Measuring ETSI ITS-G5 Communications Latencies with Commercial off-the-shelf Wi-Fi Hardware

We transmit ETSI ITS-G5 standard compliant packets using commercial off-the-shelf Wi-Fi cards based on the Atheros 9k chipset under Linux operating system and measure latencies within the transmission chain by a ping-pong scheme. While preparing, enqueing, and handing over a packet to the kernel via send() takes about 10 microseconds, a reception delay of about 500 microseconds is introduced, before the dequeing and return of recv() takes about another 10 microseconds. The 500 microsecond delay is caused by RX interrupt mitigation in the ath9k device driver and can be adjusted by a kernel patch.