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  1. #1
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    Networking in a difficult environment

    Hi guys,

    I thought I would share a problem that I've been wrestling with for some time to see if there's anything obvious I've overlooked or could improve.

    I have a system installed at a remote location, i.e. very rural location. The installation comprises two Windows XP Home machines networked together. The user needs to be able to access and control the remote machine from the local machine so the remote machine has a VNC Server, while the local machine has a client viewer.

    The VNC server machine is about 130m distant from the viewer. The viewer machine is located adjacent to the DSL Router in an old stone built property with 2 foot thick walls. The VNC Server machine is located inside a metal clad building with 3-phase electrical supply noise and compressor spikes prevalent.

    The server machine also requires internet access for upload of automatically captured data to a regulatory body. The gap between the buildings is interrupted by a couple of older buildings and regularly crossed by large machine plant. There is no phone line in the VNC Server building, so no second DSL line available. Internet access is over the link to the DSL router adjacent to the VNC Client Viewer. 2G mobile signals are excellent, but there is no 3G for mobile broadband access.

    The solution currently in place uses the DSL router connected via powerline connectors to a pair of encrypted Wireless extenders with amplifiers and external directional antennae. At the far end the wireless extender links to the VNC Server machine via Powerline again.

    Something like:

    XP Home VNC Client -> DSL Router
    DSL Router->Powerline connectors->Wireless extender.
    Wireless extender ->Wireless extender (both with with external amplifier and antennae).
    Wireless extender->Powerline connectors->XP Home VNC Server.

    The DSL router DHCP is off and all devices and PC's have fixed internal IP addresses. The PC's map to the DSL router for DNS.

    With me so far?

    OK, it works and the user is happy, but it falls over now and then and link speed is not great. Unsurprising since all the traffic needs to bounce back and forward across two powerline circuits and a wireless link.

    Any creative ideas on how to improve the system or thoughts about the network overheads?
    Last edited by Tinto Tech; 2011-06-17 at 10:18. Reason: Typos

  2. #2
    Bronze Lounger DrWho's Avatar
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    At first look, my only thought would be, "if you can't go through an object, go OVER it".

    Going back to my days in the CB Radio and Ham Radio business, when it comes to antennas,
    height is everything. I never installed an antenna on anything less than a 50' tower.

    You loose too much gain by running a WiFi signal through a length of coaxial cable, between the
    router and the antenna, but nothing through CAT5 or CAT6.
    So put the router on a tower in a weatherproof enclosure and feed it with a length of CAT5.
    Power can also be run through the CAT5 to the router.

    Cheers!
    Experience is truly the best teacher.

    Backup! Backup! Backup! GHOST Rocks!

  3. #3
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    Use CAT5 indoors, but if the cable leaves the building then use Fiber. It will be cheaper and much safer. CAT5 is too expensive when you place all the necessary safety equipment at each perimeter. With Fiber and if doing it yourself don't look at the ends of the fiber to see the light or it will blind you.

  4. #4
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    An old post, but interesting to see some ideas.

    Of course CAT5 would be the best option from the PC's to the wireless routers. In this installation however, one machine is in a residential house and the user is not keen to have cables running round the property. Hence the need for a powerline link from PC to router.

    The router in the property has an external antenna connection and uses super low-loss 50 Ohm co-ax cable to connect out from roof space to the external antenna mounted around 10 metres above ground on the gable end of the building. This antenna points to the other end of the wireless link to the second directional antenna and a mirror of the residential installation. Both co-ax runs are about 2 metres from router to antenna. Antenna gain from recollection is around 12dBi at both ends.

    At the remote end (the VNC Server end of the link), the antenna is again 10 metres above ground mounted on a gable end and the co-ax is similarly super low-loss.

    A powerline circuit is used to connect PC to router at the remote end. This could possibly be replaced with CAT5, but the physical layout of the building and it's non-human(!) occupants make it difficult to lay in extra cables - hence the use of pre-existing mains wiring. I guess this is something that could be presented to the user as a potential improvement.

    Both routers are assigned fixed IP addresses as are the VNC server and client PC.

    I suspect the problem with link speed is down to the multi hops:

    PC <---> powerline adapter
    powerline <---> powerline
    powerline <---> router
    router <---> router (wirelessly)
    router <---> powerline
    powerline <---> powerline
    powerline <---> PC

  5. #5
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    Have you considered using an RF link with 2 Directional RF dishes mounted up in the air between both buildings. There is some cost, but given the distance you are trying to cover, a RF link should meet the need and eliminate some of the network lag you are generating across all the hops. You should be able to run CAT5, CAT6 or fiber from the Windows XP machines to the network connections for the RF Antennas.

    Windows XP PC <---> Local Switch
    Local Swtich <---> Local Router with DSL Connection
    Local Router <---> Network Connection to RF Link
    RF Link <---> Network Connection from RF Link
    Network Connection from RF Link <---> Local XP PC

    Media adapters could be used to convert from Ethernet to Fiber and back. I have used such a solution to span between building located close but not easily connected via Ethernet or fiber.

    Thewizard813

  6. #6
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    Hi Wizard,

    Perhaps I wasn't clear in earlier posts: External 12dBi gain antennas are already in place to cover the long hop between the two buildings. The network connection to the RF units is via powerline "media extenders": the owner does not wish to have ethernet cables strung around his property.

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