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subject: Wireless LANs - What is Wireless Lan? [print this page]

Wireless LANs - What is Wireless Lan?
Wireless LANs - What is Wireless Lan?

Wireless LANs - What is Wireless Lan?

Wireless LANs and wired LANs operate in much the same way at the physical

level. That is, they both use electrical energy to transmit data. One encodes its

data upon an electrical impulse in a wire, and the other encodes it upon a radio

or light wave.

With a waveform, the amount of data which can be transmitted is theoretically,

directly proportional to the frequency of the wave. For example, if a particular

piece of switching equipment in a transmitter is capable of encoding

(modulating) one bit of data per cycle, then a wavelength with a frequency of 10

kHz (ten thousand cycles per second) is going to carry ten times as much data

as a wavelength having a frequency of 1 kHz in the same period of time. This

holds true for as long as the switching equipment can match the frequency.

Some modulating methods make it possible to encode up to 4 bits on a single

cycle. Considering this and the high frequencies available, wireless LANs have

the potential to transmit data at very high speeds.

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As already mentioned, the characteristics of a wave change with respect to the

rate of frequency change. The higher the frequency, the more the wave takes on

the properties of light and the more it is absorbed or reflected. This has a

number of implications; the main one being the fact that as the frequency

increases the range of the LAN decreases due to the greater attenuation of the

signal. Also, the equipment used to transmit and receive radio waves begins to

strike some physical limitations as the frequency increases, so there is an upper

limit to its practical application.

There is a wide frequency range which could potentially be used for wireless

LAN communication. The range from about 200 kHz, through the microwave

range, all the way up to the top of the infrared range at around 200 THz could be

utilized. When selecting a range upon which to build equipment, consideration

must be given to the required throughput versus transmission range. As one

increases, the other decreases as mentioned previously. Greater range can be

achieved at any frequency by increasing the transmission power. However,

most governments impose strict controls on power output through their licensing

and regulatory authorities. A more efficient antenna or a directional one can

increase the range of any transmission, but this is nowhere near as significant a

gain as simply increasing the power.

You can know more about Wirelesslan in some sites like this one.

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