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WiMax (and we shall see how, exactly, the comparisons between WiMax and WiFi are correct...i.e, wimax = cell phone AND
wifi = cordless phone....used in the home....we shall observe.....)
WiMAX is an IP based, wireless broadband access technology that
provides performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular networks.
WiMAX is also an acronym meaning "Worldwide Interoperability for Microwave Access (WiMAX).
WiMAX is a wireless
digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks".
can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile
stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet
(30 - 100m).
With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is lessened.
WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model
for wireless carriers.
At its heart, however, WiMAX is a standards initiative. Its purpose is to ensure that the
broadband wireless radios manufactured for customer use interoperate from vendor to vendor. The primary advantages of the
WiMAX standard are to enable the adoption of advanced radio features in a uniform fashion and reduce costs for all of the
radios made by companies, who are part of the WiMAX Forum™ - a standards body formed to ensure interoperability via
The more recent Long Term Evolution (LTE) standard is
a similar term describing a parallel technology to WiMAX that is being developed by vendors and carriers as
a counterpoint to WiMAX. +++++++++++++++++++++++++++++++++++++++++++++
WiFi (technically standard 802.11) and WiMAX (802.16) don't compete for broadband users or applications today. That's partly because
WiFi is widely deployed and WiMAX is still largely an unfulfilled promise and partly because the two protocols were designed
for very different situations.
However, if WiMAX is eventually widely deployed, there will be competition between them as last mile technologies.
Some people describe
the difference between WiFi and WiMAX as analogous to the difference between a cordless phone and a mobile phone.
Wifi, like a cordless
phone, is primarily used to provide a connection within a limited area like a home or an office. WiMAX is used (or planned
to be used) to provide broadband connectivity from some central location to most locations inside or outside within its service
radius as well as to people passing through in cars. Just like mobile phone service, there are likely to be WiMAX dead spots
From a techie POV, the analogy is apt at another level: WiFi, like cordless phones, operates in unlicensed spectrum
(in fact cordless phones and WiFi can interfere with each other in the pitiful swatch of spectrum that's been allocated to
them). There are some implementations of WiMAX for unlicensed spectrum but most WiMAX development has been done on radios
which operate on frequencies whose use requires a license.
Some more subversive types (they're subversive so I can't link to them)
say that WiMAX is what you get when bellheads (not a nice term) try to reinvent WiFi the way they'd like it to be. It's true
that WiMAX is much more a command and control protocol than WiFi.
Oversimplified, in a WiFi environment every device within reach
of an access point shouts for attention whenever it's got something to transmit. In that chaos, some signals tromp on other
signals; the more powerful devices and those closer to the access point tend to get more than their share of airtime like
the obnoxious kid who always has his hand up in the front of the class. In WiMAX devices contend for initial attention but
then are assigned times when they may ask to speak.
The protocol allows the operator more control over the quality of service provided —
bellheads like control.
But it's not clear that more control means better service than contentious chaos (I'm talking about technology but
the same may apply to economies or bodies politic). The Internet and its routing algorithms are chaotic; the routers just
throw away packets if they get to busy to handle them. Bellheads (and even smart people like Bob Metcalfe) were sure that design or lack thereof wouldn't scale. They were wrong.
Same people said that voice would never work
over the Internet — there's no guarantee of quality, you see. They were wrong although it's taken awhile to prove it.
Now HD voice is available on the Internet but NOT on the traditional phone network (although it could be).
Lovers of an orderly environment and those
who like to keep order were absolutely sure that WiFi couldn't work once it became popular.
Not only is it chaotic; it also operates
in the uncontrolled environment of unlicensed frequencies along with cordless phones, bluetooth headsets, walkie-talkies and
the occasional leaky microwave oven. But somehow it's become near indispensable even in places where a city block full of
access points contend for the scarce frequencies.
I'm not convinced
that WiMAX won't suffer from its own orderliness. Did you ever fume leaving an event when an amateur cop (or a professional
one) managed traffic into an endless snarl? Fact is cars at low speed usually merge better without help than otherwise. Turns
out that control comes at the expense of wasted capacity.
