| 1. |
- Bilstrup, Katrin, et al.
(författare)
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Evaluation of the IEEE 802.11p MAC method for vehicle-to-vehicle communication
- 2008
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Ingår i: 68th IEEE Vehicular Technology Conference, 2008. VTC 2008-Fall. - Piscataway, N.J. : IEEE Press. - 9781424417216 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- In this paper the medium access control (MAC) method of the upcoming vehicular communication standard IEEE 802.11p has been simulated in a highway scenario with periodic broadcast of time-critical packets (so-called heartbeat messages) in a vehicle-to-vehicle situation. The 802.11p MAC method is based on carrier sense multiple access (CSMA) where nodes listen to the wireless channel before sending. If the channel is busy, the node must defer its access and during high utilization periods this could lead to unbounded delays. This well-known property of CSMA is undesirable for time critical communications. The simulation results reveal that a specific node/vehicle is forced to drop over 80% of its heartbeat messages because no channel access was possible before the next message was generated. To overcome this problem, we propose to use self-organizing time division multiple access (STDMA) for real-time data traffic between vehicles. This MAC method is already successfully applied in commercial surveillance applications for ships (AIS) and airplanes (VDL mode 4). Our initial results indicate that STDMA outperforms CSMA for time-critical traffic safety applications in ad hoc vehicular networks.
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| 2. |
- Bilstrup, Katrin, et al.
(författare)
-
On the ability of the 802.11p MAC method and STDMA to support real-time vehicle-to-vehicle communications
- 2009
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - New York : Hindawi Publishing Corporation. - 1687-1472 .- 1687-1499. ; 2009:902414, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Traffic safety applications using vehicle-to-vehicle (V2V) communication is an emerging and promising area within the intelligent transportation systems (ITS) sphere. Many of these new applications require real-time communication with high reliability, meaning that packets must be successfully delivered before a certain deadline. Applications with early deadlines are expected to require direct V2V communications, and the only standard currently supporting this is the upcoming IEEE 802.11p, included in the wireless access in vehicular environment (WAVE) stack. To meet a real-time deadline, timely and predictable access to the channel is paramount. However, the medium access method used in 802.11p, carrier sense multiple access with collision avoidance (CSMA/CA), does not guarantee channel access before a finite deadline. In this paper, we analyze the communication requirements introduced by traffic safety applications, namely, low delay, reliable, real-time communications.We show by simulation of a simple, but realistic, highway scenario, that vehicles using CSMA/CA can experience unacceptable channel access delays and, therefore, 802.11p does not support real-time communications. In addition, we present a potential remedy for this problem, namely, the use of self-organizing time division multiple access (STDMA). The real-time properties of STDMA are investigated by means of the same highway simulation scenario, with promising results.
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| 3. |
- Bilstrup, Katrin, 1972, et al.
(författare)
-
On the ability of the IEEE 802.11p and STDMA to provide predictable channel access
- 2009
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Ingår i: Proceedings of the 16<sup>th</sup> World Congress on Intelligent Transport Systems (ITS). ; , s. 10-
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Konferensbidrag (refereegranskat)abstract
- Emerging traffic safety applications requiring low delay communications will need vehicle ad-hoc networks. The only communication standard currently supporting this is IEEE 802.11p. However, 802.11p uses the medium access method CSMA/CA, which has a major drawback: unbounded worst case channel access delay. We therefore propose an algorithm already in commercial use in the shipping industry: STDMA. With STDMA, nodes always get predictable channel access regardless of the number of competing nodes and the maximum delay is deterministic. In this paper we elaborated with different parameter settings for the two protocols with the aim of improving performance without altering the standards.
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| 4. |
- Bilstrup, Urban, et al.
