Daniel Görgen

JANE-The Java Ad Hoc Network Development Environment

This work describes a Java based development platform which is intended to support ad hoc network researchers in application and protocol design. Software development within this environment is expected to follow a bottom up approach. Basic functionality is implemented in elementary components which can be combined to more complex ones by using well defined interfaces. With dynamically changing network links being rather the common case than a failure situation, asynchronous communication has been selected as the main communication paradigm within this platform. Reusability of components in different execution contexts by providing an appropriate machine abstraction is a further important design decision which drove the platform development. Code written once can be executed in a pure simulation mode, in a hybrid setting with real devices being attached to a running simulation and, finally, in a setting using real devices only. Software development following this three-tier development process paired with the platforms rich visualization features emerged to significantly ease the burden of debugging and parameterizing in such highly dynamic and inherently distributed environments. In conjunction with a core middleware platform a rich set of generic services has been implemented with the most important ones being described in this work. Several application programs have already been implemented on top of these services. These applications which are described in this work as well serve as a proof of concept for both the platform itself and the utilized set of generic services

Planar graph routing on geographical clusters

Geographic routing protocols base their forwarding decisions on the location of the current device, its neighbors, and the packets destination. Early proposed heuristic greedy routing algorithms might fail even if there is a path from source to destination. In recent years several recovery strategies have been proposed in order to overcome such greedy routing failures. Planar graph traversal was the first of those strategies that does not require packet duplication and memorizing past routing tasks. This article introduces a novel recovery strategy based on the idea of planar graph traversal but performing routing tasks along geographical clusters instead of individual nodes. The planar graph construction method discovered so far needs one-hop neighbor information only, but may produce disconnection even if there is a path from source to destination. However, simulation results show that the proposed algorithm is a good choice from a practical point of view, since disconnection does only concern sparse networks, while in dense network the proposed algorithm competes with existing solutions and even outperforms planar graph routing methods based on one-hop neighbor information. This paper finally gives an outline of further research directions which show that geographical clusters may be the key to solve some problems that come along with planar graph routing in wireless networks.

Geographical Cluster-Based Routing in Sensing-Covered Networks

The relationship between coverage and connectivity in sensor networks has been investigated in recent research treating both network parameters in a unified framework. It is known that networks covering a convex area are connected if the communication range of each node is at least twice a unique sensing range used by each node. Furthermore, geographic greedy routing is a viable and effective approach providing guaranteed delivery for this special network class. In this work, we will show that the result about network connectivity does not suffer from generalizing the concept of sensing coverage to arbitrary network deployment regions. However, dropping the assumption that the monitored area is convex requires the application of greedy recovery strategies like traversing a locally extracted planar subgraph. This work investigates a recently proposed planar graph routing variant and introduces a slight but effective simplification. Both methods perform message forwarding along the edges of a virtual overlay graph instead of using wireless links for planar graph construction directly. In general, there exist connected network configurations where both routing variants may fail. However, we will prove three theoretical bounds which are a sufficient condition for guaranteed delivery of these routing strategies applied in specific classes of sensing covered networks. By simulation results, we show that geographical cluster-based routing outperforms existing related geographical routing variants based on one-hop neighbor information. Furthermore, simulations performed show that geographical cluster-based routing achieves a comparable performance compared to variants based on two-hop neighbor information, while maintaining the routing topology consumes a significantly reduced amount of communication resources

A Java-Based Uniform Workbench for Simulating and Executing Distributed Mobile Applications

Spontaneous multihop networks with high device mobility and frequent fluctuations are interesting platforms for future distributed applications. Because of the large number of mobile devices required for any detailed analysis, it is nearly impossible to deploy prototype applications yet. In this paper, a comprehensive approach is presented which supports experiments ranging from pure simulation of several thousand mobile devices over hybrid scenarios with interaction among simulated as well as real life devices up to dedicated field trials. Part of this paper are also conclusions drawn from experiences with a first prototype version of a self-organized auction system for ad-hoc networks.

Information Dissemination Based on the En-Passant Communication Pattern

This work presents a communication pattern for high mobile ad hoc networks. En-passant communication uses the short interaction period of passing devices to efficiently synchronize the information of each device. This is achieved by creating peer-to-peer overlays of interest domains. Missing information is determined by exchanging profiles first. As example application UbiQuiz is presented, a mobile quiz application. It exchanges questions using the en-passant communication pattern. UbiQuiz has been implemented, tested and evaluated within a simulation and on real devices.

Marketplaces as Communication Patterns in Mobile Ad-Hoc Networks*

This paper proposes a novel communication pattern for mobile multihop ad-hoc networks which is based on a marketplace metaphor. In order to substantially increase the probability that negotiating peers sucessfully reach an agreement, communication is focused on a static geographic area, called the marketplace. Users are not constrained to be at the marketplace physically, but are allowed to utilize other ones mobile devices located at the marketplace to let a software agent or a service installed on each device negotiate with others on their behalf. The forwarding and negotiation protocols needed to implement the marketplace solution are described in this work. Additionally, a prototypical implementation of the protocols is evaluated in a simulation environment. Since simulation results strongly depend on the mobility model, three realistic models based on an extension of the random way-point model are used. Their movement patterns are resulting from persons on a music festival, a university campus, and an exhibition.

Geographical cluster based routing in sensing-covered networks

The relationship between coverage and connectivity in sensor networks has been investigated in recent research treating both network parameters in a unified framework. It is known that networks covering a convex area are connected if the communication range of each node is at least twice a unique sensing range used by each node. Furthermore, geographic greedy routing is a viable and effective approach providing guaranteed delivery for this special network class. In this work, we will show that the result about network connectivity does not suffer from generalizing the concept of sensing coverage to arbitrary network deployment regions. However, dropping the assumption that the monitored area is convex requires the application of greedy recovery strategies like traversing a locally extracted planar subgraph. This work investigates a recently proposed planar graph routing variant and introduces a slight but effective simplification. Both methods perform message forwarding along the edges of a virtual overlay graph instead of using wireless links for planar graph construction directly. In general, there exist connected network configurations where both routing variants may fail. However, we will prove three theoretical bounds which are a sufficient condition for guaranteed delivery of these routing strategies applied in specific classes of sensing covered networks. By simulation results, we show that geographical cluster-based routing outperforms existing related geographical routing variants based on one-hop neighbor information. Furthermore, simulations performed show that geographical cluster-based routing achieves a comparable performance compared to variants based on two-hop neighbor information, while maintaining the routing topology consumes a significantly reduced amount of communication resources

ADS as Information Management Service in an M-Learning Environment

Leveraging the potential power of even small handheld devices able to communicate wirelessly requires dedicated support. In particular, collaborative applications need sophisticated assistance in terms of querying and exchanging different kinds of data. Using a concrete example from the domain of mobile learning, the general need for information dissemination is motivated. Subsequently, and driven by infrastructural conditions, realization strategies of an appropriate middleware service based upon an information market model are discussed.