What would cause really sporadic packet loss, when signal strength is fine

  • I have a router connected to a modem. My intention is to connect to this router from an office that's about 200 feet away and through 2 walls.

    The router signal is not strong enough to get to the remote location, so I have put a range extender in between.

    The thing that's extremely confusing is that when my computer (or any client) connects to the extender while sitting right next to it, it works perfectly (ping times of about 30ms).

    However, when I move to the remote location, even though the wifi signal strength is either 3/4 or 4/4 bars, the packet loss is massive, and the latency varies wildly where for a stretch it will report pings of about 50ms, but then will drop to 800+ and about 10% are just timed out packets altogether.

    So, my question is... if the signal strength is good, why would this distance create such horrible packet loss? And what could cause such interference? I'm in a residential neighborhood, but there is absolutely nothing, line-of-sight between the laptop and the signal repeater other than 2 walls (with whatever electrical wiring is in them).

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  • However, when I move to the remote location, even though the wifi signal strength is either 3/4 or 4/4 bars, the packet loss is massive, and the latency varies wildly where for a stretch it will report pings of about 50ms, but then will drop to 800+ and about 10% are just timed out packets altogether.

    if the signal strength is good, why would this distance create such horrible packet loss?

    Signal strength is only one metric... also consider signal to noise ratio, which is often the problem for scenarios like this.

    Wifi latency and packet loss are cousins of each other. 802.11 frames contain a sequence number that is ACK'd... if the sequence number isn't ACK'd (due to loss or a bit error in the original frame), then the sender attempts to retransmit the frame a certain number of times. These 802.11 retransmissions show up as increased latency or outright packet loss if the interference is bad enough.

    I have literally seen 802.11g latency that is over 40 seconds (yes... seconds) when I'm only 50 feet from the LWAP. That particular environment had a lot of tools that also operated in the 2.4GHz bands, so obviously the potential for errors was quite high.

    what could cause such interference? I'm in a residential neighborhood, but there is absolutely nothing, line-of-sight between the laptop and the signal repeater other than 2 walls (with whatever electrical wiring is in them).

    Wifi operates in (mostly) open spectrum bands from the FCC... bluetooth, microwave ovens, phones, toy cars, we can only speculate about the source of the interference.

    You could try using a directed antenna with a focused beam (i.e. a yagi, or a cantenna) on your stations... those might help if the interference is not in the direct path to your wifi source.

    Finally, if you have a wireless sniffer or access to a linux system (suggestion: Backtrack Linux LiveCD) then you can diagnose your wifi problems with Wireshark / tshark. Cisco also has a good reference for Wireshark 802.11 display filters, which help filter out noise so you can focus on the problems at hand.

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Content dated before 7/24/2021 11:53 AM