Hannes Hartenstein

Bio: Hannes Hartenstein is an academic researcher from Karlsruhe Institute of Technology. The author has contributed to research in topics: Vehicular ad hoc network & Wireless ad hoc network. The author has an hindex of 55, co-authored 234 publications receiving 14515 citations. Previous affiliations of Hannes Hartenstein include University of Mannheim & University of Freiburg.

GPU-Based Architectures and Their Benefit for Accurate and Efficient Wireless Network Simulations

Abstract: In recent years, a trend towards the usage of physical layer models with increased accuracy can be observed within the wireless network community. This trend has several reasons. The consideration of signals - instead of packets - as the smallest unit of a wireless network simulation enables the ability to reflect complex radio propagation characteristics properly, and to study novel PHY/MAC/NET cross-layer optimizations that were not directly possible before, e.g. cognitive radio networks and interference cancelation. Yet, there is a price to pay for the increase of accuracy, namely a significant decrease of runtime performance due to computationally expensive signal processing. In this paper we study whether this price can be reduced - or even eliminated - if GPU-based signal processing is employed. In particular, we present and discuss four different architectures that can be used to exploit GPU-based signal processing in discrete event-based simulations. Our evaluation shows that the runtime costs can not be cut down completely, but significant speedups can be expected compared to a non GPU-based solution.

Can V2X communication help electric vehicles save energy

Abstract: Battery electric vehicles (BEV) are envisioned to play a significant role in the future of personal mobility. A key challenge in the transition from internal combustion engine (ICE) powered vehicles to BEV is the limited driving range of the latter, which makes an energy-efficient operation essential. In this work, we analyze how vehicle-to-x (V2X) communication, in particular traffic-light-to-vehicle communication (TLVC), can help the drivers of BEVs save energy and thus increase driving range. Furthermore, we analyze factors impacting energy consumption which are relevant to the design of V2X applications for BEV. Our results indicate that TLVC can significantly reduce the energy consumption of BEV, up to 20% in our setup. The actual result, however, is highly dependent on a combination of traffic situation, communication range, auxiliary consumer power demand, road gradient and minimum speed requirement.

A Simulation Study of a Location Service for Position-Based Routing in Mobile Ad Hoc Networks

Abstract: Position-based routing in a mobile ad hoc network requires geographic addresses. Thus, a node that wants to send a packet to some target node has to know the target's (approximate) current position. In order to provide each node's position to the other network nodes, a distributed location service has to be used. J. Li et al. recently put forward a promising approach called the Grid Location Service' (GLS). In this paper we provide some analyses and evaluations of GLS by means of simulation with ns-2 beyond the results of the original paper. We present quantitative results with respect to location query failure rate and bandwidth consumption. We analyze in detail why queries failed and how the query failure rate can be decreased for scenarios with a low density of nodes.

Analysis of a Location Service for Position-Based Routing in Mobile Ad Hoc Networks

Abstract: Position-based routing in a mobile ad hoc network requires geographic addresses. Thus, a node that wants to send a packet to some target node has to know the target’s (approximate) current position. In order to provide each node’s position to the other network nodes, a distributed location service has to be used. J. Li et al. recently put forward a promising approach called the ‘Grid Location Service’ (GLS). In this paper we provide some analyses and evaluations of GLS by means of simulation with ns-2 beyond the results of the original paper. We present quantitative results with respect to location query failure rate and bandwidth consumption. We analyze in detail why queries failed and how the query failure rate can be decreased for scenarios with a low density of nodes.

Packet Forwarding in VANETs, the Complete Set of Results

Abstract: 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.

Random graphs

Abstract: We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Spray and wait: an efficient routing scheme for intermittently connected mobile networks

Abstract: Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.

Dedicated Short-Range Communications (DSRC) Standards in the United States

Abstract: Wireless vehicular communication has the potential to enable a host of new applications, the most important of which are a class of safety applications that can prevent collisions and save thousands of lives. The automotive industry is working to develop the dedicated short-range communication (DSRC) technology, for use in vehicle-to-vehicle and vehicle-to-roadside communication. The effectiveness of this technology is highly dependent on cooperative standards for interoperability. This paper explains the content and status of the DSRC standards being developed for deployment in the United States. Included in the discussion are the IEEE 802.11p amendment for wireless access in vehicular environments (WAVE), the IEEE 1609.2, 1609.3, and 1609.4 standards for Security, Network Services and Multi-Channel Operation, the SAE J2735 Message Set Dictionary, and the emerging SAE J2945.1 Communication Minimum Performance Requirements standard. The paper shows how these standards fit together to provide a comprehensive solution for DSRC. Most of the key standards are either recently published or expected to be completed in the coming year. A reader will gain a thorough understanding of DSRC technology for vehicular communication, including insights into why specific technical solutions are being adopted, and key challenges remaining for successful DSRC deployment. The U.S. Department of Transportation is planning to decide in 2013 whether to require DSRC equipment in new vehicles.

PORs: Proofs of Retrievability for Large Files

Abstract: In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

Securing vehicular ad hoc networks

Abstract: Vehicular networks are very likely to be deployed in the coming years and thus become the most relevant form of mobile ad hoc networks. In this paper, we address the security of these networks. We provide a detailed threat analysis and devise an appropriate security architecture. We also describe some major design decisions still to be made, which in some cases have more than mere technical implications. We provide a set of security protocols, we show that they protect privacy and we analyze their robustness and efficiency.