I thought the purpose of the revision was to deal with these issues. Am I wrong ??? // Michael Taylor
_____ From: [email protected] [mailto:[email protected]] On Behalf Of Mark Gandler Sent: Tuesday, August 21, 2007 6:43 PM To: Marko Radojicic; Ken Javor; [email protected] Subject: RE: 802.11 & similar wireless links, interference between Ken, Marco, just few comments. FCC DFS requirements did not eliminate any channels, but only forced the product to comply with the requirements from July 2007, which most of the newly designed products do. In 2.4Ghz band you will be better of with draft 11n products. In a nutshell, those products use MIMO (Multiple In Multiple Out) technology, which incorporates multiple antennas, could be 2,3 or more. If there is an interference in one of the antennas path, it will switch to another antenna, avoiding interference. Most of the 11n products have data rate and throughput higher then land Fast Ethernet LAN. Mark > Subject: RE: 802.11 & similar wireless links, interference between > Date: Tue, 21 Aug 2007 11:02:30 -0700 > From: [email protected] > To: [email protected]; [email protected] > > Ken, > > If you want to avoid interference in 802.11, use 11a. There are many > more channels available than 11b/g (exact details are dependant on the > country you are operating in). The new DFS requirements have effectively > eliminated a lot of these channels but 11a may still be the best option > for your application. > > If you are forced to use the 2.4GHz 11b/g band, there are only three > (mostly) non-interfering channels: 1, 6 and 11. > > Typically channel 6 will have the highest TX powers and thus the best > performance. Channels 1 and 11 typically have less TX power capability > in order to meet the regulatory band-edge requirements. > > There is some limited amount of interference between channels 1 & 6 and > 6 & 11 but not huge. Channels 1 & 11 have no interference. There is much > less channel-channel interference even between adjacent channels in 11a. > > The ultimate non-interference strategy, of course, is to use both 11b/g > and 11a. > > Most WLAN enterprise solutions have planning software that help users > select the AP density & location, channel selection, TX power setting, > etc. You may want to consider this option if your application is > complex. > > ...Marko > > -----Original Message----- > From: Ken Javor [mailto:[email protected]] > Sent: Wednesday, August 15, 2007 5:00 AM > To: [email protected] > Subject: Re: 802.11 & similar wireless links, interference between > > Slightly different question, based on answer below. If you had multiple > 802.11 links in the same area, would it be possible to assign fixed > "channels" to the most important ones, and exclude less important links > from > intruding on those? Also, could other links such as Bluetooth be > controlled > so as not to occupy the same bandwidth? > -- > Ken Javor > > Phone: (256) 650-5261 > > > From: "Barker, Neil" <[email protected]> > > Date: Tue, 14 Aug 2007 16:51:06 +0100 > > To: 'Ken Javor' <[email protected]>, [email protected] > > Subject: RE: 802.11 & similar wireless links, interference between > > > > Ken, > > > > I cannot quantify the effects, but I have a few observations:- > > > > A great deal will depend on the volume of 'traffic' on the link; > occasional > > data downloads from a host or server are likely to be much more robust > than > > applications such as streaming video. > > As an example, one recent 802.11 product that streams video has > performed > > well on tests in the factory, but suffered from significant > degradation at a > > trade show where there were undoubtedly many other devices using the > same > > technology. > > Much depends on the local configuration; where a device is operating > in > > infrastructure mode, it is often easy to change channels, but where a > device > > is in ad-hoc mode it is not uncommon for it to be set to a default of > > Channel 1, which is consequently heavily populated. > > Perhaps somebody who knows more about data density and the maths of > channel > > sharing can provide some correlation between data rate and the > probability > > of degradation dependent on the population distribution of WLANs > operating > > (given that a typical transmitter has up to about 300m range). > > > > Best regards > > > > Neil R. Barker CEng MIET HonFSEE MIEEE > > Manager > > Quality Engineering > > e2v technologies (uk) ltd > > 106 Waterhouse Lane > > Chelmsford > > Essex CM1 2QU > > UK > > > > Tel: (+44) 1245 453616 > > Fax: (+44) 1245 453571 > > Mob: (+44) 7801 723735 > > > > P Please consider the environment before printing this email. > > > > > > > > -----Original Message----- > > From: Ken Javor [mailto:[email protected]] > > Sent: 14 August 2007 16:15 > > To: [email protected] > > Subject: 802.11 & similar wireless links, interference between > > > > > > Does anyone have any experience, either specs/standards or empirical > > concerning how many of these type links can operate in the same area > before > > degradation begins. I realize "area' Is not a specific term, but the > idea > > is that within one factory building, how many 802.11, Bluetooth or > other > > co-frequency links can operate simultaneously without upset or > degradation? > > > > Thank you, > > > > Ken Javor > > > > Sent by E2V TECHNOLOGIES PLC or a member of the E2V group of > companies. A > > company registered in England and Wales. Company number: 04439718. > > Registered address: 106 Waterhouse Lane, Chelmsford, Essex, CM1 2QU, > UK. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. 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