Enhancing Relay Selection Scheme for Connecting VANETs to Internet Over IEEE 802.11p in Congested and Fading Environment Scenarios

Abstract

For connecting vehicular ad hoc networks (VANETs) to the Internet over IEEE 802.11p, mobility parameters of vehicles such as speed, location, direction, are often used to connect vehicles to Road Side Units (RSUs) via more stable and less hop routes. On the one side, in the fading environment, these routes may suffer from continuous packet losses due to the frequent disconnection and extra network overhead may be incurred in the PHY, MAC, or network layer to establish them (routes) due to dynamic topology caused by channel fading as well as nodes mobility. In this paper, we propose to integrate into the relay selection scheme a routing metric which combines the impact of mobility parameters and channel fading, in order to select most stable and lowest fade routes. On the other side, in congested scenarios, pausing only on these movement parameters, one vehicle may be selected as a relay by large number of vehicles, if the number of relay requests exceeds the service capacity of the vehicle, it might get overloaded, and eventually dropping packets and enforcing re-transmissions may be happening. In this paper, we base on the fuzzy logic system between channel availability and queue occupancy to adapt the value of maximum forwarding time used in contention-based forwarding approach which is adopted in our relay selection scheme, in order to reduce as much as possible having overload relays in the network. The simulation results show that the proposed protocol enhances throughput and decreases overhead with a comparable end to end delay.