LMAC: LTE-assisted MAC protocol to reduce delay for Vehicle-to-Vehicle Communications

Reducing message delivery delay in Vehicle-to-Vehicle (V2V) communications is critical to the safety of drivers, but it faces great challenges since most vehicles have not equipped with wireless radios and existing ad-hoc MAC protocols are not efficient to reduce delay due to interference. In this paper, we leverage the drivers' smartphones to realize V2V Communications and propose a LTE-assisted MAC protocol (LMAC) to reduce the delay. LMAC collects all vehicles' locations via LTE and reduce the delay using two methods. First, it introduces a centralized algorithm to assign time slots for vehicles which reduces the delay due to interference and the time to wait for the assigned slots. Second, it uses vehicle locations and message spread directions to properly eliminate the redundant transmission. Simulations show that LMAC can reduce delay by more than 30% than existing methods.