How many DWUSB should I get?


#1

A question we get often is how many DWUSB should I get?

For Two Way Ranging (TWR):

If all you want to test is TWR, the ability to measure distance between two devices, then the minimum you need to buy is 2 units. One unit will be powered by a battery and the other unit will be attached to the Linux PC via the USB port. The demo software will operate in TWR mode and display a time graph of distance and signal strengths, plus compute average and standard deviation of the readings.

If you want to test TWR between two devices with both of them being battery powered, you need 3 DWUSB units. One will be attached to the Linux PC and the other two units will be battery powered. The demo software will then show the range between the battery powered devices using the PC attached device to relay the data.

For Real Time Location Service (RTLS):

For RTLS, the ability to locate a tag in 2D or 3D space amongst a field of anchors, then the minimum DWUSB units you need to buy is 6. This provides 4 anchors, 1 tag, and 1 master node. The master node is attached to the Linux PC and manages the network of devices giving each DWUSB its role (anchor or tag) and assigning and controlling time slots so all the devices don’t collide on frequency. The master node does not participate in the location algorithm directly (that is, it isn’t another anchor for the computation).

A set of 4 anchors will allow the algorithm to locate the tag, but it is the minimum set which means the system won’t be as accurate as it could be and the occlusion or loss of any one anchor will lead to position errors, sometimes fairly large. For that reason, we generally recommend using 6 to 10 anchors if you can. 10 anchors is currently the maximum the demo software supports though we expect to increase that in a future release.

The gym videos on our web site show usage with 10 anchors. With that many anchors, the loss of one anchor or bad data from one anchor has minimal effect on the results.

If you want to track more than one tag, you will need an additional DWUSB unit for each tag. The demo software supports up to 48 tags, each tag being tracked at 20 Hz for a total of 960 locates per second. The primary limitation on locates per second is using the UWB radio for anchor data backhaul to the master node to feed the location engine.

So, for RTLS, you need 4 to 10 DWUSB for anchors, 1 DWUSB for the master node, and 1 to 48 DWUSB for tags. DWUSB firmware supports all roles and these are configured from the demo software.

Let me know if you have any questions, and I will try to respond here in the forum.

Mike C.


#3

I need to demonstrate a RTLS solution. how may kits should i order. The area is 100 meters in length and 35 meters in width and 25 meters in height. ( indoor locaiton)

I would like to test this configuation there.

Please advise
Deepak


#4

Deepak,
Your question seems simple on the surface, but is actually very difficult to answer due to other factors besides physical size. Line of sight issues, expected accuracy, precision, timing & tag battery performance etc. all play a role in answering your question accurately.
Additionally, the particular time distribution solution used by DWUSBs (Archimedes Release) is not applicable to this large of a space. The Archimedes code requires one time master to be directly seen by all anchors. This does not seem feasible given the space constraints you laid out.
Ciholas does have other hardware and software solutions that may work for your application. But this is a deeper discussion that should be taken off-line.
Thanks,
+Paul