Impact of the Burst Size on the FTM Procedure in Android Phones

Since its integration in common-off-the-shelf (COTS) devices, the IEEE 802.11mc standard for the ranging estimation between a Wi-Fi card and an Access Point (AP) has grown interest in the research community. In 2021, Android released the new version 12 of its operating system, which adds some new configurable features in the Wi-Fi fine time measurement (FTM): the possibility for the user to set different burst sizes to the FTM procedure and a new one-sided FTM mode that can work with legacy APs. This paper assesses the impact of the burst size on the performance of the Wi-Fi FTM ranging. Intuitively, one may expect a higher stability in the ranging observation when the burst size is increased; however, it would imply an increase in the overhead of the ranging procedure. The impact has been studied with several models of smartphones and APs, and working in different frequency channels. The results show that, while using the minimum size allowed is not recommended because of a significant decrease in the performance, using burst sizes higher than 8 does not bring significant advantages that justify the additional traffic injected in the network.