Bluetooth: Mesh: About Scan received rate

RE: Bluetooth: Mesh: About Scan received rate

Mttrinh — Thu, 05 Mar 2020 11:44:51 GMT

Hi,

Unfortunately, we don't have any specific numbers on how accurate nrf52 scan rate is, as there are other factors as well.

The chip is not capable of scanning on all 3 simultaneously, so the scan interval sets the timing between when the device switches channels and begins a new scanning window on a new channel. There will be a short period of a few hundred us (don't have exact numbers) after each scan interval where it will change to the next advertisment channel, during this period it can't receive any advertisement packet. It will rotate between the 3 advertisment channels after each scan interval. So if your unlucky there might be a chance for you to miss the advertisement packet in this short period even when you are scanning 100%.

But losing 1/4 of your packets are a lot. Like I mentioned in my previous answer you can try reliable message and see if that helps.

RE: Bluetooth: Mesh: About Scan received rate

Tovms zhangsan — Wed, 04 Mar 2020 01:04:46 GMT

Hi,

Currently use generic onoff server model periodic status message(Unsegment) every second. and another node scaning forever.

I'm not sure accurate package loss rate, but one node periodic 1000 message, another node receive only 750 message.

and not use retransmit and only single adv-event for every message, since want to known nrf52 accurate scan rate, let me choose better parameters(retransmit count) for later deployment

Note: There are no other wireless devices in the place I tested

Can you tell me how accurate nrf52 scan rate? So I can avoid idle work on parameter adjustment(repeatly).

Thanks.

RE: Bluetooth: Mesh: About Scan received rate

Mttrinh — Tue, 03 Mar 2020 15:08:22 GMT

Hi,

Since you are scanning 100% of the time and both devices is close, you should be able to get all the packets. But packet loss might still happen when you are sending packets too fast or because of interference.

I'm not too familiar with the zephyr BLE mesh example but you can try see if you can increase your retransmit count. Sending your messages as an reliable message when there is a timeout the stack will retransmit the data.

There shouldn't be any problem using the nRF52 series. How fast are you sending? How often do you get packet loss?

RE: Bluetooth: Mesh: About Scan received rate

Tovms zhangsan — Tue, 03 Mar 2020 03:48:09 GMT

The scanning interval is equal to the scanning duration