Hi, We are using the BlueZ 5.48 version on a Raspberry PI with Raspbian Stretch 9.1. The setup is this PI connected with a Nordic Semiconductor nRF52840 device, via an IPv6 over BLE connection. The connection is using a connection interval of 7.5 ms. Via throughput measurements with iperf, both ways (central to peripheral and peripheral to central), we are able to achieve maximally ~ 100 kbps (using the 1 Mbps PHY). However, when looking into individual packet exchanges, we notice a significant delay (up to 1 sec) in the RTT when pinging from the peripheral to the BlueZ central and back. We also see a huge fluctuation in this value and it also depends on the intervals at which the pings are fired (lower throughput gives a much higher average individual latency). When firing ping packets at a 1 sec interval, it is definitely visible. When looking into this, we found that the latency between the peripheral and the central is quite stable and low enough. But the latency between the central and peripheral is fluctuating a lot and is generally quite high. Is this something you have noticed before? We think that it could be a scheduling issue on the kernel, where higher throughput gives more priority to Bluetooth communication? Thanks in advance. Kind regards, Mathias Baert
