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  • 1.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers.
    Medium access control in vehicular networks based on the upcoming IEEE 802.11p standard2008In: 15th World Congress on Intelligent Transport Systems and ITS America Annual Meeting 2008, World Congress on ITS , 2008, 4155-4167 p.Conference paper (Refereed)
    Abstract [en]

    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.

  • 2.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers.
    Bilstrup, Urban
    Högskolan i Halmstad, Inbyggda system (CERES).
    Evaluation of the IEEE 802.11p MAC method for vehicle-to-vehicle communication2008In: 68th IEEE Vehicular Technology Conference, 2008. VTC 2008-Fall: IEEE Vehicular Technology Conference (VTC) (2008), Piscataway, N.J.: IEEE Press , 2008, Article number 4657278- p.Conference paper (Refereed)
    Abstract [en]

    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.

  • 3.
    Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Bilstrup, Urban
    Högskolan i Halmstad, Inbyggda system (CERES).
    On the ability of the 802.11p MAC method and STDMA to support real-time vehicle-to-vehicle communications2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2009, no 902414, 1-14 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 4.
    Mecklenbräuker, Christoph
    et al.
    Vienna University of Technology, Vienna, Austria.
    Bernadó, Laura
    FTW Forschungszentrum Telekommunikation Wien, Vienna, Austria.
    Klemp, Oliver
    BMW Forschung und Technik, Munich, Germany.
    Kwoczek, Andreas
    Volkswagen AG, Wolsburg, Germany.
    Paier, Alexander
    Vienna University of Technology, Vienna, Austria.
    Schack, Moritz
    Technische Universität Braunschweig, Braunschweig, Germany.
    Sjöberg, Katrin
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik
    Chalmers University of Technology, Gothenburg, Sweden.
    Tufvesson, Fredrik
    Lund University, Lund, Sweden.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Zemen, Thomas
    FTW Forschungszentrum Telekommunikation Wien, Vienna, Austria.
    Vehicle-to-Vehicle Communications2012In: Pervasive Mobile and Ambient Wireless Communications: Cost Action 2100 / [ed] Roberto Verdone & Alberto Zanella, London: Springer London , 2012, 577-608 p.Chapter in book (Other academic)
    Abstract [en]

    This chapter discusses major results and conclusions from Special Interest Group C bringing together various aspects of mobile to mobile communication from all working groups. Vehicle-to-vehicle communication scenarios are emphasized. Traffic telematics applications are currently under intense research and development for making transportation safer, more efficient, and cleaner. Communication systems which provide “always on” connectivity at data rates between 1 and 10 Mb/s to highly mobile surface traffic (cars and trains) are urgently required for developing traffic telematics applications and services. Currently much attention is given to advanced active safety, but the application area also ranges to improved navigation mechanisms and infotainment services. mobile to mobile communications need to be reliable and trusted: Drivers in cars which are equipped with vehicle to vehicle communications need to rely on the accuracy and timeliness of the exchanged data. Automotive manufacturers, road authorities, broadcast companies, and telecom providers are the key players in the value chain for such future systems. These communication systems provide an extended information horizon to warn the driver or the vehicular systems of potentially dangerous situations in an early phase.

  • 5.
    Sjöberg, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Karedal, Johan
    Dept. of Electrical and Information technology, Lund University.
    Moe, Marie
    Q-Free ASA, Trondheim, Norway.
    Kristiansen, Øyvind
    Q-Free ASA, Trondheim, Norway.
    Søråsen, Runar
    Q-Free ASA, Trondheim, Norway.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Tufvesson, Fredrik
    Dept. of Electrical and Information technology, Lund University.
    Evensen, Knut
    Q-Free ASA, Trondheim, Norway.
    Ström, Erik
    Dept. of Signals and Systems, Chalmers University of Technology.
    Measuring and using the RSSI of IEEE 802.11p2010Conference paper (Refereed)
    Abstract [en]

    The scalability of intelligent transport systems (ITS) applications is difficult to test in a field operational test (FOT) due to the high number of ITS equipped vehicles required. Therefore, computer simulations for evaluating different wireless communication technologies for ITS different applications can serve as a complement. In this paper we present results from lab measurements conducted on the CVIS hardware platform equipped with the upcoming standard IEEE 802.11p. We have measured the packet error rate versus the signal-to-noise ratio (SNR) for different packet lengths. This lab measurement is the first step towards an outdoor measurement campaign which also considers interference. The outdoor measurements will then be fed into a computer simulator together with a realistic channel model for evaluating the scalability of VANETs in a highway scenario.

