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Delay-sensitive wireless communication for cooperative driving applications
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cooperative driving holds the potential to considerably improve the level of safety and efficiency on our roads. Recent advances in in-vehicle sensing and wireless communication technology have paved the way for the development of cooperative traffic safety applications based on the exchange of data between vehicles (or between vehicles and road side units) over a wireless link. The access to up-to-date status information from surrounding vehicles is vital to most cooperative driving applications. Other applications rely on the fast dissemination of warning messages in case a hazardous event or certain situation is detected. Both message types put high requirements on timeliness and reliability of the underlying communication protocols.

The recently adopted European profile of IEEE 802.11p defines two message types,periodic beacons for basic status exchange and event-triggered hazard warnings, both operating at pre-defined send rates and sharing a common control channel. The IEEE 802.11p Medium Access Control (MAC) scheme is a random access protocol that doesnot offer deterministic real-time support, i.e. no guarantee that a packet is granted access to the channel before its deadline can be given. It has been shown that a high number of channel access requests, either due to a high number of communicating vehicles or highdata volumes produced by these vehicles, cannot be supported by the IEEE 802.11p MAC protocol, as it may result in dropped packets and unbounded delays.

The goal of the work presented in this thesis has therefore been to enhance IEEE 802.11p without altering the standard such that it better supports the timing and reliability requirements of traffic safety applications and provides context-aware andefficient use of the available communication resources in a vehicular network. The proposed solutions are mapped to the specific demands of a set of cooperative driving scenarios (featuring infrastructure-based and infrastructure-free use cases, densely and sparsely trafficked roads, very high and more relaxed timing requirements) and evaluated either analytically, by computer simulation or by measurements and compared to the results produced by the unaltered IEEE 802.11p standard.

As an alternative to the random MAC method of IEEE 802.11p, a centralized solution isproposed for application scenarios where either a road side unit or a suitable dedicated vehicle is present long enough to take the coordinating role. A random access phase forevent-driven data traffic is interleaved with a collision-free phase where timely channel access of periodic delay-sensitive data is scheduled. The ratio of the two phases isdynamically adapted to the current data traffic load and specific application requirements. This centralized MAC solution is mapped on two cooperative driving applications: merge assistance at highway entrances and platooning of trucks. Further,the effect of a context-aware choice of parameters like send rate or priority settings based on a vehicle’s position or role in the safety application is studied with the goal to reduce the overall number of packets in the network or, alternatively, use the available resources more efficiently. Examples include position-based priorities for the merge assistance use case, context-aware send rate adaptation of status updates in anovertaking warning application targeting sparsely-trafficked rural roads and an efficient dissemination strategy for warning messages within a platoon.

It can be concluded that IEEE 802.11p as is does not provide sufficient support for the specific timing and reliability requirements imposed by the exchange of safety-criticalreal-time data for cooperative driving applications. While the proper, context-awarechoice of parameters, concerning send rate or priority level, within the limits of the standard, can lead to improved packet inter-arrival rates and reduced end-to-end delays,the added benefits from integrating MAC solutions with real-time support into the standard are obvious and needs to be investigated further.

Place, publisher, year, edition, pages
Halmstad: Halmstad University Press , 2013. , 47 p.
Series
Halmstad University Dissertations, 4
Keyword [en]
Cooperative driving applications, wireless communication
National Category
Communication Systems
Identifiers
URN: urn:nbn:se:hh:diva-22164ISBN: 978-91-87045-04-2 ISBN: 978-91-87045-03-5 OAI: oai:DiVA.org:hh-22164DiVA: diva2:621760
Public defence
2013-06-07, R 1107, Halmstad University, Halmstad, 10:15 (English)
Opponent
Supervisors
Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2014-11-19Bibliographically approved
List of papers
1. Real-time communication support for cooperative, infrastructure-based traffic safety applications
Open this publication in new window or tab >>Real-time communication support for cooperative, infrastructure-based traffic safety applications
2011 (English)In: International Journal of Vehicular Technology, ISSN 1687-5702, Vol. 2011, no Article ID 541903, 17- p.Article in journal (Refereed) Published
Abstract [en]

