TD-SCDMA: Béda antarrépisi

'''TD-SCDMA''' (singketan tina kecap-kecap basa Inggris "Time Division-Synchronous Code Division Multiple Access") nyaéta salasahijisalah sahiji standar telekomunikasi 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]] <ref>[http://www.tdscdma-forum.org/nenglish/articles/article20030418.2.html]</ref>. Alesan utama dijieunna ieu standar cenah format [[3G]] lianna nyaratkeun bayaran béa patén ka sajumlah urang Barat anu mibanda hak patén<ref>[http://www.3glicensing.com/articles/News%20LowCost.pdf ''3G Licensing introduces the W-CDMA Patent Licensing Programme at the "Low Cost 3G Devices" conference''], [[London]], [[13 March]] [[2007]]</ref>. TD-SCDMA didasarkeun kana téknologi [[spéktrum sebar]] sarta kamunginan bakal bébas tina kawajiban mayar patén ka urang Barat.

Dina tanggal 20 Januari 2006, Mantri Industri Informasi [[Républik Rakyat Cina]] sacara resmi ngumumkeun yén TD-SCDMA ngarupakeunmangrupa standar boga nagara kasebut pikeun telekomunikasi 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 kalolobaanlolobana digunakeun pikeun nyadiakeun aksés Internét. Pamakéan [[TDD]] leuwih éfisién batan FDD pikeun laju data asimétrik, anu ilahar dina pamakéan Internét.

TD-SCDMA uses [[Duplex (telecommunications)#Usage in point-to-multipoint networks|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 easilyéasily 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 increasedincréased. Also, using the same carrier frequency for uplink and downlink meansméans 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 [[time division multiple access|TDMA]] in addition to the [[code division multiple access|CDMA]] used in WCDMA. This reduces the number of users in eachéach timeslot, which reduces the implementation complexity of [[multiuser detection]] and [[beamforming]] schemes, but the non-continuous transmission also reduces [[coverage]] (because of the higher peakpéak power needed), mobility (because of lower [[power control]] frequency) and complicates [[radio resource management]] algorithms.

The "S" in TD-SCDMA stands for "synchronous", which meansméans 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#Radio_communicationsRadio communications|orthogonality]] between the codes, therefore increasingincréasing system capacity, at the cost of some hardware complexity in achieving uplink synchronization.

* [http://www.china.org.cn/english/news/187783.htm China will provide 3G Service] in cities where Olympic Games 2008 are held

[[Kategori:metodaMetoda akses kanal]]