Florian Klingler

Use both lanes: Multi-channel beaconing for message dissemination in vehicular networks

We study the feasibility of multi-channel beaconing for efficient data dissemination in vehicular networks. Beaconing, i.e., sending small one-hop broadcasts in a periodic fashion, is now a state of the art method for information dissemination in vehicular networks. The main research challenge is to minimize the communication delay while efficiently using the wireless medium without ever overloading the wireless channel. Currently, several approaches to meet these demands can be identified, but they all share the disadvantage of using only a single wireless channel. This is a major bottleneck at high vehicle densities, leading to high delays or packet loss. In this work, we investigate the potentials of a multi-channel approach by extending the delay sensitive and congestion aware Adaptive Traffic Beacon (ATB) protocol to make full use of IEEE 802.11p/1609.4 DSRC/WAVE. We present a novel channel scheduling algorithm and incorporate it into an improved information dissemination protocol. We evaluate our approach in simulations, employing the extended protocol to allow vehicles to dynamically adapt their route to changing traffic conditions. We are able to demonstrate the feasibility of this multi-channel approach, showing that it successfully reduces the channel utilization and observed packet collisions without sacrificing the goodput.

Performance comparison of IEEE 802.11p and ARIB STD-T109

Vehicular networking is moving from pure research to first deployments around the world. This shifts the focus of research and development to aspects like higher layer performance; yet different regions (Japan, Europe and the U.S.) employ vastly different lower layer protocols for medium access and transmission. Without means to compare their performance it remains unclear to what degree simulation results obtained for one region (that is, one set of lower layer protocols) can be transferred to the other. Our paper fills this gap by conducting an extensive simulation study comparing the performance of IEEE 802.11p and ARIB T109 taking into account both their differences on the physical layer (5.9 GHz vs. 700 MHz band) as well as in medium access (pure CSMA/CA vs. a combination with TDMA). We base this study on the first Open Source implementation of the ARIB T109 standard we developed for the vehicular network simulation framework Veins. This also encompasses parameters for a computationally inexpensive shadow fading model for urban environments. We briefly report on the results of an extensive measurement campaign that underlies these parameters.

Faster distributed localization of large numbers of nodes using clustering

Chirp Spread Spectrum (CSS) based localization techniques are becoming more attractive as they provide improved localization accuracy and robustness compared to WiFi or ZigBee based approaches. However, a remaining problem is the necessary update frequency: In existing CSS based localization systems, the positions of the objects are determined one by one via unicast with nearby anchors instead of using broadcasts. We propose a faster distributed localization scheme for CSS based systems. A portion of nodes are considered cluster heads; they determine the locations of un-localized nodes by dynamically increasing the transmission power. Our novel scheme not only fully utilizes the spatial redundancy, which is crucial for speeding up the localization process. By also allowing to establish new anchors in a two-hop range, we can further increase speed without significantly influencing localization error. The performance of the proposed method is demonstrated through simulation.

IEEE 802.11p unicast considered harmful

We study the feasibility of IEEE 802.11p unicast communication in Vehicular Ad Hoc Networks (VANETs). In brief, we found unicast communication using MAC acknowledgement frames (ACKs) to be unsuitable for vehicular networks, because missing ACKs make protocol operations susceptible to pronounced head of line blocking effects. Worse, a transmit queue that is blocked by a missing ACK will delay messages for all protocols running on the same node that use the same access category. Other than in traditional networks, missing ACKs are especially prevalent in VANETs due to their high topology dynamics. Depending on the scenario, delays of messages could be shown to reach 200 ms and beyond - above the tolerable range of many VANET applications. Our findings are based on analytical calculations, measurements on hardware, as well as computer simulations; we conducted simulations both at small scale, for a baseline validation, and at a macroscopic level, to gauge the impact on a more complex protocol.

Demo: OpenC2X — An open source experimental and prototyping platform supporting ETSI ITS-G5

Vehicular networking is at the corner from early research to final deployment. This phase requires more field testing and real-world experimentation. Most Field Operational Tests (FOTs) are based on proprietary commercial hardware that only allows for marginal modifications of the protocol stack. Furthermore, the roll-out of updated implementations for new or changing protocol standards often takes a prohibitively long time. We developed one of the first complete Open Source experimental and prototyping platform for vehicular networking solutions. Our system supports most of the ETSI ITS-G5 features and runs on standard Linux. New protocol features and updates could now easily be done by and shared with the vehicular networking R&D community.

