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4G is an abbreviation for Fourth-Generation. It is a term used to describe the next complete evolution in wireless communications. It is also known as “Beyond 3G”. 3G is an abbreviation for Third-Generation. A 4G system will be able to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users on an "Anytime, Anywhere" basis, and at higher data rates than previous generations.
4G mobile communication systems are projected to solve still-remaining problems of 3G systems and to provide a wide variety of new services, from high-quality voice to high-definition video to high-data-rate wireless channels.
One of the terms used to describe 4G is MAGIC—Mobile multimedia, anytime anywhere, Global mobility support, integrated wireless solution, and customized personal service.
Based on the developing trends of mobile communication, 4G will have broader bandwidth, higher data rate, and smoother and quicker handoff and will focus on ensuring seamless service across a multitude of wireless systems and networks.
The key concept is integrating the 4G capabilities with all of the existing mobile technologies through advanced technologies. Application adaptability and being highly dynamic are the main features of 4G services of interest to users.
Some key 4G Technologies:
OFDMA: Orthogonal Frequency Division Multiplexing (OFDM) not only provides clear advantages for physical layer performance, but also a framework for improving layer 2 performance by proposing an additional degree of free- dom. Using ODFM, it is possible to exploit the time domain, the space domain, the frequency domain and even the code domain to optimize radio channel usage. It ensures very robust transmission in multi-path environments with reduced receiver complexity.
MIMO: uses signal multiplexing between multiple transmitting antennas (space multiplex) and time or frequency. It is well suited to OFDM, as it is possible to process independent time symbols as soon as the OFDM waveform is correctly designed for the channel. This aspect of OFDM greatly simplifies processing. The signal transmitted by m antennas is received by n antennas. Processing of the received signals may deliver several performance improvements:range, quality of received signal and spectrum efficiency.
In principle, MIMO is more efficient when many multiple path signals are received. The performance in cellular deployments is still subject to research and simulations . However, it is generally admitted that the gain in spectrum efficiency is directly related to the minimum number of antennas in the link.
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