Ryan Wishart

Context obfuscation for privacy via ontological descriptions

Context information is used by pervasive networking and context-aware programs to adapt intelligently to different environments and user tasks. As the context information is potentially sensitive, it is often necessary to provide privacy protection mechanisms for users. These mechanisms are intended to prevent breaches of user privacy through unauthorised context disclosure. To be effective, such mechanisms should not only support user specified context disclosure rules, but also the disclosure of context at different granularities. In this paper we describe a new obfuscation mechanism that can adjust the granularity of different types of context information to meet disclosure requirements stated by the owner of the context information. These requirements are specified using a preference model we developed previously and have since extended to provide granularity control. The obfuscation process is supported by our novel use of ontological descriptions that capture the granularity relationship between instances of an object type.

SafeMesh: A wireless mesh network routing protocol for incident area communications

Reliable broadband communication is becoming increasingly important during disaster recovery and emergency response operations. In situations where infrastructure-based communication is not available or has been disrupted, an Incident Area Network needs to be dynamically deployed, i.e. a temporary network that provides communication services for efficient crisis management at an incident site. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with self-healing and self-configuring capabilities. These features, combined with the ability to provide wireless broadband connectivity at a comparably low cost, make WMNs a promising technology for incident management communications. This paper specifically focuses on hybrid WMNs, which allow both mobile client devices as well as dedicated infrastructure nodes to form the network and provide routing and forwarding functionality. Hybrid WMNs are the most generic and most flexible type of mesh networks and are ideally suited to meet the requirements of incident area communications. However, current wireless mesh and ad-hoc routing protocols do not perform well in hybrid WMN, and are not able to establish stable and high throughput communication paths. One of the key reasons for this is their inability to exploit the typical high degree of heterogeneity in hybrid WMNs. SafeMesh, the routing protocol presented in this paper, addresses the limitations of current mesh and ad-hoc routing protocols in the context of hybrid WMNs. SafeMesh is based on the well-known AODV routing protocol, and implements a number of modifications and extensions that significantly improve its performance in hybrid WMNs. This is demonstrated via an extensive set of simulation results. We further show the practicality of the protocol through a prototype implementation and provide performance results obtained from a small-scale testbed deployment.

Context privacy and obfuscation supported by dynamic context source discovery and processing in a context management system

The extensive context information collection abilities of ubiquitous computing environments represent a significant threat to user privacy. In this paper we address this threat by introducing a context information privacy mechanism. Our approach relies on context-dependent ownership definitions and context owner-specified privacy preferences to control context disclosure to third-parties. These privacy preferences enable context owners to stipulate not only to whom their context information can be disclosed and the conditions of disclosure, but also the level of detail at which the context information can be disclosed. Context information that cannot be disclosed at its existing level of detail is obfuscated to meet detail level requirements stipulated by its owner. To achieve this obfuscation of context information we introduce a new approach based on dynamic discovery and processing of context sources. Our new approach is demonstrated in a Context Management System in which context source discovery and processing is facilitated by the SensorML sensor description standard being developed by the Open Geospatial Consortium.

Multi-Linked AODV Routing Protocol for Wireless Mesh Networks

Nodes in multi-hop wireless networks, and specifically in ad-hoc and mesh networks, are being increasingly equipped with multiple wireless network interfaces (radios) operating on orthogonal channels to achieve better utilisation of the frequency spectrum. In addition to reducing interference via increased channel diversity, these additional interfaces can be used to create multiple concurrent links between adjacent nodes, i.e. nodes within single-hop range of each other. Information about the availability of multiple links between nodes provides the opportunity to increase the overall performance of the network by optimally balancing traffic between the set of available inter- node links. In this paper, we present extensions to the well known Ad-hoc On-demand Distance Vector (AODV) routing protocol with the aim to discover and exploit multiple links in Wireless Mesh Networks. As demonstrated via extensive simulations, Multi-Link AODV (AODV-ML) achieves a more than 100% improvement over standard multi-radio AODV in terms of key performance metrics such as packet delivery ratio, latency and routing overhead.

Extending context models for privacy in pervasive computing environments

Privacy is widely recognised as a significant obstacle inhibiting the adoption of context-aware applications. In order to remove this obstacle, advances are required in many areas of context-awareness research. In this paper, we address the incorporation of privacy support into context models. In particular, we present extensions to our context modelling approach that address the challenges of assigning ownership to context information and enabling users to express privacy preferences for their own information.

