Interference in vehicle-to-vehicle communication networks - analysis, modeling, simulation and assessment

In wireless vehicular communication networks the periodic transmission of status updates by all vehicles represents a basic service primitive, in particular for safety related applications. Due to the limited communication resources the question raises how much data each node may provide such that the quality of service required by applications can still be guaranteed under realistic interference conditions. Local broadcasts capacity is introduced and analyzed to tackle this open question

Bug Fixes on the IEEE 802.11 DCF module of the Network Simulator ns-2.28

The Network Simulator 2 (ns-2) is largely the most used simulator in the Ad Hoc research community. However, the 802.11 DCF module implemented in the default distribution of ns-2 presents some bugs, i.e., discordances with the IEEE 802.11 Standard specifications. We present in this Technical Report the result of an extensive analysis of both the IEEE 802.11 DCF specification and the ns-2 module. We first describe the discordances found with respect to the different DCF.s procedures. Second, we describe the different behavior corresponding to the physical layer capture model that current wireless interfaces present. Finally we provide in the Appendix all source code modified in the different ns-2.28 files. All modified source code files can be found for download at http://dsn.tm.uni-karlsruhe.de/ns-2.28-DCF-PHY-UKA.php

Cumulative Noise and 5.9 GHz DSRC Extensions for ns-2.28

The network simulator ns-2 is a widely used tool in the field of wired and wireless communications research. Although the ns-2 implementation is in constant evolution, it fails, for obvious reasons, to reflect all aspects related to the newest communication technologies. One example of such technology is 5.9GHz Direct Short Range Communications (DSRC) for vehicular environments, which is currently attracting attention due to its promises to reduce the amount of road fatalities and improve vehicular traffic efficiency on public roads. The IEEE 802.11p group is currently developing a standard to enable future 5.9GHz DSRC based inter-vehicle communications. In this report, we describe the modifications realized in ns-2 in order to model more accurately future wireless communications in vehicular environments. Section 2 reports the extensions performed to the PHY and MAC modules in order to include cumulative noise capabilities. Note that vehicular environments are specially sensible to the way interferences are modeled since safety related information will be commonly transmitted in a broadcast fashion. Section 3 describes the adjustments required to the MAC and PHY modules to reflect the behavior described in the current draft of IEEE 802.11p

Interference in vehicle-to-vehicle communication networks - analysis, modeling, simulation and assessment

In wireless vehicular communication networks the periodic transmission of status updates by all vehicles represents a basic service primitive, in particular for safety related applications. Due to the limited communication resources the question raises how much data each node may provide such that the quality of service required by applications can still be guaranteed under realistic interference conditions. Local broadcasts capacity is introduced and analyzed to tackle this open question

Packet Forwarding in VANETs, the Complete Set of Results

The discrepancy between real-world radio channel behavior and its standard modeling in simulations (Unit Disk Graph) is a major reason for protocols to perform different – often worse – than predicted when deployed in a real-world setup. As researchers having to deal with real ad hoc networks are aware of, assuming a fixed border for a node’s communication range might not only lead to inaccurate results but also to a wrong judgment on the comparison between different protocols. We have set up a simulation study to investigate the effects of realistic channel characteristics on packet forwarding strategies for vehicular ad hoc networks. The contributions of this technical report are threefold: i) We provide a performance evaluation of various routing/forwarding strategies under the realistic non-deterministic Nakagami radio propagation model and compare the results with the ones obtained using the standard Two-Ray-Ground model. Validated German highway movement patterns are used to model node mobility. ii) We demonstrate that realistic channel conditions present an opportunity and not only a drawback for some forwarding strategies. More specifically, we show that for contention-based forwarding (CBF) techniques, realistic channel characteristics provide a positive impact in terms of an increased average hop distance. iii) We provide an analytical derivation of the expected hop distance for CBF that provides a basis to optimally adjust CBF parameters.

10402 Report -- Working Group on Communication Patterns

The objective of the working group communication patterns during the Dagstuhl Seminar on Vehicular Networks has been to review the current status of the communication patterns and principles and discuss the upcoming challenges the community will face in the near future. This is an executive summary of the discussions during the sessions