Ashraf Wadaa

Training a wireless sensor network

The networks considered in this paper consist of tiny energy-constrained commodity sensors massively deployed, along with one or more sink nodes providing interface to the outside world. Our contribution is to propose a scalable energy-efficient training protocol for nodes that are initially anonymous, asynchronous and unaware of their location. Our training protocol imposes a flexible and intuitive coordinate system onto the deployment area and partitions the anonymous nodes into clusters where data can be gathered from the environment and synthesized under local control. An important by-product of the training protocol is a simple and natural data fusion protocol as well as an energy-efficient protocol for routing data from clusters to the sink node. Being energy-efficient, our training protocol can be run on either a scheduled or ad-hoc basis to provide robustness and dynamic reconfiguration. We also outline a way of making the training protocol secure by using a parameterized variant of frequency hopping.

On handling QoS traffic in wireless sensor networks

Many new routing and MAC layer protocols have been proposed for wireless sensor networks tackling the issues raised by the resource constrained unattended sensor nodes in large-scale deployments. The majority of these protocols considered energy efficiency as the main objective and assumed data traffic with unconstrained delivery requirements. However, the growing interest in applications that demand certain end-to-end performance guarantees and the introduction of imaging and video sensors have posed additional challenges. Transmission of data in such cases requires both energy and QoS aware network management in order to ensure efficient usage of the sensor resources and effective access to the gathered measurements. In this paper, we highlight the architectural and operational challenges of handling of QoS traffic in sensor networks. We report on progress make to-date and outline open research problems.

A service-centric model for wireless sensor networks

Most of the current research in wireless sensor networks (WSNs) is constraint driven and focuses on optimizing the use of limited resources (e.g., power) at each sensor. While such constraints are important, there is a energy for more general performance metrics to assess the effectiveness of WSNs. There is also a need for a unified formal model that would enable comparison of different types of WSNs and provide a framework for WSN operations. We propose a new service-centric model that focuses on services provided by a WSN and views a WSN as a service provider. A WSN is modeled at different levels of abstraction. For each level, a set of services and a set of metrics are defined. Services and their interfaces are defined in a formal way to facilitate automatic composition of services, and enable interoperability and multitasking of WSNs at the different levels. A two-way mapping between two neighboring levels is then defined as a decomposition (from higher to lower level) and composition (from lower to higher level). A composite mapping between metrics at different levels connects high-level, mission-oriented metrics and low-level, capability-oriented metrics. The service-centric model consists of mission, network, region, sensor, and capability layers. Each layer has associated semantics that use lower level components as syntactic units (except for the capability layer). Within each layer there are four planes or functionality sets; communication, management, application, and generational learning. The combination of layers and planes enables a service-based visualization paradigm that can provide better understanding of the WSN. The service-centric model provides a holistic approach to measuring and presenting WSNs effectiveness. In addition, it presents a general and flexible framework in which various more specific WSN models can be represented and evaluated.

Group key management scheme for large-scale sensor networks

Wireless sensor networks are inherently collaborative environments in which sensor nodes self-organize and operate in groups that typically are dynamic and mission-driven. Secure communications in wireless sensor networks under this collaborative model calls for efficient group key management. However, providing key management services in wireless sensor networks is complicated by their ad-hoc nature, intermittent connectivity, large scale, and resource limitations. To address these issues, this paper proposes a new energy-efficient key management scheme for networks consisting of a large number of commodity sensor nodes that are randomly deployed. All sensor nodes in the network are anonymous and are preloaded with identical state information. The proposed scheme leverages a location-based virtual network infrastructure and is built upon a combinatorial formulation of the group key management problem. Secure and efficient group key initialization is achieved in the proposed scheme by nodes autonomously computing, without any communications, their respective initial group keys. The key server, in turn, uses a simple location-based hash function to autonomously deduce the mapping of the nodes to their group keys. The scheme enables dynamic setup and management of arbitrary secure group structures with dynamic group membership.

Scalable cryptographic key management in wireless sensor networks

We propose a scalable key management scheme for sensor networks consisting of a large-scale random deployment of commodity sensor nodes that are anonymous. The proposed scheme relies on a location-based virtual network infrastructure and is built upon a combinatorial formulation of the group key management problem. Primary features of our scheme include autonomously computing group keys, and dynamically computing, using a simple hash function, the mapping of nodes to group keys. The scheme scales well in the size of the network and supports dynamic setup and management of arbitrary structures of secure group communications in large-scale wireless sensor network.

Towards a new paradigm for securing wireless sensor networks

The network model assumed in this paper consists of tiny, energy-constrained, commodity sensors massively deployed alongside with one or more sink nodes that provide the interface to the outside world. The sensors in the network are initially anonymous and unaware of their location. Our main contribution is to propose a new robust and energy-efficient solution for secure operation of wireless sensor networks. The paper motivates a new paradigm where security is based upon using parameterized frequency hopping and cryptographic keys in a unified framework to provide differential security services for wireless sensor networks.

On training a sensor network

The networks considered in this paper consist of tiny energy constrained commodity sensors massively deployed, along with one or more sink nodes providing interface to the outside world. Our contribution is to propose a scalable energy-efficient training protocol for nodes that are initially anonymous, asynchronous and unaware of their locations. Training partitions the nodes into clusters where data can be gathered from the environment and synthesized under local control. Further this training provides a virtual tree for efficient communication routing from clusters to the sink. Being energy-efficient, our training protocol can be run on either a scheduled or ad-hoc basis to provide robustness and dynamic reconfiguration.

On modeling wireless sensor networks

Summary form only given. Most of the current research in wireless sensor networks (WSN, for short) is constraint driven and focuses on optimizing the use of limited resources (for example, power) at each sensor. While such constraints are important, there is a need for more general performance metrics describing the effectiveness of WSNs. There is also a need for a unified model that would enable comparison of different types of WSNs. We propose a new service-centric model that focuses on services provided by a WSN and their corresponding performance metrics. A WSN is modeled at different levels of abstraction. For each level, a set of services and a set of metrics are defined. A mapping between metrics at different levels relates high-level, mission-oriented metrics to low-level capability-oriented metrics. The proposed model consists of mission, network, region, sensor, and capability layers. Within each layer, four planes are identified, namely, communications, management, application, and generation learning. The proposed model provides a flexible, open framework for expressing and evaluating capabilities, functionalities, management, behavior, and evolution of a WSN. In addition, the proposed model provides a holistic approach to comparing WSNs and to measuring their effectiveness. The generation learning plane is unique in that it serves to extend the longevity of the network and to enhance the network effectiveness over time.

Providing Holistic Security in Sensor Networks

We propose a new paradigm for the secure operation of wireless sensor networks. The network model assumed in this paper consists of tiny, energy -constrained, commodity sensors massively deployed alongside with one or more sink nodes that provide the interface to the outside world. The sensors in the network are initially anonymous and unaware of their location. Our main contribution is a scalable and energy -efficient solution where security is based upon using parameterized frequency hopping and cryptographic keys in a unified framework to provide differential security services for wireless sensor networks.

Minitrack Summary: Wireless Sensor Networks

The field of wireless sensor networks (WSNs) is maturing, and this year¿s contributions to this minitrack reflect this growing maturity with considerable breadth in the first session and depth in the second session.