22-06-2012, 04:13 PM
4G (fourth-generation wireless)
[attachment=25115]
In telecommunications, 4G is the fourth generation of cellular wireless standards.
In 2008, the ITU-R organization specified the IMT- Advanced(International Mobile Telecommunications Advanced) requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users).
ITU Requirements and 4G wireless standards
This article uses 4G to refer to IMT Advanced (International Mobile Telecommunications Advanced), as defined by ITU-R. An IMT-Advanced cellular system must fulfil the following requirements:
Based on an all-IP packet switched network.
Dynamically share and utilize the network resources to support more simultaneous users per cell.
Approaches Principal technologies
Physical layer transmission techniques are
as follows:
MIMO: To attain ultra high spectral efficiency
by means of spatial processing including
multi-antenna and multi-user MIMO
Frequency-domain-equalization, for example Multi- carrier modulation (OFDM) in the downlink or single-carrier frequency-domain-equalization (SC-FDE) in the uplink: To exploit the frequency selective channel property without complex equalization
4G features
The 4G system was originally envisioned by the Defense Advanced Research Projects Agency (DARPA). The DARPA selected the distributed architecture, end-to-end Internet protocol (IP), and believed at an early stage in peer-to-peer networking in which every mobile device would be both a transceiver and a router for other devices in the network eliminating the spoke-and-hub weakness of 2G and 3G cellular systems.
Components Access schemes
Carriers that use orthogonal frequency-division multiplexing (OFDM) instead of time division multiple access (TDMA) or code division multiple access (CDMA) are increasingly marketing their services as being 4G, even when their data speeds are not as fast as the International Telecommunication Union (ITU) specifies. According to the ITU, a 4G network requires a mobile device to be able to exchange data at 100 Mbit/sec. A 3G network, on the other hand, can offer data speeds as slow as 3.84 Mbit/sec.
Advanced antenna systems
The performance of radio communications depends on an antenna system, termed smart or intelligent antenna. Recently, multiple antenna technologies are emerging to achieve the goal of 4G systems such as high rate, high reliability, and long range communications.
[attachment=25115]
In telecommunications, 4G is the fourth generation of cellular wireless standards.
In 2008, the ITU-R organization specified the IMT- Advanced(International Mobile Telecommunications Advanced) requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users).
ITU Requirements and 4G wireless standards
This article uses 4G to refer to IMT Advanced (International Mobile Telecommunications Advanced), as defined by ITU-R. An IMT-Advanced cellular system must fulfil the following requirements:
Based on an all-IP packet switched network.
Dynamically share and utilize the network resources to support more simultaneous users per cell.
Approaches Principal technologies
Physical layer transmission techniques are
as follows:
MIMO: To attain ultra high spectral efficiency
by means of spatial processing including
multi-antenna and multi-user MIMO
Frequency-domain-equalization, for example Multi- carrier modulation (OFDM) in the downlink or single-carrier frequency-domain-equalization (SC-FDE) in the uplink: To exploit the frequency selective channel property without complex equalization
4G features
The 4G system was originally envisioned by the Defense Advanced Research Projects Agency (DARPA). The DARPA selected the distributed architecture, end-to-end Internet protocol (IP), and believed at an early stage in peer-to-peer networking in which every mobile device would be both a transceiver and a router for other devices in the network eliminating the spoke-and-hub weakness of 2G and 3G cellular systems.
Components Access schemes
Carriers that use orthogonal frequency-division multiplexing (OFDM) instead of time division multiple access (TDMA) or code division multiple access (CDMA) are increasingly marketing their services as being 4G, even when their data speeds are not as fast as the International Telecommunication Union (ITU) specifies. According to the ITU, a 4G network requires a mobile device to be able to exchange data at 100 Mbit/sec. A 3G network, on the other hand, can offer data speeds as slow as 3.84 Mbit/sec.
Advanced antenna systems
The performance of radio communications depends on an antenna system, termed smart or intelligent antenna. Recently, multiple antenna technologies are emerging to achieve the goal of 4G systems such as high rate, high reliability, and long range communications.