(författare)
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The use of clustered wireless multihop networks in industrial settings
- 2007
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Ingår i: ETFA 2007. - Piscataway, NJ : IEEE Press. - 9781424408252 ; , s. 211-218
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Konferensbidrag (refereegranskat)abstract
- This paper suggests a cluster collision avoidance mechanism and a dual transceiver architecture to be used in a clustered wireless multihop network. These two contributions make the clustered wireless multihop network the preferred architecture for future industrial wireless networks. The wireless multihop cluster consists of one master and several slaves, where some of the slaves will act as gateways between different clusters. Frequency hopping spread spectrum is used on a cluster level and to avoid frequency collisions between clusters a "neighbor cluster collision avoidance mechanism" is proposed and evaluated through simulations. To break up the dependence between the clusters, introduced by the gateway nodes, each node is equipped with two transceivers. The paper is concluded with a suggestion to use a clustered wireless multihop network with orthogonal hopping sequences for an industrial setting.
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| 5. |
- Bilstrup, Urban, et al.
(författare)
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Using Dual-Radio Nodes to Enable Quality of Service in a Clustered Wireless Mesh Network
- 2006
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Ingår i: IEEE Conference on Emerging Technologies and Factory Automation, 2006. ETFA '06. - Piscataway, N.J. : IEEE Press. - 0780397584 ; , s. 54-61
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Konferensbidrag (refereegranskat)abstract
- In this paper some well established wireless technologies are merged into a new concept solution for a future industrial wireless mesh network. The suggested clustered wireless mesh network can handle probabilistic quality of service guarantees and is based on a dual-radio node architecture using synchronized frequency hopping spread spectrum Bluetooth radios. The proposed architecture gives a heuristic solution to the inter-cluster scheduling problem of gateway nodes in clustered architectures and breaks up the dependence between the local medium access schedules of adjacent clusters. The dual-radio feature also enables higher network connectivity, implying, for example, that a higher link redundancy can be achieved.
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| 6. |
- Bilstrup, Katrin
(författare)
-
A preliminary study of wireless body area networks
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this preliminary study is to introduce wireless body area networks (WBAN) to the reader but also to give an understanding of what possibilities and challenges there are when using short range wireless communication in this domain. Up to date, there is no standard specifically intended for low-power WBANs thus a developer is referred to use proprietary solutions which could be demanding to compare and choose. This study tries to provide the reader with the knowledge about important parameters in low-power sensor networks. Energy consumption is the really weak part of a wireless sensor network since the transceiver and other hardware equipment still drain batteries. For example the startup time for a transceiver that has been in power-down mode could consume as much as three times the energyas compared when sending the actual bits that invoked the transceiver in first place. The actual application must be the one driving the requirements on the communication. However, the application must be designed with for example the startup time in mind. A sensor network is a true cross-layer design problem where many different areas must meet such as hardware designers, application developers and communication people.
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| 7. |
- Bilstrup, Katrin
(författare)
-
A survey regarding wireless communication standards intended for a high-speed vehicle environment
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The high velocities and dynamic conditions that a vehicular environment represents introducenew and demanding challenges in the area of wireless communication. Vehicle Alert System(VAS) is a research project at Halmstad University, Sweden, focusing on reliable wirelessvehicle communication. Typical examples of applications for a vehicle alert system are pre-crash warning, communicating slippery road conditions, emergency vehicle routing etc. InVAS a set of application scenarios have been chosen specifically to illustrate as manyinteresting research aspects of a vehicle alert system as possible. The chosen scenarios includeboth vehicle-to-vehicle and vehicle-to-infrastructure communications. Research is conductedon all layers of the communication stack relevant for a vehicle alert system – application,network, data link and the physical layer. From a communication perspective a vehicle alertsystem is characterized by short event-driven control messages that have to be receivedwithout errors in time. This implies that different coding strategies, diversity andretransmission schemes must be used to achieve correctness and robustness against theimpairments of the wireless channel.This survey presents and discusses different wireless communication standards as well asproprietary solutions that are intended especially for a high-speed vehicular environment. Since VAS is aiming for real-time wireless communication, the examined standards will beevaluated