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July/August
2006 edition |
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July/August
2006 Edition
Featured
Article
WiMAX:
What You Need to Know
Nicolas
Salamina, Business Development Manager, and Ramesh Kumar,
Marketing Manager, TI’s Wireless Infrastructure
Business
With the first “fixed” WiMAX equipment
now certified by the WiMAX Forum, and “mobile”
WiMax certification expected in 2007, the impact of
this technology will soon be realized. With the promise
of higher data rates, wider frequency bandwidth and
low cost potential, WiMAX may eventually capture a significant
share of the broadband wireless market.
So, what is different about WiMAX and how does it work?
What are the implications for existing technologies
such as 3G and DSL, and how will the technology gain
momentum? Read on to find out what you need to know
about WiMAX and the role it is expected to play in the
not-so-distant future.
Defining WiMax
WiMax is a broad term that refers to two types of standard-based
technologies. First is “fixed” WiMAX that
is based on the 802.16-2004 IEEE standard, or what some
refer to as 802.16d. Equipment based on this standard
was certified in January of this year. “Fixed”
WiMAX is designed to support data rates of up to 40
mbps with base stations, and covers a radius of 3 to
10 km. The second WiMAX flavor is a "mobile"
version that will be certified in 2007. It is also referred
to as 802.16e, and supports data rates of up to 15 mbps
and coverage of only 3 km. While its coverage area will
likely require a higher density of base stations, “mobile”
WiMAX will serve both fixed and mobile applications,
and therefore is predicted to be more popular than fixed.
In fact, many service providers are skipping 802.16d
and going straight to 802.11e for this reason.
One appeal of WiMAX is in its ability to deliver wider
frequency bandwidth over current broadband wireless
technologies. This is accomplished through OFDMA, or
Orthogonal Frequency Division Multiple Access. OFDMA
supports frequency bandwidths of 10 MHZ or more. This
far exceeds the bandwidth of today’s current 3G
technologies such as CDMA2000 that supports 1.25-MHz
bandwidth, or 5-MHz bandwidth delivered through WCDMA/UMTS.
WiMAX also leverages multiple input multiple output
(MIMO) and smart antennas to support higher data rates.
The combination of wider frequency bandwidth and higher
data rates makes WiMAX suitable for a range of potential
applications, some of which have already been deployed
commercially with pre-certified equipment. These are
shown in Figure 1.
In addition, OFDMA allows WiMAX to operate without
a clear or direct line of sight between the customer-premise
equipment (CPE) and the base station, allowing WiMAX
to serve a broader number of customers in a market.
WiMAX modems can be sold in a retail outlet and installed
easily at home which lessens the need for expensive
truck rolls that other broadband wireless technologies
require for installation. The WiMAX Forum certification
process also ensures multi-vendor interoperability between
different WiMAX vendor base stations and CPEs. These
benefits all improve WiMAX’s overall appeal.
A Broad Spectrum
WiMAX can be used in frequency bands between 2 and 11
GHz, with future versions potentially operating as high
as 66 GHz. This spectral flexibility provides a competitive
edge over existing technologies in several ways.
First, WiMAX’s wide range of operation means
that a broader market can be tapped since there is no
single band available in every country. This wide market
access would result in a global cost structure for the
technology and build its position as a competitor with
technologies like DSL and 3G. One caveat, however, is
that global use would require that consumers’
products support these multiple frequency bands. Added
RF components would add to the consumers’ cost.
Second is WiMAX’s ability to operate in unlicensed
frequency bands to deliver wireless broadband access
in rural and remote areas. Spectrum licenses are expensive
and WiMAX could allow operators to lower overhead costs
and offer competitive price points with wired and wireless
services. It is important to note, however, that to
maintain quality of service (QoS) in an unlicensed band,
sophisticated filtering features would be required to
address interference issues, and that would add to equipment
costs.
Designing for WiMAX
For WiMAX to successfully take off, equipment vendors
must cost-effectively tune product to address the requirements
in the country where it will be deployed. (Figure 2.)
Programmable DSP solutions deliver the flexibility to
address those variations across frequency, power, and
emission, without having to undertake a complete redesign
for each market. Programmable DSPs also address the
evolution of WiMAX and support of frequency-agile products,
where mobile handset and laptop users will roam to countries
using different bands.
Infrastructure system designers also find themselves
in a complicated situation of designing for multiple
applications, and a range of equipment is required including
the traditional macro base stations and smaller form
factor base stations that provide in-building coverage.
In addition, to ensure support for these applications,
vendors are increasingly looking for ways to re-use
baseband or channel card hardware and software for multiple
applications. A single silicon platform capable of supporting
all the applications would help reduce overall R&D
costs.
With this in mind, TI offers a broad portfolio of WiMAX
solutions based on a single infrastructure platform
that can be quickly and cost-effectively configured
for each operator’s or country’s requirements.
This includes the TMS320TCI6482 DSP that offers a software
library that enables high density, low power solutions
for 3G applications like cdma2000, EV-DO, 3GPP UMTS,
TD-SCDMA. It is an ideal solution for OFDMA applications
like WiMAX and future applications including 802.20
and 3GPP LTE.
In Conclusion
With the first certified equipment now on the market,
vendors and service providers are just now gaining a
clearer picture of the performance and cost structure
that WiMAX technology can deliver. That information
will determine whether WiMAX can live up to its promises
of being both a competitor and complement for existing
technologies across the broadband wireless market.
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