According to DWM1001 documentation there are 3 data rate connections: 6.8 Mbps, 850K and 110K
The sensitivity varies with each one so as the ranges between the anchors
when the data rate is small the air time for each packet increases, which in turn increases the power consumption.
The number of seats stay the same : 15 seats.
Will the refresh time for each tag change ? For instance , 15 tags @ 100 ms
Are there other drawbacks, except the tag’s air time and power consumption, when the data rate is reduced?
It depends on the firmware used.
The hardware supports 3 different data rates. The Decawave supplied location firmware only supports one data rate.
If you want to run a different data rate then you’ll need to change the firmware to run at a different rate. This is require you to make changes to various rates and timings, clearly you can’t run the same refresh rate with the same number of tags if the data connection is far slower.
This also has implications for regulatory approvals if you want to sell a product.
Yes, DW1000 transceiver will support different data rates but the DWM1001 software stack (PANS) supports 6.8MBps only. If you use your own software you will need to recertify if you change any of the RF settings - CH, data rate etc
Ok guys. Thanks for the answer but reading the doc “APU001_Configuring-the-DW1000-for-Datasheet-use-cases_v1.2”, page 9 , there´s an code snippet explaining how to change the parameters. Although it is only valid for channel 2, which is not my case, seems that it is possible to change and it is not so difficult. I´m not concerned with regulations now because it is evaluated by regulatory as soon as you define what I will provide to customer. My concern is to know if the network capacity is affected and how. Also the other point is can I have different update dates for the tags either from a minute till 100 ms ? Are the parameters air time and power consumption the only ones affected? Isn’t there anything affected ? We still have 15 seats, independently of data rate.
You can do whatever you want in terms of radio data rate. Yes, it is easy to change the mode of the chip, it’s only a few registers you need to change.
But you will need to write your own ranging and position calculation firmware. This could be based on a modified version of the decawave code but you’ll need to make the changes yourself.
your question lead to a more complex answer than you might think. Getting best performance from the DW1000 while complying with the regulation is a bit like adjusting the engine. There are many parameters and details and you need to select what would best fit your application.
The performance depends on the parameters
Data rate, preamble length
a) affects total number of data/measurements, power consumption, receiver sensitivity
b) allowed transmit power - this is related only with frame length. You need to ensure not to transmit more than once from the same node if Smart Power is used.
Channel - CH2 will give you better range, but it cannot be used on DWM1001 since the antenna is tuned for CH5.
Other parameters like XTAL trim will also affect the sensitivity.
Configuring the chip is simple as Andy has mentioned. But you need to play a bit with those parameters to find what works best for you. I would suggest to start with this frame length calculator: https://www.decawave.com//TWRCalculator/TWR_power_calculator.xlsx
which would help you to see the relation between the parameters and occupied air-time.
So for PANS you cannot change the data rate or preamble length because the frames will take longer to transmit and it will not fit in the slot timing scheme used in PANS.