A one hop overlay system for Mobile Ad Hoc Networks

Peer-to-Peer (P2P) overlays were initially proposed for use with wired networks. However, the very rapid proliferation of wireless communication technology has prompted a need for adoption of P2P systems in mobile networks too. There are many common characteristics between P2P overlay networks and Mobile Ad-hoc Networks (MANET). Self-organization, decentralization, a dynamic nature and changing topology are the most commonly shared features. Furthermore, when used together, the two approaches complement each other. P2P overlays provide data storage/retrieval functionality and MANET provides wireless connectivity between clients without depending on any pre-existing infrastructure. P2P overlay networks can be deployed over MANET to address content discovery issues. However, previous research has shown that deploying P2P systems straight over MANET does not exhibit satisfactory performance. Bandwidth limitation, limited resources and node mobility are some of the key constraints. This thesis proposes a novel approach, OneHopOverlay4MANET, to exploit the synergies between MANET and P2P overlays through cross-layering. It combines Distributed Hash Table (DHT) based structured P2P overlays with MANET underlay routing protocols to achieve one logical hop between any pair of overlay nodes. OneHopOverlay4MANET constructs a cross-layer channel to permit direct exchange of routing information between the Application layer, where the overlay operates, and the MANET underlay layer. Consequently, underlay routing information can be shared and used by the overlay. Thus, OneHopOverlay4MANET reduces the typical management traffic when deploying traditional P2P systems over MANET. Moreover, as a result of building one hop overlay, OneHopOverlay4MANET can eliminate the mismatching issue between overlay and underlay and hence resolve key lookups in a short time, enhancing the performance of the overlay. v In this thesis, we present OneHopOverlay4MANET and evaluate its performance when combined with different underlay routing protocols. OneHopOverlay4MANET has been combined with two proactive underlays (OLSR and BATMAN) and with three reactive underlay routing protocols (DSR, AODV and DYMO). In addition, the performance of the proposed system over OLSR has been compared to two recent structured P2P over MANET systems (MA-SP2P and E-SP2P) that adopted OLSR as the routing protocol. The results show that better performance can be achieved using OneHopOverlay4MANET

Including context in a routing algorithm for the internet of things

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia InformáticaThe “Internet of Things” assumes that a large number of devices which are used on a daily basis will eventually become connected to the Internet. This scenario will provide room for a large set of new applications, however the network connections of an enormous set of nodes, which can be connected and disconnected, can move around and which have limitations with regards to their processing and communication capabilities, raises the need for the development of new message routing algorithms, different from those being in use today. In this thesis, a contribution is made towards the development of this type of algorithms. In particular, the idea which is tested is whether routing algorithms can improve their performance at various levels, such as, message delivery time, number of messages lost, power consumption, etc., if in the routing decisions these algorithms can make use of the concept of “Context”. Within the framework of this thesis, the “Context” is the organized collection of information which the routing algorithm collects from the environment surrounding the network nodes, and which allows it to make better routing decisions. This information can be related to low-level issues, such as, node location, power required to send a message, etc., as well as, with constraints related to the application, such as, message priority, maximum delivery time, etc. In order to evaluate this approach, this thesis proposes a routing algorithm called C-AODV. As the name suggests, it is based on the ADOV algorithm, however it is modified in several aspects; in particular, the possibility of using information collected from the context can be utilized to improve message routing. In order to test the proposed solution, several tests were performed on the NS-3 simulator which allowed the evaluation of the algorithm functionalities. The tests performed indicate that the proposed solution is valid

Hybrid routing in delay tolerant networks

This work addresses the integration of today\\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

Hybrid Routing in Delay Tolerant Networks

This work addresses the integration of today\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

Cross-layer Peer-to-Peer Computing in Mobile Ad Hoc Networks

The future information society is expected to rely heavily on wireless technology. Mobile access to the Internet is steadily gaining ground, and could easily end up exceeding the number of connections from the fixed infrastructure. Picking just one example, ad hoc networking is a new paradigm of wireless communication for mobile devices. Initially, ad hoc networking targeted at military applications as well as stretching the access to the Internet beyond one wireless hop. As a matter of fact, it is now expected to be employed in a variety of civilian applications. For this reason, the issue of how to make these systems working efficiently keeps the ad hoc research community active on topics ranging from wireless technologies to networking and application systems. In contrast to traditional wire-line and wireless networks, ad hoc networks are expected to operate in an environment in which some or all the nodes are mobile, and might suddenly disappear from, or show up in, the network. The lack of any centralized point, leads to the necessity of distributing application services and responsibilities to all available nodes in the network, making the task of developing and deploying application a hard task, and highlighting the necessity of suitable middleware platforms. This thesis studies the properties and performance of peer-to-peer overlay management algorithms, employing them as communication layers in data sharing oriented middleware platforms. The work primarily develops from the observation that efficient overlays have to be aware of the physical network topology, in order to reduce (or avoid) negative impacts of application layer traffic on the network functioning. We argue that cross-layer cooperation between overlay management algorithms and the underlying layer-3 status and protocols, represents a viable alternative to engineer effective decentralized communication layers, or eventually re-engineer existing ones to foster the interconnection of ad hoc networks with Internet infrastructures. The presented approach is twofold. Firstly, we present an innovative network stack component that supports, at an OS level, the realization of cross-layer protocol interactions. Secondly, we exploit cross-layering to optimize overlay management algorithms in unstructured, structured, and publish/subscribe platforms

