My experience is that you'll get around 500 feet of solid foliage. If you're trying to go 5 miles, you have to get the antennas WAY up in the air, or you get serious Fresnel zone losses. This means that 900 mhz is actually somewhat limited to smaller cells than you'd think otherwise. Yes, I've gotten through a 1/4 mile of trees, but that quarter mile of trees had the cpe antenna on one side, a canyon on the other, with the base station at the far side of the canyon. On the otherh and, I have a client at .7 miles from the AP, and it picks up both the AP at .7 miles and one almost 20 miles away at the same RSSI, because there's fresnel zone encroachment between the AP and the client. I tried in town, and found that 3 city blocks was the limit for a low mounted AP antenna. I could pick it up 3 miles away, at -90 but RSSI didn't really improve or association until I got to around 3 blocks, where the signal was -85. At 4 blocks, it was still -90. In other words, this stuff spreads as low level noise one heck of a long ways. We also found that diffraction was going on strangely and that RSSI was often higher pointed somewhere OTHER than the exact direction of the AP when the terrain was mountainous. And, under those conditions, extremely variable, as in '75 one moment and -91 30 seconds later.
I find that rain changes the RSSI when going through foliage, and not insignifcant amounts, either. Snow improved it, rain reduced it. Can't explain why. However, when 2.4 wouldn't even be seen due to trees/foliage, 900 mhz has worked very well. Again, distances tend to be limited not as much by foliage, but by fresnel issues. Also, I find 900 mhz interference to be common in the middle absolutely NOWHERE, as well as in town. Utilities, government, farmers, even homeowners with 900 mhz phones will cause you grief. The good news, is that XR9's and Star-OS, at least, get you pretty darn good throughput for a 5 mhz channel. Just keep the RSSI up and the rates will run 36 - 54 and you can feed several 2 mbit customers without them ever impacting each other signifcantly. XR9's have modular FCC approval and either make it visible by use a clear lid (like I do) or tag the box with "contains FCC ID blah blah inside". XR9's also perform MUCH better than SR9's do. ++++++++++++++++++++++++++++++++ <insert witty tagline here> ----- Original Message ----- From: "Mike Hammett" <[EMAIL PROTECTED]> To: "WISPA List" <wireless@wispa.org> Sent: Saturday, July 19, 2008 1:32 PM Subject: [WISPA] 900 MHz Foliage Penetration > How much foliage penetration should I expect from a 900 MHz system? > > I'm looking at an area which has 30' - 50' thick tree lines every 1/2 to > 1.5 miles. I'm looking at 13 dBi sector with an approx 24 dB radio > (figure a dB or two for cable loss). For CPE I'm looking at 13 - 15 dB > CPE antenna (the 18 dB was just too big and expensive) with 20 - 24 dB > radios. > > Looking at the XR9 radios. > > > ---------- > Mike Hammett > Intelligent Computing Solutions > http://www.ics-il.com > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: wireless@wispa.org > > 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: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
