Showing papers by "Wai-Choong Wong published in 2010"

Indoor localization with channel impulse response based fingerprint and nonparametric regression

Abstract: In this paper, we propose a fingerprint-based localization scheme that exploits the location dependency of the channel impulse response (CIR). We approximate the CIR by applying inverse Fourier transform to the receiver's channel estimation. The amplitudes of the approximated CIR (ACIR) vector are further transformed into the logarithmic scale to ensure that elements in the ACIR vector contribute fairly to the location estimation, which is accomplished through nonparametric kernel regression. As shown in our simulations, when both the number of access points and density of training locations are the same, our proposed scheme displays significant advantages in localization accuracy, compared to other fingerprint-based methods found in the literature. Moreover, absolute localization accuracy of the proposed scheme is shown to be resilient to the real time environmental changes caused by human bodies with random positions and orientations.

Access point placement for fingerprint-based localization

Abstract: Fingerprint-based localization systems mainly utilize the received signal strength (RSS) to estimate the location of a receiver, and the localization accuracy depends largely on the number and placement of access points (APs). In this paper, we propose a novel method for placing the APs, which aims to minimize the total number of similar fingerprints (SFs) over the entire array of training locations. Minimizing SFs will increase the diversity of RSS array and hence improve localization accuracy. To solve the problem using a simple brute force search would be highly computationally expensive and inefficient. Instead, we propose a heuristic optimization algorithm based on Simulated Annealing (SA). Numerical results are obtained for both the brute force search and the SA based approach. Finally, the proposed algorithm's outputs, i.e., the APs' locations, are used with a K-Nearest Neighbors based localization algorithm, and the resulting localization errors are analyzed.

Error analysis for fingerprint-based localization

Abstract: In this paper, we derive the theoretical error Probability Density Function (PDF) and Region of Confidence (RoC) conditioned on the on-line signal parameter vector, for a generalized fingerprint-based localization system. As the computations of these terms require the exact expression of the joint PDF for both the device location and the on-line signal parameter vector, which is often not available practically, we propose to approximate this joint PDF by Nonparametric Kernel Density Estimation techniques using the training fingerprints.

Secure wireless communication platform for EV-to-Grid research

Abstract: "Vehicle to Grid" power or V2G will be a new green energy scheme that allows electricity to flow from Electric Vehicles (EVs) to power lines. The objective of this paper is to design and develop a secure wireless communication platform for V2G research, with the aim to develop a suitable wireless test bed for the V2G in Singapore. First, this paper presents our system block diagram and required methods design which include V2G architecture design, integrated OBU (on-board unit) design, base station (Aggregator), Telematics, V2G authentication protocol, and schedule optimization of EVs against Grid conditions. It then focuses on the authentication protocol for secure wireless communications between the Aggregators and EVs. It addresses the new and special challenges related to EVs, such as large overhead and latency, which are crucial for secure wireless communications with dynamic and fast moving EVs. Finally, the paper presents the initial test results and shows that our authentication protocol can securely protect the exchanged information with less overhead and less authentication latency.

An optimized routing protocol for vehicular ad hoc networks

Abstract: The rise in the number of vehicles on the streets today has led to an increasing need for traffic safety on roads. The emerging vehicular ad hoc networks (VANETs) are fast becoming a reality and will enable a variety of applications for safety, traffic efficiency, driver assistance, as well as infotainment. In order to provide stable communication linkages between vehicles, a good routing protocol is needed. Currently, there are several routing protocols for mobile ad hoc networks (MANETs) which may be used to find the best route to the destination vehicle in VANETs. However, due to the difference in the characteristics of the two networks, mobility characteristics that are present in VANETs could be added into current MANET routing protocols, so as to allow the routing protocol to achieve a better routing performance by finding the best route to the destination vehicle. This paper presents the optimizations made to a MANET routing protocol and shows an increase in routing performance validated through simulations.

