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

[Otso Jousimaa]

Hello, 

We're piloting updating our sensor beacons RuuviTags to use Coded PHY for better range. The current design has nRF52832, our update would be to drop in a nRF52811.

The beacons work by broadcasting sensor data in manufacturer specific format in advertisements, there's no GATT connection. 

Our test setup had 5+5 tags and 2 prototypes of Ruuvi Gateway as receiver. Ruuvi Gateways have nRF52811 + LNA on BLE side and ESP32 to send the data to the Cloud via WiFi. The gateway collects all advertisements to 10 second batches and sends the data in one batch, if a tag is received at least once in 10 second window it's considered to be in range. 52832 tags sent at 221 ms interval, 52811 tags at 1285 ms interval to compensate for energy consumption of Coded PHY. Both tags send at +4dBm. 

We placed the gateways on a harbor by a lake and started speeding away in a boat with tags pointed to gateways, i.e. as clear line of sight as possible. The 1 MBit / s tags dropped first after a bit over kilometer range and Coded PHYs about 10 % later. We were expecting the range to be doubled.

Is there something specific in our test setup which would explain the result of only 10 % more range? For example our use case is extremely tolerant for dropped packets, to be considered in range 52832 can lose 44/45 packets in 10-second period, 97 % packet loss is acceptable. On the other hand 52811 can tolerate losing only 6/7 packets => 77% packet loss is acceptable.

[Otso Jousimaa]

Marjeris Romero said:

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

 

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

[Marjeris Romero]

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?

[Otso Jousimaa]

We're using S140v6.1.1

[Marjeris Romero]

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

[Otso Jousimaa]

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.