10 Mbit/s problem in your network

Mon Feb 18 00:32:13 UTC 2013

On Feb 17, 2013, at 4:17 PM, joel jaeggli <joelja at bogus.com> wrote:

> On 2/17/13 12:18 PM, Jay Ashworth wrote:
>> ----- Original Message -----
>>> From: "Owen DeLong" <owen at delong.com>
>>> I think by A you actually mean 5Ghz N. A doesn't do much better than G, though
>>> you still have the advantage of wider channels and less frequency congestion
>>> with other uses.
>> No, my ThinkPad doesn't *do* N, 5GHz or otherwise.  Neither does my Sprint
>> EVO, nor, as near as I can tell, the Galaxy S4 I'm going to replace it
>> with this year (though on that one, I'm a tad less certain).
>> 
>> I'd forgotten that N was dual band, though, yes.  I can't say I've ever
>> needed the extra bandwidth N provides, personally, though certainly the
>> hotels we've been discussing might need more to share around.
> entirely orthonal to the frequency band used spatial division multipluxing as used by 802.11n is generally going to increase the SNR.
> 
> so what you get out of A/N is:
> 
> * more non-overlapping bands and therefore a much easier map coloring problem)
> * greater attenuation, which implies more limited range, but also less interferance.

Greater attenuation is an oversimplification.  5Ghz penetrates things like stucco and concrete better than 2.4. OTOH, 2.4 gets through trees and moist air better. In dry air and/or a vacuum, they're similar. Neither penetrates humans particularly well, though 5 tends to do slightly better. 

> * with N-mimo higher SNR if you have >= 2 antennas
> 
> All of those things make the 5Ghz band a more attractive alternative for lots of applications. given that it's 5Ghz it also requires more power, which is a problem for cellphones, but not so much for tablets and laptops.

OTOH, with 5Ghz, a high-gain antenna is ½ - ⅛ the size (depending on the type of antenna) the size of a 2.4Ghz which also has advantages in portable applications.

Owen