Page 164 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes 10.1.2 Adaptive Modulation

WiFi make use of adaptive modulation and varying levels of forward error correction to optimize
transmission rate and error performance.
As a radio signal loses power or encounters interference, the error rate will increase. Adaptive
modulation means that the transmitter will automatically shift to a more robust, though less
efficient, modulation technique in those adverse conditions.

There are following issues which are assumed to be the cause of the sluggish adoption of Wi-Fi
technology:

z z Security Problems: Security concerns have held back Wi-Fi adoption in the corporate
world. Hackers and security consultants have demonstrated how easy it can be to crack the
current security technology, known as wired equivalent privacy (WEP), used in most Wi-
Fi connections. A hacker can break into a Wi-Fi network using readily available materials
and software.

z z Compatibility and Interpretability: One of the bigger problems with Wi-Fi is compatibility
and interpretability, for example 802.11a products are not compatible with 802.11b
products, due to the different operating frequencies, and 802.11a hotspots would not help
a 802.11b client. Due to lack of standardization, harmonization and certification, different
vendors come out with products that do not work with each other.

z z Billing Issues: Wi-Fi vendors are also looking for ways to solve the problem of back-end
integration and billing that has dogged the roll-out of commercial Wi-Fi hotspots. Some
of the ideas under consideration for Wi-Fi billing include per day, per hour and unlimited
monthly connection fees.
WiFi is a universal wireless networking technology that utilizes radio frequencies to transfer
data. WiFi allows for high speed Internet connections without the use of cables or wires.
The term Wi-Fi is a contraction of “wireless fidelity” and commonly used to refer to wireless
networking technology. The Wi-Fi Alliance claims rights in its uses as a certification mark for
equipment certified to 802.11x standards.
Wi-Fi is a freedom, freedom from wires. It allows you to connect to the Internet from just about
anywhere - a coffee shop, a bed in a hotel room or a conference room at work without wires.
And the best thing of all, it’s super fast - almost 10 times faster than a regular dial-up connection.
Wi-Fi networks operate in the unlicensed 2.4 radio bands, with an 11 Mbps (802.11b) or 54 Mbps
(802.11a) data rate, respectively.

To access Wi-Fi, you need enabled devices (laptops or PDAs). These devices can send and receive
data wirelessly from any location equipped with Wi-Fi access.
What is Next ?

Now the focus in wireless is shifting to the wide area. WiMax, short for Worldwide Interoperability
for Microwave Access, is defined in IEEE 802.16 standards is designed to deliver a metro area
broadband wireless access (BWA) service, and is being promoted by the WiMax Forum.
!

Caution WiMAX is similar wireless system to 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.

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