p2p communication_ transmission time and packet lost

Firmware/software/electronics/mechanics
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Hada Hamdi
Beginner
Posts: 28
Joined: Wed Jul 22, 2020 4:19 am

p2p communication_ transmission time and packet lost

Post by Hada Hamdi »

Hello,

I am using your API p2p, and I am trying to know the transmission time of a message. So I find a time between 3500 us and 4000 us of each message.
and for the packet lost, I find for example, for 3 crazyflies and for a distance 10 cm between crazyflies, 45% lost packets and for, for example a distance= 100 cm with obstacle between crazyflies, packets lost =70%.

Is that reasonable? for transmission time and packet lost.

Thank you very much for your help!
arnaud
Bitcraze
Posts: 2391
Joined: Tue Feb 06, 2007 12:36 pm

Re: p2p communication_ transmission time and packet lost

Post by arnaud »

Hi,

This is not the performance I would expect if the Crazyflie is not connected to a PC via the Crazyradio. If a PC is connected though, there is a competition between P2P and regular CRTP packet comming from the Crazyradio and the Crazyradio is using a very big amount of the air-time so this is something that can happen.

Are you connected to one or both the Crazyflies via radio from a PC? If so, you can try to only connect one Crazyflie with USB in order to still get feedback without affecting the radio.
Hada Hamdi
Beginner
Posts: 28
Joined: Wed Jul 22, 2020 4:19 am

Re: p2p communication_ transmission time and packet lost

Post by Hada Hamdi »

Hi Arnaud,

Thank you for your reply !

I am working with 3 crazyflies, I connect just one to a usb and the radio is not connected to the computer during the tests.

where can the problem be?

Thanks!
arnaud
Bitcraze
Posts: 2391
Joined: Tue Feb 06, 2007 12:36 pm

Re: p2p communication_ transmission time and packet lost

Post by arnaud »

It is hard to know what the problem could be without more information. Can you explain your setup in a bit more details?

For instance, one thing that could happen is packet collision. How many of the drones are transmitting, at what rate, and is there any randomness added to the transmission time?

One random though: the bluetooth stack can affect communication. One way to disable bluetooth is to connect with the Crazyradio and then disconnect. Actually BLE is disabled as soon as one Crazyradio packet is received so scanning a couple of times from the client would be enough to disable BLE on all your Crazyflie (until they are restarted). This is something you could test to see if BLE has any effect on the P2P performance.

And since this is radio, there is always the chance that there is another powerful transmitter in the same channel in your environment. Changing the channel can help if that is the case.
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