Hey everyone! I'm diving into a project for a client in the cybersecurity field, and I need some insight. The idea is to detect or at least get a count of all signal-emitting devices in a very small area, like an exhibition booth during a trade show. Just to clarify, I'm not interested in identifying the devices or tracking their data, just getting an approximate count of how many are active within a defined space of about 10 to 30 square meters. We're looking to do this in something close to real time in a crowded RF environment. Here are my main concerns: 1. Is it even feasible to estimate the number of unique signal sources in this setup? 2. Do I need to focus on specific frequency bands like 2.4 GHz, or would wideband TV SDR hardware be necessary? 3. How much of a challenge is it with MAC randomization, bursty transmissions, and devices that may be on standby? 4. Is there a way to limit detection to just inside the booth versus nearby booths without needing complex antenna setups? 5. Are there any existing research papers, commercial systems, or techniques that address this problem? I have a feeling this is quite a tough nut to crack, especially in a busy venue, but I would love to hear your thoughts.
3 Answers
This isn't a totally new challenge! Check out proximity beacons, particularly BTLE models. They're commonplace in retail settings to track customer movements and interactions. There are also WiFi options, but they may be less reliable due to MAC randomization issues. There's plenty of discussion and ideas about this kind of tech at events like Defcon, too!
It's a tough task, but definitely doable! You'll need to triangulate each nearby signal and filter out anything not within your target area. If you're just counting signals, MAC randomization shouldn't be an issue, but keep in mind that bursty transmissions will require you to scan quickly and for longer durations. The bands you focus on will depend on the devices you're interested in, so plan accordingly!
I like the triangulation idea but I'm a bit worried about multipath effects in enclosed spaces. Filtering effectively inside a booth might get tricky with reflections.
You can definitely make it work if you're okay with setting some limits on detection signal strength. This could give you a rough idea of how many devices are close by without being overwhelmed with noise from reflections indoors.
True, setting an RSSI limit would help! But I’m also concerned about how noisy it might get with fluctuating power levels from different devices.
Great tips! I was thinking about what you said, and I agree that the choice of bands plays a big role. Also, you're right about needing a good observation period to catch those sporadic transmissions.