How often to poll wifi signal strength?

Question

Ideally I would like to monitor the signal strength of a wireless network in near real-time, say every 100ms, but such a high frequency is probably overkill.

I'm using the Managed Wifi library to poll RSSI. I instantiate a WlanClient client = new WlanClient(); once and re-use that client to measure signal strengths every second or so (but I'd like to do it more often):

foreach (WlanClient.WlanInterface wlanInterface in _client.Interfaces)
{
    Wlan.WlanBssEntry[] wlanBssEntries = wlanInterface.GetNetworkBssList();
    foreach (Wlan.WlanBssEntry wlanBssEntry in wlanBssEntries)
    {
        int sigStr = wlanBssEntry.rssi; // signal strength in dBm
        // ...
    }
}

What is the fastest practical polling delay and is this the best way to measure signal strength?

Answer 1

For most cases where you want to monitor anything a reasonable guideline is to work out what is as seldom as possible to fulfil your purpose, then increase the frequency a bit beyond that to catch delays and unexpected spikes.

If for example you were going to display this to a user, then much more than once per half a second is going to mean changes too quick for the user to meaningfully make sense of, so around a quarter of a second should be more than enough to be sure you're catching everything you need.

If you are logging, then it depends on how long your log period will be for. Once every few minutes is likely to catch any serious problem times, so once a minute should do fine.

In all, while there is often some practical maximum frequency, its not worth considering unless the maximum useful frequency is higher, and that depends on your purposes.

Answer 2

I'm afraid the smallest polling delay will vary, with your driver stack but I suspect also with the number of Access Points around. WiFi is a protocol based on time slots.

From my (limited) experience a 1 sec interval is about right, you will already see that the list of stations isn't always complete (ie stations missing on 1 scan, back on the next).

is this the best way to measure signal strength?

Depends, but how fast do you expect it to change? When walking around, the signal won't vary much over a second.