How do wireless signals disperse themselves?

Maybe this question is unanswerable. Maybe not.

Just how are wireless signals dispersed from a wireless router? I mean are they sent forth upwards, downwards, sideways. Do they cover an area like a fog, seeping into every penetrable space until they reach their maximum range or collide with an impenetrable or non-porous object such as a cement wall or steel beam?


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dejola said the following on 1/5/2006 4:06:

In my layman's view, I think of them as ripples in a pond, but the pond has objects in it that cause the ripple to bounce around.


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They tend to go out roughly perpendicular to the antenna(s), though only roughly. You can pretty much consider the entire router to be an isotropic (emits equally in all directions) radiator.

You can think of them as waves or particles, that will reflect from some surfaces and be partially absorbed or blocked by others. Very generally, you can go through a wall or two and a floor without too much attenuation, assuming stick construction and no metal-faced insulation in the way.

Multipath effects and interference will further complicate the issue, as will the client radio, so it's not something subject to prior analysis.

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William P.N. Smith

"dejola" hath wroth:

Wireless signals are not dispersed from a wireless router. They are radiated from the antenna plugged into the wireless router. The general idea is much like your fog, except that the fog is much thicker in a plane perpendicular to the vertical antenna, than in line with the antenna. Were you to represent this thickening of the fog as a function of equal signal strength around the antenna, it would look like a torus (donut).

The fog is also not static in that radio waves don't just sit there looking like a donut and going nowhere. They radiate outwards at the speed of light in all directions. It's just that the strength of these waves are stronger in a plane perpendicular to the omni antenna. Other equal signal strength shapes are possible with different antenna geometry.

As the fog radiates away from the antenna, it occupies a larger and large volume as it moves farther and farther away from the antenna. The strength of the signal varies with the square of the distance from the source. Double the distance and you get 1/4 the delivered signal (i.e. -6dB).

The waves will begin to hit objects near the router and in the room. These objects can be roughly classified as either translucent, absorbent, or reflective. No object is truely transparent and many are simultaneously both absorbent and reflective. Concrete is a good example of both. The rebar inside reflects, while the water inside absorbs. The exact effects are difficult to calculate and model.

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Jeff Liebermann

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The radio environment?Several issues affect the way the radio signal travels from one device to another: ? Radio energy attenuates when it propagates. As radio waves propagate outwards spherically, the energy spreads over an ever-increasing area. In free space, doubling the distance decreases the received power by a factor of 4?the so-called 1/r2 behavior. Radio signals also attenuate when they pass near or through objects such as floors, walls, furniture and people. The attenuation increases with the object's conductivity (due to metal or water content, for example). The combination of these two attenuation effects reduces radio signal strength by 1/r3 to 1/r4, or even 1/r5. In other words, each time you double the distance, the received power might decrease by 8 to 16 times. ? Antenna designs affect how much radio-frequency (RF) energy is transmitted or received and where it is directed. ? Scattering and multi-path cause fading effects. Signal strength can change rapidly as a function of location because the received signal is the sum of potentially numerous signals scattered from nearby objects. As the transmitter or other objects in the environment move, the scattered signals sometimes add together and sometimes cancel each other. Fading can change significantly over distances of a wavelength or so (12.5cm at 2.4 GHz and 6 cm at 5 GHz). Fading also occurs over time as well as location. Even small changes in the environment (for example, people or other objects moving) can affect the fading pattern. This means that the received signal strength can also change quite quickly over time, even when the receiver and transmitter are fixed. ? Scattering and multi-path results in delay spread. The received signal might contain several slightly delayed copies of the transmitted signal, as the scattered signals travel via different physical paths of different lengths.

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Hi, And it has vertcial and horizontal polarized componenet. Type of antenna has lot to do with this. But no signal is 100% V or H. Matvching antenna type at both end is good idea. Also there is technique using diversity; frequency, space, polarization to combine received signal for better reception quality.

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