Pascal Lorenz

Wireless communication technologies for ITS applications [Topics in Automotive Networking]

Intelligent transport systems are the rising technology in the near future to build cooperative vehicular networks in which a variety of different ITS applications are expected to communicate with a variety of different units. Therefore, the demand for highly customized communication channel for each or sets of similar ITS applications is increased. This article explores the capabilities of available wireless communication technologies in order to produce a win-win situation while selecting suitable carrier( s) for a single application or a profile of similar applications. Communication requirements for future ITS applications are described to select the best available communication interface for the target application(s).

Networking — ICN 2001

A bandwidth management scheme is proposed that can support the seamless QoS in face of handoff in mobile networks. The proposed scheme is based on the time-selective bandwidth reservation with the reduced signaling and computational overhead. The reservation parameters are adjusted dynamically to cope with user mobility. Throughout the computer simulations, the performance of the proposed scheme is evaluated. The simulation results show that the handoff call blocking probability can be remarkably improved with a slight degradation of other parameters such as new call blocking probability and bandwidth utilization efficiency.

High-Speed Networks and Multimedia Communications

Various Internet applications involve multiple parties and usually adopt a one-to-many communication paradigm (multicast). The presence of multiple receivers in a multicast session rises the problem of inter-receiver fairness. Transmitting with a rate which matches the slowest receiver will limit the throughput of other receivers and thus their satisfaction. A multi-rate mechanism where the receivers are distributed into subgroups with similar capacities, can improve the inter-receiver fairness for multicast sessions. In this paper, we deal with the problem of receivers partitioning and propose a simple algorithm based on the receivers RTT variations where an explicit estimation of the receivers capacities is avoided. Our partitioning algorithm, although simple, performs an on-the-fly partitioning depending on the receivers’ feedback. We show that our partitioning algorithm approximates and in many cases, achieves the optimal solution with a minimum computation effort.

Telecommunications and Networking - ICT 2004

How to represent the genetic code? Despite the fact that it is extensively known, the DNA mapping into proteins remains as one of the relevant discoveries of genetics. However, modern genomic signal processing usually requires converting symbolic-DNA strings into complex-valued signals in order to take full advantage of a broad variety of digital processing techniques. The genetic code is revisited in this paper, addressing alternative representations for it, which can be worthy for genomic signal processing. Three original representations are discussed. The inner-to-outer map builds on the unbalanced role of nucleotides of a ‘codon’ and it seems to be suitable for handling information-theory-based matter. The two-dimensional-Gray map representation is offered as a mathematically structured map that can help interpreting spectrograms or scalograms. Finally, the world-map representation for the genetic code is investigated, which can particularly be valuable for educational purposes besides furnishing plenty of room for application of distance-based algorithms.

Connectivity, Energy and Mobility Driven Clustering Algorithm for Mobile Ad Hoc Networks

In the context of mobile ad hoc networks (MANETs) routing, we propose a clustering algorithm called Connectivity, Energy and Mobility driven Clustering Algorithm (CEMCA). The aim of CEMCA consists in appropriately choosing the cluster head to reduce routing overhead. In order to reduce traffic and energy consumption, the control messages are sent only when needed, according to the speed of the node. Each node has a quality that indicates its suitability as a cluster head. This quality takes into account the node connectivity, battery energy and mobility. These parameters are very important for the stability of the cluster. Simulation experiments are carried out to validate our algorithm in terms of stability of the clusters and their members and the quality of the connectivity. The results are compared to a previous approach called Weight Clustering Algorithm (WCA) and they show that CEMCA is performing better.

A survey of V2V channel modeling for VANET simulations

Most Vehicle to Vehicle (V2V) network protocols are evaluated by simulation. However in most network simulators, the physical layer suffers from a lack of realism. Therefore, realistic V2V channel modeling has become a crucial issue in Intelligent Transportation Systems (ITS) networks. V2V channels are known to exhibit specific features which imply the design of new simulation models. In this survey paper, we first recall the main physical features of such wireless time and frequency dispersive channels. Next, three “simulation-ready” V2V channel models found in the literature are reviewed. Finally, two complete VANET simulation frameworks are presented. They illustrate the importance of a realistic channel and physical layer modeling in vehicular networking.

