SNR Cutoff Recommendations http://wi-figurus.com Thu, 09 Sep 2010 18:35:27 +0100 FeedCreator 1.7.2 http://wi-figurus.com/content/view/308/#josc5 Dear Jim, Excellent article. While I tend to agree with you, I have often found that most wifi cards (which use ndis drivers) do not report the noise levels at all, so the SNR is incorrectly reported as equal to the Signal. What do you suppose one could do in such cases? outbackwifi Tue, 26 Jun 2007 06:53:37 +0100 http://wi-figurus.com/content/view/308/#josc8 I guess you need to purchase site survey software from either Ekahau, AirMagnet or Helium that supports collection of noise values and calculates SNR in a relaible fashion. This would cost you a few hundred dollars in case of Helium or thousand or more with AM or Ekahau :( [color=maroon][/color] chris_91504 Thu, 28 Jun 2007 12:53:26 +0100 http://wi-figurus.com/content/view/308/#josc18 802.11 cards cannot \'see\' ambient RF noise - only the \'effect\' of noise on packets. Thus 802.11 cards are not very effective at all in reporting accurate \'noise\' - only a SpecAn can do that. I can easily show how to \'fake out\' the noise functions of many cards - to either show lots of noise where there is little, or report no noise where there is a lot. Yes - a nice gap from the reported noise floor to the reported signal strength is great - but just not reflective of actual \'RF Noise\' Keith Parsons Tue, 10 Jul 2007 14:49:21 +0100 http://wi-figurus.com/content/view/308/#josc23 You\'\'ve all made good points here. I recommend using a spectrum analyzer (or other tool designed to accurately measure noise) to measure noise levels. You might consider what Cognio has to offer. jimgeier Wed, 11 Jul 2007 13:21:52 +0100 http://wi-figurus.com/content/view/308/#josc30 I got my hands on the Wi-Spy this month. This is a tool from metageek. I will post a more detailed review later on. I could spot my 2.4Ghz cordless phone showing up along with my wifi signal. Have any of you used it/come across it? What I like about it best is that it has a software that runs on Linux too (Though Kismet has support for wispy too)!! outbackwifi Mon, 16 Jul 2007 12:24:39 +0100 http://wi-figurus.com/content/view/308/#josc70 I couldn\'t agree more with Jim. I do a lot of predictive designs with the Ekahau tool, and I ALWAYS use SNR as the main design criteria, along with resired data rate, network load, and the appropriate client card to determine my cell edges. If the signal is strong and the noise is also strong, then the SNR is too low to support a good connection. I explain it to my customers this way: Signal strength is a measure of the [i][b]quantity[/b][/i] of signal present, and SNR is a measure of the [i][b]quality[/b][/i] of signal present. Without good signal [b]quality[/b], it doesn\'t matter how much quantity you have. As for the cost of the Ekahau and AirMagnet tools - totally worth every penny. I also carry a Wi-Spy with me as a \"quick-and-dirty\" means of demonstrating that interference is present, leading to a full spectrum analysis with Cognio - also a tool totally worth the price. karl1949 Mon, 08 Oct 2007 16:41:59 +0100 http://wi-figurus.com/content/view/308/#josc440 The Xirrus Arrays provide a spectrum analyzer for zero cost in every array, it can give you the noise for each and every 2.4 and 5Ghz channel. Surveying for SNR is important, but having the tool available all the time is a huge benefit we use frequently - since you diagnose networks bottom up on the ISO stack, without this available you\'d just have to skip layer one as a problem - kind of like root causing a wired client without checking the cables... RIDICULOUS. sunaandmoon Mon, 01 Dec 2008 12:56:02 +0100