Azman Osman Lim

Activity Recognition Using Context-Aware Infrastructure Ontology in Smart Home Domain

Nowadays, activity recognition has been proposed in several researches. It is attractive to improve the ability of the activity recognition system because existing research on activity recognition systems still have an error in an ambiguous cases. In this paper, we introduce the novel technique to improve the activity recognition system in smart home domain. We propose the three contributions in this research. Firstly, we design the context-aware infrastructure ontology for modelling the users context in the smart home. The innovative data, human posture, is added into the users context for reducing the ambiguous cases. Secondly, we propose the concepts to distinguish the activities by object-based and location-based concepts. We also present the description logic (DL) rules for making the human activity decision based on our proposed concepts. Lastly, We conduct the Ontology Based Activity Recognition (OBAR) system for two purposes: to recognize the human activity, and to search the semantic information in the system, called semantic ontology search (SOS) system. The results show the system can recognize the human activity correctly and also reduce the ambiguous case.

A hybrid centralized routing protocol for 802.11s WMNs

Wireless mesh networks (WMNs) are being widely accepted as a critical wireless access solution for various applications. Due to minimal mobility in mesh nodes, a backbone topology can be effectively maintained in WMN using a proactive routing protocol. In IEEE 802.11s standard, a tree-based routing (TBR) protocol is adopted as a viable proactive routing protocol for a WMN with user traffic flowing to/from a wired network through a root (i.e., a mesh portal). However, the performance of the TBR protocol degrades rapidly as the user traffic becomes dominated by intra-mesh traffic. The reason is that the routing path through the root even for intra-mesh traffic unnecessarily overloads the root. Furthermore, the TBR performance becomes more severe when the network size of WMN is large, which could lead to the huge amount of intra-mesh traffic towards the root. To overcome these problems, we propose a new routing mechanism, root driven routing (RDR) protocol, for the root to quickly determine the best-metric route for any source-destination pair of intra-mesh traffic. For inter-mesh traffic, the original TBR protocol is employed. Thus, the hybrid centralized routing protocol that combines TBR and RDR and is adaptive to all traffic scenarios. Our simulation results reveal that the proposed RDR protocol outperforms the TBR protocol with much lower average end-to-end delay and much higher packet delivery ratio for intra-mesh traffic. The simulation results also provide some insight into the right tradeoff between the TBR protocol and the RDR protocol to achieve the best performance of the hybrid centralized routing protocol for WMNs.

PID Controller for Temperature Control with Multiple Actuators in Cyber-Physical Home System

Nowadays, the need of temperature control at home is significantly demanded as the current controller used in buildings are not efficient and enough flexible to be adapted to any changes. In this research, we are focused on controlling two actuators (i.e., air-conditioner and window) using a PID controller and a hybrid controller during the summer season. We model the home temperature control (HTC) system, which is applied to monitor the desired room temperature all the times with optimal resource cost. The objective of this research is to investigate how the PID controller and the hybrid controller maintain the desired room temperature with only two actuators and minimal resource cost. In addition, we also aim to develop the practical application of cyber-physical system (CPS) for HTC system. Through MATLAB/Simulink simulation, we study and verify our proposed CPS-based HTC system.

OAM: An Ontology Application Management Framework for Simplifying Ontology-Based Semantic Web Application Development

Although the Semantic Web data standards are established, ontology-based applications built on the standards are relatively limited. This is partly due to high learning curve and efforts demanded in building ontology-based Semantic Web applications. In this paper, we describe an ontology application management (OAM) framework that aims to simplify creation and adoption of ontology-based application that is based on the Semantic Web technology. OAM introduces an intermediate layer between user application and programming and development environment in order to support ontology-based data publishing and access, abstraction and interoperability. The framework focuses on providing reusable and configurable data and application templates, which allow the users to create the applications without programming skill required. Three forms of templates are introduced: database to ontology mapping configuration, recommendation rule and application templates. We describe two case studies that adopted the framework: activity recognition in smart home domain and thalassemia clinical support system, and how the framework was used in simplifying development in both projects. In addition, we provide some performance evaluation results to show that, by limiting expressiveness of the rule language, a specialized form of recommendation processor can be developed for more efficient performance. Some advantages and limitations of the application framework in ontology-based applications are also discussed.

