Reading raw WiFi beacon frames

[m3g4by73]

Hi guys, I'm using WiFi fingerprinting on an IoT tracking project and I'd like to reduce the power usage.

Currently my project uses an ESP8266 to:
1. Scan for local WiFi networks and read the BSSIDs.
2. Transmit the BSSIDs to my cloud server using LoRaWAN, Sigfox or NB-IoT.
3. My server queries Google's Geolocation API with the BSSIDs to obtain the location of the sensor.

I don't use GPS is because there is no signal where my tracker spends the majority of its life.

Unfortunately the ESP8266:
-is an absolute power hog,
-takes a while to start up,
-drains large current spikes on boot to calibrate its Rf circuits.

I feel the ESP8266 is way too complicated for sniffing a few frames and I was wondering if there's a way to use a 2.4GHz Rx-Only IC to read the raw WiFi data and then I could just decode the beacon frames. If so, can anyone recommend a chip that would be suitable or other plan of attack?

[llkiwi2006]

Unfortunately wifi uses quite a large bandwidth and quite complex modulation schemes, so you are pretty much stuck with ICs designed for wifi. From what I could find online, I don't really see any wifi modules that uses much less power than esp8266.

Keep in mind you will want to capture for at least a few seconds at a time (maybe even more), since beacons are sent only (by default) every 100ms, and you need to hop between the 13 channels. You should measure how much power is spent powering up vs during the capture to decide if it's actually a problem.

[tmbinc]

The interesting thing though is that Beacon frames will always be modulated with the lowest supported modulation scheme (MCS-0 I think?). But the bandwidth is still 20 MHz, so there's most likely not a great reduction of power required (as opposed to demod complexity, but that's just logic).

Active probing is slightly faster since you don't need to wait for the default 100ms per channel.