Actually - believe it or not - having looked at enough spectrum displays I really wouldn't be surprised if this were true. I'M NOT SAYING THAT IT IS TRUE. But the FCC definition of channel occupancy and ours may be a bit different - when the FCC defined what a channel was, spectrum analyzers were entirely analog instruments. They seemed to like <1% energy outside the channel bandwidth (or fitting the deviation within -20 dBc) Today we can make much better measurements. And spread spectrum has that randomness of code division modulation. The FCC doesn't say how long you need to sit there and store to capture every random event, and what about the sweep on the spectrum analyzer?
I think the question really is - how much overlap (3%, 6%, 100%, etc) can two adjoining "cells" (for lack of a better term) tolerate before they start to suffer. And - question 2 - how bad do they really suffer? If it's just a few more CRC errors, pile 'em on. I have seen two adjoining networks on the same frequency, different ssids, and yes there were lost packets, but the users just attributed it to a "bad spot" and went on with life. This was in a medical building. When I stuffed a system into 2442-2449 Mhz, it obviously didn't all fit - but that was the only quiet block in 2400-2483 in the area I was surveying, so I had no choice. Granted it was like parking a Hummer in a Harley spot, but it came up and worked 100% on channel 7 which was the only channel that occupied 2442-2449. At that point, we said "if it works... " and walked away happy - it's been up ever since and hasn't logged any errors. (Every system I work on I setup to send syslogd messages back to my unix servers so I can track errors - more of a curiosity thing - but it lets me know what works over the long term and what doesn't - figure learn from the experience, and be prepared for any phone calls down the road.) The only issue I can see is so many "default" systems on channel 6 out there already. That's the nice thing about 1,6,11 - it lets the default guys stay where they are and works around them. Nowadays, though, out of the box systems go looking for clear channels - my neighbors got 802.11 boxes and stayed far away from my system here - and they're the type who throw out the instructions with the packing material. They sure don't read this list (I hope!) Everett > > Hi, > > At 22:29 10/10/2003, Jeff Schwartz wrote: > >I remember reading a study a year or so ago which said that if you use > >channels 1, 4, 8, 11, at most you get 3% overlap. I've done this > >successfull; and having the extra channel gives you greater flexibility. > > > >Does anyone remember where to find this article?... I seem to have > >misplaced it. > > First link on Google with "802.11 4 channels"... > > http://www.extremetech.com/article2/0,3973,708876,00.asp > > Jacques. > > > -- Jacques Caron, IP Sector Technologies > Join the discussion on public WLAN open global roaming: > http://lists.ipsector.com/listinfo/openroaming > > > -- > general wireless list, a bawug thing <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless > -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
