A Comparative Experimental Analysis of Channel Access Protocols in Vehicular Networks

Abstract

The deployment of vehicular networks is considered crucial for traffic safety of future vehicles. Thus, researchers are making extensive efforts to improve the performance of the IEEE802.11p standard. Many researchers have proposed various MAC protocols to mitigate the chronicle problems of the IEEE802.11p -for example, the unreliable transmission of safety-related messages. However, most of the previous evaluations of the reliability problem have been done either via mathematical analysis or simulations. In this paper, we conducted actual experiments and analyzed the performance of two MAC protocols: IEEE802.11p and HCMAC, a hybrid MAC protocol recently reported. Using commercial V2X devices, we measured the performance in terms of received signal strength indicator (RSSI), packet delivery ratio (PDR), and packet inter-reception time (PIR). We tested the connectivity performance under various mobility scenarios. In addition, this paper investigates the impact of collisions on the overall performance. For a range of collision levels, an extensive set of experiments demonstrate that HCMAC outperforms the MAC of IEEE802.11p in terms of PDR and PIR up to 88% and 47%, respectively. INDEX TERMS VANET, IEEE802.11p, HCMAC, Cohda wireless, field testing. 1 DSRC standard defines such a beacon message as a Basic Safety Message (BSM). Hereafter, the terms ''beacon'' and ''BSM'' are interchangeably used.

Highly Reliable MAC Protocol Based on Associative Acknowledgement for Vehicular Network

“…The experiment conducted in [32] proved that relative speed of vehicles does not particularly affect packet delivery ratio. According to the results in [32], vehicles travelling at 200 km/h relative speed experience only 4% drop in their packet delivery ratio.…”

“…The experiment conducted in [32] proved that relative speed of vehicles does not particularly affect packet delivery ratio. According to the results in [32], vehicles travelling at 200 km/h relative speed experience only 4% drop in their packet delivery ratio. Therefore, the results acquired from our experiment scenario can be considered quite reliable, even though we did not consider velocity by fixing position of the devices at predefined locations.…”

Channel-Aware Congestion Control in Vehicular Cyber-Physical Systems

“…In VANETs, the channel will become congested as the vehicle density increases because V2V safety applications periodically broadcast vehicle status information with at least the minimum beacon rate. In study of [5] showed that packet collisions in IEEE 802.11p significantly degrade the beaconing performance.…”

Review of MAC Protocols for Vehicular Ad Hoc Networks

“…When the channel is busy or colliding, each access vehicle adopts the mode of random back-off until the channel is idle for a period. IEEE 802.11p does not provide reliable broadcast mechanism and limited transmission delay, which cannot guarantee the strict QoS requirements of safety applications, such as low delay and high packet delivery rate (PDR) [51,52]. The safety information is broadcasted on the CCH without require-to-send/clear-to-send (RTS/CTS) handshake and acknowledgment (ACK) mechanisms to indicate whether the reception is successful or not, which increases the collision probability of hidden terminals, especially under high traffic load.…”