2.2 Forwarding data between two junctions
Once the destination junction is determined, the
improved greedy strategy is used to forward packets
towards the selected junctions. For that, all data
packets are marked by the location of this junction.
Each vehicle maintains a neighbor table in which
position, velocity and direction of each neighbor
vehicle are recorded. This table is updated through
hello messages exchanged periodically by all vehicles.
Thus, when a packet is received, the forwarding
vehicle computes the new predicted position of each
neighbor using the recorded information (velocity,
direction and the latest known position), and then
selects the next hop neighbor (i.e. the closest to the
destination junction).
Recovery strategy:
Despite the improved greedy routing strategy, the
risk remains that a packet gets stuck in a local
optimum3
(the forwarding vehicle might be the closest
to the next junction). Hence, a recovery strategy is
required. The repair strategy of GyTAR is based on the
idea of "carry and forward": the forwarding vehicle of
the packet in a recovery mode will carry the packet
until the next junction or until another vehicle, closer
to the destination junction, enters/reaches its
transmission range.