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Low power mode in TWR

Posted: Wed Feb 27, 2019 4:56 pm
by anaimp

I am a student at University of L’Aquila and I am new to Loco Positioning System.
I have read on Decawave documentiation about different low power mode I can use in order to set DW1000 anchors in TWR (i.e. “Low-Power Listening”, “Sniff Mode”, “Low Duty Cycle Sniff Mode”).

As far as I can work out, if I want to save power, I can choose one of these modes configuring my anchors and using the following configuration mode: PRF (16MHz), data rate (6.8 Mbps), Preamble length (128 symbols), releated to the Short Range TWR use-case.

I wonder know according to what I can select one low power mode or the other in order to minimize the power consumption and if it is possible to do that for TWR.


Re: Low power mode in TWR

Posted: Thu Feb 28, 2019 10:01 am
by arnaud
I am not sure to understand the question. You are interested into lowering the power consumption of the anchors in a TWR system.

The biggest power consumption for a TWR anchor is that the anchor is continuously in receive mode, and receive mode for a UWR radio can easily consume more than transmitting. I am not aware of big differences of receive mode consumption when changing the PRF, but the datarate and preamble length will most likely not have a great effect. What Decawave is proposing with the low duty cycle sniff is to disable the radio most of the time, this will work best with a long preamble actually since for ranging you want receive as much as possible of the preamble.

As a side note, the lowest power anchor we have is TDoA2 and the reason is that TDoA2 is using timeslots: the radio is switched ON only when needed. I think that at the end of the day this is the goal: the radio in any modes will consume power when turned-ON, it should be OFF most of the time to optimize the power consumption.

Re: Low power mode in TWR

Posted: Thu Feb 28, 2019 4:03 pm
by anaimp
Thank you for your answer, it was very useful.
One more question please.
In 802.15.4 standard there is a section about the LQI (Link Quality Indicator).
I wonder know if does Decawave implement this parameter and eventually where can I find that implementation.


Re: Low power mode in TWR

Posted: Mon Mar 04, 2019 1:54 pm
by arnaud
I have not been looking at that in details. Decawave has a lot of documentation and application notes discussing the estimation of the receiving quality. One that is of most interest for us is a formula that would allow to estimate if the packet we received has been flying in direct line of sight or not. Unfortunately I have never managed to get reliable line of sight/non line of sight estimation using Decawave's formula. If you find anything in your research that works and can indicate the timing quality of a received packet do not hesitate to share the info back here :-).