Abstract
The IEEE 1609.4 legacy standard for multichannel communications in vehicular ad hoc networks (VANETs), specifies that the control channel (CCH) is dedicated to broadcast safety messages, while the service channels (SCHs) are dedicated to transmit infotainment service content. However, the SCHs can be used as an alternative to transmit high priority safety messages in the event that they are invoked during the service channel interval (SCHI). This implies that there is a need to transmit safety messages across multiple available utilized channels to ensure that all vehicles receive the safety message. Transmission across multiple SCHs using the legacy IEEE 1609.4 requires multiple channel switching and therefore introduces further end-to-end delays. Given that safety messaging is a life critical application, it is important that optimal end-to-end delay performance is derived in multichannel VANET scenarios to ensure reliable safety message dissemination. To tackle this challenge, three primary contributions are in this article: first, a cooperative multichannel coordinator (CMD) selection approach based on the least average separation distance (LAD) to the vehicles that expect to tune to other SCHs and operates during the control channel interval (CCHI) is proposed. Second, a model to determine the optimal time intervals in which CMD operates during the CCHI is proposed. Third, a contention back-off mechanism for safety message transmission during the SCHI is proposed. Computer simulations and mathematical analysis show that CMD performs better than the legacy IEEE 1609.4 and a selected state-of-the-art multichannel message dissemination scheme in terms of end-to-end delay and packet reception ratio.
Highlights
Nowadays, intelligent transport systems (ITS) are one of the key drivers for the evolution of smart cities
Observations show that the proposed channel Emergency Message Dissemination Protocol (CMD) maintains lower total end-to-end delays compared to WSD and the legacy IEEE 1609.4 when more than two service channels (SCHs) are utilized during the SCH interval (SCHI)
The result shows that the proposed CMD offers a greater Packet reception ratio (PRR) within a shorter end-to-end delay compared to the WSD and IEEE 1609.4 legacy system especially when considering total coverage of all SCH’s with the BSM
Summary
Intelligent transport systems (ITS) are one of the key drivers for the evolution of smart cities. In the event of a high priority message during the SCHI, the invoking vehicle schedules the transmission of the emergency message across all the SCH’s based on a schedule determined by the SCH which has the smallest fraction of the delay divided by the number of vehicles in the SCH This implies that in WSD, the emergency message invoking vehicle performs the channel coordination function. The information collection routine during the CCHI based on the service advertisements is the same as that of the WSD except that each vehicle only collects the separation distance information between the vehicles in its communication range and the expected SCH they expect to tune to during the SCHI. A multi-channel coordinator selection approach based on the LAD to vehicles tuned to other SCHs with the purpose of forwarding emergency messages with minimum end-to-end delay.
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