Pooya Karimian

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Replacing Fiber With 10 Gigabit/Second Wireless

[Link] http://mobile.slashdot.org/article.pl?sid=08/10/03/1544226
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Posted to Computer»Network by pooya at October 3, 2008 10:42 AM

Posted by: Ehsan at October 3, 2008 11:36 AM

Many of these attempts use optimistic conditions that do not exist in real life situations. For instance, raining will cause the attenuation experienced by such network to be too high and will significantly reduce the actual throughput.

Furthermore, optical transmissions rely on line-of-sight which may not be true in this case, but still makes me doubt they can tolerate thick walls and hills between source and destination.

Posted by: Pooya Karimian at October 3, 2008 12:12 PM

@Ehsan: Insightful - you're the expert. Btw, how come recently I start hearing high frequency can't penetrate materials? I was always thinking the higher the frequency the more the penetration. Isn't that the case?

But if they can make it commercial, having a 10gbps point-to-point connection over near 1km is still pretty cool.

Posted by: Ehsan Nourbakhsh at October 3, 2008 04:09 PM

Yeah, in principal higher frequencies penetrate material as they have higher energies. The problem starts when the wavelength is so small that *all* of the wave passes through rain drops and oxygen molecules. For a frequency f, \lambda = \frac{c}{f} If f is order of 60 \times 10^10, then \lambda will be (3 \times 10^8)/(60 \times 10^9) which is almost 0.005m, or 0.5 cm. This value for FM radios is about 3 meters! Thus the attenuation caused by the changes in environment affect it significantly more than regular FM or SW radios, or even the WiFi 2.4GHz waves.

See this: http://en.wikipedia.org/wiki/Rain_fade

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