  In this paper we present a graph-based resource allocation scheme for
sidelink broadcast vehicle-to-vehicle (V2V) communications. Harnessing
available information on the geographical position of vehicles and spectrum
resources utilization, eNodeBs are capable of allotting the same set of
sidelink resources to several different vehicles in order for them to broadcast
their signals. Hence, vehicles sharing the same resources would ideally be in
different communications clusters for the interference level-generated due to
resource repurposing-to be maintained under control. Within a communications
cluster, it is crucial that vehicles transmit in orthogonal time resources to
prevent conflicts as vehicles-with half-duplex radio interfaces--cannot
transmit and receive simultaneously. In this research, we have envisaged a
solution based on a bipartite graph, where vehicles and spectrum resources are
represented by vertices whereas the edges represent the achievable rate in each
resource based on the signal-to-interference-plus-noise ratio (SINR) that
vehicles perceive. The aforementioned constraint on time orthogonality of
allocated resources can be approached by aggregating conflicting vertices into
macro-vertices which, in addition, narrows the search space yielding a solution
with computational complexity equivalent to the conventional graph matching
problem. We show mathematically and through simulations that the proposed
approach yields an optimal solution. In addition, we provide simulations
showing that the proposed method outperforms other competing approaches,
specially in scenarios with high vehicular density.
