Infrastructure-less peer-to-peer network

Wireless Connectivity Ultra-Wideband
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1

Hi,

Reading the DW1000 User Manual i found this chapter titled “Infrastructure-less peer-to-peer network” (12.3.4.4).

I am interested in a system where more mobile tags finds the distance between them, without a true localization, but used as proximity sensor.
This chapter seem to talk about something similar and ends with “Further details are available from Decawave”.
There is some more detailed document relative to this argument?

Thanks,

Daniele

2

Hi Daniele,
We have implemented this solution, if you are interested you can see the link: https://www.bleindoor.com/soluzioni/bleindoor-distance-keeper/

3

Hi blue,
Your system works in a situation with 50 or more tags in the same place?
In this case, the problem i found is that there are too many data (one tag must send its distance to other 49 tags) and a simple uwb packet isn’t enough.

4

Hi DieM,
what do you mean by the same place?
Obviously it is not possible to manage a very large number of devices in the same place without infrastructure, for now we manage up to 15 devices every 25 square meters in standalone mode (without infrastructure)
It is possible to increase this value by installing a very light infrastructure (1 fixed device every 250 square meters)

5

The “same place” means devices within radio range of each other. This means a set of devices that can hear each other and thus could possibly range to each other or could interfere with each other. The radio signals don’t know to magically stop at some precise distance, otherwise, we’d use that feature alone to do this.

Consider a room that is 30 x 30 meters. That’s 540 people at 15 per 25 square meters, and they are all within UWB radio range of each other leading to 145,530 unique distances between pairs of people. Without any infrastructure, you can detect when people get within 2 meters of each other and do that often enough to be useful, and not deplete the batteries rapidly? Doesn’t seem possible since this implies a distance measurement every 7 microseconds.

Can you more precisely describe what you are actually achieving? Expressing it as a simple tag density doesn’t compute.

Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
mikec@ciholas.com
+1 812 962 9408

6

Hi Ciholas,
we also use other mechanisms, but what you say is true, the battery drains quickly, at the moment we have a duration of 50 hours with a 1100 mA battery.
it is enough for a working week

7

Yes, for “same place” i means within radio range.
I am studying a system where tags emits a sound alarm when too close to each other.
The problem is that this must work in scenarios where a large amount of tags is expected (even >100, maybe) and a random number of tag can approach each other.

With double side asymmetric twr, the number of message can be 2N (N=number of tags).
The workflow can be:
Each seconds, tags try to communicate, start TWR with synchronization based on uwb_id (for example), and each tag ends sending a final message in broadcast with the distance between each others.
But, if for some reason, a large number of tag come close in same place, the uwb message cannot keep Tround and Treply of every tag. With long frame mode i have 1023 bytes and this can be sufficient, but transmissions time increase, so i don’t know if this is the best solution.

Thanks for the reply.

Daniele.