Protecting informative messages over burst error channels in chain-based wireless sensor networks

Regardless of the application, the way that data and information are disseminated is an important aspect in Wireless Sensor Networks (WSNs). The wireless data dissemination protocol should often guarantee a minimum reliability requirement. In this regard and to well-balance the energy and reliability, the more important packets should be protected by more powerful error control codes than the less important ones. This information-aware capability allows a system to deliver critical information with high reliability but potentially at a higher resource cost. In this paper, we first find and evaluate the factors that may influence the importance level of a packet and then design an error control approach by adaptively selecting codes for each individual links which experience long-term-fading and for each individual packet at run-time instead of applying network-wide settings prior to deployment. Moreover, we target the poor-explored chain-based topology that is of interest for many applications (e.g. monitoring bridge, tunnel, etc.). Simulation results validate the superiority of our approach compared with a number of Reed-Solomon-based error control approaches

Study of Reliable Data Communication in Wireless Sensor Networks

A distributed wireless sensor network consists of numerous tiny autonomous sensing nodes deployed across a wide geographical area. These sensor nodes self organize and establish radio communication links with the neighboring nodes to form multi-hop routing paths to the central base station. The dynamic and lossy nature of wireless communication poses several challenges in reliable transfer of data from the sensor nodes to the sink. There are several applications of sensor networks wherein the data collected by the sensors in the network are critical and hence have to be reliably transported to the sink. An example of such an application is sensors with RFID readers mounted on them to read tag information from the objects in a factory warehouse. Here, the tag information recorded by the RFID reader is a critical piece of information which may not be available at a later point of time and hence has to be reliably transported to the sink. We study the various issues and analyze the design choices proposed in literature in addressing the challenge of sensors-to-sink reliable data communication in such applications. A cross-layer based protocol with MAC layer retransmissions and NACK (Negative Acknowledgment) based rerouting of data packets is developed to overcome link failures and provide reliability. The protocol is implemented on TinyOS and the performance of NACK based rerouting protocol in terms of percentage successful message reception is compared with NACK based retransmission protocol by running simulations on TOSSIM. The NACK based rerouting protocol provides greater reliability under different metrics like varying network size, network traffic and percentage of failed links in the network

Improving network reliability by exploiting path diversity in ad hoc networks with bursty losses

In wireless mobile ad hoc networks, end-to-end connections are often subject to failures which do not make the connection non-operational indefinitely but interrupt the communication for intermittent short periods of time. These intermittent failures usually arise from the mobility of hosts, dynamics of the wireless medium or energy-saving mechanisms, and cause bursty packet losses. Reliable communication in this kind of an environment is becoming more important with the emerging use of ad hoc networks for carrying diverse multimedia applications such as voice, video and data. In this thesis, we present a new path reliability model that captures intermittent availability of the paths, and we devise a routing strategy based on our path reliability model in order to improve the network reliability. Our routing strategy takes the advantage of path diversity in the network and uses a diversity coding scheme in order not to compromise efficiency. In diversity coding scheme, if the original information is encoded by using a (N,K) code, then it is enough for the destination to receive any K bits correctly out of N bits to successfully decode the original information. In our scheme, the original information is divided into N subpackets and subpackets are distributed among the available disjoint paths in the network. The distribution of subpackets among the diverse paths is a crucial decision. The subpackets should be distributed 'intelligently' so that the probability of successful reconstruction of the original information is maximized. Given the failure statistics of the paths, and the code rate (N, K), our strategy determines the allocation of subpackets to each path in such a manner that the probability of reconstruction of the original information at the destination is maximized. Simulation results justify the accuracy and efficiency of our approach. Additionally, simulation results show that our multipath routing strategy improves the network reliability substantially compared to the single path routing. In wireless networks, a widely used strategy is to place the nodes into a low energy consuming sleep mode in order to prolong the battery life. In this study, we also consider the cases where the intermittent availability of the nodes is due to the sleep/awake cycles of wireless nodes. A sleep/awake scheduling strategy is proposed which minimizes the packet latency while satisfying the energy saving ratio specified by the energy saving mechanism

Design of implicit routing protocols for large scale mobile wireless sensor networks