Application Layer Architectures for Disaster Response Systems

Traditional disaster response methods face several issues such as limited situational awareness, lack of interoperability and reliance on voice-oriented communications. Disaster response systems (DRSs) aim to address these issues and assist responders by providing a wide range of services. Since the network infrastructure in disaster area may become non-operational, mobile ad-hoc networks (MANETs) are the only alternative to provide connectivity and other network services. Because of the dynamic nature of MANETs the applications/services provided by DRSs should be based on distributed architectures. These distributed application/services form overlays on top of MANETs. This thesis aims to improve three main aspect of DRSs: interoperability, automation, and prioritization. Interoperability enables the communication and collaboration between different rescue teams which improve the efficiency of rescue operations and avoid potential interferences between teams. Automation allows responders to focus more on their tasks by minimizing the required human interventions in DRSs. Automation also allows machines to operate in areas where human cannot because of safety issues. Prioritization ensures that emergency services (e.g. firefighter communications) in DRSs have higher priority to receive resources (e.g. network services) than non-emergency services (e.g. new reporters’ communications). Prioritizing vital services in disaster area can save lives. This thesis proposes application layer architectures that enable three important services in DRSs and contribute to the improvement of the three aforementioned aspects of DRSs: overlay interconnection, service discovery and differentiated quality of service (QoS). The overlay interconnection architecture provides a distributed and scalable mechanism to interconnect end-user application overlays and gateway overlays in MANETs. The service discovery architecture is a distributed directory-based service discovery mechanism based on the standard Domain Name System (DNS) protocol. Lastly, a differentiated QoS architecture is presented that provides admission control and policy enforcement functions based on a given prioritization scheme. For each of the provided services, a motivation scenario is presented, requirements are derived and related work is evaluated with respect to these requirements. Furthermore, performance evaluations are provided for each of the proposed architectures. For the overlay interconnection architecture, a prototype is presented along with performance measurements. The results show that our architecture achieves acceptable request-response delays and network load overhead. For the service discovery architecture, extensive simulations have been run to evaluate the performance of our architecture and to compare it with the Internet Engineering Task Force (IETF) directory-less service discovery proposal based on Multicast DNS. The results show that our architecture generates less overall network load and ensures successful discovery with higher probability. Finally, for the differentiated QoS architecture, simulations results show that our architecture not only enables differentiated QoS, it also improves overall QoS in terms of the number of successful overlay flows

Location-aware mechanism for efficient video delivery over wireless mesh networks

Due to their flexibility, ease of use, low-cost and fast deployment, wireless Mesh Networks have been widely accepted as an alternative to wired network for last-mile connectivity. When used in conjunction with Peer-to-Peer data transfer solutions, many innovative applications and services such as distributed storage, resource sharing, live TV broadcasting or Video on Demand can be supported without any centralized administration. However, in order to achieve a good quality of service in such variable, error-prone and resource-constrained wireless multi-hop environments, it is important that the associated Peer-to-Peer overlay is not only aware of the availability, but also of the location and available path link quality of its peers and services. This thesis proposes a wireless location-aware Chord-based overlay mechanism for Wireless Mesh Networks (WILCO) based on a novel geographical multi-level ID mapping and an improved finger table. The proposed scheme exploits the location information of mesh routers to decrease the number of hops the overlay messages traverse in the physical topology. Analytical and simulation results demonstrate that in comparison to the original Chord, WILCO has significant benefits: it reduces the number of lookup messages, has symmetric lookup on keys in both the forward and backward direction of the Chord ring and achieves a stretch factor of O(1). On top of this location-aware overlay, a WILCO-based novel video segment seeking algorithm is proposed to make use of the multi-level WILCO ID location-awareness to locate and retrieve requested video segments from the nearest peer in order to improve video quality. An enhanced version of WILCO segment seeking algorithm (WILCO+) is proposed to mitigate the sometimes suboptimal selection of the WILCO video segment seeking algorithm by extracting coordinates from WILCO ID to enable location-awareness. Analytical and simulation results illustrate that the proposed scheme outperforms the existing state-of-the-art solutions in terms of PSNR and packet loss with different background traffic loads. While hop count is frequently strongly correlated to Quality of Service, the link quality of the underlying network will also have a strong influence on content retrieval quality. As a result, a Cross-layer Wireless Link Quality-aware Overlay peer selection mechanism (WLO) is proposed. The proposed cross-layer mechanism uses a Multiplication Selector Metric (MSM) to select the best overlay peer. The proposed MSM overcomes the two issues facing the traditional summation-based metric, namely, the difficulty of bottleneck link identification and the influence of hop count on behavior. Simulation results show that WLO outperforms the existing state-of-the-art solutions in terms of video quality at different background loads and levels of topology incompleteness. Real life emulation-based tests and subjective video quality assessments are also performed to show that the simulation results are closely matched by the real-life emulation-based results and to illustrate the significant impact of overlay peer selection on the user perceived video quality

