  Vehicular WiFi is different from conventional WiFi access. Firstly, as the
connections arise opportunistically, they are short lived and intermittent.
Secondly, at vehicular speeds channel conditions change rapidly. Under these
conditions, the MAC bit rate adaptation plays a critical role to ensure that
devices can maximize throughput performance. The goal of this work is to gain a
deeper understanding of current MAC bit rate adaptation algorithms and their
interaction with higher layer protocols under vehicular settings. Towards this
end, we evaluate the performance of four MAC bit rate adaptation algorithms;
SampleRate, AMRR, Minstrel, and RRAA, and their interactions with transport
layer protocols such as TCP in real world vehicular settings. Our experimental
study reveals that in general these algorithm perform poorly in vehicular
settings, and can have an extremely adverse impact on TCP performance.
