Showing papers by "Hannes Hartenstein published in 2002"

Stochastic properties of the random waypoint mobility model: epoch length, direction distribution, and cell change rate

Abstract: The random waypoint model is a commonly used mobility model for simulations of wireless communication networks. In this paper, we present analytical derivations of some fundamental stochastic properties of this model with respect to: (a) the length and duration of a movement epoch, (b) the chosen direction angle at the beginning of a movement epoch, and (c) the cell change rate of the random waypoint mobility model when used within the context of cellular networks. Our results and methods can be used to compare the random waypoint model with other mobility models. The results on the movement epoch duration as well as on the cell change rate enable us to make a statement about the 'degree of mobility' of a certain simulation scenario. The direction distribution explains in an analytical manner the effect that nodes tend to move back to the middle of the system area.

A comparison of routing strategies for vehicular ad-hoc networks

Abstract: On this paper we investigate the use of ad-hoc routing algorithms for the exchange of data between vehicles There are two main aspects that are of interest in this context: the specific characteristics of ad-hoc networks formed by vehicles and the applicability of existing ad-hoc routing schemes to networks that display these characteristics In order to address both aspects we generate realistic vehicular movement patterns of highway traffic scenarios using a well validated traffic simulation tool Based on these patterns we show that the characteristics of vehicular ad-hoc networks are quite different from the frequently used random waypoint model We then proceed to evaluate the performance of a reactive ad-hoc routing protocol (DSR) and of a position-based approach (greedy forwarding as done in GPSR) in combination with a simple reactive location service Our analysis suggests that for vehicular networks where communication spans more than 2 or 3 hops position-! based ad-hoc routing has significant advantages over reactive non-position-based approaches both in the number of successfully delivered packets and in routing overhead

A Reactive Location Service for Mobile Ad Hoc Networks

Abstract: We present and analyze a reactive location service RLS for mobile ad hoc networks. RLS provides a mobile node in a wireless ad-hoc network with the means to inquire the current geographical position of another node on-demand and can be used as a building block for location-based routing. We provide a comparison of RLS to an ideal omniscient location service as well as to the complex Grid Location Service (GLS). In addition, we compare the performance of greedy location-based routing in combination with RLS to the performance of a non-location-based ad hoc routing approach, namely Dynamic Source Routing (DSR). DSR was chosen for the comparison since RLS can be considered an adaptation of DSR\'s route discovery mechanisms to the location-based domain. We also introduce and study possible optimizations for RLS, in particular caching, random re-broadcast jitter, and re-broadcast suppression. The quantitative results of our NS-2 simulation study show a very good perform! ance of RLS combined with greedy routing, outperforming GLS and DSR for scenarios with high mobility and high node density.

Analysis of a Location Service for a 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.

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.

Positionsbasiertes Routing für die Kommunikation zwischen Fahrzeugen (Position-Based Routing for Inter-Vehicle Communication)

Abstract: In the near future communication between vehicles by means of wireless technology will enhance both safety and comfort of the passengers. One main challenge in realizing this communication will be the routing of messages from one sender to one or more receivers. In this paper we propose a position-based ad-hoc routing protocol which solves this problem. In this protocol all vehicles work together, thus no pre-established infrastructure is required. As a consequence, the resulting network is inexpensive and robust. In order to prove the viability of the approach, a simulation study was performed using the ns-2 network simulator. As a basis for this study realistic car movement patterns were used. The study shows that even over large distances requiring message forwarding by multiple vehicles, high success rates for the delivery of messages are achieved.

A Robust Header Compression Simulator & Visualizer

Abstract: IP-based realtime multimedia communication provides for a large Layer-3 and Layer-4 header overhead due to usually small payload sizes of single packets in a realtime flow. Because of the restricted bandwidth of wireless links, header compression represents an essential prerequisite for the Mobile Internet, i.e., whenever an IP-based mobile end device has to communicate with an IP-based infrastructure. RFC 3095 on Robust Header Compression (ROHC) represents the state-of the-art header compression proposal. It provides a complex framework that allows to fine-tune compression efficiency versus robustness against link errors. We present a Java-based simulator/visualizer currently running ROHC Profile 2 (UDP/IP) in Uni-directional Mode that allows experimentation with all relevant ROHC parameters (like state transition timers and repeat counters) as well as with various link conditions. We present the implementation and report on simulation results. An average header length of about 2.8 bytes is achieved. In general, the tool is useful as an educational tool for assessing ROHC performance and to see Robust Header Compression 'at work', i.e., to explore the underlying parameter space. For the future, the simulator will be also used to generate realistic audio/video packet flows for evaluation with respect to audio/video decompression handling in the presence of packet losses.

Forwarding data, especially data packets, involves all suitable nodes receiving data, deciding using parameter(s) whether to forward to next or destination node or sender selecting node for forwarding

Abstract: The method involves forwarding data via different nodes (1-4,6) to the destination node (Z). A node is suitable for forwarding to the next node to the destination node if it can receive data from the sender. All suitable nodes can receive the data and each node can decide based on at least one parameter whether to forward to the next node or to the destination node or the sender (S) can select a node for forwarding by exchanging messages.