Reliable communication using Erasure Codes for monitoring bats in the wild

We show the feasibility of using Erasure Codes (ECs) for reliable communication in strongly energy-constrained sensor network applications. In particular, we aim at observing group dynamics of bats in their natural habitat. Bats are to be equipped with ultra-light sensor nodes to continuously monitor contacts between each other and to track their flights. This data needs to be uploaded to a stationary ground network whenever a bat comes into communication range. As the quality of this communication link is fluctuating, reliability improvement techniques need to be implemented. ECs allow to enhance the reliability of data transmissions with only a marginal overhead. After showing the improvements using ECs in simulation, we now implemented the full system using a prototype platform to study the general feasibility in a more realistic environment.

Not All VANET Broadcasts Are the Same: Context-Aware Class Based Broadcast

A major building block of Vehicular Ad Hoc Networks (VANETs) is broadcasting: the use of wireless communication for sharing information among vehicles, or between the vehicles and infrastructure. Dozens of broadcast protocols have been developed in recent years, including protocols for 1-hop broadcasting of vehicle status information (beaconing) and for geocasting-based applications. However, most of these protocols were designed for one application and cannot co-exist, nor can one broadcast solution meet the demands of all applications. These observations motivated our effort to develop a holistic network layer for VANETs. We identify the need for making VANET broadcast context-aware, and for supporting four different classes of broadcast protocols, each with its own properties. These classes are not only able to co-exist on the same network layer, but also to complement one another’s functionality. Thus, large applications as well as more holistic Transport protocols can be designed by combining two or more broadcast classes. We discuss the specific characteristics of these classes and design candidate protocols for each class.

Duplicate Suppression for Efficient Floating Car Data Collection in Heterogeneous LTE-DSRC Vehicular Networks

Abstract Collecting data from a large number of agents scattered over a region of interest is becoming an increasingly appealing paradigm to feed big data archives that lay the ground for a vast array of applications. Vehicular Floating Car Data (FCD) collection is a major representative of this paradigm. Massive data collection from floating vehicles is the key to Intelligent Transportation Systems. We address the design and performance evaluation of a data collection protocol for the use case of periodic data collection. We target robustness, optimizing the amount of data and the value of the collection period, keeping in mind the goals of autonomous node operation and minimal coordination effort. From a system point of view, we believe that best solutions should jointly exploit the Long Term Evolution (LTE) cellular access network and the Dedicated Short-Range Communication (DSRC) based Vehicular Ad Hoc Network (VANET). Through a detailed comparative analysis, we show that such a hybrid approach offers superior performance, especially as for offloading the cellular radio access. A lightweight signaling procedure is designed, based on the DSRC VANET, which is able to avoid most of the duplicated data records, even if a distributed operation approach is pursued. The impact of the proposed protocol on the VANET load is evaluated and proved to be quite small, so that it does not interfere with other VANET-specific messages.

Poster: Field Testing Vehicular Networks using OpenC2X

We present OpenC2X, an Open Source approach to field testing of vehicular networking solutions. Field Operational Test (FOT) and real-world experimentation are becoming more relevant to our research community as well as to industry and regulation. Unfortunately, available commercial solutions make experimental modifications to the protocol stack time consuming or prohibit it completely. To overcome this limitation, we implemented the ETSI ITS-G5 stack on a standard embedded PC hardware and running Linux system. OpenC2X is the first complete Open Source experimentation and prototyping platform. Our system is fully interoperable to commercial solutions, yet easily extensible with new protocols and applications for vehicular networks.

Poster: Connecting Simulation and Real World: IEEE 802.11p in the Loop

We present LAN Radio, an Open Source prototyping system to couple simulation and real world for the wireless channel of IEEE 802.11p based communication. Our main focus is the use in a vehicular networking environment, where field testing and real world experimentation is becoming more relevant these days. Large Field Operational Tests (FOTs) are expensive and difficult to handle in terms of reproducibility and controllability -- particularly for application development and integration tests for automotive Electronic Control Units (ECUs). To support such experiments, we developed an approach to integrate a real system to test into a large scale simulation scenario without the need to change the physical and access layer parts of the communication stack of this system. We closely followed the Hardware In The Loop (HIL) simulation concept but also integrated a wireless communication channel into the picture. LAN Radio is building upon the well established and Open Source development platform OpenWRT to provide optimal extensibility.