Congestion Aware Routing in Hybrid Wireless Mesh Networks

Multi-radio Wireless Mesh Networks (WMN) are gaining lot of popularity owing to their increased application to community and public safety networks. WMNs form a static wireless backhaul to provide connectivity to mobile clients. The wireless medium, being shared and contended for, creates a number of hurdles including congestion, interference and noise. Multi-radio nodes can take advantage of the wider frequency spectrum. However, current mesh technologies employ a simplistic approach by assigning one channel for client servicing and another for the backhaul network. The improper reuse of the same channel across multiple hops causes extensive co-channel interference leading to lower bandwidth. The problem is aggravated in a hybrid WMN where the mobile clients act as routers for other clients. In this paper, we propose a congestion aware routing protocol, which can successfully establish channel diverse routes through least congested areas of a hybrid WMN. The prime advantage of the protocol is its ability to discover optimal routes in a distributed manner without the requirement of an omniscient network entity. Simulation results show that the congestion aware routing protocol can successfully achieve a high packet delivery ratio with lower routing overhead and latency in a hybrid WMN.

Evaluation of Wireless Mesh Network Handoff Approaches for Public Safety and Disaster Recovery Networks

In public safety and disaster recovery (PSDR) scenarios, reliable communication is an imperative. Unfortunately, communication infrastructure is often destroyed or overwhelmed by whatever precipitated the scenario (e.g., a hurricane or terrorist attack). Thus, the PSDR workers must often deploy their own communications infrastructure on-site. Wireless mesh networks (WMN) have been identified as being ideally suited to this task. WMN offer a high-capacity wireless backhaul network, provided by mesh routers, through which clients can connect to one another or with external networks. Mobility of clients within the mesh is particularly important for public service and disaster recovery scenarios. This creates a challenging problem as clients may move out of range of the mesh router they were using to connect to the mesh and need to associate with another. Client handoff mechanisms provide this functionality. In this paper we provide a critical survey of client handoff approaches applicable to IEEE 802.11 WMN evaluating them based on the strict QoS requirements established by the US Department of Homeland Security for PSDR networks.

MeshVision: An Adaptive Wireless Mesh Network Video Surveillance System

The major surveillance camera manufacturers have begun incorporating wireless networking functionality into their products to enable wireless access. However, the video feeds from such cameras can only be accessed within the transmission range of the cameras. These cameras must be connected to backbone infrastructure in order to access them from more than one hop away. This network infrastructure is both time-consuming and expensive to install, making it impractical in many rapid deployment situations (for example to provide temporary surveillance at a crime scene). To overcome this problem, we propose the MeshVision system that incorporates wireless mesh network functionality directly into the cameras. Video streams can be pulled from any camera within a network of MeshVision cameras, irrespective of how many hops away that camera is. To manage the trade-off between video stream quality and the number of video streams that could be concurrently accessed over the network, MeshVision uses a Bandwidth Adaptation Mechanism. This mechanism monitors the wireless network looking for drops in link quality or signs of congestion and adjusts the quality of existing video streams in order to reduce that congestion. A significant benefit of the approach is that it is low cost, requiring only a software upgrade of the cameras.

MeshVision: an adaptive wireless mesh network video surveillance system

The major surveillance camera manufacturers have begun incorporating wireless networking functionality into their products to enable wireless access. However, the video feeds from such cameras can only be accessed within the transmission range of the cameras. These cameras must be connected to backbone infrastructure in order to access them from more than one hop away. This network infrastructure is both time-consuming and expensive to install, making it impractical in many rapid deployment situations (e.g., to provide temporary surveillance at a crime scene). To overcome this problem, we propose the MeshVision system that incorporates wireless mesh network functionality directly into the cameras. Video streams can be pulled from any camera within a network of MeshVision cameras, irrespective of how many hops away that camera is. To manage the trade-off between video stream quality and the number of video streams that could be concurrently accessed over the network, MeshVision uses a bandwidth adaptation mechanism. This mechanism monitors the wireless network looking for drops in link quality or signs of congestion and adjusts the quality of existing video streams in order to reduce that congestion. A significant benefit of the approach is that it is of low cost, requiring only a software upgrade of the cameras.

A Light-Weight Client Mobility Approach for Infrastructure Mesh Networks

Infrastructure mesh networks offer a high-capacity wireless backhaul network through which clients, such as PDAs, can connect to one another or with external networks. To use the mesh network, a client must route its outbound traffic via one of the mesh routers in the infrastructure mesh. As the clients are mobile, they may move out of range of the mesh router they were using and need to associate with another. Client handoff mechanisms enable this change in mesh routers to occur in a manner that limits disruption to any transport or application layer sessions the client may be running. In this paper we present an extremely light-weight handoff approach for clients that relies on gratuitous ARP messages broadcast at regular intervals from mesh routers within the infrastructure mesh. An evaluation of our approach using a 5 node testbed has shown that client handoffs can be conducted quickly, and with minimal loss of packets for both TCP and UDP traffic.