Is there a method or tool(s) to prove network outages?

Warren Bailey wbailey at satelliteintelligencegroup.com
Sun Dec 1 23:26:30 UTC 2013


I would hold off on considering Multipath as a problem until you see the
RSL. There is no reason to go to the worst case scenario. In addition to
that, there are some mitigation techniques we use (OFDM, XPIC, etc.) that
will help null out some multi path should that be the case. With that
being said, you should probably hire an RF Engineer rather than try to
attempt this yourself. If you guys are having path problems, talk to the
guy who designed the path. If there ³wasn¹t² a ³guy² who ³designed² the
path - this is what you get.

//warren


On 12/1/13, 1:02 PM, "William Waites" <wwaites at tardis.ed.ac.uk> wrote:

>On Sun, 1 Dec 2013 20:25:36 +0000, Sina Owolabi <notify.sina at gmail.com>
>said:
>
>    > Its cyclical, but I have not tried to graph/measure its
>    > repetition before now...  Body of tidal water..could be
>
>This is speculation until you have measurements, but if this is the
>case I'd wager you are having reflected signal interference off of the
>water. The water acts like a mirror and as it moves up and down the
>reflected signal will move in and out of phase with the main
>signal. At certain points you'll get near complete cancellation and
>the link will fail.
>
>See section 4 here for some explanations, fig 5 and 6 for what you
>could expect the graphs of signal strength, time, link capactity to
>look like:
>
>    http://homepages.inf.ed.ac.uk/mmarina/papers/mobicom_winsdr08.pdf
>
>But not having access to the RF part you can't measure this
>directly. If you can get tide tables for a nearby location, what you
>could do is say that signal strength is 1 if the link is working and 0
>if it is not. Measure for a while then scatterplot that against the
>level of the tide. If the measurements of 0 group tightly together
>in a few spots then you know definitely what is happening. Perhaps
>that plot together with a pointer to a nice academic paper would be
>enough to convince the provider of what is happening.
>
>What could you do about this?
>
>If you are lucky and the interference does not complete a full cycle
>from destructive to constructive and back with the largest amplitude
>of the tides that you experience in that place, you could try moving
>the antenna up or down. How much depends on the frequency and
>distances involved but I'd try 25cm increments up to a couple of
>meters if you can. You'll still get degradation but can hopefully
>avoid the deep nulls that take the link out completely.
>
>If you are able and willing to replace the end-site radios or antennas
>with your own, and the link uses some sort of 2xN MIMO, you could
>arrange vertical spacing between the antennas so that you have a good
>signal at one antenna when the other one is experiencing a null. This
>should get you on average half the best-case throughput the equipment
>is capable of but it should get you that consistently. The actual
>spacing depends on the distances and heights involved.
>
>-w




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