  • 6.
    Sjöberg, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers Technical University, Gothenbur, Sweden.
    Delay and interference comparison of CSMA and self-organizing TDMA when used in VANETs2011In: IWCMC 2011: IWCMC 2011 - 7th International Wireless Communications and Mobile Computing Conference / [ed] IEEE, New York, NY: IEEE Press , 2011, 1488-1493 p.Conference paper (Refereed)
    Abstract [en]

    IEEE 802.11p is the proposed wireless technology for communication between vehicles in a vehicular ad hoc network (VANET) aiming to increase road traffic safety. In a VANET, the network topology is constantly changing, which requires distributed self-organizing medium access control (MAC) algorithms, but more importantly the number of participating nodes cannot be restricted. This means that MAC algorithms with good scalability are needed, which can fulfill the concurrent requirements on delay and reliability from road traffic safety applications. The MAC method of IEEE 802.11p is a carrier sense multiple access (CSMA) scheme, which scales badly in terms of providing timely channel access for a high number of participating nodes. We therefore propose using another MAC method: selforganizing time division multiple access (STDMA) with which all nodes achieve timely channel access regardless of the number of participating nodes. We evaluate the performance of the two MAC methods in terms of the MAC-to-MAC delay, a measure which captures both the reliability and the delay of the delivered data traffic for a varying number of vehicles. The numerical results reveal that STDMA can support almost error-free transmission with a 100 ms deadline to all receivers within 100 m, while CSMA suffers from packet errors. Moreover, for all considered cases, STDMA offers better reliability than CSMA.

  • 7.
    Sjöberg, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Chalmers University of Technology.
    How severe is the hidden terminal problem in VANETs when using CSMA and STDMA?2011In: IEEE Vehicular Technology Conference (VTC Fall) / [ed] IEEE, Piscataway, N.J.: IEEE conference proceedings , 2011, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    The hidden terminal problem is often said to be the major limiting performance factor in vehicular ad hoc networks. In this article we propose a definition of the hidden terminal problem suitable for broadcast transmissions and proceed with a case study to find how the packet reception probability is affected by the presence of hidden terminals. Two different medium access control methods; carrier sense multiple access (CSMA) from IEEE 802.11p and self-organizing time division multiple access (STDMA), are subject of investigation through computer simulations of a highway scenario with a Nakagami fading channel model. The results reveal that the presence of hidden terminals does not significantly affect the performance of the two MAC protocols. STDMA shows a higher packet reception probability for all settings due to the synchronized packet transmissions.

  • 8.
    Sjöberg-Bilstrup, Katrin
    et al.
    Högskolan i Halmstad, Inbyggda system (CERES).
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Ström, Erik G.
    Dept. Signals and Systems, Chalmers University of Technology.
    Scalability issues of the MAC methods STDMA and CSMA of IEEE 802.11p when used in VANETs2010In: 2010 IEEE International Conference on Communications Workshops (ICC), 2010, Article number 5503941- p.Conference paper (Refereed)
    Abstract [en]

    Position messages will be the foundation for many emerging traffic safety applications based on wireless communications. These messages contain information about the vehicle’s position, speed, direction, etc. and are broadcasted periodically by each vehicle. The upcoming IEEE 802.11p standard, intended for vehicle unpredictable behavior of its medium access control (MAC) scheme, which imply that traffic safety applications cannot be supported satisfactorily when the network load increases. We study the MAC mechanism within IEEE 802.11p being a carrier sense multiple access (CSMA) algorithm and compare it with a self-organizing time division multiple access (STDMA) scheme when used for broadcasting periodic position messages in a realistic highway scenario. We investigate their scalability in terms of the number of vehicles that the VANET can support using metrics such as channel access delay, probability of concurrent transmissions and interference distance. The results show that STDMA outperforms CSMA of 802.11p even when the network is not saturate

     

1 - 8 of 8
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