The implementation of ITS (Intelligent Transport Systems) services offers great potential to improve the level of safety, efficiency and comfort on our roads. Although cooperative traffic safety applications rely heavily on the support for real-time communication, the Medium Access Control (MAC) mechanism proposed for the upcoming IEEE 802.11p standard, intended for ITS applications, does not offer deterministic real-time support, that is, the access delay to the common radio channel is not upper bounded. To address this problem, we present a framework for a vehicle-to-infrastructure-based (V2I) communication solution extending IEEE 802.11p by introducing a collision-free MAC phase assigning each vehicle an individual priority based on its geographical position, its proximity to potential hazards and the overall road traffic density. Our solution is able to guarantee the timely treatment of safety-critical data, while minimizing the required length of this real-time MAC phase and freeing bandwidth for best-effort services (targeting improved driving comfort and traffic efficiency). Furthermore, we target fast connection setup, associating a passing vehicle to an RSU (Road Side Unit), and proactive handover between widely spaced RSUs. Our real-time MAC concept is evaluated analytically and by simulation based on a realistic task set from a V2I highway merge assistance scenario.

Place, publisher, year, edition, pages
New York: Hindawi Publishing Corporation, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-16211 (URN)10.1155/2011/541903 (DOI)s2.0-80052747029 (Scopus ID)
Note

Copyright © 2011 Annette Böhm and Magnus Jonsson. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Available from: 2011-09-12 Created: 2011-09-12 Last updated: 2014-11-19Bibliographically approved
2. Adaptive Cooperative Awareness Messaging for Enhanced Overtaking Assistance on Rural Roads
Open this publication in new window or tab >>Adaptive Cooperative Awareness Messaging for Enhanced Overtaking Assistance on Rural Roads
2011 (English)In: IEEE Vehicular Technology Conference (VTC Fall 2011), Piscataway, N.J.: IEEE Press, 2011, 1-5 p.Conference paper, (Refereed)
Abstract [en]

Cooperative traffic safety applications such as lane change or overtaking assistance have the potential to reduce the number of road fatalities. Many emerging traffic safety applications are based on IEEE 802.11p and periodic position messages, so-called cooperative awareness messages (CAM) being broadcasted by all vehicles. In Europe, ETSI defines a periodic report rate of 2 Hz for CAMs. Although a high report rate is the key to early hazard detection, the 2 Hz rate has been chosen to avoid congestion in settings where the vehicle density is high, e.g., on major highways and in urban scenarios. However, on rural roads with a limited number of communicating vehicles, a report rate of 2 Hz leads to unnecessary delay in cooperative awareness. By adapting the CAM report rate depending on the specific application and road traffic density, and by making use of the priority levels provided by the 802.11p quality of service mechanism, we show that hazards can be detected earlier and the available bandwidth is used more efficiently, while not overexploiting the network resources.

Place, publisher, year, edition, pages
Piscataway, N.J.: IEEE Press, 2011
Series
IEEE Vehicular Technology Conference (VTC Fall), ISSN 1090-3038 ; 2011
Keyword
access protocols, mobile radio, road traffic, cooperative traffic safety, telecommunication standards, telecommunication traffic, wireless LAN
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-16467 (URN)10.1109/VETECF.2011.6093162 (DOI)000298891500350 ()2-s2.0-83755181459 (Scopus ID)978-1-4244-8328-0 (ISBN)
Conference
4th International Symposium on Wireless Vehicular Communications (WIVEC 2011), San Fransisco, USA, September 5-6, 2011
Note

©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Category number CFP11VTF-ART; Code 87844

Available from: 2011-10-18 Created: 2011-10-18 Last updated: 2014-11-19Bibliographically approved
3. Co-existing periodic beaconing and hazard warnings in IEEE 802.11p-based platooning applications
Open this publication in new window or tab >>Co-existing periodic beaconing and hazard warnings in IEEE 802.11p-based platooning applications
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A platoon of trucks driving at the same, mutually agreed speed while keeping a minimum inter-vehicle distance will reduce fuel consumption, enhance transport efficiency as well as improve the safety of other adjacent road users. The European profile of IEEE 802.11p for inter-vehicle communications uses a single 10 MHz control channel dedicated to safety-critical data, shared by periodic status updates, CAM (Cooperative Awareness Message), and event-triggered warnings, DENM (Decentralized Environmental Notification Message). Coupled with the random access delay inherent to the 802.11p medium access method, the strict timing and reliability requirements of platoon applications are not easily met. To this end, we evaluate by simulation the effect of IEEE 802.11p-compliant send rate adaptations and message type prioritizations and the choice of warning dissemination strategy on CAM transmissions and DENM dissemination in a platooning scenario. Simulation studies of a platoon of 10-20 vehicles in a busy highway scenario show that the context-aware choice of send rate, priority class and dissemination strategy not only reduce the dissemination delay of DENMs but even has a significant effect on the throughput of CAMs exchanged by platoon members.

