| 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)
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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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| 3. |
- Morsi Mahmod, Mohamed, et al.
(författare)
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Wireless strategies for future and emerging ITS applications
- 2008
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Ingår i: 15th World Congress on Intelligent Transport Systems. - New York : World Congress on Intelligent Transport Systems (ITS). ; , s. 12-
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Konferensbidrag (refereegranskat)abstract
- Within the Intelligent Transportation Systems (ITS) field, many applications of a diverse nature are considered and thus their communication requirements differ significantly. This makes it difficult for one wireless carrier to support all or most of these applications. Therefore, we have complied a list of communication requirements for future ITS applications and used it to analyze different ITS applications as well as different wireless carriers. Accordingly, the applications can be grouped into different requirements profiles with recommended wireless carriers assigned to each profile. The concept of profiling can also be used to classify the applications according to their non-technical requirements and hence accelerate their future deployment by encouraging involved stakeholders to make the most common requirements available. It can also be useful when developing a roadmap for deployment of future ITS applications defining which application will most likely be implemented first.
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| 4. |
- Strandén, Lars, et al.
(författare)
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State of the art survey of wireless vehicular communication projects
- 2008
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Ingår i: 15th World Congress on Intelligent Transport Systems. - : World Congress on Intelligent Transport Systems (ITS). ; 8, s. 5656-5665
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Konferensbidrag (refereegranskat)abstract
- In this paper the results of a state of the art survey, using publicly available information, are presented. The scope of the survey concerns projects that include wireless communication vehicle-to-vehicle and vehicle-to-infrastructure. Since there is a vast amount of information available, a specific methodology has to be developed and applied. This paper presents such a methodology which is based on a matrix representation that enables the definition of specific metrics. These metrics can then be used for further evaluation. The objectives of this work are threefold; to gather relevant project information, to define and apply a methodology for handling this information, and to compare and draw some general conclusions about the nature of projects carried out in Europe, USA and Japan.
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| 5. |
- Uhlemann, Elisabeth, et al.
(författare)
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Hard decision packet combining methods for industrial wireless relay networks
- 2008
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Ingår i: Second International Conference on Communications and Electronics, 2008. ICCE 2008. - Piscataway, N.J. : IEEE Press. - 9781424424252 ; , s. 104-108
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Konferensbidrag (refereegranskat)abstract
- We consider wireless relay networks for use in industrial applications with strict requirements on both reliable and timely communications. In most cases commercially available transceivers must be used, which implies that only hard decision detector outputs are available. Since relay networks typically use retransmissions of erroneous packets, packet combining methods have the potential to increase the information reliability without excessive delay. We evaluate three different hard decision packet combining methods for different placement of the source, the relay node and the destination. Packet combining can in general be improved with knowledge of the current channel state information, which, however, is often not available. In this paper we find a packet combining method which does not use channel state information but which delivers similar performance as the scheme that has knowledge of the channel state.
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| 6. |
- Uhlemann, Elisabeth, et al.
(författare)
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Joint design of relay and packet combining schemes for wireless industrial networks
- 2008
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Ingår i: 2008 IEEE 67th Vehicular Technology Conference-spring. - Piscataway, N.J. : IEEE Press. - 9781424416448 ; , s. 2441-2445
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Konferensbidrag (refereegranskat)abstract
- Wireless industrial networks differ in many respects from other types of wireless networks. In particular, since many applications impose tight real-time and reliability requirements at the same time, and packet sizes tend to be small. In this paper we design a simple and practically implementable protocol in which relaying and packet combining work together to improve the probability that packets are delivered within a prescribed deadline over fading channels. The results indicate that such a combination can be fruitfully employed in wireless industrial networks.
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| 7. |
- Willig, Andreas, et al.
(författare)
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PRIOREL-COMB : A protocol framework supporting relaying and packet combining forwireless industrial networking
- 2008
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Ingår i: WFCS 2008. - Piscataway, NJ : IEEE Press. - 9781424423491 ; , s. 45-54
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Konferensbidrag (refereegranskat)abstract
- The PRIOREL-COMB framework presented here integrates support for relaying and packet combining into wireless industrial networks. The selection of suitable relay nodes is made using distributed algorithms which includes different eligibility tests as well as different priority assignments. The framework improves performance in terms of probability to successfully deliver packets before their deadline and it can be implemented on top of commercial transceivers without modification of the physical layer. This class of protocols will therefore be a valuable addition to future wireless industrial communication systems.
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