Integrating Wireless Sensor Networks and Mobile Ad-hoc NETworks for enhanced value-added services

In some situations where the standard telecommunication infrastructure is not available, Mobile Ad hoc NETworks (MANETs) can be deployed to provide the required communication. These networks are established "on the fly" without a need for prior communication organization and are composed of autonomous mobile devices, such as cell phones, PDAs or laptops. In similar conditions, such as in emergency response operations, integrating MANETs and Wireless Sensor Networks (WSNs) can notably enhance the MANET participant's end-user experience. WSNs sense and aggregate ambient information, such as physiological, environmental or physical data related to a nearby phenomenon. The integration, which provides end-user availability to WSN required information, is feasible via gateways. However, when the ambient information collected by WSNs is intended for applications residing in MANETs, centralized and fixed gateways are not practicably feasible. This is mainly due to ad-hoc nature, lack of centralized control and constraints on the end-user devices that are used in MANETs. These devices are usually limited in power and capacity and cannot host centralized gateways. In this thesis we exploit the integration of WSN and MANET in order to provide novel value-added services which enhance the end-user experience of MANET participants. Motivating scenarios are introduced, background information is presented, requirements are derived and the state of the art regarding the integration of WSN with existing networks, including MANETs, is evaluated. Based on the evaluation, none of the existing solutions satisfies all of our derived requirements. Therefore, we propose an overall two-level overlay architecture to integrate WSNs (with mobile sinks) and MANETs. This architecture is based on the distributed gateway and applications which form the P2P overlays. Overlays are application-layer networks which are created on top of the exiting MANET. To interconnect gateway and application overlays we derive corresponding requirements and evaluate the existing approaches. Since none of these approaches fulfills all of our requirements, we propose protocols, mechanisms and design corresponding modules for the interconnection of overlays. Finally we refine our overall architecture based on the interconnection aspects. As a proof of concept, we implement a prototype for the inter-overlay information exchange. This implementation is based on SIP extensions and uses two existing P2P middlewares. We also simulate our prototype using Oversim simulation tool and collect experimental results. Based on these results, we can see that our architecture is a valid and promising approach for interconnecting different P2P overlays and can be deployed to provide the overall solution for WSN and MANET integrated system

A Peer-to-Peer Network Framework Utilising the Public Mobile Telephone Network

P2P (Peer-to-Peer) technologies are well established and have now become accepted as a mainstream networking approach. However, the explosion of participating users has not been replicated within the mobile networking domain. Until recently the lack of suitable hardware and wireless network infrastructure to support P2P activities was perceived as contributing to the problem. This has changed with ready availability of handsets having ample processing resources utilising an almost ubiquitous mobile telephone network. Coupled with this has been a proliferation of software applications written for the more capable `smartphone' handsets. P2P systems have not naturally integrated and evolved into the mobile telephone ecosystem in a way that `client-server' operating techniques have. However as the number of clients for a particular mobile application increase, providing the `server side' data storage infrastructure becomes more onerous. P2P systems offer mobile telephone applications a way to circumvent this data storage issue by dispersing it across a network of the participating users handsets. The main goal of this work was to produce a P2P Application Framework that supports developers in creating mobile telephone applications that use distributed storage. Effort was assigned to determining appropriate design requirements for a mobile handset based P2P system. Some of these requirements are related to the limitations of the host hardware, such as power consumption. Others relate to the network upon which the handsets operate, such as connectivity. The thesis reviews current P2P technologies to assess which was viable to form the technology foundations for the framework. The aim was not to re-invent a P2P system design, rather to adopt an existing one for mobile operation. Built upon the foundations of a prototype application, the P2P framework resulting from modifications and enhancements grants access via a simple API (Applications Programmer Interface) to a subset of Nokia `smartphone' devices. Unhindered operation across all mobile telephone networks is possible through a proprietary application implementing NAT (Network Address Translation) traversal techniques. Recognising that handsets operate with limited resources, further optimisation of the P2P framework was also investigated. Energy consumption was a parameter chosen for further examination because of its impact on handset participation time. This work has proven that operating applications in conjunction with a P2P data storage framework, connected via the mobile telephone network, is technically feasible. It also shows that opportunity remains for further research to realise the full potential of this data storage technique