> In high noise areas you'll be better off to use almost anything but WiFi. > It's the least noise tolerant protocol that I know of.
Sorry, but the opposite is true. 802.11 is actually a good protocol to combat noise, when the noise is someone elses. It has built-in re-transmission into the protocol, and the -CA adds variations in transit time to increase changes of missing noise. Wifi (802.11) is a contention based protocol, purposely allowing multiple people to access the spectrum in a best effort manner. The opposite is true, that basic TDD based gear is more harmed by noise, as by default it does not re-transmit at layer2, and it transmits on schedule with out checking if its free to transmit. The exception to that is high end gear like Trango, that has Built-in ARQ to re-transmit lost packets. One of the reasons Wimax 802.16e, in less suited for unlicensed than licensed. What Wifi is bad for, is SELF interference/ self noise. The famous hidden node problem. 802.11 added RTS/CTS, to help solve this, at a significant performance impact. And Proxim and (karlnet) added polling feature to help solve this on Wifi style gear. Likewise highend gear like Trango, also adds polling. With that said, I prefer using TDD based gear in high nosie environment. The reason is that even though it might be less advantages from a contention point of view, TDD gear is a constant carrier product, so it always transmits a signal at your assigned power level. The benefit of this is that you let other people know that you are there. Therefore they can design around you, until they don't hear your signal, by selective antenna choice and pointing. Many OEM WIFI gear are poor performers in high noise environements, but it is not because the Wifi protocol. Its because its inexpensive equipment, without good filtering, low grade receivers, and OFDM modulations. OFDM high modulations really aren't very good for noise, because they require such a large Signal to noise ratio. The secret to noise environments is being clear what the QOS requirements are. TDD is sometimes the only way to have predictable QOS levels. And sometimes the only way to get TDD to work in a high noise floor area is at a low modualtion such as DSSS or FSK, or lowest modulation of OFDM. Equipment choice is a factor of what you need, and the best way to deliver that. For example Canopy has one of the loweest C/I ratios, making it favorable in high noise environments. Sometimes the OFDM speeds are essential, and the best choice is the best quality OFDM product, such as Alvarion that also has very high end filters embedded. I personally chose trango for my high noise environments, because of its unique abilty to avoid interference, with real time flexibility of polarities, and DSSS noise resilience. And also its ability to accurately scan for interference/noise. And sometimes, I use StarOS or Ligo and narrow beam antennas, because it allows me 5 and 10Mhz channels, all thats available, in my largest noise floor environments. And most importnatly you need to decide what type noise you are avoiding... Your own noise, or others? Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Marlon K. Schafer" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "WISPA General List" <[email protected]> Sent: Thursday, June 12, 2008 11:58 AM Subject: Re: [WISPA] good multiradio wifi units for noise environments? > In high noise areas you'll be better off to use almost anything but WiFi. > It's the least noise tolerant protocol that I know of. > > marlon > > ----- Original Message ----- > From: "Rogelio" <[EMAIL PROTECTED]> > To: "WISPA General List" <[email protected]> > Sent: Wednesday, June 11, 2008 11:07 PM > Subject: [WISPA] good multiradio wifi units for noise environments? > > >>I am looking for multiradio wifi units that handle well in environments >> with high floor noise levels, particularly in city areas where the >> unlicensed band is very congested. >> >> Any suggestions? >> >> >> -------------------------------------------------------------------------------- >> 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/ > > > > -------------------------------------------------------------------------------- > 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/ -------------------------------------------------------------------------------- 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/
