Hung Keng Pung

Ontology based context modeling and reasoning using OWL

Here we propose an OWL encoded context ontology (CONON) for modeling context in pervasive computing environments, and for supporting logic-based context reasoning. CONON provides an upper context ontology that captures general concepts about basic context, and also provides extensibility for adding domain-specific ontology in a hierarchical manner. Based on this context ontology, we have studied the use of logic reasoning to check the consistency of context information, and to reason over low-level, explicit context to derive high-level, implicit context. By giving a performance study for our prototype, we quantitatively evaluate the feasibility of logic based context reasoning for nontime-critical applications in pervasive computing environments, where we always have to deal carefully with the limitation of computational resources.

A service-oriented middleware for building context-aware services

The advancement of wireless networks and mobile computing necessitates more advanced applications and services to be built with context-awareness enabled and adaptability to their changing contexts. Today, building context-aware services is a complex task due to the lack of an adequate infrastructure support in pervasive computing environments. In this article, we propose a Service-Oriented Context-Aware Middleware (SOCAM) architecture for the building and rapid prototyping of context-aware services. It provides efficient support for acquiring, discovering, interpreting and accessing various contexts to build context-aware services. We also propose a formal context model based on ontology using Web Ontology Language to address issues including semantic representation, context reasoning, context classification and dependency. We describe our context model and the middleware architecture, and present a performance study for our prototype in a smart home environment.

A middleware for building context-aware mobile services

Computing becomes increasingly mobile and pervasive today; these changes imply that applications and services must be aware and adapt to highly dynamic environments. Today, building context-aware mobile services is a complex and time-consuming task. We present a service-oriented context-aware middleware (SOCAM) architecture for the building and rapid prototyping of context-aware mobile services. We propose an ontology-based approach to model various contexts. Our context model supports semantic representation, context reasoning and context knowledge sharing. We take a service-oriented approach to build our middleware which supports tasks including acquiring, discovering, interpreting, accessing various contexts and interoperability between different context-aware systems.

Toward an OSGi-based infrastructure for context-aware applications

Applications and services must adapt to changing contexts in dynamic environments. However, building context-aware applications is still complex and time-consuming due to inadequate infrastructure support. We propose a context-aware infrastructure for building and rapidly prototyping such applications in a smart-home environment. This OSGi-based infrastructure manages context-aware services reliably and securely and efficiently supports context acquisition, discovery, and reasoning. A formal, ontology-based context model enables semantic context representation, reasoning, and knowledge sharing. We propose an ontology-based context model that leverages Semantic Web technology and OWL (Web Ontology Language). OWL is an ontology markup language that enables context sharing and context reasoning. Based on our context model, we also propose a service-oriented context-aware middleware (SOCAM) architecture, including a set of independent services that perform context discovery, acquisition, and interpretation.

epSICAR: An Emerging Patterns based approach to sequential, interleaved and Concurrent Activity Recognition

Recognizing human activities from sensor readings has recently attracted much research interest in pervasive computing. This task is particularly challenging because human activities are often performed in not only a simple (i.e., sequential), but also a complex (i.e., interleaved and concurrent) manner in real life. In this paper, we propose a novel Emerging Patterns based approach to Sequential, Interleaved and Concurrent Activity Recognition (epSICAR). We exploit Emerging Patterns as powerful discriminators to differentiate activities. Different from other learning-based models built upon the training dataset for complex activities, we build our activity models by mining a set of Emerging Patterns from the sequential activity trace only and apply these models in recognizing sequential, interleaved and concurrent activities. We conduct our empirical studies in a real smart home, and the evaluation results demonstrate that with a time slice of 15 seconds, we achieve an accuracy of 90.96% for sequential activity, 87.98% for interleaved activity and 78.58% for concurrent activity.

Object relevance weight pattern mining for activity recognition and segmentation

Monitoring daily activities of a person has many potential benefits in pervasive computing. These include providing proactive support for the elderly and monitoring anomalous behaviors. A typical approach in existing research on activity detection is to construct sequence-based models of low-level activity features based on the order of object usage. However, these models have poor accuracy, require many parameters to estimate, and demand excessive computational effort. Many other supervised learning approaches have been proposed but they all suffer from poor scalability due to the manual labeling involved in the training process. In this paper, we simplify the activity modeling process by relying on the relevance weights of objects as the basis of activity discrimination rather than on sequence information. For each activity, we mine the web to extract the most relevant objects according to their normalized usage frequency. We develop a KeyExtract algorithm for activity recognition and two algorithms, MaxGap and MaxGain, for activity segmentation with linear time complexities. Simulation results indicate that our proposed algorithms achieve high accuracy in the presence of different noise levels indicating their good potential in real-world deployment.

