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How to improve long distance WDS reception?

Discussion in 'DD-WRT Firmware' started by frankc29, Jan 7, 2007.

  1. frankc29

    frankc29 LI Guru Member

    Well I've got 2 WRT54G v6 routers working in a WDS arrangement about a mile apart using 2 20dbi yagi antennas I bought off ebay. I'm out in the sticks and I'm trying to share a Direcway satellite connection between these two locations (a house and an office). I eyeballed the pointing. My reception is reporting back a solid 30% for one router and a bouncing 15%-30% for the other. This is odd, I figured both should always be the same. Anyhow I've got both routers transmitting at 100mw. How should I proceed in improving reception? Is eyeball pointing not acceptable, is it that sensitive? Should I boost the transmission mw? The connection seems fairly reliable, it hasn't dropped a single time since it came online about 4 hours ago, but the internet speed has taken a nice hit at the location without the hard wired satelite connection. I don't know if this is a natural result of a WDS arrangement or if it's due to poor wireless reception. Any help appreciated!
     
  2. ybbmadysu

    ybbmadysu Network Guru Member

    sucks that no one has answered you, so I will try and give some kind of help.

    Well a yagi (how many elements? more elements=better) has only a couple of degrees of sig spread. It is very important that you acheive a clear line-of-sight, no trees or any other disturbance and that they are perfectly pointing at each other. make sure the antenna, and if it has a metal mast, have a solid ground. 5ft rod as close as posible to the mast and to your city water line (if copper or stainless). even if the antennas are mounted on a chimney or cement bldg, give it the best ground possible. how many ft between your router and the antenna, how long is the coax and what type of coax, mfg?????

    I have WDS setup here with 6 other wrt54gs ddwrt 23sp2 std running here at home and mini on all the others. the antenna here is mounted on my roof, about 5 feet up off the roof crest. My antenna is a home built 16 element collinear omni directional. my coax is semi-rigid inserted very tightly inside copper water tube (refrigerator water tube) to help protect from sig loss. There is no speed loss here or at my 'paid-customers' (haha). this covers a very large area. the sig measures between 30-60% average, but still no speed loss. I run a file server for music and movies, no loss there either.

    if after you verify alignment, line of sight, ground conn, sig strength and still have a prob.. then you might want to try changing the coax to a high grade and retest. Still bad, find a good sat dish (fta dishes) make the necessary mod and retest.

    other than that, i dont know.
     
  3. HennieM

    HennieM Network Guru Member

    I assume dd-wrt micro firmware if it's V6 WRTs.

    In addition to ybbmadysu's suggestions above, I'd suggest this:

    There is a "wireless tweaks" (or similarly named) page on this site. See if you can get some hints there.

    I have found that the eyeballed orientation is not necessarily the best orientation of a directional antenna (nor is the laser aligned always the best - it seems directional antennas's direction is off sometimes, i.e. the main beam is not 100% in front, but slightly off).
    So, set dd-wrt to show the signal/quality of the WDS link (Status > Wireless). Then, one one side at a time, make small changes to the orientation of the yagi, L/R and Up/Dn. (Seeing if these slight changes actually makes a difference is an art on its own, as the signal jumps around a bit - be patient, and work out some system of recording the average). Yagis have, to the best of my knowledge, a beam width of between about 10 and 30 degrees, so I guess changes of say 3 estimated degrees at a time will be in order.
    Once you get the optimal signal, lock the antenna in place, and then go do the same on the other side.

    You can monitor your error rate on the same dd-wrt System > Wireless page, then experiment with setting the Transmission Rate (under Wireless > Advanced Settings) to a fixed rate. Start perhaps at the lowest setting (1 Mbps) and gradually take it up to a level where you reckon you can live with the error rate. Bear in mind though, that rain/snow and humidity all degrades the signal, so if you still want to be connected when it rains, be conservative.

    Set both your Tx and Rx antenna to only the external Yagi. If you have local wireless clients, they may still get enough signal from the Yagi's side/back lobes.

    Make sure FrameBurst is enabled. This seems to make quite a difference, while Speedbooster/Afterburner does not make a huge difference and only seems to work when you have very strong signals anyway.

    Why WDS? If you don't need to serve local wireless clients at either end, a better option may be WET (wireles ethernet bridge) or client mode. I don't exactly know if you incur a performance penalty with WDS if you don't have wireless clients in addition to the WDS link, but maybe you can see if WET mode makes a performance difference.

    Setting Tx power to much higher than 100mW does not make much of a difference according to some experts - something to do with noise generated/clarity of signal. I don't know, but I would experiment a bit with higher Tx power. At the risk of stating the obvious, bear in mind that setting A to higher Tx power, makes a difference on B's Rx signal.
     
  4. radiohead

    radiohead Network Guru Member

    One more thing that wasn't mentioned here is the polarity of your antenna. Make sure both antenna have the same polarity meaning the elements are on both antenna pointing in the same direction (vertical or horizontal). If yo have one vertical and the other horizontal, you will loose 20db of signal.

    Good luck,
     
  5. azeari

    azeari LI Guru Member

    u might wanna play around with other wireless settings like the preamble and stuff to see if it makes a difference too. i remember somewhere mentioning using long preambles, but i've never tried it, so no confirmation here
     

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