Department of Electrical Engineering

In this paper, we develop a signal model for the transmission of discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-SOFDM) in a frequency selective channel. Although maximum likelihood (ML) estimation of the transmitted signal in the DFT-SOFDM system gives the optimum bit-error rate (BER) performance, it incurs exponential complexity due to its exhaustive search implementation. However, our signal model allows the use of sphere decoding algorithm (SDA) which significantly reduces the complexity of ML estimation. Computer simulation of an DFT-SOFDM system at signal-to-noise ratio (SNR) of 5 dB demonstrates that the SDA searches 39 points compared to 216 in the original ML implementation

Abstract Web service search has been a serious concern for service-oriented software development. The challenge is how to find the right Web services efficiently and effectively for a given development task. There have been many efforts on developing techniques or systems to search services. Though effective in certain scenarios, existing techniques do not form systems for public use; or are based on one query modal--keyword query, which cannot give the matched services accurately.

The efficiency of QoS-aware service composition is important since most service composition problems are known to be NP-hard. With the growing number of web services, service composition is like a decision problem on selecting services or/and execution plans to satisfy the users' end-to-end QoS requirements (eg response time, throughput). Composite services with the same functionality may have different execution plans, which may cause different end-to-end QoS.

Abstract Service dependency graph (SDG) is an AND/OR graph showing input output dependencies among service operations. As dependencies in an SDG are indirectly expressed by reasoning on data models used by service interface definitions, their re-usability and expressiveness are limited. In this paper, we propose an enhanced version of service dependency graph, namely SDG+.

Abstract Localization is of great importance in mobile and wireless network applications. TDOA is one of the widely used localization schemes, in which a to-be-located object emits a signal and a number of receivers record the arriving time of the signal. By calculating the time difference of different receivers, the location of the object is estimated. In such a scheme, receivers must be precisely synchronized, even slight noises are completely unacceptable for centimeter-level localization.

Abstract This technical note presents strategies for systematic ways to control mobile actuators in distributed wireless sensor and actuator networks. The efficiency, responsiveness, and service lifetime of the mobile actuators depend on the allocation of the workload to each individual actuator.

Abstract This paper is concerned with the efficiency of Web service discovery and composition. We proposed a quick Web service discovery and composition approach in SWSDS. In our approach, an index-based algorithm is adopted in both syntactic and semantic match during service discovery and composition. This paper is to introduce SWSDS and its discovery and composition algorithm

Abstract In delay tolerant networks (DTNs), the lack of continuous connectivity, network partitioning, and long delays make design of network protocols very challenging. Previous DTN research mainly focuses on routing and information propagation. However, with large number of wireless devices' participation, how to maintain efficient and dynamic topology of the DTN becomes crucial.

Abstract Semantic information, which is well-regulated and easy to be retrieved, has greatly enriched the expressive ability of the Web. These advantages can be applied in Web Services to meet the increasing complexity of Web applications. In this paper, we propose a service composition approach. It combines the large-scaled Web Services and semantic information which is described in WSCpsila09. Besides, QoS has become a critical issue to evaluate the performance of Web applications.

Abstract K-coverage is a classic issue in wireless sensor network (WSN) deployment. Existing works typically assumes that every position in the monitoring field is covered by at least k sensor nodes at any given time. This may not always be necessary because certain events to be monitored will last only for a short period of time.

Abstract Web services are new paradigm of using the Web. One of emerging challenges is to discover Web services efficiently and precisely. Unfortunately, existing systems like UDDI often have the problems of low availability, low accuracy, and bad performance. In this paper, we propose an approach of semantic Web services discovery in P2P environment. Firstly, Web services are published and deployed in same Web server to guarantee the availability.

Abstract We propose a service-oriented web application framework named iWeb, which enables web application adaptive to both context and QoS. In iWeb, a context model is established and context information is collected systematically according to the context model. An innovative service selection approach based on context and QoS is proposed in the framework as the leverage of implementation of application adaption. This approach can select the best services respect to QoS and context.

Abstract Energy efficiency has proven to be an important factor dominating the working period of WSN surveillance systems. Intensive studies have been done to provide energy efficient power management mechanisms. In this paper, we present PAS, a Prediction-based Adaptive Sleeping mechanism for environment monitoring sensor networks to conserve energy. PAS focuses on the diffusion stimulus (DS) scenario, which is very common and important in the application of environment monitoring.

Abstract With the increasing stress and unhealthy lifestyles in people's daily life, mental health problems are becoming a global concern. In particular, mood related mental health problems, such as mood disorders, depressions, and elation, are seriously impacting people's quality of life. However, due to the complexity and unstableness of personal mood, assessing and analyzing daily mood is both difficult and inconvenient, which is a major challenge in mental health care.

It is a new challenge to provide priority-based delivery in low duty-cycled sensor networks where there are not always-awake communication paths and the wireless links are very time-varying and unreliable. In this paper, we propose a Dynamic Routing Algorithm for priority Guarantee (called DRAG) in low duty-cycled sensor networks. Both schemes of dynamic forwarding decision making and priority-based schedule are used in DRAG to achieve priority guarantee in low duty-cycled sensor networks.

Abstract Quality-of-Service (QoS) performance guarantee for service-oriented systems (SOS) has become a critical problem. With the increasing number of offered services comes the challenge of efficiently building large-scale SOS to meet the required QoS criteria. Optimization of QoS-driven semantic Web service composition is known to be NP-hard. We address the efficiency issue by developing a polynomial time algorithm (QDA) for shortest sequence composition.

Abstract This paper studies one of the standards about Web service conversations, the WSCL specification. We propose a method to verify conversations in WSCL. In this method we first propose using a translator to convert WSCL documents into promela, the modeling language of the model checker SPIN. Then, we run SPIN to check the conversation model against the correctness properties specified by the designer. A toolkit for WSCL verification is introduced at the end of this paper.