Positioning Accuracy Improvement via Distributed Location Estimate in Cooperative Vehicular Networks

The development of cooperative vehicle safety (CVS) applications, such as collision warnings, turning assistants, and speed advisories, etc., has received great attention in the past few years. Accurate vehicular localization is essential to enable these applications. In this study, motivated by the proliferation of the Global Positioning System (GPS) devices, and the increasing sophistication of wireless communication technologies in vehicular networks, we propose a distributed location estimate algorithm to improve the positioning accuracy via cooperative inter-vehicle distance measurement. In particular, we compute the inter-vehicle distance based on raw GPS pseudorange measurements, instead of depending on traditional radio-based ranging techniques, which usually either suffer from high hardware cost or have inadequate positioning accuracy. In addition, we improve the estimation of the vehicles' locations only based on the inaccurate GPS fixes, without using any anchors with known exact locations. The algorithm is decentralized, which enhances its practicability in highly dynamic vehicular networks. We have developed a simulation model to evaluate the performance of the proposed algorithm, and the results demonstrate that the algorithm can significantly improve the positioning accuracy.Comment: To appear in Proc. of the 15th International IEEE Conference on Intelligent Transportation Systems (IEEE ITSC'12

Towards Comfortable Cycling: A Practical Approach to Monitor the Conditions in Cycling Paths

This is a no brainer. Using bicycles to commute is the most sustainable form of transport, is the least expensive to use and are pollution-free. Towns and cities have to be made bicycle-friendly to encourage their wide usage. Therefore, cycling paths should be more convenient, comfortable, and safe to ride. This paper investigates a smartphone application, which passively monitors the road conditions during cyclists ride. To overcome the problems of monitoring roads, we present novel algorithms that sense the rough cycling paths and locate road bumps. Each event is detected in real time to improve the user friendliness of the application. Cyclists may keep their smartphones at any random orientation and placement. Moreover, different smartphones sense the same incident dissimilarly and hence report discrepant sensor values. We further address the aforementioned difficulties that limit such crowd-sourcing application. We evaluate our sensing application on cycling paths in Singapore, and show that it can successfully detect such bad road conditions.Comment: 6 pages, 5 figures, Accepted by IEEE 4th World Forum on Internet of Things (WF-IoT) 201

Adaptive Distributed Resource Allocation in Wireless Sensor Networks

Wireless sensor networks have emerged as a promising technology for a wide range of important applications. A major research challenge in this field is the distributed resource allocation problem, which concerns how the limited resources in a wireless sensor network should be allocated or scheduled to minimize costs and maximize the network capability. In this paper, we propose the Adaptive Distributed Resource Allocation (ADRA) scheme, an adaptive approach for distributed resource allocation in wireless sensor networks. Our scheme specifies relatively simple local actions to be performed by individual sensor nodes in a wireless sensor network for mode management. Each node adapts its operation over time in response to the status and feedback of its neighboring nodes. Desirable global behavior results from the local interactions between nodes. We study the effectiveness of the ADRA scheme for a realistic application scenario; namely, the sensor mode management in an acoustic sensor network to track vehicle movement. We evaluated the scheme via simulations, and also prototyped it using the Crossbow MICA2 motes. Our simulation and hardware implementation results indicate that the ADRA scheme provides a good tradeoff between performance objectives such as coverage area, power consumption, and network lifetime.Singapore-MIT Alliance (SMA

Wavelet-based Burst Event Detection and Localization in Water Distribution Systems

In this paper we present techniques for detecting and locating transient pipe burst events in water distribution systems. The proposed method uses multiscale wavelet analysis of high rate pressure data recorded to detect transient events. Both wavelet coefficients and Lipschitz exponents provide additional information about the nature of the signal feature detected and can be used for feature classification. A local search method is proposed to estimate accurately the arrival time of the pressure transient associated with a pipe burst event. We also propose a graph-based localization algorithm which uses the arrival times of the pressure transient at different measurement points within the water distribution system to determine the actual location (or source) of the pipe burst. The detection and localization performance of these algorithms is validated through leak-off experiments performed on the WaterWiSe@SG wireless sensor network test bed, deployed on the drinking water distribution system in Singapore. Based on these experiments, the average localization error is 37.5 m. We also present a systematic analysis of the sources of localization error and show that even with significant errors in wave speed estimation and time synchronization the localization error is around 56 m.Singapore-MIT Alliance for Research and Technolog