An efficient power supply system using phase control in 2D communication

The two-dimensional (2D) communication is a novel physical form of communication that utilizes the surface as a communication medium to provide data communication and power supply services to the devices placed on top of it. In the previous works, we have developed 2D communication systems that allow the devices to simultaneously perform both data and power transmission wherever it is placed on the 2D sheet. Instead of spreading the microwave thoroughly in the thin 2D sheet, we can also concentrate it only on the place where the device is put, by adjusting the phase of the multiple input signals. To largely strengthen the efficiency of power supply in the 2D communication, in this paper, we build up an efficient power supply system by using phase control to converge the microwave on a specific area in the 2D sheet, and evaluate its performance by measuring the output power over the developed 2D communication system.

Range-based algorithm for posture classification and fall-down detection in smart homecare system

Human posture classification is one of the most challenging issues in smart homecare system. To achieve high classification accuracy, we propose a new algorithm, called range-based algorithm. In this paper, a range means the distance between body parts. The ranges between body parts are investigated to classify the human posture and to detect a possible fall-down accident. Furthermore, we also proposed an adaptive posture window scheme to recognize the human posture in real-time even though human change the posture in different speed. The results reveal that our proposed can classify the human posture and detect fall-down with high accuracy and reliability.

I-Swifter: Improving chunked network coding for peer-to-peer content distribution

Network coding has been proposed as a promising approach for peer-to-peer content distribution in recent literature. Not only reducing the average download time, but also improving resilience to peer churn has been showed as the benefits brought by network coding. State-of-the-art network coding content distribution systems perform network coding within segments or chunks, in order to reduce computational overhead. In our previous work (Xu et al. 2008), we proposed to schedule segment requests at a local-rarest-first basic. Local-rarest-first segment scheduling, as we demonstrated, is superior to the random scheduling. In this paper, we make a further step towards improving chunked network coding content distribution systems. We propose a requests reducer that reduces the overhead in control traffic and an encoding vectors reducer that eliminates the transmission of encoding vectors. Our contributions are to save unnecessary requests from downstream peers, and to reduce encoding vectors payload when the upstream peer owns the complete requested segment. This paper presents a realistic implementation, named I-Swifter. And we also make a comparative study on various related implementations. Experimental results show that there is about 10–20% of encoding vectors can be saved in I-Swifter. Moreover, I-Swifter improves average and maximum download time, the server load as well.

SMSS: Symmetric-Masquerade Security Scheme for VANETs

Security plays an important role in the system design with the development of VANETs. Because of the unreliable communications in VANETs, security protocols need more considerations, such as privacy, authentication, and consistency of messages. However, efficiency has been overlooked before, because previous methods incur significant communication overhead. In this paper, we propose a novel security scheme, named Symmetric-Masquerade Security Scheme (SMSS), which can achieve the security requirements while keeping a low system overhead. In SMSS, we focus on the vehicle-to-vehicle communications, which is among the typical scenarios in VANETs. The symmetric encryption is employed in our scheme to ensure the consistency of the messages, the local pseudonyms are equipped to protect the privacy, and the pre-shared keys are introduced to implement the authentication. This paper makes a detailed description of the novel scheme, then analyzes its performance in comparison with that of the PKI security scheme.

A Novel Receiver-Aided Scheme for Improving TCP Performance in Multihop Wireless Networks

In general, TCP sender will take all the packet losses as congestion caused and reduce the packet sending rate to avoid the worsening of network condition. In multihop wireless networks, the long propagation time, poor link quality and high bit error rate make this scheme slow-moving, overcompensated and inefficient.This paper proposes a new optimized data delivery scheme, called TCP receiver-aided (TCP-RA) scheme. By continuously observing the packets end-to-end delay condition, the receiver can estimate the congestion degree and sense the changes of situation. When packet losses happen, the receiver will estimate the reason of loss and assist the sender to control sending rate more efficiently in congestion control. Compared with several contemporary TCP schemes, experimental studies reveal that the TCP-RA scheme can accurately differentiate various packet losses and efficiently improve the throughput performance by control the sending rate smartly.

Using game theory for power and rate control in wireless ad hoc networks

To attain an optimum network performance, a game theory approach is the best tools that may be used to model the interaction among independent devices in order to design the state-of-the-art communication protocol for wireless ad hoc networks, which are characterized by the complexity of mobility and traffic models, the dynamic topology, and the unpredictability of link quality. In this paper, we describe how various interactions in wireless ad hoc networks can be modeled as a game. To be more specific, we use a game-theoretic approach to specify how to efficiently use locally transmit power and assign optimally the transmission rate. The criterion of optimality is the stability of the underlying communications protocols, carrying out our proposed joint power and rate control scheme. By computer simulations, we investigate the performance of proposed scheme assuming the wireless ad hoc environment and show our simulation results in terms of utility, goodput, and power consumption.