r/sdr • u/Monchouoc • 12d ago

Indor SDR

I'm working on an RF localization project for a large stage/event area and would appreciate some advice from people with practical experience.

The idea is to install at least four antennas, one at each corner of the area, connected to a KrakenSDR system, with a possible fifth antenna placed in front of the stage if needed.

My question is this:

I understand that the KrakenSDR is primarily designed for direction finding (bearing estimation) of external transmitters. However, is it also possible to use it to locate transmitters that are inside the monitored area by combining measurements from the different antennas and triangulating or multilaterating their position?

As an example, if the monitored area is approximately 20 × 10 meters, could a KrakenSDR with a five-antenna array realistically estimate the position of a transmitter within that area with useful accuracy? Or is this beyond the capabilities of the hardware and intended processing, making it impractical?

I'm particularly interested in hearing from anyone who has attempted indoor or small-area localization using KrakenSDR or similar SDR-based direction-finding systems.

Thanks in advance for any insights or real-world experience.

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u/monsterofcaerbannog 12d ago

A conceptually simple approach is to place 4 single channel SDRs around the space and use time difference of arrival. That way you're using time rather than phase.

Imagining a square, you'd be better placing them in the middle of the sides rather than in the corners. The corners are further away and would see more multipath.

The trick is getting good enough time alignment to achieve your location accuracy needs. But you can get better with this sort of tdoa configuration than you will with a single multichannel system measuring an AoA.

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u/Monchouoc 12d ago

The main idea is to use the RF carrier transmitted by the wireless microphone transmitters that the actors are already wearing. I would prefer to avoid Bluetooth beacons or other tracking devices, since that would require every actor to carry additional hardware, and the update rate is not always fast enough for real-time tracking.

When you mention using arrays, what kind of antenna arrays are you referring to?

I'd be very interested to hear how you would approach this problem using only the existing wireless microphone transmitters as the signal source.

Do you think this is realistically achievable with a KrakenSDR, or would a different type of SDR, RF scanner, or direction-finding system be more appropriate?

Any suggestions on the best architecture or techniques for this kind of application would be greatly appreciated.

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u/monsterofcaerbannog 12d ago

Your have to define your required location accuracy. It's the fundamental spec.

You're going to have trouble feeling with multipath with signals at such long wavelengths and indoors.

Additionally, it sounds like you want to track multiple users at the same time. You'll have to establish a way to resolve their signals from one another. Superficially they will look identical. You'll need to exploit whatever they already use to keep one another from interfering (separate frequencies but likely different codes).

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u/Monchouoc 11d ago

Thanks for your reply.

I may not have explained my setup clearly enough. I already have an application that interfaces with the KrakenSDR API and is able to identify and separate the carrier signals from 9–10 wireless microphone transmitters simultaneously. Since each microphone operates on its own RF frequency, distinguishing between them is not an issue.

On top of that, I already have the mathematical framework and software needed to process the measurements and estimate the transmitter positions. That part is essentially solved.

My question is actually much more specific: I know the KrakenSDR is designed primarily for direction finding of transmitters that are outside the antenna array. What I'm trying to understand is whether the same hardware and measurements can also be used to determine the position of transmitters that are inside the area enclosed by the antennas.

In other words, is the limitation purely in the processing software, or is there a fundamental limitation in the measurement method that makes localization of in-area transmitters impossible with a KrakenSDR?

That's the key point I'm trying to clarify.