چکیده (انگلیسی):

Vehicular Ad hoc Networks (VANETs) are a specific class of Mobile Ad hoc Networks (MANETs). Since
vehicles tend to move in a high speed, the network topology is rapidly changed. Thus vehicle’s connectivity
problem is one of the interesting issues in VANETs. Ad hoc On-demand Multipath Distance Vector
(AOMDV) is an extended version of ad hoc on-demand distance vector (AODV). AOMDV is designed to
overcome a connectivity problem due to highly dynamic network topology. It provides multipath for data
packets delivery from the source to the destination. However, AOMDV’s multipath establishment and
maintenance generate more control packets than those of AODV’s unipath. Meanwhile, both protocols
degrade their performance when the vehicle speed is increasing. Thus in this study, we added probabilistic
relay, which enables adjacent vehicles to probabilistically relay unsuccessful data packet transmission into
IEEE 802.11 as a MAC standard model and proposed AODV with Probabilistic Relay (AODV-PR) and
AOMDV with Probabilistic Relay (AOMDV-PR). Based on our simulation results, the addition of
probabilistic relay clearly helps those protocols to improve their performances especially in packet delivery
ratio under highly dynamic environments. Probabilistic relay adds the number of generated beacon messages,
but does not produce any additional routing messages. We evaluate those protocol performances based on
several metrics such as packet delivery ratio, routing overhead, average delivery delay, hop count and number
of relays under variation of vehicle speed and beacon interval. We show that beacon interval has a huge
influence in the performance of AODV-PR and AOMDV-PR especially for their routing overhead.