07-01-2011, 04:24 PM
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Presented By:
Sainik Kumar Mahata
Introduction
Fourth generation(4G) wireless system is a packet switched wireless system with wide area coverage and high throughput. It is designed to be cost effective and to provide high spectral efficiency. Data rate of 20 mbps is employed. Frequency band is 2-8 GHz., it gives the ability for worldwide roaming to access cell anywhere.
Features
Support for interactive multimedia, voice, streaming video, Internet, and other broadband services
IP based mobile system
High speed, high capacity, and low cost-per-bit
Global access and service portability
Better spectral efficiency
Ultra Wide Band (UWB)
A UWB transmitter spreads its signal over a wide portion of the RF spectrum, generally 1 GHz wide or more, above 3.1GHz. The FCC has chosen UWB frequencies to minimize interference to other commonly used equipment, such as televisions and radios. This frequency range also puts UWB equipment above the 2.4 GHz range of microwave ovens and modern cordless phones, but below 802.11a wireless Ethernet, which operates at 5 GHz.
One distinct advantage of UWB is its immunity to multi-path distortion and interference. Multi-path delay causes the information symbols in the signal to overlap, confusing the receiver—this is known as inter-symbol interference (ISI).
The short time-span of UWB waveforms—typically hundreds of picoseconds to a few nanoseconds—means that delays caused by the transmitted signal bouncing off objects are much longer than the width of the original UWB pulse, virtually eliminating ISI from overlapping signals. This makes UWB technology particularly useful for intra-structure and mobile communications applications, minimizing S/N reduction and bit errors.
Millimeter Wireless
Using the millimeter-wave band (above 20 GHz) for wireless service is particularly interesting, due to the availability in this region of bandwidth resources committed by the governments of some countries to unlicensed cellular and other wireless applications. If deployed in a 4G system, millimeter wireless would constitute only one of several frequency bands, with the 5 GHz band most likely dominant.
Future
We do have are good reasons for 4G development and a variety of current and evolving technologies to make 4G a reality. Highlighting the primary drivers for 4G wireless systems are cost, speed, flexibility, and universal access. Data-rate increases of 10-50X over 3G systems will place streaming audio and video access into the hands of consumers who, with each wireless generation, demand a much richer set of wireless-system features.
4G’s flexibility will allow the integration of several different LAN and WAN technologies. This will let the user apply one 4G appliance, most likely a cell-phone/PDA hybrid, for many different tasks—telephony, Internet access, gaming, real-time information, and personal networking control, to name a few.
Finally, a 4G wireless phone would give a user the capability of global roaming and access—the ability to use a cell phone anywhere worldwide.
