Network Coding in Disruption Tolerant Networks

In recent years, wireless communication technologies have been increasingly deployed in challenging environments where there is no communication infrastructure, as evidenced by the many efforts in building and deploying wireless sensor networks for wildlife tracking [22, 43], underwater sensor networks [38, 41]

Design and performance study of algorithms for consensus in sparse, mobile ad-hoc networks

PhD ThesisMobile Ad-hoc Networks (MANETs) are self-organizing wireless networks that consist of mobile wireless devices (nodes). These networks operate without the aid of any form of supporting infrastructure, and thus need the participating nodes to co-operate by forwarding each other’s messages. MANETs can be deployed when urgent temporary communications are required or when installing network infrastructure is considered too costly or too slow, for example in environments such as battlefields, crisis management or space exploration. Consensus is central to several applications including collaborative ones which a MANET can facilitate for mobile users. This thesis solves the consensus problem in a sparse MANET in which a node can at times have no other node in its wireless range and useful end-to-end connectivity between nodes can just be a temporary feature that emerges at arbitrary intervals of time for any given node pair. Efficient one-to-many dissemination, essential for consensus, now becomes a challenge: enough number of destinations cannot deliver a multicast unless nodes retain the multicast message for exercising opportunistic forwarding. Seeking to keep storage and bandwidth costs low, we propose two protocols. An eventually relinquishing (}RC) protocol that does not store messages for long is used for attempting at consensus, and an eventually quiescent (}QC) one that stops forwarding messages after a while is used for concluding consensus. Use of }RC protocol poses additional challenges for consensus, when the fraction, f n, of nodes that can crash is: 1 4 f n < 1 2 . Consensus latency and packet overhead are measured through simulation indicating that they are not too high to be feasible in MANETs. They both decrease considerably even for a modest increase in network density.Damascus University

Zuverlässige Gruppenkommunikation in mobilen Ad-hoc-Netzen auf Basis eines verzögerungstoleranten Kommunikationsdienstes

Ein zuverlässiges Netz für die Kommunikation ist die Basis für eine erfolgreiche Organisation und Koordination von Rettungskräften in Katastrophenfällen. Die heutige Kommunikationstechnik der Rettungskräfte basiert auf dem digitalen Funksystem Terrestrial Trunked Radio (TETRA). TETRA bietet keine ausreichende Datenrate für Multimediadaten und ist bei zerstörter Infrastruktur nur eingeschränkt nutzbar. Deshalb ist es notwendig die Kommunikation in Katastrophenfällen auf anderen Netztypen aufzubauen und Protokolle weiterzuentwickeln. Die vorliegende Arbeit befasst sich mit der zuverlässigen Gruppenkommunikation in Katastrophenfällen. Durch die oft fehlende Infrastruktur in solchen Szenarien, werden Mobile Ad-hoc Networks (MANETs) verwendet, um eine Kommunikation kurzfristig wieder herzustellen. MANETs bilden sich selbständig und sind in ihrer Reichweite eingeschränkt. Das kann dazu führen, dass mehrere zu einer Kommunikationsgruppe gehörende Kommunikationspartner nicht direkt miteinander verbunden sind. Um trotzdem eine Kommunikation zu ermöglichen, wurde unter Nutzung eines verzögerungstoleranten Kommunikationsdienstes (Delay Tolerant Networking (DTN)) ein Gruppenkommunikationsprotokoll entwickelt. Dieses Protokoll (Reliable Multicast over Delay Tolerant Mobile Ad Hoc Networks (RMDA)) übermittelt Gruppennachrichten mit einer hohen wählbaren Zuverlässigkeit an die gewünschten Gruppenmitglieder unter Optimierung des Speicherplatzbedarfs der DTN-Knoten.A reliable network for communication is the basis for a successful organization and coordination of rescue services in case of disasters. Today’s communication technology of the emergency services is based on the digital radio system Terrestrial Trunked Radio (TETRA). TETRA provides no sufficient data rates for multimedia data. In case of destroyed infrastructure it is available only to a limited extent. Therefore in case of disasters, it is necessary to provide communication services based on other network types and further development of protocols. This thesis is concerned with reliable group communication in disaster scenarios. By the frequent lack of infrastructure in such scenarios, Mobile Ad-hoc Networks (MANETs) are used to restore quickly. MANETs build themselves autonomously and are locally limited. As a result, group members belonging to one multicast group could be not directly connected. Therefore, to enable a communication, a group communication protocol was developed using a delay-tolerant communication service (Delay Tolerant Networking (DTN)). This protocol (Reliable Multicast over Delay Tolerant Mobile Ad Hoc Networks (RMDA)) sends group messages with selectable high degree of reliability to the desired group members, while optimizing the buffer required on the DTN nodes