Re: RE: 300mw?

> It would be nice to have much better receive specs on the various  
> radios.

The "receive specs" are on Tony's site, but they are, in a word,  
somewhat unbelievable.

Tony claims on his site that this Prism 2.5 design will do -91dBm rx  
sensitivity @ 11Mbps,  
(http://www.demarctech.com/products/reliawave-rwz/reliawave-rwz-300mw- 
prism2-5-pcmcia-card.html) but this is a bit better than anyone else  
has been able to do with a Prism 2.x design.   The limit seems to be  
-89dBm for all but the Atheros based designs.   I once asked Atheros  
about their (higher) claims, (which, btw, not only are quite close to  
the theoretical limit (they exceed it until you account for coding  
gain), and, better, bear out in testing), and was given a long  
technical explanation which I can't repeat here (NDAs) but basically  
reduces to: "we burn more gates than anyone else on a CCK receiver".

Which is why the Atheros strategy of "all-CMOS, all the time" might  
just win.  CMOS gates are cheap when you're pad-limited.  (Not that I'm  
saying that Atheros is pad-limited...  almost everyone was pad-limited  
as soon as CMOS went under .25 micron.)

Last year, I quoted the Atheros rx specs back to several Taiwanese ODMs  
who build Atheros-based products, most of whom were quite ... scared is  
the only word.   Much backpedaling.  They just didn't want to sign up.   
(Two were bold enough to ask me "How?")  Keeping that tight a spec  
in-production at low cost can be quite challenging.  Nevertheless, I  
have reason (but no proof) to doubt the claims on rx sensivity of  
Tony's cards.   Perhaps when these finally start shipping, I can  
purchase one and a) test it or b) pull it apart to see what they've  
used for the LNA and PA.

As for matching the EIRP between AP and STA (below), I see great  
potential for 'hidden node' issues in the setup that Tony details.

I've found that a slightly higher EIRP on the AP is useful, because  
common STAs are, in a word, horrible, and a 2dBm advantage will assist  
these less  worthy receiver blocks in decoding the sent frame.

In my last message, I detailed why these 300mW cards won't result in  
higher EIRPs if the people using them intend on staying inside the FCC  
PTP limits.  Anyone who intentionally violates these should be treated  
with distain.  2.4GHz is bad enough without these bad actors.

I'm curious about the FCCID for the 300mW Zcomax cards.

	RWQ is the grantee code for Zcomax, but there are no FCCIDs under this  
code.
	M4Y is Z Com, but I can't find anything about the 300mW cards.

There is a XI-330HP/XI-330H that is rated at 23.5dBm, but that is as  
high as I could find.  Perhaps I missed something, and perhaps Tony  
will post the FCCID for the new 300mW cards.   (I hope they have one,  
or he and Zcomax have violated the "offer for sale" rule.)

Jim

On Apr 14, 2004, at 7:31 PM, <[email protected]> wrote:

> Brian
>
> I agree with you if the system is not engineered correctly you will  
> have a asymmetrical system but when done correctly is can be
> symmetrical, as an example system:
>
> At the base 300mW radio plus a 11.2 dBi 120* antenna for a total of  
> 36dBm EIRP, on the client side lets use a 100mW radio and a
> 15dBi 30* you have a balanced system.
>
> Sincerely, Tony Morella
> Demarc Technology Group, A Wireless Solution Provider
> Office: 908-996-7995 Fax: 908-847-0202
> http://www.demarctech.com
>
>
> -----Original Message-----
> From: Brian Lloyd [mailto:[email protected]]
> Sent: Wednesday, April 14, 2004 9:20 AM
> To: [email protected]
> Subject: Re: [BAWUG] RE: 300mw?
>
> [email protected] wrote:
>
>> I agree with you on a basic setup but if a system is engineered
>> correctly, its very easy to have a balanced systems. The main benefit
>> to a 300mW/400mW (soon) radio is a lower gain antenna thus a larger
>> vertical beam width at the base station, this is NOT the best setup
>> for all applications but it does add additional options to the WISP
>> tool box.
>
> Jim has a very good point.  If you have a much more powerful  
> transmitter at the AP you will have an asymmetrical path.  if one side
> has a 6db transmit advantage it also needs a 6db receive advantage in  
> order to retain a reciprocal path (excluding noise issues).
> Yes, you can use higher transmit power and lower antenna gain to  
> maintain the transmit field strength but that doesn't help the
> other guy reach you.  I run into problems all the time with my APs  
> where users can hear the AP (200mw) but the AP can't hear them
> reliably.
>
> The worst thing of all is an alligator radio.  All mouth and no ears.   
> It would be nice to have much better receive specs on the
> various radios.
>
> -- 
> Brian Lloyd                         6501 Red Hook Plaza
> [email protected]                     Suite 201
> http://www.lloyd.com                St. Thomas, VI 00802
> +1.340.998.9447 (voice)             +1.360.838.9669 (fax)
>
>
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