Peter Baumung

Improving delivery ratios for application layer multicast in mobile ad-hoc networks

Delivering multicast data using so-called overlay networks offers many advantages. Overlay networks only consisting of a multicast group’s members that are connected by means of transport links, non-members (especially routers) no longer need to bother about multicast routing and keeping a group’s state information. While existing application layer multicast protocols mainly were designed for the fixed Internet, first attempts to adapt such protocols for mobile ad-hoc networks start emerging. Because these adaptions however still suffer from a relatively high rate of packet losses, this paper outlines generic mechanisms that improve the overall delivery ratio for application layer multicast protocols. Although the proposed mechanisms are illustrated at the example of the NICE-MAN protocol (which is an adaption of the NICE protocol, originating from the Internet), they may be applied to arbitrary overlays. Furthermore, this paper shows how overlay networks combined with the developed mechanisms can be used, to significantly improve delivery ratios for existing multicast protocols (like ODMRP, M-AODV) that reside on the network layer.

Improving delivery ratios for application layer multicast in mobile ad hoc networks

Delivering multicast data using application layer approaches offers different advantages, as group members communicate using so-called overlay networks. These consist of a multicast groups members connected by unicast tunnels. Since existing approaches for application layer delivery of multicast data in mobile ad hoc networks (short MANETs) only deal with routing but not with error recovery, this paper evaluates tailored mechanisms for handling packet losses and congested networks. Although illustrated at the example of a specific protocol, the mechanisms may be applied to arbitrary overlays. This paper also investigates how application layer functionality based on overlay networks can turn existing multicast routing protocols (like ODMRP, M-AODV,...) into (almost) reliable transport protocols.

Stable, congestion-controlled application-layer multicasting in pedestrian ad-hoc networks

Ad-hoc networks enable mobile devices to communicate without any fixed infrastructure. While reliable multicasting has been identified as a key application in this context, we analyze different aspects of ad-hoc networks and their impact on application-layer multicast. As a result, we propose a technique of local broadcast-clustering, making use of the wireless mediums broadcast capability. We further describe a simple congestion control and also a technique for avoiding an overlays routing inconsistencies and, thus, for stabilizing the delivery of multicast data.

P2P-Based Semantic Service Management in Mobile Ad-hoc Networks

Service management in mobile ad-hoc networks has been a hot research topic in the past few years. With this demonstrator, we present the first service-oriented middleware that unifies semantic service description, service query management and Peer-to-Peer-based query dissemination. By adding a comfortable graphical interface on top of our middleware, we provide and demonstrate a fully functional software package that lets end-users elegantly manage and share application-level services on their wireless devices.

Banishing Patch-Cables from LAN Parties

Although playing real-time multi-player games online over the Internet became more and more popular in the past few years, people still enjoy meeting for so-called “LAN Parties” because of higher social interaction. As the number of participants increases, the deployment of the required infrastructure (i.e. the LAN) however gets more and more bothersome. With the current availability of computers featuring WLAN support, substituting the LAN by an infrastructureless ad-hoc network seems a long awaited and time-saving step. This paper investigates how the wireless environment, its scarce bandwidth and the strong requirements of multi-player games regarding packet latencies constrain the number of a WLAN party’s participants.

Application-Layer Multicast in MANETs: To Broadcast or not to Broadcast?

Mobile ad-hoc networks allow wireless devices to freely communicate without the need of any fixed infrastructure. While many applications rely on group communication, providing a multicast service on the network layer turns out to be difficult because of diverging application requirements. Research in the past year has thus focused on application-layer multicast protocols: These can easily be deployed among group members and flexibly be customized to meet an applications requirements. As group members handle packet duplication they are required to repeatedly access the medium for packet forwarding. Especially in areas of increased group member density this process can result in heavy performance degradation: Indeed, as in this area the wireless medium will be accessed respectively often for forwarding one single packet, the achievable multicast throughput will drop. Broadcast transmissions can improve the situation since one single medium access will forward a data packet to an arbitrary number of group members located within transmission range. With common MAC layers such as IEEE 802.11, broadcasts, however, are not covered by retransmissions and thus show to be more prone to packet errors than unicasts. Depending on the nature of emitted traffic and a multicast groups size, we in this paper analyze in which situations broadcasting data pays for application-layer multicast protocols and in which situations it hurts.