Intelligent network design: User Layer architecture and its application

Abstract: This paper addresses building networks that emphasizes on user-centric human computer interaction and context awareness. To achieve this user-centric intelligent network goal, we propose to explicitly take the end-user into account by defining a new layer called the User Layer above the traditional application layer. By exposing some lower layer information to the end-user, the new User Layer establishes a feedback loop between the end-user and the underlying network infrastructure, empowering the end-user to control and influence network performance based on his own behavior and preferences. A cross-layer design approach using a shared database between the different lower layers is adopted. To illustrate the User Layer in action, we present an exemplary implementation of the User Layer, which can dynamically allocate network resources by leveraging on the TCP flow control mechanism. We evaluated network performance via simulation and show that such a design improves the user perceived quality of service (QoS).

Displacement estimation in micro-sensor motion capture

Abstract: The use of wearable micro-sensors provides an easy-to-use and cost-efficient way for human motion capture. It is essential but difficult to estimate the global displacements of human walking in micro-sensor motion capture system. This paper proposes a novel method to estimate the global displacements of walking based on the pedestrian dead reckoning technique. The global displacements are obtained from the estimated walking distance and the heading direction. Walking distance is calculated using the extension and flexion angles of the lower limbs. Heading is estimated by the fusion of magnetometer and gyroscope readings accomplished by a complementary Kalman filter. The displacements are used to drive a skeleton model to animate the walking movements of the subject. Walking experiments have demonstrated that the proposed method can estimate the displacements accurately and animate the human walking motions smoothly and vividly.

LASPD: A Framework for Location-Aware Service Provision and Discovery in Mobile Environments

Abstract: In this paper, we propose a three-tier framework for Location-Aware Service Provision and Discovery (LASPD), with special emphasis on mobile service provisioning. In the first tier, the world is geographically divided into autonomous areas to facilitate local service administration and management. In the second tier, service providers of an area with adequate computing capability are organized into a structured peer-to-peer network. The third tier supports mobile service providers equipped with less capable devices such as smart phones or PDAs. These providers are allowed to delegate their services to one of the designated peer nodes of the second tier, known as "proxy". In LASPD, the location-awareness is achieved during a service discovery by exploiting the locality-preserving property of the Hilbert space filling curve. Besides, we leverage on our previously proposed rewiring mechanism to make the network navigable and self-organized. To have a better understanding of the framework characteristics, we conduct simulations to study the routing behaviors of peer nodes in different tiers as well as measuring the performance of the prototype in real-world environments.

SOLE: context-aware sharing of living experience in mobile environments

Abstract: In this paper we present the design of an application framework for context-aware Sharing Of Living Experience (SOLE) in mobile environments. With SOLE, users can share their experience of daily activities. They can specify where to store their information - on their mobile devices to have full access control over their data, or in the distributed SOLE application servers for ease of access by others. SOLE leverages on our service-oriented middleware (Coalition) to achieve context-awareness. To cater for resource constraints of mobile devices, the concept of "proxy" is introduced. As a proof of concept, we develop a prototype of SOLE for mobile Android phone users. Preliminary experiments have been carried out to test the performance of the framework.

When Ambient Intelligence Meets Internet Protocol Stack: User Layer Design

Abstract: Recently there has been increasing interest in building networks with Ambient Intelligence (AmI), which incorporates the user-centricity and context awareness. However, both the Internet TCP/IP protocol stack and the seven-layer OSI reference model are not suitable for AmI networks, because they do not specifically take the end-user requirements into consideration in their architecture design. Under the client-server architecture, we propose to explicitly take the end-user into account by defining a new layer called User Layer above the traditional application layer. The User Layer empowers the end-users to influence network performance based on their interaction activities with the networks. We adopt the Model Human Processor (MHP) approach for building the User Model. After that we present an exemplary User Layer implementation to illustrate how the User Layer interacts with the underlying protocol stack and improves end-user's satisfaction with network performance.

