A modified TC-MAC protocol for multi-hop cluster communications in VANETs

Abstract

The transmission of safety/update message aims to inform the nearby vehicles about the senders current status and/or a detected dangerous situation. This type of transmission is designed to help in accident and danger avoidance. Moreover, it requires high message generated rate and high reliability. On the other hand, the transmission of non-safety message aims to increase the comfort on vehicles by supporting several non-safety services, from notifications of traffic conditions to file sharing. Unfortunately, the transmission of non-safety message has less priority than safety messages, which may cause shutting down the comfort services. The goal of this paper is to design a MAC protocol in order to provide the ability of the transmission of nonsafety message with little impact on the reliability of transmitting safety message even if the traffic and communication densities are high in a multi-hop cluster. Our protocol is based on modifying TC-MAC which uses TDMA technique for slot reservation based on clustering of vehicles.

An enhanced TDMA Cluster-based MAC (ETCM) for multichannel vehicular networks

“…Several enhancements have been proposed to improve the IEEE 1609.4 multichannel MAC performance, which can be categorized into i) synchronous adaptive adjustment of CCH/SCH intervals [5], ii) asynchronous distributed multichannel negotiation [6], and iii) TDMA cluster-based slot allocation [7][8][9]. As an example synchronous adaptive adjustment of CCHI/SCHI, Wang et al [5] present a variable control channel interval approach, which dynamically adjusts the duration of the CCHI and SCHI according to the number of active nodes in the network.…”

“…Moreover, in the variable control channel interval approach, it is assumed that the number of vehicles and packet size are known by the RSUs, which may not be possible in distributed scenario. From the three categories of multichannel MAC schemes, the conflict-free multichannel MAC with TDMA protocols provide better performance in safety message delivery and overall throughput of service channels [7][8], [11]. Yu and Biswas [10] proposed Vehicular Self-Organizing vehicular MAC (VeSOMAC) which reduces the delay of the safety messages by giving sequential TDMA time slot based on the vehicles relative position.…”

“…This issue develops more severe as the network is more mobile where the topology changes frequently. The TC-MAC is a dynamic TDMA slot reservation technique for cluster-based VANETs [7] [8]. In TC-MAC, each vehicle gets one mini-slot and one SCH slot in a logical frame of each sync interval.…”

“…Recently, many research results reported that the synchronous split-phase contention-based multichannel access scheme in current IEEE 1609.4 demonstrates poor performance in the aggregated service channel throughput and QoS provisioning in dense VANETs environment [5]- [8]. Especially, the fixed duration of CCHI and SCHI prohibits adaptive intelligent allocation of time intervals in response to variable traffic demands, while the contention-based channel access in CCH produces a higher possibility of contentions in SCHs, which may result in inefficiency due to continued collisions in dense large-scale vehicular Ad Hoc networks [5].…”

Pre-Emptive Traffic Management for a Cluster-Based TDMA System in Vehicular Communications

“…The scheme proposed in [21] has extended by modifying the length of TDMA frames as presented in [22], where multi-hop intra-cluster communication is also discussed. For a multichannel network, Enhanced TDMA Cluster-based MAC (ETCM) [23] is purposed.…”