina ku Chinese Academy of Telecommunications Technology (CATT), Datang sarta Siemens AG, dina raraga supaya henteu gumantung kana téknologi urang Barat . Alesan utama dijieunna ieu standar cenah format 3G lianna nyaratkeun bayaran béa patén ka sajumlah urang Barat anu mibanda hak patén.  TD-SCDMA didasarkeun kana téknologi spéktrum sebar sarta kamunginan bakal bébas tina kawajiban mayar patén ka urang Barat.

Pamasangan jeung pamakéan jaringan 
Dina tanggal 20 Januari 2006, Mantri Industri Informasi Républik Rakyat Cina sacara resmi ngumumkeun yén TD-SCDMA mangrupa standar boga nagara kasebut pikeun télékomunikasi mobil 3G. Dina tanggal 15 Pébruari 2006, pamaréntah Cina ngumumkeun jadwal waktu pikeun pamasangan jaringan TD-SCDMA di Cina, sarta ngémbarkeun uji coba pra komérsial dimimitian saenggeus réngséna sajumlah uji jaringan di sababaraha kota anu dipilih. Uji coba ieu dilaksanakeun ti bulan Maret nepi ka bulan Oktober 2006, tapi hasilna teu nyugemakeun. Pangwangunan jaringan-jaringan nu ngagunakeun standar 3G lianna (WCDMA katut CDMA2000 EV/DO) ditunda nepi ka siapna TD-SCDMA.

Standar kasebut geus diadopsi ku 3GPP. TD-CDMA (nu leuwih deukeut kana W-CDMA), ditawarkeun salaku air interfaces pikeun sistem UMTS-TDD, kaol UMTS anu lolobana digunakeun pikeun nyadiakeun aksés Internét. Pamakéan TDD leuwih éfisién batan FDD pikeun laju data asimétrik, anu ilahar dina pamakéan Internét.

Ringkesan teknis
TD-SCDMA uses TDD, in contrast to the FDD scheme used by W-CDMA.  By dynamically adjusting the number of timeslots used for downlink and uplink, the system can more éasily accommodate asymmetric traffic with different data rate requirements on downlink and uplink than FDD schemes.  Since it does not require paired spectrum for downlink and uplink, spectrum allocation flexibility is also incréased.  Also, using the same carrier frequency for uplink and downlink méans that the channel condition is the same on both directions, and the base station can deduce the downlink channel information from uplink channel estimates, which is helpful to the application of beamforming techniques.

TD-SCDMA also uses TDMA in addition to the CDMA used in WCDMA.  This reduces the number of users in éach timeslot, which reduces the implementation complexity of multiuser detection and beamforming schemes, but the non-continuous transmission also reduces coverage (because of the higher péak power needed), mobility (because of lower power control frequency) and complicates radio resource management algorithms.

The "S" in TD-SCDMA stands for "synchronous", which méans that uplink signals are synchronized at the base station receiver, achieved by continuous timing adjustments.  This reduces the interference between users of the same timeslot using different codes by improving the orthogonality between the codes, therefore incréasing system capacity, at the cost of some hardware complexity in achieving uplink synchronization.

Rujukan

Tempo ogé
 Dynamic TDMA

Tumbu kaluar
 TD-SCDMA Forum
 TD-SCDMA Industry Alliance     
 China will not interfere in 3G standard selection
 China will provide 3G Service in cities where Olympic Games 2008 are held

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