Strathclyde theses - ask staff. Thesis no. : T13189Most developments in wireless sensor networks (WSNs) routing protocols address static network scenarios. Schemes developed to manage mobility in other mobile networking implementations do not translate effectively to WSNs as the system design parameters are markedly different. Thus this research focuses on the issues of mobility and scalability in order to enable the full potential of WSNs to self-organise and co-operate and in so doing, meet the requirements of a rich mix of applications. In the goal of designing efficient, reliable routing protocols for large scale mobile WSN applications, this work lays the foundation by firstly presenting a strong case supported by extensive simulations, for the use of implicit connections. Then two novel implicit routing protocols - Virtual Grid Paging (VGP) and Virtual Zone Registration and Paging (VZRP) - that treat packet routing from node mobility and network scalability viewpoints are designed and analysed. Implicit routing exploits the connection availability and diversity in the underlying network to provide benefits such as fault tolerance, overhead control and improvement in QoS (Quality of Service) such as delay. Analysis and simulation results show that the proposed protocols guarantee significant improvement, delivering a more reliable, more efficient and better network performance compared with alternatives.Most developments in wireless sensor networks (WSNs) routing protocols address static network scenarios. Schemes developed to manage mobility in other mobile networking implementations do not translate effectively to WSNs as the system design parameters are markedly different. Thus this research focuses on the issues of mobility and scalability in order to enable the full potential of WSNs to self-organise and co-operate and in so doing, meet the requirements of a rich mix of applications. In the goal of designing efficient, reliable routing protocols for large scale mobile WSN applications, this work lays the foundation by firstly presenting a strong case supported by extensive simulations, for the use of implicit connections. Then two novel implicit routing protocols - Virtual Grid Paging (VGP) and Virtual Zone Registration and Paging (VZRP) - that treat packet routing from node mobility and network scalability viewpoints are designed and analysed. Implicit routing exploits the connection availability and diversity in the underlying network to provide benefits such as fault tolerance, overhead control and improvement in QoS (Quality of Service) such as delay. Analysis and simulation results show that the proposed protocols guarantee significant improvement, delivering a more reliable, more efficient and better network performance compared with alternatives

Diseño e implementación de un protocolo de transporte para una red ieee 802.15.4 con protocolo de encaminamiento NST-AODV

Este trabajo se enmarca dentro de las redes de sensores de tipo mesh, redes sin infraestructura. Las redes de sensores están formadas por dispositivos inalámbricos de bajas prestaciones y consumo reducido con capacidad para actuar como terminal y router. Estas redes presentan enlaces de calidad variable, nodos con movilidad y velocidades de transmisión muy reducidas, obligando a la creación de una pila de protocolos nueva. Actualmente, un amplio porcentaje de los dispositivos utilizan módulos radio inalámbricos compatibles con el estándar IEEE 802.15.4. Este estándar cubre los niveles físico y de acceso al medio para abordar los problemas mencionados anteriormente

Diseño e implementación de un protocolo de transporte para una red ieee 802.15.4 con protocolo de encaminamiento NST-AODV

Este trabajo se enmarca dentro de las redes de sensores de tipo mesh, redes sin infraestructura. Las redes de sensores están formadas por dispositivos inalámbricos de bajas prestaciones y consumo reducido con capacidad para actuar como terminal y router. Estas redes presentan enlaces de calidad variable, nodos con movilidad y velocidades de transmisión muy reducidas, obligando a la creación de una pila de protocolos nueva. Actualmente, un amplio porcentaje de los dispositivos utilizan módulos radio inalámbricos compatibles con el estándar IEEE 802.15.4. Este estándar cubre los niveles físico y de acceso al medio para abordar los problemas mencionados anteriormente

Information assurance in sensor networks

Sensor networks are deployed to monitor the surroundings and keep the end-user informed about the events witnessed. Different types of events have different levels of importance for the user. Information Assurance is an ability to disseminate different information at different assurance levels to the end-user. The assurance level is determined by the criticality of the sensed phenomenon. Thus, information assurance capability allows a sensor network to deliver critical information with high assurance albeit potentially at a higher cost, while saving energy by delivering less important information at a lower assurance level. In this paper, we look at the problem of efficient information assurance in sensor networks when the assurance level of information is defined as the probability of information delivery (desired reliability) to the sink. We propose a new scheme for information delivery at a desired reliability using hop-by-hop broadcast. We show how the wireless broadcast can be utilized to increase the packet delivery rate at each hop and attain a desired reliability at minimal cost. Finally, we derive the optimal strategy for allocation of desired reliabilities at each hop in order to attain any given desired end-to-end reliability