Thursday, August 20, 2009

3G


3G is a technology for mobile service providers. Mobile services are provided by service providers that own and operate their own wireless networks and sell mobile services to end-users, usually on a monthly subscription basis. Mobile service providers7 use licensed spectrum to provide wireless telephone coverage over some relatively large contiguous geographic serving area. Historically, this might have included a metropolitan
area. Today it may include the entire country. From a users perspective, the key feature of mobile service is that it offers (near) ubiquitous and continuous coverage. That is, a consumer can carry on a telephone conversation while driving along a highway at 100
Km/hour. To support this service, mobile operators maintain a network of interconnected and overlapping mobile base stations that hand-off customers as those customers move
among adjacent cells. Each mobile base station may support users up to several kilometers away. The cell towers are connected to each other by a backhaul network that also provides interconnection to the wireline Public Switched Telecommunications Network (PSTN) and other services. The mobile system operator owns the end-to-end network from the base stations to the backhaul network to the point of interconnection to the PSTN (and, perhaps, parts thereof).

The first mobile services were analog. Although mobile services began to emerge in the 1940s, the first mass market mobile services in the U.S. were based on the AMPS (Advanced Mobile Phone Service) technology. This is what is commonly referred to as first generation wireless. The FCC licensed two operators in each market to offer AMPS service in the 800-900MHz band. In the 1990s, mobile services based on digital mobile technologies us hered in the second generation (2G) of wireless services that we have today. In the U.S., these were referred to as Personal Communication Systems (PCS)8 and used technologies such as TDMA (Time Division Multiple Access), CDMA (Code Division Multiple Access) and GSM (Global System for Mobile Communications). From 1995 to 1997, the FCC auctioned off PCS spectrum licenses in the 1850 to 1990 MHz band. CDMA and TDMA were deployed in the various parts of the U.S., while GSM was deployed as the common standard in Europe.9 The next or Third Generation (3G) mobile
technologies will support higher bandwidth digital communications and are expected to
be based on one of the several standards included under the ITU's IMT-2000 umbrella of
3G standards.

The chief focus of wireless mobile services has been voice telephony. However, in recent years there has been growing interest in data services as well. While data services are available over AMPS systems, these are limited to quite low data rates (<10Kbps). Higher speed data and other advanced telephone services are more readily supported over the digital mobile 2G systems. The 2G systems also support larger numbers of subscribers and so helped alleviate capacity problems faced by older AMPS systems in more congested environments. Nevertheless, the data rates supportable over 2G systems are still quite limited, offering only between 10-20Kbps. To expand the range and capability of data services that can be supported by digital mobile systems, service providers will have to upgrade their networks to one of the 3G technologies. These can support data rates of from 384Kbps up to 2Mbps, although most commercial deployments are expected to offer data rates closer to 100Kbps in practice. While this is substantially below the rates supported by the current generation of wireline broadband access services such as DSL or cable modems, it is expected that future upgrades to the 3G or the transition to 4G mobile services will offer substantially higher bandwidths. Although wireline systems are likely to always exceed the capacity of wireless ones, it remains unclear precisely how much bandwidth will be demanded by the typical consumer and whether 3G services will offer enough to meet the needs of most consumers.

Auctions for 3G spectrum licenses occurred in a number of countries in 2000 and the first commercial offerings of 3G services began in Japan in October 2001. More recently, Verizon Wireless has announced "3G" service in portions of its serving territory(although this is not true-3G service).

No comments:

Post a Comment

Hi thank you for comment in Assignment Lanka " Book Mark on me' To future references.

Tag

Assignment Lanka Tag Cloud
Computer Networks The History of Local Area Networks, LAN, The Topologies of a Networks, LANs describe different types of transmission Medias, Local Area Networks Access Methods, Carrier Sense Multiple Access with Collision Detect, Development of LAN Technologies. LAN -Token Ring, LAN Ethernet Digital, LAN - Ethernet Sun microsystems, LAN - Ethernet Mixed Environment, LAN - Token Ring was introduced by IBM LAN - IBM implementation of Token Ring, Token Ring Novell, LAN Token Ring - in a mixed environment, LAN - Fiber Distributed Data Interface, LAN - ATM, LAN Components, LAN Switching Methods, Virtual Local Area Network, Port based VLAN, Mac based VLAN, Protocol based VLAN, User Base VLAN, PC networks Components, PC networks Shared resources, PC Network operating systems, PC networks Novell Netware, PC networks Windows NT, PC networks IBM LAN Server Computer Programming Languages HTML Language, The Generations of Programming Languages, Different types of High Level Languages, Different types of High Level Languages Disadvantages
Computer Networks - IBM LAN Server, Windows NT Networks, Novell Netware, Network operating systems, Networks Shared, Networks Components, User Base, Protocol based, Mac based, Port based, VLAN, LAN Switching, LAN Components, ATM, Fiber Data, Token Ring, Token Ring Novell, IBM implementation, Ethernet, Sun microsystems, Ethernet Digital, Token passing, LAN Technologies, CSMA/CD, Access Methods, Transmission, Networks, The History of Local Area Networks, LAN