850 foot wireless bridge design

Discussion in 'Wireless Internet' started by kjbann, Jan 21, 2007.

  1. kjbann

    kjbann Guest

    I would like to create a bridge between our house and a recreational
    cabin we have on the farm in order to have internet service at the
    cabin. I presently have a D-Link Di624 wireless router connected to the
    satellite modem. This is situated about 5 feet from a window which has
    clear line of site to a cabin window 850 feet away. All I need in the
    cabin is wireless internet. I presently have computers and printer
    connected to the DI624 and a wireless notebook.

    I am considering a WAP54G at each end of the bridge with (2) Ez12 12dB
    antennas from www.freeantennas.com on each.

    1. Is there a better approach?
    2. Assuming the Ez12's will block the signal in the cabin, what is the
    best remedy for this?
    3. Are the rubber duckies good enough or will it require the 7dB high
    gain antennas?
    4. What about signal conflicts between the DI624 and WAP54G in the
    house?

    I am basically looking for experienced help in designing the best (ie
    most economical) system to add the internet access at the cabin.
    Retaining the DI624 is not a must. I do need to retain the wired
    network and wireless access in the house.

    The satellite modem has to have ip address 192.168.0.1
    The WAP's will be sitting at the windows.

    I've researched the group and learned a lot, but I'd appreciate a
    little expert help.

    Thanks in advance,
    Ken


    House
    ------------------------------------------------------
    | wireless notebook |
    | |
    | -------- |
    | satellite | |----- |
    | modem -----| D-Link |----- |
    | | | DI-624 |----- cat5 to other rooms |
    | 5 ft. | | |
    | | -------- |
    --|window|--------------------------------------------
    |
    850 ft.
    | Cabin
    --|window|------------------
    | |
    | |
    | |
    | |
    | |
    | wireless notebook |
    ----------------------------
     
    kjbann, Jan 21, 2007
    #1
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  2. kjbann

    kjbann Guest

    Sorry, my sketch didn't come thru too well.
    Ken
     
    kjbann, Jan 21, 2007
    #2
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  3. kjbann

    Ian Guest

    I have set up quite a few low cost systems like this for farmers.
    Assuming no other problems such as interference, parking machinery in
    the line of site etc, since it is a do it yourself job, I would start
    small and work my way up. You could use a couple of WAP54G's one as
    access point and the other one at the far end as a repeater and see what
    happens.

    From past experience, at that distance you will probably need to use
    one of the 12dbi antennas at the main farm house mounted externally, and
    the repeater in the window at the other end.

    If the connection isn't reliable then add the other 12dbi at the remote
    end. Sometimes you can get enough signal off of the external antenna to
    be functional inside the building. If you can't get enough signal
    inside, then you might want to set them up as a point to point bridge
    and add a third access point or router inside.

    Some people have reported issues with the WAP54G but so far I haven't
    had any and have found them to be quite reliable - touch wood.

    As an alternative to the WAP54G you could use WRT54GL routers running
    DD-WRT.

    A couple of things to remember - as far as I know the WAP54G can only
    serve as a repeater using WEP. In point to point mode you can use WPA.
    The people in the other house will be on your network.

    If you need to keep them off your network I would place a WRT54GL router
    running DD-WRT in front of your existing router and use WDS to connect
    it to another WRT54GL running DD-WRT sitting in the remote window. In
    this setup you can use WPA.

    I haven't tried the 7dbi antennas before.

    Selecting different channels (use 1, 6 or 11) and you shouldn't have a
    problem with your existing setup.

    Ian
     
    Ian, Jan 22, 2007
    #3
  4. I've had erratic hang problems with WAP54G v3.1 firmware v3.04 in
    bridge mode. It does not hang in access point and access point client
    mode.
    Yep. Recommended. However, I prefer Buffalo WHR-HP-G54.
    Not so. The WAP54G in repeater mode will work with WPA-PSK. See
    release notes for v2.08 at:
    <http://www.linksys.com/servlet/Sate...oBlobs&blobwhere=1130826433584&ssbinary=true>
    However, in bridge mode, only WEP is supported. Strangely, it will
    let you configure WPA-PSK, but it will not connect.
     
    Jeff Liebermann, Jan 22, 2007
    #4
  5. hath wroth:
    Yes. Put the DI-624 wireless in the window, not the modem. The
    wireless needs the line of sight to the cabin, not the modem.
    Not easily. It might be possible to install a power splitter at the
    DI-624 sending half the power to a directional antenna pointed at the
    cabin and the other half throughout the house.
    See calculations below.
    What WAP54G? In the cabin?
    A WDS repeater will probably be the cheapest.
    So, everything is moving to the cabin? Could you describe where the
    computers are located and how they are intended to connect when you're
    done with the system, not in its current arrangement?

    Ok, lets grind the numbers. I've only done this about 20 times in
    this newsgroup, but once more won't hurt (much):

    See examples in the Wireless FAQ at:
    <http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations>

    From what we know so far, we have 850ft range, unknown antennas,
    conventional radios, and are looking for at least a 20dB fade margin.
    I'll assume 12Mbits/sec connection speed for 6 Mbits/sec thruput.

    TX power = +15 dBm
    TX coax loss = 2dB (to window mounted antenna)
    TX antenna gain = unknown
    Distance = 0.16 miles (850ft)
    Rx antenna gain = unknown
    RX coax loss = 2dB (to windows mounted antenna)
    RX sens = -84 dBm (at 12 Mbits/sec)
    Fade margin = 20 dB

    Plugging into:
    <http://www.terabeam.com/support/calculations/som.php>
    and trying various values of antenna gain until I get 20dB fade
    margin, I get antenna gains of 7dBi each for both antennas. If you
    have line of sight, and a clear Fresnel zone, a pair of rubber ducky
    gain antennas should work. The total gain of 14dBi can be distributed
    unequally. For example, the stock 2dBi omni can be used on one end,
    with a 12dBi directional panel on the other end.

