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Vương Quốc Anh33 » Linh tinh » Hỏi - đáp Tiếng Anh » 3G
bitbitDate: Thứ ba, 13-04-2010, 8:13 PM | Message # 1
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"Third generation" redirects here. For third-generation immigrants, see Immigrant generations.
International Mobile Telecommunications-2000 (IMT-2000), better known as 3G or 3rd Generation, is a family of standards for mobile telecommunications fulfilling specifications by the International Telecommunication Union,[1] which includes UMTS, and CDMA2000 as well as the non-mobile wireless standards DECT[citation needed] and WiMAX[citation needed]. While the GSM EDGE standard also fulfils the IMT-2000 specification, EDGE phones are typically not branded 3G. Services include wide-area wireless voice telephone, video calls, and wireless data, all in a mobile environment. Compared to 2G and 2.5G services, 3G allows simultaneous use of speech and data services and higher data rates (at least 200 kbit/s peak bit rate to fulfill to IMT-2000 specification). Today's 3G systems can offer practice of up to 14.0 Mbit/s on the downlink and 5.8 Mbit/s on the uplink.

In 1999, ITU approved five radio interfaces for IMT-2000 as a part of the ITU-R M.1457 Recommendation; WiMAX were added in 2007.[2]

There are evolutionary standards that are backwards-compatible extensions to pre-existing 2G networks as well as revolutionary standards that require all-new networks and frequency allocations.[3] The later group is the UMTS family, which consists of standards developed for IMT-2000, as well as the independently developed standards DECT and WiMAX, which were included because they fit the IMT-2000 definition.

The first pre-commercial 3G network was launched by NTT DoCoMo in Japan branded FOMA, in May 2001 on a pre-release of W-CDMA technology.[7] The first commercial launch of 3G was also by NTT DoCoMo in Japan on 1 October 2001, although it was initially somewhat limited in scope;[8][9] broader availability was delayed by apparent concerns over reliability.[10] The second network to go commercially live was by SK Telecom in South Korea on the 1xEV-DO technology in January 2002. By May 2002 the second South Korean 3G network was by KT on EV-DO and thus the Koreans were the first to see competition among 3G operators.

The first European pre-commercial network was at the Isle of Man by Manx Telecom, the operator then owned by British Telecom, and the first commercial network in Europe was opened for business by Telenor in December 2001 with no commercial handsets and thus no paying customers. These were both on the W-CDMA technology.

The first commercial United States 3G network was by Monet Mobile Networks, on CDMA2000 1x EV-DO technology, but this network provider later shut down operations. The second 3G network operator in the USA was Verizon Wireless in October 2003 also on CDMA2000 1x EV-DO. AT&T Mobility is also a true 3G network, having completed its upgrade of the 3G network to HSUPA.

The first pre-commercial demonstration network in the southern hemisphere was built in Adelaide, South Australia by m.Net Corporation in February 2002 using UMTS on 2100 MHz. This was a demonstration network for the 2002 IT World Congress. The first commercial 3G network was launched by Hutchison Telecommunications branded as Three in March 2003.

In December 2007, 190 3G networks were operating in 40 countries and 154 HSDPA networks were operating in 71 countries, according to the Global Mobile Suppliers Association (GSA). In Asia, Europe, Canada and the USA, telecommunication companies use W-CDMA technology with the support of around 100 terminal designs to operate 3G mobile networks.

In Europe, mass market commercial 3G services were introduced starting in March 2003 by 3 (Part of Hutchison Whampoa) in the UK and Italy. The European Union Council suggested that the 3G operators should cover 80% of the European national populations by the end of 2005.

Roll-out of 3G networks was delayed in some countries by the enormous costs of additional spectrum licensing fees. (See Telecoms crash.) In many countries, 3G networks do not use the same radio frequencies as 2G, so mobile operators must build entirely new networks and license entirely new frequencies; an exception is the United States where carriers operate 3G service in the same frequencies as other services. The license fees in some European countries were particularly high, bolstered by government auctions of a limited number of licenses and sealed bid auctions, and initial excitement over 3G's potential. Other delays were due to the expenses of upgrading equipment for the new systems.

By June 2007 the 200 millionth 3G subscriber had been connected. Out of 3 billion mobile phone subscriptions worldwide this is only 6.7%. In the countries where 3G was launched first – Japan and South Korea – 3G penetration is over 70%.[11] In Europe the leading country is Italy with a third of its subscribers migrated to 3G. Other leading countries by 3G migration include UK, Austria, Australia and Singapore at the 20% migration level. A confusing statistic is counting CDMA2000 1x RTT customers as if they were 3G customers. If using this definition, then the total 3G subscriber base would be 475 million at June 2007 and 15.8% of all subscribers worldwide.

