Using DWM1001c Modules in an outdoor setting for university project

Wireless Connectivity Ultra-Wideband
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1

Good day,

I’m a university student currently developing a real time interactive course using DWM1001C chips for spatial tracking in an outdoor setting. We plan on having our event spaced out on several hundred meters placing custom PCBs with DWM1001C chips as anchors and about 30 to 40 tags in hand held objects. As this course is separated in two distinct zones, we will need at least two gateways to handle the tags in their respected zones.

Preliminary testing has shown that our setup does work with a few issues… Here are some details:

The course was conducted in on a downtown alley spanning around 100’ x 35’
1x Gateway - Placed in the center of the course and connected via Ethernet
4x Anchors (DWM1001-DEV) - Placed on corners of the course
1x Anchor (DWM1001-DEV) - Placed in center of the course near gateway
3x Active Tags (DWM1001-DEV) - Inside lantern shape hand-held device (made in majority of 1/2" wood)
2x Ubiquity Antennas - Placed on longest side aimed towards center
(I have attached a schematic of how the course was setup)

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During the test we had a the following issue:

  • Near Anchors 3 & 4, the tracking was really unstable and drifting sporadically by 1 - 1.5 meters

I have read through the documentation but can’t seem to find clear answers to the following questions:

  1. Does the fact that our course was in a downtown setting with a lot of wireless traffic causing interference?
  2. Does the orientation of the Gateway have an impact on reception?
  3. Does the Gateway have a maximum range?
  4. If we were to scale up our project (in a park semi-isolated from wireless interference), would we have to deploy more than two gateways to have a good range of connection?
  5. Are the anchors interconnected in a mesh network or do they need to have individual line of site with the Gateway?

Thank you all for your time and your help,

Nik

2

Hi @niksigouin
there not clear answers on your questions but let see if I can give you some answers

First some general notes:

  1. For the best performance you should have square like grid, which yo actually don’t have as the anchor 5 is in the center. That makes it triangles not squares. Even for you grid 35m x 10m ( 100’ x 35’) the apect ratio is bad, I thing that the recommended maximum is something like 1:2.5, but you have there anchor 5 which makes slightly better.
  2. The precision of Anchor aiming is important here.
  3. The Tag is tying to do a calculation with a 4 anchors anyway but it might poorly select the 4th one as the grid is not square like. In such case when you go closer to the edge anchors the worst case distance between Tag and addition could be like 36.4m (the distance between A3 and A1).
  4. I would not recommend to have distance between Tag and anchor over 25m
  5. In your case I would put A5 between A3 nad A2 and one additional anchor between A4 and A1, that should significantly (I hope) improve your system.

Regarding your questions:

  1. Does the fact that our course was in a downtown setting with a lot of wireless traffic causing interference?
    No I don’t think so, but near strong signal from BTS could oversaturate the radio. But I dont think that is this case. So far I just heard that it is possible, bit I dont have a personal experience.

  2. Does the orientation of the Gateway have an impact on reception?
    Yes it does, unfortunately the antenna is not perfectly omni directional so antenna orientation affects the reception rate. Check this picture https://www.decawave.com/sites/default/files/dwm1001_datasheet.pdf - Page 15 - YZ plane - dark blue “circle”. It is not a perfect circle. But your gateway is located in Raspberry Pi a it could get worse as it will be affected by the raspberry Pi board.

  3. Does the Gateway have a maximum range?
    Yes, the same as AN or TN - In LOS it would be between 20-30m

  4. If we were to scale up our project (in a park semi-isolated from wireless interference), would we have to deploy more than two gateways to have a good range of connection?
    Yes, this always helps. You can have as many gateways as you want.

  5. Are the anchors interconnected in a mesh network or do they need to have individual line of site with the Gateway?

There is no UWB mesh network between gateways. The gateway can communicate with any node within its range.

Cheers
JK