This paper explores how an all pair shortest path can be obtained in a wireless sensor network when sensors fail. Sensors are randomly deployed in a predefined geographical area, simulating the deployment of sensors from an airplane, and finding shortest path between all the sensors deployed based on distance. A major problem to address in wireless sensor networks is the impact of sensor failures on existing shortest paths in the network. An application is developed to simulate a network and find shortest paths affected by a sensor failure and find alternative shortest path. When a sensor fails, all the shortest paths and all the remaining sensors in the network are checked to see if the sensor failure has any impact on the network. Alternative shortest path is calculated for those paths affected by sensor failures.

In recent years, the development of a large variety of mobile computing devices has led to wide scale deployment and use of wireless ad hoc and sensor networks. Wireless Sensor Networks consist of battery powered, tiny and cheap "motes", having sensing and wireless communication capabilities. Although wireless motes have limited battery power, communication and computation capabilities, the range of their application is vast. In the first part of the dissertation, we have addressed the specific application of Biomedical Sensor Networks. To solve the problem of data routing in these networks, we have proposed the Adaptive Least Temperature Routing (ALTR) algorithm that reduces the average temperature rise of the nodes in the in-vivo network while routing data efficiently. For delay sensitive biomedical applications, we proposed the Hotspot Preventing Routing (HPR) algorithm which avoids the formation of hotspots (regions having very high temperature) in the network. HPR forwards the packets using the shortest path, bypassing the regions of high temperature and thus significantly reduces the average packet delivery delay, making it suitable for real-time applications of in-vivo networks. We also proposed another routing algorithm suitable for being used in a network of id-less biomedical sensor nodes, namely Routing Algorithm for networks of homogeneous and Id-less biomedical sensor Nodes (RAIN). Finally we developed Biocomm, a cross-layer MAC and Routing protocol co-design for Biomedical Sensor Networks, which optimizes the overall performance of an in-vivo network through cross-layer interactions. We performed extensive simulations to show that the proposed Biocomm protocol performs much better than the other existing MAC and Routing protocols in terms of preventing the formation of hotspots, reducing energy consumption of nodes and preventing network congestion when used in an in-vivo network. In the second part of the dissertation, we have addressed the problems of habitat-monitoring sensor networks, broadcast algorithms for sensor networks and the congestion problem in sensor networks as well as one non-sensor network application, namely, on-chip communication networks. Specifically, we have proposed a variation of HPR algorithm, called Hotspot Preventing Adaptive Routing (HPAR) algorithm, for efficient data routing in Networks On-Chip catering to their specific hotspot prevention issues. A protocol similar to ALTR has been shown to perform well in a sensor network deployed for habitat monitoring. We developed a reliable, low overhead broadcast algorithm for sensor networks namely Topology Adaptive Gossip (TAG) algorithm. To reduce the congestion problem in Wireless Sensor Networks, we proposed a tunable cross-layer Congestion Reducing Medium Access Control (CRMAC) protocol that utilizes buffer status information from the Network layer to give prioritized medium access to congested nodes in the MAC layer and thus preventing congestion and packet drops. CRMAC can also be easily tuned to satisfy different application-specific performance requirements. With the help of extensive simulation results we have shown how CRMAC can be adapted to perform well in different applications of Sensor Network like Emergency Situation that requires a high network throughput and low packet delivery latency or Long-term Monitoring application requiring energy conservation.

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Today, wireless sensor networks (WSNs) are no longer a nascent technology and future networks, especially Cyber-Physical Systems (CPS) will integrate more sensor-based systems into a variety of application scenarios. Typical application areas include medical, environmental, military, and commercial enterprises. Providing security to this diverse set of sensor-based applications is necessary for the healthy operations of the overall system because untrusted entities may target the proper functioning of applications and disturb the critical decision-making processes by injecting false information into the network. One way to address this issue is to employ en-route-filtering-based solutions utilizing keys generated by either static or dynamic key management schemes in the WSN literature. However, current schemes are complicated for resource-constrained sensors as they utilize many keys and more importantly as they transmit many keying messages in the network, which increases the energy consumption of WSNs that are already severely limited in the technical capabilities and resources (i.e., power, computational capacities, and memory) available to them. Nonetheless, further improvements without too much overhead are still possible by sharing a dynamically created cryptic credential. Building upon this idea, the purpose of this thesis is to introduce an efficient and secure communication framework for WSNs. Specifically, three protocols are suggested as contributions using virtual energies and local times onboard the sensors as dynamic cryptic credentials: (1) Virtual Energy-Based Encryption and Keying (VEBEK); (2) TIme-Based DynamiC Keying and En-Route Filtering (TICK); (3) Secure Source-Based Loose Time Synchronization (SOBAS) for WSNs.

