4G_Telecommunications

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4G_Telecommunications

Post by laterunknown on Mon Apr 09, 2012 11:39 pm

In telecommunications, 4G is the fourth generation of cell phone mobile communications standards. It is a successor of the third generation (3G) standards. A 4G system provides mobile ultra-broadband Internet access, for example to laptops with USB wireless modems, to smart phones, and to other mobile devices. Conceivable applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing and 3D television.

Key features
The following key features can be observed in all suggested 4G technologies:
• Physical layer transmission techniques are as follows:
o MIMO: To attain ultra high spectral efficiency by means of spatial processing including multi-antenna and multi-user MIMO
o 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
o Frequency-domain statistical multiplexing, for example (OFDMA) or (single-carrier FDMA) (SC-FDMA, a.k.a. linearly precoded OFDMA, LP-OFDMA) in the uplink: Variable bit rate by assigning different sub-channels to different users based on the channel conditions
o Turbo principle error-correcting codes: To minimize the required SNR at the reception side
• Channel-dependent scheduling: To use the time-varying channel
• Link adaptation: Adaptive modulation and error-correcting codes
• Mobile-IP utilized for mobility
• IP-based femtocells (home nodes connected to fixed Internet broadband infrastructure)
As opposed to earlier generations, 4G systems does not support circuit switched telephony.

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