The reason that the Internet or WiFi radios can work is that the computing
power necessary to deal with chaos from the edge of the network is far cheaper and less subject to disruption or misallocation
than the computing power (and communication) for central command and control.
WiMAX may be too well-controlled for its own good. Moreover, if
it is used only in regulated spectrum where most frequencies are idle most of the time AND licenses for the frequencies have
to be purchased, it will be even less efficient than if it could contend for unlicensed spectrum.
By the way, WiFi CAN operate at distances
as great as WiMAX but there are two reasons why it doesn't. One reason is that radios operating in the unlicensed frequencies
are not allowed to be as powerful as those operated with licenses; less power means less distance.
These regulations are based on the dated
assumption that devices can't regulate themselves — but the assumption MAY be correct over great enough distances.
The second reason why
WiFi access points don't serve as wide an area as WiMAX access points are planned to do is the engineering belief that the
problem of everybody shouting at once, even if it's surmountable in a classroom, would be catastrophic in a larger arena.
licensed spectrum is being made available for WiMAX and other technologies NOT including WiFi — for example, the valuable
700MHz frequencies currently used by analog over the air TV. WiMAX could have a good run because it is allowed to operate
in that efficient spectrum while WiFi will eventually run out of the pitifully little spectrum that's been allocated to it.
policy and politics and not engineering but could still be a reason for WiMAX success. ++++++++++++++++++++++++++++++++++
WiMAX is similar
to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speeds. A nomadic version would keep WiMAX-enabled
devices connected over large areas, much like today.s cell phones. We can compare it with Wi-Fi based on the following factors.
Wi-Fi is based on IEEE
802.11 standard where as WiMAX is based on IEEE 802.16. However both are IEEE standards.
Wi-Fi typically provides local network access
for around a few hundred feet with speeds of up to 54 Mbps, a single WiMAX antenna is expected to have a range of up to 40
miles with speeds of 70 Mbps or more. As such, WiMAX can bring the underlying Internet connection needed to service localWi-Fi
Wi-Fi is intended for
LAN applications, users scale from one to tens with one subscriber for each CPE device. Fixed channel sizes (20MHz).
WiMAX is designed to
efficiently support from one to hundreds of Consumer premises equipments (CPE)s, with unlimited subscribers behind each CPE.
Flexible channel sizes from 1.5MHz to 20MHz.
Wi-Fi works at 2.7 bps/Hz and can peak up to 54 Mbps in 20 MHz channel.
WiMAX works at 5 bps/Hz and can peak up to
100 Mbps in a 20 MHz channel.
Quality of Service:
Wi-Fi does not guarantee any QoS but WiMax will provide your several level of QoS.
As such, WiMAX can bring the underlying Internet
connection needed to service local Wi-Fi networks. Wi-Fi does not provide ubiquitous broadband while WiMAX does.
The answer to this question probably generates more confusion than any other single aspect
the early days of WiMAX it was common to see statements in the media describing WiMAX multipoint coverage extending 30 miles.
In a strict technical sense (in some spectrum ranges) this is correct, with even greater ranges being possible in point to
point links. In practice (and especially in the license-free bands) this is wildly overstated especially where non line of
sight (NLOS) reception is concerned.
Due to a variety of factors explained in more detail in other FAQ answers, the average cell ranges for most WiMAX
networks will likely boast 4-5 mile range (in NLOS capable frequencies) even through tree cover and building walls. Service
ranges up to 10 miles (16 Kilometers) are very likely in line of sight (LOS) applications (once again depending upon frequency).
Ranges beyond 10 miles are certainly possible, but for scalability purposes may not be desirable for heavily loaded networks.
cases, additional cells are indicated to sustain high quality of service (QOS) capability. For the carrier class approach,
especially in regards to mobility, cells larger than this seem unlikely in the near future. The primary WiMAX focused US carrier
Clearwire has stated that its cell sites are planned at about 1.5 miles apart for mobile purposes.
This choice is clearly one intended to meet
NLOS requirements. In licensed frequencies, expect similar performance or better for WiMAX than in traditional cellular systems.
RF Frequencies does WiMAX work in?