In Canada, Rogers Wireless was the first to implement 3G technology, with HSDPA services in eastern Canada in late 2006.[12] Their subsidiary Fido Solutions offers 3G as well. Because they were the only incumbent carrier (out of 3) with UMTS/HSDPA capability. Realizing they would miss out on roaming revenue from the 2010 Winter Olympics, Bell and Telus formed a joint venture and rolled out a shared HSDPA network using Nokia Siemens technology. Bell launched their 3G wireless lineup on 4 November 2009, and Telus followed suit a day later on 5 November 2009.[13]

Mobitel Iraq is the first mobile 3G operator in Iraq. It was launched commercially on February 2007.

China announced in May 2008, that the telecoms sector was re-organized and three 3G networks would be allocated so that the largest mobile operator, China Mobile, would retain its GSM customer base. China Unicom would retain its GSM customer base but relinquish its CDMA2000 customer base, and launch 3G on the globally leading WCDMA (UMTS) standard. The CDMA2000 customers of China Unicom would go to China Telecom, which would then launch 3G on the CDMA2000 1x EV-DO standard. This meant that China would have all three main cellular technology 3G standards in commercial use. Finally in January 2009, Ministry of industry and Information Technology of China has awarded licenses of all three standards,TD-SCDMA to China Mobile, WCDMA to China Unicom and CDMA2000 to China Telecom. The launch of 3G occurred on 1 October 2009, to coincide with the 60th Anniversary of the Founding of the People's Republic of China.

In November 2008, Turkey has auctioned four IMT 2000/UMTS standard 3G licenses with 45, 40, 35 and 25 MHz top frequencies. Turkcell has won the 45 MHz band with its €358 million offer followed by Vodafone and Avea leasing the 40 and 35 MHz frequencies respectively for 20 years. The 25 MHz top frequency license remains to be auctioned.

The first African use of 3G technology was a 3G videocall made in Johannesburg on the Vodacom network in November 2004. The first commercial launch of 3G in Africa was by EMTEL in Mauritius on the W-CDMA standard. In north African Morocco in late March 2006, a 3G service was provided by the new company Wana.

T-Mobile, a major Telecommunication services provider has recently rolled out a list of over 120 U.S. cities which will be provided with 3G Network coverage in the year 2009.[14]

In 2008, India entered into 3G Mobile arena with the launch of 3G enabled Mobile and Data services by Mahanagar Telephone Nigam Limited (MTNL)in Delhi and Mumbai. MTNL is the first Mobile operator in India to launch 3G services. Government owned Bharat Sanchar Nigam Ltd (BSNL) has already been provided with a 3G license and has been operating its services in 380 cities by the end of March 2010. Nation wide auction of 3G wireless spectrum in April 2010 has been announced, and 3G services by private service providers are expected by the September 2010.

[edit] Data rates
ITU has not provided a clear definition of the data rate users can expect from 3G equipment or providers. Thus users sold 3G service may not be able to point to a standard and say that the rates it specifies are not being met. While stating in commentary that "it is expected that IMT-2000 will provide higher transmission rates: a minimum data rate of 2 Mbit/s for stationary or walking users, and 384 kbit/s in a moving vehicle,"[15] the ITU does not actually clearly specify minimum or average rates or what modes of the interfaces qualify as 3G, so various rates are sold as 3G intended to meet customers expectations of broadband data.

[edit] Security
3G networks offer greater security than their 2G predecessors. By allowing the UE (User Equipment) to authenticate the network it is attaching to, the user can be sure the network is the intended one and not an impersonator. 3G networks use the KASUMI block crypto instead of the older A5/1 stream cipher. However, a number of serious weaknesses in the KASUMI cipher have been identified [16].

In addition to the 3G network infrastructure security, end-to-end security is offered when application frameworks such as IMS are accessed, although this is not strictly a 3G property.

[edit] Applications
The bandwidth and location information available to 3G devices gives rise to applications not previously available to mobile phone users. Some of the applications are:

Mobile TV – a provider redirects a TV channel directly to the subscriber's phone where it can be watched.
Video on demand – a provider sends a movie to the subscriber's phone.
Video conferencing – subscribers can see as well as talk to each other.
Tele-medicine – a medical provider monitors or provides advice to the potentially isolated subscriber.
Location-based services – a provider sends localized weather or traffic conditions to the phone, or the phone allows the subscriber to find nearby businesses or friends.
[edit] Evolution
Both 3GPP and 3GPP2 are currently working on extensions to 3G standard that are based on an all-IP network infrastructure and using advanced wireless technologies such as MIMO, these specifications already display features characteristic for IMT-Advanced (4G), the successor of 3G. However, falling short of the bandwidth requirements for 4G (which is 1 Gbit/s for stationary and 100 Mbit/s for mobile operation), these standards are classified as 3.9G or Pre-4G.

3GPP plans to meet the 4G goals with LTE Advanced, whereas Qualcomm has halted development of UMB in favour of the LTE family.[5]

On 14 December 2009, Telia Sonera announced in an official press release that "We are very proud to be the first operator in the world to offer our customers 4G services."[17] With the launch of their LTE network, initially they are offering pre-4G (or beyond 3G) services in Stockholm, Sweden and Oslo, Norway.


KháchDate: Thứ năm, 06-03-2014, 1:31 AM | Message # 2

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