    Expect reflection problems if you're shooting through a window frame.

    For 850ft the Fresnel Zone radius clearance at midpoint:
    <http://www.terabeam.com/support/calculations/fresnel-zone.php>
    must be 7.4ft. That means your antennas must be 7.4ft off the ground
    for this to work reliably. This may be a problem with your
    topography.

    Change the numbers to match your speed requirements or antenna
    configuration that affect coax loss and antenna gain.

    For a radio at the cabin end, you can use just about any of the
    wireless client bridge radios listed at:
    <http://wireless.wikia.com/wiki/Wi-Fi#Wireless_Ethernet_Bridges>
    that support a client mode. Not all do so please check first. I
    would be tempted to use a "universal" solution, such as Buffalo
    WHR-HP-G54, which can be configured as a client bridge or WDS bridge.

    The problem with using just a wireless client bridge is that you
    cannot connect to it via wireless from your notebook. In order to do
    that, you'll need to build a WDS (wireless distribution system)
    bridge. WDS allows the device to simultaneously act as a repeater and
    an access point. Replace the DI-624 in the house with a router that
    supports WDS and add an identical router in the cabin. You can
    connect to the one on the cabin with either wired or wireless.

    The catch is that you will see a 50% minimum slowdown for the wireless
    laptop connection, but the wired connection will run at full speed.
    Also, WDS setup is often a bit challenging:
    <http://www.dd-wrt.com/wiki/index.php?title=WDS_Linked_router_network>
    <http://www.wi-fiplanet.com/tutorials/article.php/3628576> (2 pages)
     
    Jeff Liebermann, Jan 22, 2007
    #5
  6. kjbann

    Peter Pan Guest

    Depends.. How do you have power to the cabin? At my place in North Idaho, I
    had the sat/wireless/wired in the house, and wanted wireless back at the
    outbuilding (about 1000 ft from the main house), however, we had power from
    the house to the outbuilding, and found powerline networking to be much more
    reliable (winter precipitation, summer growth from the bushes/trees)..

    Netgear makes two types of devices, one is a powerline bridge for wired
    stuff, and the other is a bridge to a remote AP (plug on in inside, the
    other in the outbuilding).. See the info at
    http://www.netgear.com/Products/PowerlineNetworking.aspx?for=All usually
    around $99-$130 for both parts... (that's for the 54Mbps devices, same speed
    as wireless).. While they do make 200 Mbps devices, those are for Gigabit
    ethernet, Not the usual 100 Mbps stuff in most homes

    If you have a wap/router in the house, just use a cat5(or cat 6) cable to go
    from the router part, to the input of one of the powerline devices, second
    part plugs in and either has a wired connection/or a wireless ap (comes as
    ssid NETGEAR)
     
    Peter Pan, Jan 22, 2007
    #6
  7. kjbann

    kjbann Guest

    Wish I had power run to the cabin. That would be a nice approach.
    At present, we only have generator power. I've thought I could probably
    power the network equipment at the cabin with 12 volt batteries if we
    don't want to run the generator. Seems like most of the equipment I've
    looked at is </= 12 vdc.

    Ken
     
    kjbann, Jan 22, 2007
    #7
  8. kjbann

    kjbann Guest

    Ian,
    Thanks for your help. I am going to take a look at recommendations from
    you and Jeff. I'll probably have more questions then.
    Ken
     
    kjbann, Jan 22, 2007
    #8
  9. kjbann

    kjbann Guest

    Jeff,
    It will take me a little time to digest all this and look at the
    equipment mentioned.. Here is more info on the existing system at the
    house which will continue as is after addition of the cabin internet
    service:

    House:
    Satellite modem --- DI624 wireless router --- ethernet computers &
    ethernet printer + wireless notebook.

    The cabin only needs wireless internet capabilities for one or two
    notebooks. The cabin doesn't need to share the house network for file
    sharing, etc.

    I think I can get the 7.4 ft. antenna clearance above the ground at
    both windows. Between buildings the ground drops away considerably
    more. Transmission angle thru the windows will be approx 45°+/-.

    As I mentioned, The DI624 can be replaced in the interest of a
    better/cleaner system if necessary.
    Thanks,
    Ken
     
    kjbann, Jan 22, 2007
    #9
  10. kjbann

    Peter Pan Guest

    Lots of stuff for 12v (check the trucking and RV'ng newsgroups), however,
    what sort of bushes/trees/etc are in the line of sight at your intended
    place... We ended up doing the ditch/power/powerline networking, cuz in the
    spring all sorts of stuff grew, and green leafy stuff atentuates a WiFi
    signal BIG time.... Line of sight was fine in the winter, but during the
    spring and summer, forgetaboutit... too much green stuff grew in the way..

    Just an aside, our cabin/guest house, was about 1000 ft back on our acreage
    (in the forest area).. We just bit the bullet and ran a direct burial AC
    cable to the outbuilding (was about $600 for the cable, and $180 to rent the
    "ditch witch" to dig the ditch)... A bit more than we intended to spend,
    but figured we may as well kill two birds with one stone... (actually 3.. we
    also buried a 20 conductor utility cable in the ditch while we were at it,
    use it for phone/intercom/etc, was another $180 bucks.. Direct burial
    electric cables only have to be about 2ft down (perfect for a ditch witch,
    it only makes a 2 ft deep trench), it's water and sewer that has to be
    buried about 4ft down ((or at least below the frost line for your area, and
    sewer has to be angled/graded))).
     
    Peter Pan, Jan 22, 2007
    #10
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