08-06-2012, 01:37 PM
WiMAX: The Innovative Broadband Wireless Access Technology
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INTRODUCTION
Telecommunications has grown at a tremendous rate in
the last ten to twenty years. Improved semiconductor and
electronics manufacturing technology, and the growth of
the internet and mobile telecommunications have been
some of the factors which have fueled this growth in
telecommunications. The deployment of state of the art
telecommunications infrastructure and services has
however been restricted to the developed world. The least
developed countries have been left in the technological
dark ages with few or none of the next generation
networks installed. Developed countries now boast high
speed connections with a large percentage of homes
having access to the internet and broadband services at an
affordable fee. The underdeveloped countries are yet to
enjoy such facilities. This is referred to as the digital
divide [1].
NETWORK ARCHITECTURE
WiMAX has a flexible architecture. The Mobile
WiMAX End-to-End network architecture is based on an
All-IP platform, all packet technology and no circuit
switch telephony.
The open IP architecture gives network operators great
flexibility when selecting solutions that work with legacy
networks or that use the most advanced technologies, and
in determining what functionality they want their network
to support. They can choose from a vertically integrated
vendor that provides a turnkey solution or they can pick
and choose from a dense ecosystem of best-of-breed
players with a more narrow focus. The architecture
allows modularity and flexibility to accommodate a broad
range of deployment options such as small scale to large
scale, urban, suburban and rural coverage, mesh
topologies , flat , hierarchical and their variant, and
finally, co-existance of fixed , nomadic portable and
mobile usage models [4].
TECHNOLOGIES EMPLOYED BY WIMAX
Mobile WiMAX operates in licensed frequency bands
in the range of 2 to 6 MHz. The technologies employed
by mobile WiMAX include the following:
Scalable Orthogonal Frequency Division
Multiple Access (SOFDMA) on the physical
layer
MIMO
IP (Internet Protocol)
Adaptive antenna systems (AAS)
Adaptive Modulation schemes (AMS)
Advanced Encryption Standard (AES) encryption
WiMAX Cell Site Design
One of the most important technical and business
issues of any wireless technology is efficiently (cost and
performance) providing coverage and capacity, while
avoiding the build-out of a large number of new base
stations. The first step in designing a wireless system is
to develop a page link budget. Link budget is the loss and gain
sum of signal strength as it travels through different
components in the path between a transmitter and
receiver. The page link budget determines the maximum cell
radius of each base station for a given level of reliability
and is comprised of two types of components: system
related components and non-system related components
[17].
