Packet loss in example ¨ble_app_att_mtu_throughput¨¨

[usman]

Hi 

I am testing the example ¨¨ble_app_att_mtu_throughput¨¨ on nRF52840 by changing different paremeters incuding data length, MTU, transmitting power and PHY.

when I make a test by keeping both devices central and peripheral close the transmission time I am getting is less but when I am making test to take one board far then it takes more time.( time difference is a lot so it is not just due to on air travel time of packet)

I want to check that how many packet are dropped and retransmission happen.

I want to know if there is any flag that count the numbers of retransmission.

Thanks

[Edvin]

Hello,

The difference in time is probably caused by packet loss and retransmissions, as you say. Unfortunately, there is no easy way to see how many packets that were retransmitted. The softdevice hides this very well. What you can do is to enable radio notifications (which will give you a notification right before the nRF will use the radio), and count how many BLE_GATTS_EVT_HVN_TX_COMPLETE events you get in the ble_evt_handler between each connection event. How many that you should have depends on the connection parameters. Perhaps it only queue one large packet each connection interval, or maybe it queues several small. This depends on the connection event length, the MTU length and data length on the link.

What you can do is to print these values, and see if, for some connection events this number is less than the average/normal number. 

Best regards,

Edvin

[usman]

Hi Edvin

I will check and will come back to you if there will any further issue

thanks