An adaptive and cooperative MAC protocol for safety applications in cognitive radio enabled vehicular Ad-hoc networks

Abstract

Rapid broadcast of safety message (sm) is critical for real-time applications in cognitive radio vehicular ad hoc networks (CR-VANETs). The arrival of primary users (PU) and the relative unpredictability of traffic emerge as network bottleneck constraints, resulting in unreliable broadcast services. The requirement is for a Medium Access Control (MAC) protocol that allows for fair contention, is adaptive, and includes a makeup strategy for rebroadcasting failed transmissions. There are intricate tradeoff optimisation relationships in which a value for the contention window that is inadequate will not result in optimal network performance. In this paper, we develop a dynamic contention window backoff mechanism using Karush–Kuhn–Tucker (KKT) conditions that enhances network performance by modifying the backoff time according to traffic density. Then we amalgamate this algorithm with a cooperative makeup strategy to design a novel adaptive and cooperative MAC protocol that is operable in a dynamic CR-VANET paradigm (ACCRV-MAC). A Markov chain decision model characterises the protocol, and Network Simulator -2 analyses various performance parameters. The study reveals that ACCRV-MAC improves throughput by 38.3% and reduces network latency by 49% compared to existing MAC protocols.