accordingly. Real-time communication implies that there is an upper bound on thecommunication delay such that if the data never reaches its intended recipient before a certaindeadline this will have a more or less negative impact on the system performance. One of themost important features of a real-time communication system (and perhaps even more crucialin a wireless high-speed vehicular environment) is the medium access method. If it is notdeterministic (i.e., if there exists no upper bound on the delay before a station gets access tothe wireless channel) it is not possible to give guarantees about meeting the deadlines.All currently existing standards, draft specifications and proprietary solutions with explicitintention for being used in a vehicular environment are covered in this survey. In preparationof this document the standard/draft documents themselves have been studied and forproprietary solutions the respective company’s home pages and in some cases articles havebeen used for collecting information. One of the currently most discussed standards is thedraft IEEE 802.11p which has been thoroughly studied here. It inherits features from theQuality of Service amendment IEEE 802.11e and the physical layer supplement IEEE802.11a. The full protocol suite WAVE, also developed by IEEE, incorporates the 802.11p.Other standards, drafts and proprietary solutions that have been studied are IEEE 802.16,IEEE 802.20, flash-OFDM, national DSCR systems, CALM and IEEE 802.21. These systemsrange from being simple RFID-look-a-like DSRC systems to more advanced centralized WMAN standards. It can be concluded that none of the standards or proprietary solutions described in this surveyis suitable for applications such as those considered in the VAS research project. Within thedifferent standards there certainly are features suitable for a vehicle alert system but nostandard totally fit the requirements of VAS. One lacking feature common for all standardsinvestigated is the ability of providing deterministic medium access for vehicle-to-vehiclecommunication.
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| 8. |
- Bilstrup, Katrin, et al.
(författare)
-
Medium access control in vehicular networks based on the upcoming IEEE 802.11p standard
- 2008
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Ingår i: 15th World Congress on Intelligent Transport Systems and ITS America Annual Meeting 2008. - : World Congress on ITS. - 9781615677566 ; , s. 4155-4167, s. 12-
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Konferensbidrag (refereegranskat)abstract
- In this paper, initial simulations are presented showing that the upcoming IEEE 802.11p standard is not suitable for traffic safety applications requiring reliable, low delay communication between vehicles. The medium access control procedure is one of the most important parts in the design of delay-constrained communication systems, and emerging vehicle safety applications put new stringent demands on timely and reliable delivery of data packets. The medium access procedure used in 802.11p is carrier sense multiple access, which is inherently unsuitable for time-critical data traffic since it is contention-based and cannot provide a finite upper bound on the time to channel access. The simulation results indicate that with IEEE 802.11p, channel access cannot be granted in a manner that is sufficiently predictable to support reliable, low-delay communications between vehicles on a highway.
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| 9. |
- Bilstrup, Katrin, et al.
(författare)
-
Report on the Collaboration between CVIS and CERES in the Project Vehicle Alert System (VAS)
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In March 2007, an agreement was made for interchange of experiences between CVIS and the Centre for Research on Embedded Systems (CERES) at Halmstad University in Sweden. The majority of the work relating to this collaboration has been conducted within the CERES project Vehicle Alert System (VAS), aiming to use vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications to provide different types of warning messages. The main focus of the VAS project is on communication and in particular the lower layers of the communication stack are investigated. VAS involves academic researchers from Halmstad University as well as researchers from Volvo Technology, SP Technical Research Institute of Sweden and the company Free2move. This report presents the results of the VAS project, its publications, and other issues of interest both to the CVIS consortium as well as a broader scope.
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| 10. |
- Bilstrup, Katrin, et al.
(författare)
-
Vehicle Alert System
- 2007
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Ingår i: Proceedings of 14th world congress on intelligent transport system (ITS). ; , s. 2-9
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Konferensbidrag (refereegranskat)abstract
- The Vehicle Alert System (VAS) project focuses on cooperative alert services based on timely and reliable communication under the challenging circumstances pertaining to a highly mobile vehicular network. Through a cross-layer design, we gain the flexibility needed to adapt the system to the individual requirements of three chosen application scenarios that represent different situations where cooperation between vehicles can make a significant impact. The VAS project is a collaboration involving academic as well as industrial partners and the final stage of the project is a demonstrator that implements results from the research.
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