Max Distance Ranging

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jdiep
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Joined: Mon Feb 25, 2019 2:03 pm

Max Distance Ranging

Post by jdiep » Wed Jun 26, 2019 11:34 pm

Hi,

I would like to use the LPS to positioning a drone outdoor on a football field. Does someone knows what the max ranging capacity of the LPS nodes are? And also are there any research done considering optimal anchor placement?

Thanks in advance!



kimberly
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Joined: Fri Jul 06, 2018 11:13 am

Re: Max Distance Ranging

Post by kimberly » Fri Jun 28, 2019 11:04 am

Hi!

Did you check out this wiki page yet? https://wiki.bitcraze.io/misc:investiga ... -max-range ;)

jdiep
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Re: Max Distance Ranging

Post by jdiep » Fri Jun 28, 2019 10:46 pm

perfect, havent seen that yet. thanks a lot, cheers!

jdiep
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Re: Max Distance Ranging

Post by jdiep » Wed Jul 10, 2019 7:35 am

I did a few tests myself outdoor on a race track. The furthest distance I was able to get a continuous stream of range data was approximately 25m at max power. However, your investigation lists a max range of 50-70m. How is this difference possible?

kimberly
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Re: Max Distance Ranging

Post by kimberly » Fri Jul 19, 2019 9:50 am

Very good that you have done your own investigation. Always good to double check! But it's interesting to see that it is a lot less.

Could you share which setting you put the TX_power registry to as in the DWM1000 datasheet as comparison? I wasn't present at the time these experiments were done but I'll ask the others which other settings they used as well.

jdiep
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Re: Max Distance Ranging

Post by jdiep » Mon Jul 22, 2019 8:47 am

I enalbed Force TX Power and set it to maximum (33.5 dB)

kristoffer
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Re: Max Distance Ranging

Post by kristoffer » Mon Jul 22, 2019 10:03 am

Hi!

I'm not sure why you only get up to 25 m in your tests. How did you do your test? Two way ranging as in the wiki page linked by Kimberly?
As far as I remember we basically just configured an anchor and a Crazyflie to full power, went to the local park where we walked away from each other until we did not get any updates on the range.
Just to double check, have you set the power in both the anchor and the Crazyflie? In Two way ranging both sides are transmitting and thus the TX power must be set in both devices.

It is possible to adjust preamble length and bitrate to get longer ranges as well but that adds some more complexity. Please let me know if you want to try this out.

For anchor placements in a large space (like a football field) I don't think there are any special requirements compared to smaller spaces. Putting the anchors in the corners is probably a good start.
It is worth noting that it is likely hard to get good Z data from the system, unless it is possible to put some anchors very high up. This comes from pure geometrical properties if the anchors are placed in the corners of a large "flat" space.

jdiep
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Joined: Mon Feb 25, 2019 2:03 pm

Re: Max Distance Ranging

Post by jdiep » Mon Jul 22, 2019 10:54 am

Yes, I enabled full power on both tag and anchor. However, since I am planning on attaching one LPS node onto our custom drone, I am not using the crazyflie. Therefore, in my experiment, I am using two LPS as anchor and tag respectively. Additionally, I rewrote the firmware for an additional Sniffer module in order to receive ranging data from the tag. This is done such that after each Report package received at the tag, the tag sends the calculated distance forward to the Sniffer.

So to summarize: I am working with 3 modules, 1 is set in Anchor mode, 1 in Tag mode and 1 in Sniffer mode. All 3 modules are set to full power.

jdiep
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Re: Max Distance Ranging

Post by jdiep » Mon Jul 22, 2019 10:59 am

Here a couple of images on the test:

Distance measurement: https://share.icloud.com/photos/0K9dOrL ... 0vM_YR1v4g
Usual drone attachment: https://share.icloud.com/photos/0I1-7kG ... C9kpyy_84g

In the second image, you can see my usual experiment. One sniffer node connected to my computer, one tag node on the drone and one anchor node.

The usual testing space looks like this: https://share.icloud.com/photos/0uStIt5 ... SaXWKrPm4g

The anchors are attached to wooden staff and the goal is to place these outside on a football field.

kristoffer
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Re: Max Distance Ranging

Post by kristoffer » Mon Jul 22, 2019 12:21 pm

Looks good to me :-)
The only difference I can think of right now, compared to when we did the tests, is that your tag is closer to the ground. We were holding the devices in our hands (at around 1 m) and walking away from each other. Maybe it is worth trying to see if it makes a difference?

Otherwise preamble length/bitrate might be a way forward. It is a bit complex in TWR though since the timing changes.

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