3G TO 4G Technology..........

4G refers to the fourth generation of cellular wireless and is a successor to 3G and 2G standards. The rest of this article associates 4G with International Mobile Telecommunications-Advanced (IMT Advanced), though 4G is a broader term and could include standards outside IMT-Advanced. A 4G system may upgrade existing communication networks and is expected to provide a comprehensive and secure IP based solution where facilities such as voice, data and streamed multimedia will be provided to users on an "Anytime, Anywhere" basis and at much higher data rates compared to previous generations.

4G is being developed to accommodate the QoS and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV content, Digital Video Broadcasting (DVB), minimal services like voice and data, and other services that utilize bandwidth.

The 4G working group has defined the following as objectives of the 4G wireless communication standard:

1.A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site),

2.High network capacity: more simultaneous users per cell,

3.A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,

4.A data rate of at least 100 Mbit/s between any two points in the world,

5.Smooth handoff across heterogeneous networks,

6.Seamless connectivity and global roaming across multiple networks,

7.High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)

8.Interoperability with existing wireless standards, and

9.An all IP, packet switched network.

In summary, the 4G system should dynamically share and utilize network resources to meet the minimal requirements of all the 4G enabled users.

According to the members of the 4G working group, the infrastructure and the terminals of 4G will have almost all the standards from 2G to 4G implemented. Although legacy systems are in place to adopt existing users, the infrastructure for 4G will be only packet-based (all-IP). Some proposals suggest having an open Internet platform. Technologies considered to be early 4G include: Flash-OFDM, the 802.16e mobile version of WiMax (also known as WiBro in South Korea), and HC-SDMA (see iBurst). 3GPP Long Term Evolution may reach the market 1–2 years after Mobile WiMax is released.

An even higher speed version of WiMax is the IEEE 802.16m specification. LTE Advanced will be the later evolution of the 3GPP.

Principal Technologies:

1.Baseband techniques

2.OFDM: To exploit the frequency selective channel property

3.MIMO: To attain ultra high spectral efficiency

4.Turbo principle: To minimize the required SNR at the reception side

5.Adaptive radio interface

6.Modulation, spatial processing including multi-antenna and multi-user MIMO

7.Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-  mode protocol.