I could not agree more Cliff. Your points about 802.11g explain a key distinction regarding what is intended for indoor use and what must be enabled to work successfully in the outdoor environment. All our systems, and the OFDM is no different, is optimized for outdoor environments. That includes environmentals, timing, authentication, security, as well as adjustiong the OFDM modulation for multipath conditions resulting from miles, not feet.
I am not sure about the specific numbers you have requested so I have sent off a mail to get them. When I have my reply, I'll share them. Regards, Patrick -----Original Message----- From: Cliff Skolnick [mailto:[EMAIL PROTECTED] Sent: Thursday, July 24, 2003 11:31 PM To: Patrick Leary Cc: 'Tim Pozar'; Ladjicke Diouf; [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: Re: [BAWUG] 802.11b Long Range non line of sight Theory is great, but in practice I've had problem with OFDM as specified for 802.11g. Depending on how you tune your gear multipath can kill you, but timings can be adjusted to handle it well, even use it. I've not experienced this personally as I've only use 802.11a and 802.11g indoors, but I've heard stories. The biggest problem which I have totally experienced is the current lack of adjacent channel rejection for OFDM of the current generation for adjacent yet non-overlapping channels (1, 6, 11). I was involved with a large roll out a will tons of 802.11b on 1 and 11, and the 802.11g on 6. The 802.11g was getting beat up performance wise so we looked into it. The numbers I was quoted were a 30db rejection for 802.11b (orinoco gear) and a < 6db rejection (I'm being nice here) for linksys and other G cards. Next time we will pick 1 or 11 for the 802.11g gear :/ What kind of adjacent channel rejection does your gear have? and have you adjusted your OFDM timings to handle multipath where the bit shift is larger than 802.11g? So far I've not been impressed with the stability of 802.11a or 802.11g gear, but I think the issues were not OFDM's fault, more implementation issues. Cheers, Cliff On Thursday, Jul 24, 2003, at 19:45 US/Pacific, Patrick Leary wrote: > Tim, your understanding of OFDM is way off. Extraordinarily stability > is > achieved with OFDM - far more than with our FHSS or our DSSS. We have > examples of links having only a single packet error over several > weeks. I am > not basing these off theory, but off actual field results both beta and > commercial deployments. Here is a link to some such tests done using > our > 3.5GHz OFDM PMP which has been shipping for 18 months and is in use in > major > carrier deployments around the world. This paper includes detailed > photo > examples of the links. > > http://www.alvarion-usa.com/RunTime/Materials/KnowledgePoolFiles/ > alv_OFDM%20 > wp.pdf > > Keep in mind, this is 3.5GHz equipment > http://www.alvarion-usa.com/RunTime/ > Products_2020.asp?tNodeParam=33working > off a very small channelization, so the max data rate is lower than > our same > products using 20MHz 5GHz channels (BreezeACCESS VL and BreezeACCESS > LB). > VL: http://www.alvarion-usa.com/RunTime/Products_2020.asp?tNodeParam=39 > LB: http://www.alvarion-usa.com/RunTime/Products_2020.asp?tNodeParam=35 > > Patrick > Alvarion > > > > -----Original Message----- > From: 'Tim Pozar' [mailto:[EMAIL PROTECTED] > Sent: Thursday, July 24, 2003 8:43 PM > To: Patrick Leary > Cc: Ladjicke Diouf; [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: [BAWUG] 802.11b Long Range non line of sight > > > On Thu, Jul 24, 2003 at 05:32:38PM -0700, Patrick Leary wrote: >> Tim, I am not sure if you are talking about OFDM or DSSS. With OFDM, >> you >> DON'T need LOS. Of course its not going to connect forever with NLOS, >> but >> for a few miles, it is a no brainer. We have ample empirical data that >> proves it. > > I haven't see your report but if you are basing it on using things > like knife-edge diffraction or even multipath as your method of > getting from point A to point B. I *would* be cautious about giving > the link a high "up-time". > > Looking forward to the report... > > Tim > > > This mail passed through mail.alvarion.com > > *********************************************************************** > ***** > ******** > This footnote confirms that this email message has been scanned by > PineApp Mail-SeCure for the presence of malicious code, vandals & > computer > viruses. > *********************************************************************** > ***** > ******** > -- > general wireless list, a bawug thing <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless > -- "Capitalism is the astounding belief that the most wickedest of men will do the most wickedest of things for the greatest good of everyone." - John Maynard Keynes This mail passed through mail.alvarion.com **************************************************************************** ******** This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. **************************************************************************** ******** -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
