Bluetooth 5.1 maximum range

[Siddharth Venkatesh]

Hi 

I am planning to use the nRF52833 for the AoA direction finding application. On that I had two questions.

1. Currently I have two nRF52833 DKs for transmission and receiving. I am planning on designing my own PCB and I want to use only the nrf52833 bluetooth 5.1 chip in it. My question is can I directly program the nRF52833 SoC or do I need to use another micro to talk to the SoC. 

2. What is the maximum range I can expect for this kind of application. How far can these special direction finding packets (with CTE) travel? Can I use a transmission amplifier if it cannot go very far?

Thanks

[Dmitry]

Hi,

Siddharth Venkatesh said:

My question is can I directly program the nRF52833 SoC or do I need to use another micro to talk to the SoC.

Yes, you can program it with nRF52833 DK, you need four pins for programming.

Siddharth Venkatesh said:

What is the maximum range I can expect for this kind of application. How far can these special direction finding packets (with CTE) travel?

I think not much further than a packets without CTE :)  Direction finding works at 1M and 2M PHY (documentation doesn't say anything about coded PHY support), and in any case receiver has to decode a packet (at least an access address and packet header) to trigger direction finding engine - the distance will not be higher than with BLE data exchange. Also, an accuracy will drop noticeably when increasing distance because of lower signal-to-noise ratio.

Siddharth Venkatesh said:

Can I use a transmission amplifier if it cannot go very far

Of course, just bear in mind an allowed maximum TX power for your country.

[Simonr]

Hi 

Dmitry is absolutely correct in his statements here. I just want to add one thing regarding Coded PHY and direction-finding: In the Bluetooth Core Specification Version 5.1 | Vol 1, Part A page 281 the following is stated:

"An LE device can make its direction available for a peer device by transmitting
direction-finding enabled packets. Using direction information from several
transmitters and profile-level information giving their locations, an LE radio can
calculate its own position.

This feature is supported over the LE Uncoded PHYs, but not over the LE
Coded PHY."

This means that Coded PHY and CTE are mutually exclusive, so you won't be able to use direction-finding in long-range applications.

Best regards,

Simon

[Siddharth Venkatesh]

Hi

So what would you say is the maximum range. Can direction finding at least work within 100m. 

Thanks

[Dmitry]

It's hard to say.. link distance may vary from 10-20m in a noisy office to more than 300m outdoors. And you will get some data over the whole range, but quality of these data will get worse to the edges - an accuracy will depend on the length of CTE and filtering/averaging technics in your algorithm.

100m is quite achievable with this method of location.

[Simonr]

Hi

You should also keep in mind that getting an accurate fix will be harder the further away devices are from each other, as the same difference in angle will mean a longer distance at 100m than at 10m. This is, of course, up to the requirements of your application, but remember that accuracy will decrease at increased range.

Best regards,

Simon