Synergy study on charge transport dynamics in hybrid organic solar cell: photocurrent mapping and performance analysis under local spectrum

Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from 2.6 × 1027 m−3s−1 (Jsat = 79.7 A m−2) to 2.9 × 1027 m−3s−1 (Jsat = 90.8 A m−2) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3–13.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%

Efficient Integration of Compiler-directed Cache Coherence And Data Prefetching

Cache coherence enforcement and memory latency reduction and hiding are very important and challenging problems in the design of large-scale distributed shared-memory (DSM) multiprocessors. We propose an integrated approach to solve these problems through a compiler-directed cache coherence scheme called the Cache Coherence with Data Prefetching (CCDP) scheme. The CCDP scheme enforces cache coherence by prefetching the potentially stale references in a parallel program. It also prefetches the nonstale references to hide their memory latencies. To optimize the performance of the CCDP scheme, some prefetch hardware support is provided to efficiently handle these two forms of data prefetching operations. We also developed the compiler techniques utilized by the CCDP scheme for stale reference detection, prefetch target analysis and prefetch scheduling. We evaluated the performance of the CCDP scheme via execution-driven simulations of several numerical applications from the SPEC CFP95 and the Perfect benchmark suites. The simulation results show that the CCDP scheme provides significant performance improvements for the applications studied, comparable to that obtained with a full-map hardware cache coherence scheme

The implementation of a functional/daplex interface for the multi-lingual database system.

Traditionally, the design and implementation of a conventional database system begins with the choice of a data model followed by the specification of a model-based data language. Thus, the database system is restricted to a single data model and a specific data language. An alternative to this traditional approach to database-system development is the multi-lingual database system (MLDS). This alternative approach enables the user to access and manage a large collection of databases via several data models and their corresponding data languages without the aforementioned restriction. In this thesis we present the implementation of a functional/Daplex language interface for MLDS. Specifically, we present the implementation of an interface which translates Daplex language calls into attribute-based data language (ABDL) requests which, as the kernel language, support all other data language interfaces.http://archive.org/details/implementationof00limbCivilian, Ministry of Defense, Republic of SingaporeApproved for public release; distribution is unlimited

On the Integration of Compiler-Directed Cache Coherence and Data Prefetching

128 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1999.To evaluate the performance impact of the CCDP scheme on a real system, we have prototyped it on the Cray T3D. We applied the scheme on five applications from the SPEC CFP95 and CFP92 benchmark suites and executed the resulting codes on the system. The experimental results indicate that for all of the applications studied, our scheme provides significant performance improvements. We further evaluate the effectiveness of the CCDP scheme via execution-driven simulations of several applications from the SPEC CFP95 and the Perfect benchmark suites. The simulation results show that our prefetch hardware support can provide more performance improvements for the CCDP scheme compared to that of a conventional prefetch hardware design. Furthermore, the CCDP scheme can provide a performance comparable to that of a directory-based hardware cache coherence scheme.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

A compiler-directed cache coherence scheme using data prefetching

Cache coherence enforcement and memory latency reduction and hiding are very important problems in the design of large-scale shared-memory multiprocessors. In this paper, we propose a compiler-directed cache coherence scheme which makes use of data prefetching. The Cache Coherence with Data Prefetching (CCDP) scheme uses compiler analysis techniques to identify potentially-stale data references, which are references to invalid copies of cached data. The key idea of the CCDP scheme is to enforce cache coherence by prefetching the up-to-date data corresponding to these potentially-stale references from the main memory. Application case studies were conducted to gain a quantitative idea of the performance potential of the CCDP scheme on a real system. We applied the CCDP scheme on four benchmark programs from the SPEC CFP95 and CFP92 suites, and executed them on the Cray T3D. The experimental results show that for the programs studied, our scheme provides significant performance improvements by caching shared data and reducing the remote shared-memory access penalty incurred by the programs.