Is Packet Dropping a Suitable Congestion Control Mechanism for Vehicular Networks?
M. Sepulcre, J. Mira, G. Thandavarayan, J. Gozalvez
IEEE 91st Vehicular Technology Conference (VTC2020-Spring)  (Antwerp, Belgium, 25-28 May 2020)
 ISBN:978-1-7281-5207-3  ISSN:2577-2465  DOI:10.1109/VTC2020-Spring48590.2020.9128822


Vehicular networks are based on the wireless exchange of information between vehicles and between vehicles and road side units. To avoid overloading the radio channel, different distributed congestion control mechanisms have been proposed in the literature. A widely adopted mechanism to control congestion is packet rate control. It controls the number of packets that each vehicle transmits to the radio channel through packet dropping. Packet dropping has been shown to effectively improve the radio communications performance thanks to the reduction of the channel load and packet collisions. However, from the application perspective, packets dropped by congestion control mechanisms are not transmitted and are therefore lost. This paper demonstrates for the first time that, while packet dropping can improve the performance at the radio level, it degrades the performance at the application level. This raises the question on whether current congestion control protocols based on packet dropping are actually suitable for vehicular networks.