I'm not sure what HCCA, PA, PAPR, or EVM are, but I don't think that WISPs need to.
----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com -------------------------------------------------- From: "Gino Villarini" <[email protected]> Sent: Sunday, October 04, 2009 6:04 AM To: "WISPA General List" <[email protected]> Subject: Re: [WISPA] To G or not to G :-) > Lawrence post wasn't too technical at all .... Stuff wisps operators or > at least the RF guy of a wisp should know > > > > Gino A. Villarini > [email protected] > Aeronet Wireless Broadband Corp. > tel 787.273.4143 fax 787.273.4145 > > ________________________________ > > From: [email protected] [mailto:[email protected]] On > Behalf Of Jack Unger > Sent: Sunday, October 04, 2009 1:40 AM > To: [email protected]; WISPA General List > Subject: Re: [WISPA] To G or not to G :-) > > > > Yep it's too bad that many wireless ISPs have no interest in learning > about wireless. > > Scottie Arnett wrote: > > I am reading your response and can not decipher all your algorithms? > Point that out and I will have a much more understanding of what you are > scientifically trying to say. Most WISPS have absolutely no scientific > background! > > John > > ---------- Original Message ---------------------------------- > From: "Lawrence E. Bakst" <[email protected]> <mailto:[email protected]> > > Reply-To: WISPA General List <[email protected]> > <mailto:[email protected]> > Date: Sun, 4 Oct 2009 00:15:45 -0400 > > > > I think you guys know most of this already, but here is my take > FWIW. > > I'm not a WISP, but I spent 5 years leading the design and > development of an 802.11[agb] security system. We did our own polling > solution based on 802.11e HCCA to solve the RTS/hidden node problem. > > All things being equal (which they often aren't) 802.11b will > give you a higher S/N and C/I than 802.11g, because in almost all cases > and especially at higher speeds. 802.11g has to lower the PA power > because of the PAPR of OFDM and meeting the 802.11g EVM spec. > > It is true that 2.4 GHz can be very polluted. We found the noise > floor to be really awful. You would be surprised by the number of > "entities" that know they are way over the FCC max power in 2.4 GHz, but > I digress. We once measured over 300 PHY errors a second on an "unused" > 2.4 GHz channel. The number went down to 150 PHY errors a second inside > an FCC chamber, if you can believe that. > > Having said all that we didn't use 802.11b at all because it's > data rates are too low for video. > > Also while we supported 2.4 GHz, we mostly deployed at 5.8 GHz > ISM because of the increased power available there and the pollution was > much less, but that maybe different now. > > For 802.11[ag] mutlipoint, the sweet spot speed wise is 18-36 > Mbps. It's very hard to keep a multipoint system at 48 or 54 Mbps > because you need a great deal of link margin and with all cards you > loose power as the speed increases to maintain PAPR/EVM. For point to > point with direction antenna relief you can often maintain 48 or 54. > > Antennae make a big difference, as others have noted horizontal > polarization is usually best and make the beam as narrow as you can > afford because it raises the effective gain. However, if you are in an > area where everyone else is horizontal it can make sense to try > vertical. With some of the antennae we used that was as simple as > rotating the antenna 90 deg at both ends. > > Watch out for crappy antennae, cheap cable, bad connectors, and > so on. That can often cost you a few dB. In the product I designed I > spent more time then I care to admit trying to make a very tough loss > budget that I set out as a goal. > > There is no substitute for link margin, you can never really > have enough. > > I can confirm that our sweeps with a spectrum analyzer show lots > of opportunity to use 5 and 10 MHz channels, as others have also noted. > For WISPs it would be "nice" if chip vendors designed the radios so that > you could set the channel bandwidth from 5-40 MHz in 1 MHz increments. > It can be done but probably won't be, although maybe the Microsoft > WhiteFI stuff force the chip vendors to do it. In WiMax and LTE they are > already doing some things close to this. Still 5, 10, and 20 isn't bad > and probably hits the sweet spot or 80/20 rule. > > One of the down sides of fitting a 5 or 10 MHz channel in a > sweet spot is that it can change at any time. > > Best, > > leb > > At 9:58 AM -0500 10/1/09, Jason Hensley wrote: > > > In 2.4 land, if you have a lot of noise, which protocol > is better - B or G? > Is it better to run an AP as locked into one mode or is > it OK to do a mix? > > Max I want off of 2.4 customers is 3meg so not that > worried about the extra > speed that G will provide, but, I would like to know > which is more stable? > I've always thought that B was more stable overall but > just provided less > bandwidth. I've gotten some info that may counter that. > What's the > real-world experience with folks in a high-noise > environment, combined with > a higher useage AP? > > I've got an AP that we've run in B mode only for a > while. We've started > having problems with it - speeds go from 3meg at the > customer to 200k and > fluctuate constantly. We've worked with RTS, ACK > timeouts, etc etc and > nothing seems to have improved the stability. For > testing purposes we put > up another AP right next to the one we're having trouble > with. Switched two > of our gaming clients to that one (setup as G mode only) > and they seem to be > doing better, but not quite as good as we feel they > could be. This is on > Deliberant AP's (Duos). The backhaul part of it is not > the issue - we can > pull close to 15meg back to our office when cabled into > the AP. We have > other Deliberant APs that are running MANY more clients > than this one so we > know it's not limitations of the equipment. AP is on > top of a water tower. > Have taken all clients off and brought them back on one > by one and it did > not reveal anything significant. With just one customer > on the AP started > acting up again. Swapped radios in the AP thinking we > could have one going > bad and still no luck. > > 2.4 antennas are H-pol. We have a ton of noise in the > area, but we've been > through basically every channel and it did not help > either. Other AP's in > the vicinity are performing fine. Thought of the > multipath issue so we > raised our test AP up a little higher than the other > one. As I said, the > test AP seems to be better, but next to it on top of the > tower we can get > around 8 or 9 meg down (locked into G mode), but at the > CPE's we're still > barely getting 2.5-2.8meg. > > Any thoughts? We changed everything we can. The new > "test" AP has a 9db > antenna compared to the 13db on the "production" AP. > Other than that, they > are identical as far as equipment goes. > > So, back to the subject question though, what's > real-world experience with > G-only mode in the field? > > > > > > ------------------------------------------------------------------------ > -------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > > ------------------------------------------------------------------------ > -------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > -- > [email protected] > > > > > ------------------------------------------------------------------------ > -------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > > ------------------------------------------------------------------------ > -------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > --- > [This E-mail scanned for viruses by Declude Virus] > > > > > > Wireless High Speed Broadband service from Info-Ed, Inc. as low as > $30.00/mth. > Check out www.info-ed.com/wireless.html for information. > > > ------------------------------------------------------------------------ > -------- > WISPA Wants You! 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