Context-aware middleware for pervasive elderly homecare

The growing aging population faces a number of challenges, including rising medical cost, inadequate number of medical doctors and healthcare professionals, as well as higher incidence of misdiagnosis. There is an increasing demand for a better healthcare support for the elderly and one promising solution is the development of a context-aware middleware infrastructure for pervasive health/wellness-care. This allows the accurate and timely delivery of health/medical information among the patients, doctors and healthcare workers through a widespread deployment of wireless sensor networks and mobile devices. In this paper, we present our design and implementation of such a context-aware middleware for pervasive homecare (CAMPH). The middleware offers several key-enabling system services that consist of P2P-based context query processing, context reasoning for activity recognition and context-aware service management. It can be used to support the development and deployment of various homecare services for the elderly such as patient monitoring, location-based emergency response, anomalous daily activity detection, pervasive access to medical data and social networking. We have developed a prototype of the middleware and demonstrated the concept of providing a continuing-care to an elderly with the collaborative interactions spanning multiple physical spaces: person, home, office and clinic. The results of the prototype show that our middleware approach achieves good efficiency of context query processing and good accuracy of activity recognition.

NETWORKING 2008 Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet

Ad-Hoc and Sensor Networks.- XIAN Automated Management and Nano-Protocol to Design Cross-Layer Metrics for Ad Hoc Networking.- Cross-Layer Optimized Congestion, Contention and Power Control in Wireless Ad Hoc Networks.- Early Overhearing Avoidance in Wireless Sensor Networks.- Preamble MAC Protocols with Non-persistent Receivers in Wireless Sensor Networks.- An Overlay Maintenance Protocol for Overlay Routing on Top of Ad Hoc Networks.- An Overlay Architecture for Vehicular Networks.- DBR: Depth-Based Routing for Underwater Sensor Networks.- Channel Allocation for Multiple Channels Multiple Interfaces Communication in Wireless Ad Hoc Networks.- Resilience to Dropping Nodes in Mobile Ad Hoc Networks with Link-State Routing.- 3-D Localization Schemes of RFID Tags with Static and Mobile Readers.- Performance Evaluation and Enhancement of Surface Coverage Relay Protocol.- On Extending Coverage of UMTS Networks Using an Ad-Hoc Network with Weighted Fair Queueing.- Next Generation Internet.- A Performance Analysis of Authentication Using Covert Timing Channels.- PassPattern System (PPS): A Pattern-Based User Authentication Scheme.- A Secure and Efficient Three-Pass Authenticated Key Agreement Protocol Based on Elliptic Curves.- On the Robustness of Complex Networks by Using the Algebraic Connectivity.- On the Social Cost of Distributed Selfish Content Replication.- On Performance Evaluation of Handling Streaming Traffic in IP Networks Using TFRC Protocol.- Efficient Heuristic for Minimum Cost Trees Construction in Multi-Groups Multicast.- Delay Bounds and Scalability for Overlay Multicast.- A Distributed Algorithm for Overlay Backbone Multicast Routing in Content Delivery Networks.- Network Performance Assessment Using Adaptive Traffic Sampling.- On the Applicability of Knowledge Based NAT-Traversal for Home Networks.- IP Performance Management Infrastructure for ISP.- Can Critical Real-Time Services of Public Infrastructures Run over Ethernet and MPLS Networks?.- Shim6: Reference Implementation and Optimization.- A Measurement Study of Bandwidth Estimation in IEEE 802.11g Wireless LANs Using the DCF.- Hierarchical Logical Topology in WDM Ring Networks with Limited ADMs.- A Novel Class-Based Protection Algorithm Providing Fast Service Recovery in IP/WDM Networks.- End-to-End Proportional Loss Differentiation in OBS Networks.- The Effect of Peer Selection with Hopcount or Delay Constraint on Peer-to-Peer Networking.- T2MC: A Peer-to-Peer Mismatch Reduction Technique by Traceroute and 2-Means Classification Algorithm.- Towards an ISP-Compliant, Peer-Friendly Design for Peer-to-Peer Networks.- Cache Placement Optimization in Hierarchical Networks: Analysis and Performance Evaluation.- Towards a Two-Tier Internet Coordinate System to Mitigate the Impact of Triangle Inequality Violations.- Efficient Multi-source Data Dissemination in Peer-to-Peer Networks.- Modeling Priority-Based Incentive Policies for Peer-Assisted Content Delivery Systems.- AQCS: Adaptive Queue-Based Chunk Scheduling for P2P Live Streaming.- E2E Blocking Probability of IPTV and P2PTV.- Cooperative Replication in Content Networks with Nodes under Churn.- Congestion Avoiding Mechanism Based on Inter-domain Hierarchy.- A Novel Bandwidth Broker Architecture Based on Topology Aggregation in Delay|Bandwidth Sensitive Networks.- Client-Side Adaptive Search Optimisation for Online Game Server Discovery.- A Model for Endpoint Admission Control Based on Packet Loss.- Convergence of Intra-domain Routing with Centralized Control.- Improving the Interaction between Overlay Routing and Traffic Engineering.- Designing Optimal iBGP Route-Reflection Topologies.- A Study of Path Protection in Self-Healing Routing.- The CPBT: A Method for Searching the Prefixes Using Coded Prefixes in B-Tree.- On the Effectiveness of Proactive Path-Diversity Based Routing for Robustness to Path Failures.- On Robustness and Countermeasures of Reliable Server Pooling Systems Against Denial of Service Attacks.- DDoS Mitigation in Non-cooperative Environments.- Generalized Self-healing Key Distribution Using Vector Space Access Structure.- A Model for Covert Botnet Communication in a Private Subnet.- Traffic Engineering and Routing in IP Networks with Centralized Control.- Distributed PLR-Based Backup Path Computation in MPLS Networks.- Adaptive Multi-topology IGP Based Traffic Engineering with Near-Optimal Network Performance.- Modeling TCP in Small-Buffer Networks.- Active Window Management: Performance Assessment through an Extensive Comparison with XCP.- AIRA: Additive Increase Rate Accelerator.- Performance Evaluation of Quick-Start TCP with a Linux Kernel Implementation.- Lightweight Fairness Solutions for XCP and TCP Cohabitation.- Concurrent Multipath Transfer Using SCTP Multihoming: Introducing the Potentially-Failed Destination State.- Energy-Efficient Mobile Middleware for SIP on Ubiquitous Multimedia Systems.- A Secure Mechanism for Address Block Allocation and Distribution.- Asset Localization in Data Centers Using WUSB Radios.- Improving the Performance of DCH Timing Adjustment in 3G Networks.- Wireless Networks.- Link Adaptation Algorithm for the IEEE 802.11n MIMO System.- Thorough Analysis of 802.11e Star Topology Scenarios in the Presence of Hidden Nodes.- A Mobility-Adaptive TDMA MAC for Real-Time Data in Wireless Networks.- High Performance Distributed Coordination Function for Wireless LANs.- Turning Hidden Nodes into Helper Nodes in IEEE 802.11 Wireless LAN Networks.- Performance Evaluation of 802.11 Broadcasts for A Single Cell Network With Unsaturated Nodes.- Optimal Placement of Mesh Points in Wireless Mesh Networks.- A Distributed Channel Access Scheduling Scheme with Clean-Air Spatial Reuse for Wireless Mesh Networks.- A Unified Service Discovery Architecture for Wireless Mesh Networks.- Using Predictive Triggers to Improve Handover Performance in Mixed Networks.- Medium Access Cooperations for Improving VoIP Capacity over Hybrid 802.16/802.11 Cognitive Radio Networks.- ERA: Effective Rate Adaptation for WLANs.- On the Probability of Finding Non-interfering Paths in Wireless Multihop Networks.- Multi-commodity Flow Problem for Multi-hop Wireless Networks with Realistic Smart Antenna Model.- Evolutionary Power Control Games in Wireless Networks.

