Small Worlds: Strong Clustering in Wireless Networks

Small-worlds represent efficient communication networks that obey two distinguishing characteristics: a high clustering coefficient together with a small characteristic path length. This paper focuses on an interesting paradox, that removing links in a network can increase the overall clustering coefficient. Reckful Roaming, as introduced in this paper, is a 2-localized algorithm that takes advantage of this paradox in order to selectively remove superfluous links, this way optimizing the clustering coefficient while still retaining a sufficiently small characteristic path length.Comment: To appear in: 1st International Workshop on Localized Algorithms and Protocols for Wireless Sensor Networks (LOCALGOS 2007), 2007, IEEE Compuster Society Pres

Localized Support for Injection Point Election in Hybrid Networks

Ad-hoc networks, a promising trend in wireless technology, fail to work properly in a global setting. In most cases, self-organization and cost-free local communication cannot compensate the need for being connected, gathering urgent information just-in-time. Equipping mobile devices additionally with GSM or UMTS adapters in order to communicate with arbitrary remote devices or even a fixed network infrastructure provides an opportunity. Devices that operate as intermediate nodes between the ad-hoc network and a reliable backbone network are potential injection points. They allow disseminating received information within the local neighborhood. The effectiveness of different devices to serve as injection point differs substantially. For practical reasons the determination of injection points should be done locally, within the ad-hoc network partitions. We analyze different localized algorithms using at most 2-hop neighboring information. Results show that devices selected this way spread information more efficiently through the ad-hoc network. Our results can also be applied in order to support the election process for clusterheads in the field of clustering mechanisms.Comment: The Sixth International Conference on Networking (ICN 2007

Multimedia Content Distribution in Hybrid Wireless Networks using Weighted Clustering

Fixed infrastructured networks naturally support centralized approaches for group management and information provisioning. Contrary to infrastructured networks, in multi-hop ad-hoc networks each node acts as a router as well as sender and receiver. Some applications, however, requires hierarchical arrangements that-for practical reasons-has to be done locally and self-organized. An additional challenge is to deal with mobility that causes permanent network partitioning and re-organizations. Technically, these problems can be tackled by providing additional uplinks to a backbone network, which can be used to access resources in the Internet as well as to inter-link multiple ad-hoc network partitions, creating a hybrid wireless network. In this paper, we present a prototypically implemented hybrid wireless network system optimized for multimedia content distribution. To efficiently manage the ad-hoc communicating devices a weighted clustering algorithm is introduced. The proposed localized algorithm deals with mobility, but does not require geographical information or distances.Comment: 2nd ACM Workshop on Wireless Multimedia Networking and Performance Modeling 2006 (ISBN 1-59593-485

A taxonomic Approach to Topology Control in Ad-hoc and Wireless Networks

Topology Control (TC) aims at tuning the topology of highly dynamic networks to provide better control over network resources and to increase the efficiency of communication. Recently, many TC protocols have been proposed. The protocols are designed for preserving connectivity, minimizing energy consumption, maximizing the overall network coverage or network capacity. Each TC protocol makes different assumptions about the network topology, environment detection resources, and control capacities. This circumstance makes it extremely difficult to comprehend the role and purpose of each protocol. To tackle this situation, a taxonomy for TC protocols is presented throughout this paper. Additionally, some TC protocols are classified based upon this taxonomy.Comment: The Sixth International Conference on Networking, ICN 200

HyCast-Podcast Discovery in Mobile Networks

Podcasts are a popular way to provide multimedia information about certain topics. A multitude of podcast servers exist in the Internet, allowing people to subscribe to them. Typically, podcasts are downloaded onto desktop computers and copied on mobile devices to be played while being on the move. In this paper, we extend the idea of podcasts, making them available in mobile network environments. In particular, HyCast does not rely on central podcast directories. Instead, HyCast also allows discovering, subscribing to, and downloading podcasts and episodes in the local neighborhood. For the dissemination of podcast information, we introduce and evaluate two different strategies. One is based on peer-to-peer communication between one-hop neighbors. The second one employs clustering to reduce the overhead of the podcast information dissemination

Stabilizing cluster structures in mobile networks for OLSR and WCPD as Basis for Service Discovery

International audienceService discovery is one of the most fundamental building blocks of self-organization. While mature approaches exist in the realm of fixed networks, they are not directly applicable in the context of MANETs. We investigate and compare two different protocols as basis for service discovery, namely OLSR and WCPD. OLSR is a proactive routing protocol while WCPD is a path discovery protocol integrating node and link stability criteria. Two conflicting objectives of service discovery are the coverage of service queries together with the required bandwidth. Simulations are performed based on a setting in a city center with human mobility. We show that OLSR outperforms WCPD in terms of coverage. Due to its proactive nature, however, bandwidth consumption is high. WCPD on the other hand is much more bandwidth efficient, but at the cost of lower coverage. Finally, we motivate employing OLSR on top of an overlay topology maintained by WCPD. This fosters stability while reducing overhead and keeping coverage high. As a first step towards a hybrid protocol, we aim at increasing the stability of the communication paths. To do so, an adaptive approach is used, which increases the robustness of the network topology structures

OLSR and WCPD as Basis for Service Discovery in MANETs

ISBN : 978-0-7695-3367-4International audienceService discovery is one of the most fundamental building blocks of self-organization. While mature approaches exist in the realm of fixed networks, they are not directly applicable in the context of MANETs. We investigate and compare two different protocols as basis for service discovery, namely OLSR and WCPD. OLSR is a proactive routing protocol while WCPD is a path discovery protocol integrating node and link stability criteria. Two conflicting objectives of service discovery are the coverage of service queries together with the required bandwidth. Simulations are performed based on a setting in a city center with human mobility. We show that OLSR outperforms WCPD in terms of coverage. Due to its proactive nature, however, bandwidth consumption is high. WCPD on the other hand is much more bandwidth efficient, but at the cost of lower coverage.Finally, we motivate employing OLSR on top of an overlay topology maintained by WCPD. This fosters stability while reducing overhead and keeping coverage high