Monitoring Drone FPV Frequency Usage with a USRP Software Defined Radio
Over on YouTube balint256 (Balint), a researcher at Ettus (creators of the USRP line of software defined radios) has uploaded a video showing how he is using his USRP to help with frequency management at FPV time trial racing events. FPV a.k.a First Person View is a term used to describe the act of flying a remote controlled aircraft such as a quadcopter with an onboard camera that transmits live video down to the pilot. FPV racing is a new sport where pilots race FPV controlled drones around a track.
One important technical challenge at these events is frequency management. FPV drones use many frequencies at around 2.4 GHz for control and 5.8/2.4/1.3 GHz for video. With many drones in the air it is important that frequencies are managed appropriately so as to not jam each others signals.
To try and solve this problem Balint has been using GNU Radio coupled with a USRP X310 software defined radio to get very wide band RF spectrum waterfall views of the 2.4 and 5.8 GHz bands. In the waterfalls he is able to see when control signals and video signals are transmitted and at what frequency, and is able to tell if any are overlapping and jamming each other.
In addition to this, Balint has also been working on his custom software defined radio based digital video downlink. Back in March we posted about his earlier work on this concept. In the video Balint demonstrates his drone with an on board USRP E310 which is used to send a custom 4.2 Mbps video downlink.
Using a 100MHz board to watch 300MHz of bandwidth in one waterfall is nice, a bit like a realtime version of rtl_power.
… repeat …
OK you will always miss out on 2/3’s of the data, but for a graphical representation of the RF spectrum it is still very useful. And a waterfall never displays the full spectrum in realtime anyhow, it is normally like 10 or less display updates per second, due to the CPU requirements for the FFT’s.