North American Network Operators Group

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Re: wifi for 600, alex

  • From: Alexander Harrowell
  • Date: Fri Feb 16 12:06:00 2007
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On 2/16/07, JAKO Andras <[email protected]> wrote:

Please don't forget that 802.11 uses the CSMA/CA protocol. All nodes,
including the AP and _all_ the clients should hear each others'
transmissions so that they can decide when to transmit (when the medium is

Yes. But so long as they can all interfere with each other, you're still going to pay a cost in informational overhead to sort it out at a higher protocol layer, and you're still going to have the "electronic warfare in a phone box" problem at places like NANOG meetings. 3GSM is the same - even the presence of ~10,000 RF engineers doesn't prevent the dozens of contending networks..

Essentially, this is a problem that perhaps shouldn't be fixed. Having an open-slather RF design and sorting it out in meta means that WLAN is quick, cheap, and hackable. Trust me, you don't want to think about radio spectrum licensing. On the other hand, that particular "sufficiently advanced technology is indistinguishable from magic" quality about it causes problems.

Intentionally limiting the clients' TX powers to the minimum needed to
communicate with the AP makes RTS/CTS almost obligatory, which may be
considered a bad thing. Once again, in the ideal situation all nodes hear
each other, at least from the CSMA/CA's point of view.

I'm not sure that's ideal in my point of view, in so far as we're talking about a point-to-multipoint network rather than a mesh. And why would anyone ever want to use more power/create more entropy than necessary?

This argument sailed around in the early days of WiMAX, when people were talking about running it in unlicensed 5.8GHz spectrum and "finally getting away from the telcos and the government", until they realised that it's not "big wi-fi" and isn't designed to cope with contending networks..