Performance modelling and evaluation of IEEE 802.11 distributed coordination function in multihop wireless networks

Initially designed for WLANs, IEEE 802.11 medium access control (MAC) has also been widely used in the research of multihop wireless networks. The core MAC technique of IEEE 802.11 is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme combined with binary exponential backoff (BEB). In this paper we present an analytical model to derive the saturation throughput of DCF in multihop wireless networks with nodes randomly placed according to a two-dimensional Poisson distribution. The proposed framework applies to both packet transmission schemes employed by DCF, namely, the basic access and the RTS/CTS access mechanisms. By means of the proposed model, we evaluate throughput performance of DCF in multihop wireless networks. Our model indicates that the RTS/CTS access method with the default parameters operates in a region almost optimal in terms of saturation throughput.

Towards a flexible service discovery

To support m-commerce applications, a service discovery mechanism where services can announce their presence and mobile users can locate these services is needed. Service discovery in dynamic mobile environments poses many challenges such as service providers may create and delete services or servers anytime; mobile services may be deployed in various forms, etc. In this paper, we propose a design for a Service Locating Service (SLS), which addresses some of these issues to provide a flexible service discovery mechanism for m-commerce applications. In our architecture, we adopt a dynamic tree structure for organizing SLS servers to meet the dynamic requirements of services and servers; we introduce service aggregation for fast locating; and we also propose multiple service matching mechanisms, which contain an attribute matching engine and a semantic matching engine for different service interfaces. We describe our concepts, architecture and implementation, and present a performance study for our prototype.