Service Assurance with Partial and Intermittent Resources

In this paper we present a framework to mediate the allocation of bandwidth between adaptive and non-adaptive applications. The approach is based on utility function information and provides fair allocation solutions. Novel aggregate utility functions are proposed to allow the solution to scale according to the number of individual flows in the system and to facilitate implementation using common network mechanisms. Numerical results confirm the advantage of using our proposal to avoid the starvation problem whenever adaptive and non-adative flows share network links.Bandwidth Allocation.- Fair Bandwidth Allocation for the Integration of Adaptive and Non-adaptive Applications.- A Managed Bandwidth Reservation Protocol for Ad Hoc Networks.- Predictive Dynamic Bandwidth Allocation Based on Multifractal Traffic Characteristic.- Bandwidth Allocation Management Based on Neural Networks Prediction for VoD System Providers.- Policy-Based Operations.- Policy-Based Management of Grids and Networks Through an Hierarchical Architecture.- Policy-Based Service Provisioning for Mobile Users.- Dynamic IP-Grouping Scheme with Reduced Wireless Signaling Cost in the Mobile Internet.- 3G Wireless Networks Provisioning and Monitoring Via Policy Based Management.- Service Monitoring.- Combined Performance Analysis of Signal Level-Based Dynamic Channel Allocation and Adaptive Antennas.- Exploring Service Reliability for Content Distribution to Partial or Intermittent DVB-S Satellite Receivers.- Priority-Based Recovery Assurance for Double-Link Failure in Optical Mesh Networks with Insufficient Spare Resources.- Service Model and Its Application to Impact Analysis.- Intelligent Architectural Systems.- Active Networks and Computational Intelligence.- Distributed Artificial Intelligence for Network Management Systems - New Approaches.- Network Traffic Sensor for Multiprocessor Architectures: Design Improvement Proposals.- Software Modeling for Open Distributed Network Monitoring Systems.- Mobility and Wireless.- Analysis and Contrast Between STC and Spatial Diversity Techniques for OFDM WLAN with Channel Estimation.- Cumulative Caching for Reduced User-Perceived Latency for WWW Transfers on Networks with Satellite Links.- Mobility Agent Advertisement Mechanism for Supporting Mobile IP in Ad Hoc Networks.- Agent Selection Strategies in Wireless Networks with Multihomed Mobile IP.- Protocol Mechanisms.- An On-Demand QoS Routing Protocol for Mobile Ad-Hoc Networks.- Point-to-Group Blocking in 3-Stage Switching Networks with Multicast Traffic Streams.- Considerations on Inter-domain QoS and Traffic Engineering Issues Through a Utopian Approach.- Probabilistic Routing in Intermittently Connected Networks.- Performance Across Domains.- Communication Protocol for Interdomain Resource Reservation.- Performance Evaluation of Shortest Path Computation for IP and MPLS Multi-service Networks over Open Source Implementation.- Design and Evaluation of Redundant IPC Network Adequate for an Edge Router.- Leaky Bucket Based Buffer Management Scheme to Support Differentiated Service in Packet-Switched Networks.- An Improved Service Differentiation Scheme for VBR VoIP in Ad-Hoc Networks Connected to Wired Networks.

Object-oriented modeling and simulation of optical burst switching networks

Optical burst switching (OBS) is becoming an interesting technology for the optical Internet, since it does not need optical buffers like optical packet switching (OPS), and is capable of a better performance than optical circuit switching (OCS). Although OBS has been recently an object of intense research, it still raises a number of important questions. Due to the high costs of an OBS network infrastructure, simulators are a good choice for predicting the behavior of this kind of networks. In this paper, we describe the proposal, implementation and validation of a simulator for OBS networks. The simulator, named OBSim, mimics the behavior of OBS networks in an object-oriented approach.

A Stable Clustering Algorithm for Highly Mobile Ad Hoc Networks

The dynamic topology of ad hoc networks is an important issue on which a lot of research is carried out. Because of higher speeds of movement and networks of larger scale, the algorithms of auto-organization and clustering may be inefficient. Therefore, we propose a fully distributed clustering algorithm for mobile ad hoc networks in which the nodes can move at higher speeds. The main objectives of this algorithm consists in reducing the reconstruction of the topology and stabilizing it as a long time as possible. This clustering algorithm can be used by several routing algorithms for ad hoc networks. Under proper simulations, we show that optimal cluster head characteristics: connectivity, energy and mobility, lead to a stable topology in terms of reconfiguration frequency.

Fast address translation techniques for distributed shared memory compilers

The distributed shared memory (DSM) model is designed to leverage the ease of programming of the shared memory paradigm, while enabling the high-performance by expressing locality as in the message-passing model. Experience, however, has shown that DSM programming languages, such as UPC, may be unable to deliver the expected high level of performance. Initial investigations have shown that among the major reasons is the overhead of translating from the UPC memory model to the target architecture virtual addresses space, which can be very costly. Experimental measurements have shown this overhead increasing execution time by up to three orders of magnitude. Previous work has also shown that some of this overhead can be avoided by hand-tuning, which on the other hand can significantly decrease the UPC ease of use. In addition, such tuning can only improve the performance of local shared accesses but not remote shared accesses. Therefore, a new technique that resembles the translation look aside buffers (TLBs) is proposed here. This technique, which is called the memory model translation buffer (MMTB) has been implemented in the GCC-UPC compiler using two alternative strategies, full-table (FT) and reduced-table (RT). It would be shown that the MMTB strategies can lead to a performance boost of up to 700%, enabling ease-of-programming while performing at a similar performance to hand-tuned UPC and MPI codes.