Cooperative spectrum sensing strategies with multiple relays

Abstract: In this paper, we consider the cooperative spectrum sensing problem for a cognitive radio (CR) mesh network. Based on multiple relay model, we propose two cooperative spectrum sensing strategies called amplify-and-relay (AR) and detect-and-relay (DR), and also derive the closed-form expressions of false alarm and detection probabilities. Simulation results show that our proposed strategies achieve better performance than a non-cooperative (or non-relay) spectrum sensing method and an existing cooperative detection method. As expected, the detection performance improves as the number of relays increases.

Context Data Management for Mobile Spaces

Abstract: Context-aware applications can monitor and detect the surrounding Context-aware applications can monitor and detect the surrounding situation changes of context entities, and adapt to these situations automatically. As context-aware applications can reside in mobile entities such as cars and mobile phone, an efficient context data management mechanism is required for mobile context-aware applications. In this paper, we propose a new mechanism to model and represent mobile entities. In addition, we also propose new system services to support mobile applications so that disruptions caused by mobility can be minimized.

Semantic P2P Overlay for Dynamic Context Lookup

Abstract: Context-aware applications generally need to retrieve various kinds of dynamic context data from a large number of context sources. A middleware managing context sources must provide an efficient context lookup mechanism to ease application development. In this paper, we categorize the context sources as operating spaces and propose semantic peer-to-peer overlays over these spaces to accelerate dynamic context lookup in a context-aware middleware. Our proposed overlay structure is specially designed to deal with dynamic sensory context such as a person’s location and temperature that are frequently changing and difficult to be promptly retrieved using traditional peer-to-peer protocols. Our overlay and indexing method has a low maintenance overhead. Measurement results show that the proposed overlay achieves a good response time and accuracy for context lookup as well as requires low maintenance overhead. (Less)

Semantic P2P Overlay for Dynamic Context Lookup

Abstract: Context-aware applications generally need to retrieve various kinds of dynamic context data from a large number of context sources. A middleware managing context sources must provide an efficient context lookup mechanism to ease application development. In this paper, we categorize the context sources as operating spaces and propose semantic peer-to-peer overlays over these spaces to accelerate dynamic context lookup in a context-aware middleware. Our proposed overlay structure is specially designed to deal with dynamic sensory context such as a person’s location and temperature that are frequently changing and difficult to be promptly retrieved using traditional peer-to-peer protocols. Our overlay and indexing method has a low maintenance overhead. Measurement results show that the proposed overlay achieves a good response time and accuracy for context lookup as well as requires low maintenance overhead. (Less)

Semantic P2P Overlay for Dynamic Context Lookup

Abstract: Context-aware applications generally need to retrieve various kinds of dynamic context data from a large number of context sources. A middleware managing context sources must provide an efficient context lookup mechanism to ease application development. In this paper, we categorize the context sources as operating spaces and propose semantic peer-to-peer overlays over these spaces to accelerate dynamic context lookup in a context-aware middleware. Our proposed overlay structure is specially designed to deal with dynamic sensory context such as a person’s location and temperature that are frequently changing and difficult to be promptly retrieved using traditional peer-to-peer protocols. Our overlay and indexing method has a low maintenance overhead. Measurement results show that the proposed overlay achieves a good response time and accuracy for context lookup as well as requires low maintenance overhead. (Less)

Query-enabled sensor networks using the cyclic symmetric wakeup design

Abstract: The problem of conserving energy under multiple constraints of query waiting delays and sensing coverage preservation in query-based wireless sensor networks is addressed. We propose a network architecture based on the cyclic symmetric block design class of wakeup schemes. Using a target tracking application as an example, specific requirements of the application translates to design parameters in our proposed solution. Our proposal demonstrates good delay performances, high target tracking accuracies and low target identification errors, without the need for costly double-radio channels while increasing network lifetimes by a factor of four to eight over traditional methods.