OEC-MAC: A Novel OFDMA Based Efficient Cooperative MAC Protocol for VANETS

Abstract

In vehicular ad hoc networks (VANETs), mobility between vehicles can cause rapid topology changes with frequent disconnections, which result in collisions and packet losses that make communications unstable. Alternatively, cooperative transmission can increase the reliability of communication by eliminating these problems in VANETS. In heavy traffic conditions, carrier sense multiple access with collision avoidance (CSMA/CA) suffers from collision, and it is not effective when high data rate is required. Therefore, orthogonal frequency division multiple access (OFDMA) is proposed. With the use of OFDMA, throughput is increased and delay is decreased by reducing the probability of collision in high traffic scenario. In this study, a novel OFDMA based efficient cooperative MAC protocol (OEC-MAC) is proposed for VANETs. Subcarrier channels assignment and access mechanisms are provided. The mechanism is presented not only for choosing the appropriate transmission mode but also for selecting the optimum relay. New control messages are defined to support cooperative communication. The performance of OEC-MAC protocol is examined by providing analytical analysis based on Markov chain model. Numerical results are demonstrated, which reveal that OEC-MAC protocol ensures a remarkable increase in throughput and also satisfies the strict delay requirement of 100 ms in VANETs for safety messages (sm). In addition, communication reliability is increased by reducing the packet dropping rate (PDR). Numerical results are compared with existing protocols, and a quantitative comparison is provided. It has been seen form results that proposed OEC-MAC protocol is better than existing schemes, especially under heavy traffic scenarios.

Review of MAC Protocols for Vehicular Ad Hoc Networks

“…The WAVE standard adopts orthogonal frequency division multiplexing (OFDM) technology [ 40 , 41 ], and all used carriers are orthogonal with each other, which reduces the transmission interference between carriers. It allows data rates from 6 to 27 Mbps.…”

Performance analysis of an adaptive OFDMA‐based CSMA/CA scheme on a wireless network

“…The work in [18] develops a MAC protocol for cognitive WLAN, wireless sensor networks featuring channel usage by licensed users and cognitive radios. OFDMA is another efficient technology adopted by recently developed communication standards such as 802.11ax due to its ability to withstand interference [7] and its effective resource utilisation that alleviates the hidden node problem. Bazzi et al .…”

“…Handshaking is also plagued by the time and data overhead problems. Even with the handshaking, the hidden node problem persists as the number of nodes increases in dense networks and significantly degrades the performance of the DCF due to high collision rates [7]; fourth, the DCF algorithm does not perform resource allocation effectively. It allocates the entire channel to a user irrespective of whether the user is using it or not hence lowering channel utilisation; and finally, the DCF algorithm is not cognisant of the wireless channel conditions.…”

An Energy Efficient Message Dissemination Scheme in Platoon-Based Driving Systems

“…To reduce the frame error probability and increase signal-to-noise ratio (SNR), they analyzed link characteristics over dedicated relay and presented an optimal power allocation scheme. In [21], the authors proposed an orthogonal frequency-division multiple access (OFDMA)-based cooperative MAC protocol for VANETs. If a failure occurs over the direct transmission link from a source to a destination, the source sends the message again to the destination with the help of relays using different frequency bands to increase the reliability of the communication.…”