nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Marjeris Romero — Wed, 28 Apr 2021 07:04:03 GMT

Hi,

Testing over water is more difficult as water have different absorption and reflection/refraction properties, if the tag was very close to the water the water might absorb most of the signal. But to be honest I don't know how much range would it be expected under these conditions, as we haven't conducted tests over water.

This test was conducted over the line of sight in the coast, but with mostly land and only some water below the two points: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/testing-long-range-coded-phy-with-nordic-solution-it-simply-works-922075585

If you are having a similar range to the test above it's perhaps as good as it gets under your testing conditions. The test above is also performed using +8dBm, +4dBm will give a lower range.

You can also check with a sniffer if you are in fact transmitting CODED PHY packets or if for some reason the phy update failed (but in that case you would have gotten a phy_update error return value).

Best regards,

Marjeris

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Mon, 26 Apr 2021 10:03:10 GMT

It's been a while, but here's a follow-up :)

We have not been able to get a practical range improvement using Long Range over using +4 dBm broadcasting at 1 MBit / s PHY. This is probably in big part because of our data transmission model, we put the data in BLE advertisement manufacturer specific field and we can tolerate a lot of packet losses.

The limiting factor in the range is always the environment, either the Fresnel zone or metal and concrete in urban environment

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Mon, 05 Oct 2020 15:22:23 GMT

As a summary, we'll test with equal advertising rates and try to find taller poles to hang our tags from. I'm not sure how we're going to get over 4 meters in practice though, maybe we should place the tags in a mast of a sailboat :)

I marked on my TODO to follow-up on this, but on the other hand the important discovery for us is the Fresnel zone limitation. Vast majority of our customers won't be installing the sensors above their reach without ladders, and if the Coded PHY is more sensitive to 2.4 GHz noise we're probably not going to see improvement in noisy environments either.

Thanks for your help, I'll mark this answered and will follow-up when/if we have a more controlled test result.

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Marjeris Romero — Mon, 05 Oct 2020 14:32:23 GMT

I see, then the Softdevice is not a problem. I just asked about this because in some earlier versions the support for long range was still not maximize for max range, but this was a long time ago, S140 v6.1.1 is pretty new and one version older than the one used in our latest test: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/testing-long-range-coded-phy-with-nordic-solution-it-simply-works-922075585

I think we just need to wait until you do new testing taking care of all the considerations mentioned above and see if the results are different then. We are very interested in knowing what kind of range customers achieve with our products in different conditions so please keep us updated!

Best regards,

Marjeris

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Fri, 02 Oct 2020 15:36:59 GMT

We're using S140v6.1.1

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Marjeris Romero — Fri, 02 Oct 2020 14:23:37 GMT

I see, then it doesn't look like that would be a problem, 7 seconds should be more than enough.

Can I also ask which Softdevice version you were using in your tests?

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Fri, 02 Oct 2020 13:56:38 GMT

[quote userid="73427" url="~/f/nordic-q-a/66439/nrf52832-1-mbit-s-vs-nrf52811-coded-phy-range-improvement-10---expected-100/272757#272757"] Depends on the size of your scan window. If the scan window is too small you will risk dropping packets.[/quote]

That's another point I didn't consider, but we're using 7 seconds per channel anyway so that should not be an issue.

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Marjeris Romero — Fri, 02 Oct 2020 13:45:16 GMT

[quote user="ojousima"]We had scan on at 100% duty cycle, this should not be an issue[/quote]

Depends on the size of your scan window. If the scan window is too small you will risk dropping packets.

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Fri, 02 Oct 2020 11:05:32 GMT

Hello Marjeris, thanks for the reply.

Make sure you are advertising on all three BLE channels

Yes

You can try to adjust the scan window and scan interval in the gateway device when the advertising interval of the tags has been adjusted for coded PHY. Sending packets more often or scaning more when using 1M PHY could explain why the differences were small between the two modes in your first test.

We had scan on at 100% duty cycle, this should not be an issue

It could be interesting if you can do the test with 221ms interval on coded PHY as well so you can the results with the same interval settings.

Yes, we'll need to retest this

Check if there is a lot of 2.4GHz activity in the area which could be interfering with your measurements?

No, it was in a lake in a middle of forest

[quote userid="73427" url="~/f/nordic-q-a/66439/nrf52832-1-mbit-s-vs-nrf52811-coded-phy-range-improvement-10---expected-100/272686#272686"]Just wanted to add that Coded PHY is generally more sensitve to interference because of the longer packets[/quote]

This was news for me, I thought that Coded PHY should be more interference-tolerant because the packets have the error correction codes. Thanks :)

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Marjeris Romero — Fri, 02 Oct 2020 10:07:27 GMT

Hi,

I think you already got a good answer about checking the Fresnel zone, there are different Fresnel zone clearance calculators online which you can use to calculate the best high for the poles. Just wanted to add that Coded PHY is generally more sensitve to interference because of the longer packets so it's difficult to say for sure what improvements in range one can expect, but I agree that 10% sounds a bit low.... Here are also some other things you can check when you are back on the boat:

Make sure you are advertising on all three BLE channels
You can try to adjust the scan window and scan interval in the gateway device when the advertising interval of the tags has been adjusted for coded PHY. Sending packets more often or scaning more when using 1M PHY could explain why the differences were small between the two modes in your first test.
It could be interesting if you can do the test with 221ms interval on coded PHY as well so you can the results with the same interval settings.
Check if there is a lot of 2.4GHz activity in the area which could be interfering with your measurements?

I wish you good luck with further testing. Let us know if you are able to achieve a longer range next time.

Best regards,

Marjeris

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

Otso Jousimaa — Mon, 28 Sep 2020 17:32:48 GMT

Thanks, our tester confirmed that the devices were ~4 meters off ground level, which actually coincides pretty well with the linked fresnel clearance zones. We'll try again with higher poles

RE: nRF52832 1 MBit/s vs nRF52811 Coded PHY range improvement 10 % - expected 100 %

hmolesworth — Mon, 28 Sep 2020 16:51:06 GMT

Try adjusting the height above the ground plane (== water); I find very poor results close to ground, plus it's a good excuse to get back on the boat. This link might be useful testreport