Problem :
What I want to do:
I want to do some experiments with devices such as a Raspberry Pi in environments, where there is noise in the 2.4GHz and 5GHz band.
What I tried so far:
My idea was to simply use the wireless tools in Linux, such as iwconfig, wpa_cli, which can in theory display dBm values for both the signal strength (which works without problems) and the noise floor (which I am not able to get).
However, as far as I understand whether a reasonable noise value is actually calculated is dependent on the support by the driver of the WiFi chipset. To my bad luck, it seems that I am not in possession of any such chipset and I find a hard time to see, which chipset drivers actually do support a noise measurement (Chipsets tested BCM43438, AR9271, RTL8723BE, RTL8188CU). See also e.g. this question.
The reason this noise value would be very attractive to me, is that it is already the product of a specific algorithm that takes the radio spectrum in the WiFi channel of choice and processes this input to give a single value for noise. (If anybody knows anything about those algorithms used, please let me know, I would also be interested in that).
Can anybody help me:
In order to perform meaningful WiFi noise measurements in the 2.4 GHz (and possibly also the 5 GHz WiFi-band), I was wondering, if I need special drivers for my WiFi hardware that can provide the noise information? Could anybody point me into some direction how I could get a reasonable noise measurement with any standard WiFi chipset.
Solution :
I posit you are just not using the correct software – it would seem very strange for any WIFI chip to not be able to tell you the signal level. (On my Ubuntu box) I just typed :
iwlist wlan0 scanning | egrep "SSID|Quality"
To get a list of SSIDs and their signal levels. FWIW I have a Dell laptop with built in Wifi. LSPCI lists the card as Intel Corporation Wireless 3165 (rev 79)
I did the same thing on my Asus RT-AC68U router (running dd-wrt), and once I worked out that the interface was eth1 for WIFI device, this worked as well. this device claims to have a BCM4360 802.11ac Wireless Network Adptor (rev 03)
Note that these tools will only detect interference from other Wifi gear – if interference is coming from something that does not speak the Wifi protocol (Microwave, analog interface for an arduino, electric fence), you may need expensive equipment. That said, it might be possible to make some inferences by connecting to an AP and processing the output of
cat /proc/net/wireless
Inter-| sta-| Quality | Discarded packets | Missed | WE
face | tus | link level noise | nwid crypt frag retry misc | beacon | 22
wlan0: 0000 70. -27. -256 0 0 0 0 42 0