

Why wireless networks are slow - mryall
http://mattryall.net/blog/2011/08/why-wireless-networks-are-slow

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DavidSJ
This may be an incredibly naive question, but is there any reason wireless
communication isn't directional, to mitigate some of these interference and
square of distance problems? You'd obviously need some lower-bandwidth
isotropic mechanism to locate other devices, and then a number of heuristics
to track and predict motion.

Perhaps this is already how these things work?

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mryall
People have managed to achieve much greater ranges (like more than a
kilometre) with 802.11 technology using "cantennas" -- directional antennas
like what you're talking about.

While it's theoretically possible, I'm not sure whether this is practical for
general use on a LAN. You'd probably have to have a wireless antenna poking
out of your laptop, which you'd point at the access point. Seems a little bit
inconvenient.

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mturmon
Pointing a big antenna is not how it would work.

You don't need to point the antenna at anything; you can use multiple antennas
that steer the beam ("beamforming") in a desired direction. Link:

<http://en.wikipedia.org/wiki/Smart_antenna>

Basically you can have a "phased array" of N antennas (2 counts as an array,
but you can think of a line of say N=8 antennas) that delay their broadcasts
relative to each other in such a way that the N signals interfere
constructively along some directions and destructively along other directions.
This is because, from far away,

    
    
      cos(angle_from_line_of_antenna_array) = const*propagation_delay_between_antennas

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mryall
Ah, clever! Thanks for the link.

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Geee
We are just now tapping on the spatial dimension of wireless channels; up to
now we have just used frequency, time, and polarization for orthogonality.
Spatial processing allows theoretically unlimited (bounded by computation,
solved by Moore) channel capacity. At the same time, we are beginning to use
the available channel resources more efficiently with cognitive radios, which
allows much better spectrum utilization. Today, with statically allocated
spectrum use, I'd guess that less than 10% of allocated spectrum and time is
in active use at any time.

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Swannie
My first thought before even reading the article was:
<http://www.bufferbloat.net/>

Good to see someone else commented about it.

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riledhel
Nice article. The collision avoidance algorithm explanation is very simple,
but overall the post is interesting.

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orijing
Why can't we create more open spectrum?

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forensic
Would it be illegal to sell firmware that uses more spectrum and boosts wifi
speeds?

I'm just wondering how hard it would be to jailbreak WiFi.

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AndrewDucker
It would probably not be illegal to sell the firmware - but it would
definitely be illegal to use it.

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clistctrl
It's unfortunate there's no mention of using MIMO spatial correlation
techniques to increase Performance.

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reedlaw
check the end of the article

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donnaware
got to 3gpp.org and read up on how LTE works, many of these problems have been
addressed.