An opportunistic large array (OLA) is a form of cooperative diversity in which a large group of simple, inexpensive relays or forwarding nodes operate without any mutual coordination, but naturally fire together in response to energy received from a single source or another OLA. When used for broadcast, OLAs form concentric rings around the source, and have been shown to use less energy than conventional multi-hop protocols. This simple broadcasting scheme, which is already known, is called Basic OLA. The OLA Concentric Routing Algorithm (OLACRA), which is our contribution, takes advantage of the concentric ring structure of broadcast OLAs to limit flooding on the upstream connection. By limiting the node participation, OLACRA saves over 80% of the energy compared to Basic OLA, without requiring GPS, individual node addressing, or inter-node interaction. This thesis analyzes the performance of OLACRA over 'deterministic channels' where transmissions are on non-faded orthogonal channels and on 'diversity channels' where transmissions are on Rayleigh flat fading limited orthogonal channels. The performance of diversity channels is shown to approach the deterministic channel at moderate orders of diversity. Enhancements to OLACRA to further improve its efficiency by flooding in the initial upstream level and limiting the downlink 'step sizes' are also considered. The protocols are tested using Monte Carlo evaluation.

Master of Science / Department of Computing and Information Sciences / Gurdip Singh / Ad hoc based routing protocol is a reactive protocol to route messages between mobile nodes. It allows nodes to pass messages through their neighbors to nodes which they cannot directly communicate. It uses Route Request (RREQ) and Route Reply (RREP) messages for communication. Wireless sensor networks consist of tiny sensor motes with capabilities of sensing, computation and wireless communication. This project aims to implement data collector application to collect the temperature data from the set of wireless sensor devices located within a building, which will help in gathering the information by finding the route with minimum number of hops to reach destination and generates low message traffic by not encouraging the duplicate message within the network. Using this application, wireless devices can communicate effectively to provide the network information to the user. This system consists of a mobile wireless sensor device called base station which is connected to a PC to communicate and is the root of the network. It also consists of set of client sensor devices which are present in different parts of the building. This project has been evaluated by determining how well the ad hoc protocol performs by measuring the number of messages and time consumed in learning about the complete topology. This application will eventually find the path with minimum number of hops. Simple Network Management Protocol (SNMP) is also used to monitor the sensor nodes remotely. This project was developed using nesC and C programming languages with TinyOS and UNIX based operating systems. It has been tested with a sufficient number of motes and evaluated based on the number of messages generated and number of hops traveled for each route request.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Several algorithms have been proposed for solving constraint satisfaction and the more general constraint optimization problem in a distributed manner. In this paper we apply two such algorithms to the task of dynamic resource allocation in the sensor network domain using appropriate abstractions. The aim is to effectively track multiple targets by making the sensors coordinate with each other in a distributed manner, given a probabilistic representation of tasks (targets). We present simulation results and compare the performance of the DBA and DSA algorithms under varying experimental settings.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Sensor networks can demand large amounts of bandwidth if the raw sensor data is transferred to a central location. Feature recognition and sensor fusion algorithms can reduce this bandwidth. Unfortunately the designers of the system, having not yet seen the data which will be collected, may not know which algorithms should be used at the time the system is first installed. This paper describes a flexible architecture which allows the deployment of data reduction algorithms throughout the network while the system is in service. The network of sensors approach not only allows for signal processing to be pushed closer to the sensor, but helps accommodate extensions to the system in a very efficient and structured manner.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / Recent technological advancements in low-power, low-cost, small-footprint embedded processors, sensors, and radios are resulting in the very rapid growth of wireless sensor network deployments. Wireless sensor networks merge the scalability and distributed nature of networked systems with the size and energy constraints of remote embedded systems. With the ever increasing need to develop less intrusive, more scalable solutions for instrumentation systems, wireless sensor technologies present several benefits. They largely eliminate the need for power and network wiring, thus potentially reducing cost, weight, and deployment time; their modularity provides the flexibility to rapidly change instrumentation configurations and the capability to increase the coverage of an instrumentation system. While the benefits are exciting and varied, as with any emerging technology, many challenges need to be overcome before wireless sensor networks can be effectively and successfully deployed in instrumentation applications, including throughput, latency, power management, electromagnetic interference (EMI), and band utilization considerations. This paper describes some approaches to addressing these challenges and achieving a useful system.