The most recent versions of both WiMAX standards in 802.16 cover spectrum
ranges from at least the 2 GHz range through the 66 GHz range. This is an enormous spectrum range. However, the practical
market considerations of the Forum members dictated that the first product profiles focus on spectrum ranges that offered
Forum vendors the most utility and sales potential.
The International standard of 3.5 GHz spectrum was the first to
enjoy WiMAX products. The US license free spectrum at 5.8 GHz has a few WiMAX vendors building products. Licensed spectrum
at 2.5 GHz used both domestically in the US and fairly widely abroad is the largest block in the US. Also, in the US and in
Korea products are shipping for the 2.3 GHz spectrum range. Also in the US the 3.65 GHz band of frequencies now has WiMAX
gear shipping to carriers.
The technology appears easily extensible to lower frequencies including the valuable 700
MHz spectrum range at which the nation's largest auction (in terms of money spent) concluded in 2008. More likely near term
frequencies likely to be supported include the new 4.9 GHz public safety band (sometimes described as a Homeland security
The second largest block of frequencies ever auctioned (in terms of money spent) occurred in the summer of 2006 with
the AWS auction from the FCC. This spectrum was split with the bulk being at 1.7 GHz and the rest at 2.1 GHz. At this point,
the Forum is not expected to develop a product profile for this range as most licensees have announced support for LTE systems
or plan to use it for existing GSM/UMTS networks.
The physics of radio signals typically place two primary constrictions
To generalize, the higher the spectrum frequency the greater the amount of bandwidth that can be transported---lower
frequencies transport less bandwidth. Secondly, the lower the frequency the greater the carry range and penetration of a signal.
For example: A 900 MHz license free radio will travel farther and penetrate some tree cover fairly easily at ranges up to
one to two miles.
But it can carry much less bandwidth than a 2.4 GHz signal which cannot penetrate any tree cover whatsoever, but
can deliver a lot more data. The caveat that can somewhat alter this equation is power. Licensed band spectrum such as 2.5
GHz by virtue of being dedicated to one user is allotted significantly higher power levels which aids in tree and building
Where did the idea of WiMAX come from?
Much of the credit for
the formation of the WiMAX Forum™ and to the founding members of the WiMAX
Forum, which committed themselves early to the process of creating a collaborative standards body.
As a founding member
of the WiMAX Forum, Intel recognized that a well developed ecosystem was necessary to drive adoption and thereby drive lower
hardware costs. Intel was also instrumental in getting other silicon chip manufacturers involved whose products would form
the core of WiMAX technology.
What factors will most greatly affect range
for WiMAX products?
Many factors affect range for any broadband wireless product. Some factors include the terrain
and density/height of tree cover. Hills and valleys can block or partially reflect signals. Bodies of water such as rivers
and lakes are highly reflective of RF transmissions.
Fortunately OFDM can often turn this to an advantage---but not
always. The RF shadow of large buildings can create dead spots directly behind them, particularly if license-free spectrums
are being used (with their attendant lower power allotments). How busy the RF environment of a city or town is can greatly
degrade signals---meaning that properly designed and well thought out networks are always desired.
of radio transmission dictate that the greater the range between the base station and customer radio, the lower the amount
of bandwidth that can be delivered, even in an extremely well-designed network. The climate can affect radio performance---despite
this there are ubiquitous wireless networks deployed today with great success in frozen Alaskan oil fields as well as lush
South American and Asian climates.
And increasingly WiMAX radio antenna technology coupled with the inherent advantages of
OFDM/OFDMA based radios can be a major factor in range and bandwidth capability. The new multiple input multiple output (MIMO)
and adaptive antenna systems (AAS) based antenna systems promise to maintain and even link connection and link budgets with
much higher bandwidth than older technology.
No two cities are exactly alike in terms of the challenges and opportunities
presented. In many respects, broadband wireless remains very much an art form. However, this is also true for the cellular
carriers most of us use daily. It can be done quite well. Mobile broadband wireless will be more difficult.
high quality of service (QOS) will be easier with fixed broadband wireless. Despite all of these challenges, current broadband
wireless is very effectively serving customers even in the most challenging environments. ++++++++++++++++++++++++++++++++++++