National Category
Communication Systems
Identifiers
urn:nbn:se:hh:diva-22162 (URN)
Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2014-11-19Bibliographically approved
4. Performance evaluation of a platooning application using the IEEE 802.11p MAC on a control channel vs. a centralized real-time MAC on a service channel
Open this publication in new window or tab >>Performance evaluation of a platooning application using the IEEE 802.11p MAC on a control channel vs. a centralized real-time MAC on a service channel
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Recent advances in cooperative driving hold the potential to significantly improve safety, comfort and efficiency on our roads. An application of particular interest is platooning of trucks, where it has been shown that keeping a minimum inter-vehicle distance results in considerably reduced fuel consumptions. This, however, puts high requirements on timeliness and reliability of the underlying exchange of control messages between platoon members. The European profile of IEEE 802.11p, recently adopted by ETSI, defines two message types to this end, periodic beacons for basic cooperative awareness (CAM) and event-triggered decentralized environmental notification messages (DENM), both using the common control channel. The IEEE 802.11p employs a random medium access protocol, with excessive delays that may prevent proper functionality of a platooning application. To mitigate the effects of this, ETSI standardizes a decentralized congestion control algorithm to, e.g., lower the CAM frequency when needed. Some service channels with less strict requirements on send rates, data traffic types or medium access methods are available. In this paper we compare the performance of decentralized, standard-compliant inter-platoon communication using IEEE 802.11p on the control channel with a solution based on a service channel, which combines a random access phase for DENM with a centralized, scheduled access phase for CAM. A dedicated service channel for platooning applications enables us to always guarantee timely channel access of CAM packets before a specified deadline and our simulations show that this is achieved at very small sacrifices in DENM dissemination delay.

National Category
Communication Systems
Identifiers
urn:nbn:se:hh:diva-22163 (URN)
Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2014-11-19Bibliographically approved
5. Evaluating CALM M5-based vehicle-to-vehicle communication in various road settings through field trials
Open this publication in new window or tab >>Evaluating CALM M5-based vehicle-to-vehicle communication in various road settings through field trials
2010 (English)In: Proceedings - Conference on Local Computer Networks, LCN, (2010 12 01): 613-620, Piscataway, N.J.: IEEE Press, 2010, 613-620 p.Conference paper, (Refereed)
Abstract [en]

Future cooperative Intelligent Transport Systems (ITS) applications aimed to improve safety, efficiency and comfort on our roads put high demands on the underlying wireless communication system. To gain better understanding of the limitations of the 5.9 GHz frequency band and the set of communication protocols for medium range vehicle to vehicle (V2V) communication, a set of field trials with CALM M5 enabled prototypes has been conducted. This paper describes five different real vehicle traffic scenarios covering both urban and rural settings at varying vehicle speeds and under varying line-of-sight (LOS) conditions and discusses the connectivity (measured as Packet Reception Ratio) that could be achieved between the two test vehicles. Our measurements indicate a quite problematic LOS sensitivity that strongly influences the performance of V2V-based applications. We further discuss how the awareness of these context-based connectivity problems can be used to improve the design of possible future cooperative ITS safety applications.

Place, publisher, year, edition, pages
Piscataway, N.J.: IEEE Press, 2010
Keyword
empirical study, field measurements, IEEE 802.11p, V2V communication, VANET
National Category
Computer and Information Science
Identifiers
urn:nbn:se:hh:diva-6004 (URN)10.1109/LCN.2010.5735781 (DOI)2-s2.0-79955007492 (Scopus ID)9781424483877 (ISBN)
Conference
35th Annual IEEE Conference on Local Computer Networks, LCN 2010, Denver, CO, USA, 10 - 14 October, 2010
Note

Article number 5735781; Code 84547

Available from: 2010-09-24 Created: 2010-09-24 Last updated: 2014-11-19Bibliographically approved

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
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  • Other locale
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Output format
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  • asciidoc
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