Abstract
Recently, the interest regarding Drive-thru Internet systems has been rapidly arising in industrial and academic fields in view of the widespread adoption of IEEE 802.11 networks and its great potential to provide cost-effective Internet access. Drive-thru Internet systems are multiple-access wireless networks in which users in moving vehicles request/receive services such as digital map update and MP3 download to/from a Road Side Unit (RSU) as the vehicles pass through the coverage range of the RSU. For the purpose of efficiently supporting various services, Wireless Access in Vehicular Environment (WAVE), which is the standard for VANETs communications, specifies multichannel utilization, where the overall bandwidth is subdivided into seven channels, namely, one Control Channel (CCH) and six Service Channels (SCHs). However, originally designed for quasi-static single-channel-based small-scale indoor applications, the performance of IEEE 802.11 in the outdoor vehicular environment, where a large number of fast-moving vehicles simultaneously contend for channel access in the multichannel environment, is still unclear. In this article, a unified analytical framework is established to study the performance of multichannel Drive-thru Internet systems. Specifically, taking account of channel access contention of vehicles and power reception probability of an RSU, the message arrival rate at the RSU on the uplink channel (i.e., CCH) is derived. Then, a multiserver queueing model, which plays the role of a bridge connecting the uplink and downlink (i.e., SCHs) communications, is developed for the purpose of accurately capturing the dynamics of the multichannel environment. Based on the developed framework, it can be noticed that as the intensity of channel contention increases, the saturated throughput of SCHs decreases rapidly, and the system becomes unstable due to the reason that vehicles have to wait for a very large amount of time to receive the requested service messages, or even worse, cannot receive the messages before leaving the coverage of RSU. In order to keep the throughput at the maximum level regardless of the channel contention intensity while maintaining the system stability, we propose a centralized coordination mechanism. Simulation experiments are carried out to validate the accuracy of the developed analytical framework and the effectiveness of the proposed centralized coordination mechanism.
Highlights
The past years have witnessed an exponential growth of interest regarding Vehicular Ad-hoc Networks (VANETs) in view of its crucial role in Intelligent Transportation Systems (ITS)The associate editor coordinating the review of this manuscript and approving it for publication was Celimuge Wu .to reduce heavy casualty tolls that are caused by vehicle crashes, and provide commercial and entertainment services that ensure comfort and efficient journeys for drivers [1]
We note that compared to our model that significantly reduces the computational complexity by directly mapping the mean vehicular population into analytical framework, Zhuang‘s model investigates the system performance for every possible vehicular population separately, after which these derived performance metrics are summed and averaged by the number of them to derive a specific overall system metric, which entails very large computational complexity
Based on the fact that a message transmitted by a vehicle is perceived by the Roadside Unit (RSU) as an arriving message only if it is successfully received, the mean and variance of message arrival rate are derived using a power reception threshold-based channel contention model
Summary
The past years have witnessed an exponential growth of interest regarding Vehicular Ad-hoc Networks (VANETs) in view of its crucial role in Intelligent Transportation Systems (ITS). The performance of a multichannel Drive-thru Internet system is affected by a number of factors, namely, the arrival rate of SRMs to the RSU on the CCH, the data transmission rate and the number of SCHs where service messages are transferred from the RSU to vehicles. A novel queueing model considering various behavioral characteristics is proposed to accurately quantify the performance metrics Their analytical model was developed on top of restrictive assumptions specific to the context of a particular scenario, where a vehicle navigating outside the coverage of any RSU remotely uploads only one SRM to the nearest possible RSU via a multihop connection, and receives the requested service data message during its residence. After receiving the acknowledgement message, the requesting vehicle will switch its SCH radio (i.e, the radio which hops among SCHs) onto the announced SCH for service message reception at the indicated time
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