Wireless Access

last person joined: 14 hours ago 

Access network design for branch, remote, outdoor and campus locations with Aruba access points, and mobility controllers.
Expand all | Collapse all

Electrical Interference on 7km bridge

  • 1.  Electrical Interference on 7km bridge

    Posted Feb 06, 2020 10:44 PM

    I need to build a 7km bridge but there is a small electrical sub-station less than 500m from one of the end-points.  Is there any AP device that could successfully overcome electrical interference or do I need to build a secondary bridge to bypass the interference?

  • 2.  RE: Electrical Interference on 7km bridge

    Posted Feb 07, 2020 02:36 AM

    Did you experience of measure the influence of the sub station?


    Will you be using WiFi? Which APs? Which antennas? Do you have free line-of sight? Enough height to account for your Fresnel zones?


    A point-to-point link over 7km is not something obvious, and I'd estimate there are only a few people in the world who actually have experience with such links. I'd try to find a professional or company who has experience in similar projects.

  • 3.  RE: Electrical Interference on 7km bridge

    Posted Feb 07, 2020 10:01 AM

    7km with clear line of sight and clear fresnel zone, using the AP-374 with ANT-4x4-5314 antennas is doable so long as you are in a regulatory domain that allows maximum EIRP *and* the RF is clear. It also depends on what your bandwidth requirements are or what kind of traffic you are wanting to carry over it. Bandwidth will be determined by SNR and channel bandwidth. Multicast traffic of any kind of a non-starter.


    Longest shot I have done is 12km/7mi with the AP-374/274 and out 30x30 14dBi antenna, in US at max power. While it worked, it was not super reliable. 7km is only a bit over 4mi, so barring 


    In most cases, electricity generators and substations, if they generate any significant interference, usually does so in the 2.4Ghz band, which would would not want to run mesh over anyway. 5Ghz should be clearer, but you should validate that with a spectrum analyzer. No one will be able to answer that for you but you, on site with the tools.


    What country/region is this for and I can look up regulatory. 

  • 4.  RE: Electrical Interference on 7km bridge

    Posted Feb 13, 2020 05:40 PM

    Northern Alberta, Canada.


    This is definitely all unicast... simple bridge from point a to point b and there is nothing significant in between except this power sub-station.  I attached a couple pics from the roof of the one building looking at the horizon 7km away

  • 5.  RE: Electrical Interference on 7km bridge

    Posted Mar 06, 2020 05:43 PM

    "While it worked, it was not super reliable."


    Is there any Aruba hardware that would be considered more reliable or should I be looking at a more 'enterprise' solution?

  • 6.  RE: Electrical Interference on 7km bridge

    Posted Mar 09, 2020 04:04 AM

    Edit: Missed that the statement was a quote from a previous answer.


    What was not reliable? In throughput? In link drops? In packet retries? Was that all constant or changing over time?


    What AP and antennas did you use?

    Did you align the antennas? How?

    Do you have the metrics on the achieved signal strengths & interference level on both ends when the link was up? If you have low SNR, higher gain antenna or better alignment may work.

    What channels did you use?

    Did you see DFS channel changes?

    Did you do a spectrum analysis on both sides of the link to see if the spectrum was clear and which are the best channels to use?

    Did you do a link-budget calculation with your antennas and APs?


    The solution is as enterprise as you can have. Longer distance point-to-point need to be carefully designed, and depending on the exact requirements you can implement such a design or not.

  • 7.  RE: Electrical Interference on 7km bridge

    Posted Mar 09, 2020 07:19 AM

    @jhoward said that his link was not reliable at 7mi.  The OP is looking for a device that will overcome electrical interference.

  • 8.  RE: Electrical Interference on 7km bridge

    Posted Apr 14, 2020 06:15 PM

    I can't find any information from Aruba.  Their tech support won't help me because I have no serial number and their pre-sales wont help me because I am asking technical questions about the frequencies, range, and PoE requirements with the antenna.

    Do you know of any good sites that can help me with the config of these things if I can actually buy them?

  • 9.  RE: Electrical Interference on 7km bridge

    Posted Feb 13, 2020 05:34 PM

    I have a clear line of sight but on the side closest to the power station I am much lower and closer to their interference.  It was suggested that I might need to use lasers but I had hoped the WiFi solution would be resilient enough.  Anything not affected by electromagnetic interference is very pricey.


    I could also run a second bridge to a tower 200m away and then from there run a bridge to the 7km distance bypassing the sub-station.  This would require two bridges and a tower to be constructed but might end up lower cost.