Showing papers by "Min-You Wu published in 2006"

An Overview of MAC Protocols with Directional Antennas in Wireless ad hoc Networks

Abstract: Although directional antennas have been used in mobile communications systems for quite a long time, realistic applications of directional or smart antennas in wireless ad hoc network have emerged just in recent years. Directional antennas provide numerous benefits, such as higher gains, increased transmission range and low interferences. Wireless medium access schemes play a crucial role in ensuring the efficient and fair sharing of wireless resources. Therefore there are many research work on mechanisms at the wireless medium access layer by using directional antennas. The new features of MAC with directional antennas can cause not only location dependent carrier sensing problems, which have appeared in omnidirectional wireless networks, but also novel issues related to directional antennas. In this paper, an introduction of directional antennas is given. We give a classification of the current wireless MAC protocols using directional antennas. We also present different MAC protocols and compare them. This survey discusses the challenges in the design of these MAC protocols.

ShanghaiGrid: an Information Service Grid

Abstract: The goal of the ShanghaiGrid is to provide information services to the people. It aims to construct a metropolitan-area information service infrastructure and establish an open standard for widespread upper-layer applications from both communities and the government. The Information Service Grid Toolkit and a typical application called the Traffic Information Grid are discussed in detail. Copyright © 2005 John Wiley & Sons, Ltd.

An Overview of MAC Protocols with Directional Antennas in Wireless ad hoc Networks

Abstract: Although directional antennas have been used in mobile communications systems for quite a long time, realistic applications of directional or smart antennas in wireless ad hoc network have emerged just in recent years. Directional antennas provide numerous benefits, such as higher gains, increased transmission range and low interferences. Wireless medium access schemes play a crucial role in ensuring the efficient and fair sharing of wireless resources. Therefore there are many research work on mechanisms at the wireless medium access layer by using directional antennas. The new features of MAC with directional antennas can cause not only location dependent carrier sensing problems, which have appeared in omnidirectional wireless networks, but also novel issues related to directional antennas. In this paper, an introduction of directional antennas is given. We give a classification of the current wireless MAC protocols using directional antennas. We also present different MAC protocols and compare them. This survey discusses the challenges in the design of these MAC protocols.

PChord: Improvement on Chord to Achieve Better Routing Efficiency by Exploiting Proximity

Abstract: Routing efficiency is the critical issue when constructing peer-to-peer overlay. However, Chord has often been criticized on its careless of routing locality. A routing efficiency enhancement protocol on top of Chord is illustrated in this paper, which is called PChord. PChord aims to achieve better routing efficiency than Chord by exploiting proximity of the underlying network topology. The simulation shows that PChord has achieved lower RDP per message routing.

Inductive charging with multiple charger nodes in wireless sensor networks

Abstract: Energy consumption in Wireless Sensor Network (WSN) remains a challenging problem. Better Solutions of this problem not only can prolong the lifetime of WSNs, but also can support more complex protocols to improve the network performance. We propose an approach of inductive charging, by using mobile nodes to deliver power to deployed active sensors. Infrequently visited by mobile nodes, the sensors can perpetually work without any human intervention. In order to power a WSN of a large number of sensor nodes in wide geographical range effectively, we propose three schemes for inductive charging. Simulation results demonstrate the effectiveness of these algorithms.

Scheduled video delivery-a scalable on-demand video delivery scheme

Abstract: Continuous media, such as digital movies, video clips, and music, are becoming an increasingly common way to convey information, entertain and educate people. However, limited system and network resources have delayed the widespread usage of continuous media. Most existing on-demand services are not scalable for a large content repository. In this paper, we propose a scalable and inexpensive video delivery scheme, named Scheduled Video Delivery (SVD). In the SVD scheme, users submit requests with a specified start time. Incentives are provided so that users will specify the start times that reflect their real needs. The SVD system combines requests to form the multicasting groups and schedules these groups to meet the deadline. SVD scheduling has a different objective from many existing scheduling schemes. Its focus has been shifted from minimizing the waiting time toward meeting deadlines and at the same time combining requests to form multicasting groups. SVD compliments most existing video delivery schemes as it can be combined with them. It requires much less resources than other schemes. Simulation study for the SVD performance and the comparison to other schemes are presented.

An Interference Graph Based MAC Protocol for Ad Hoc Wireless Networks

Abstract: Due to using the simplified interference model, IEEE 802.11 MAC protocol introduces the hidden and exposed terminal problems which significantly decrease the performance of ad hoc wireless networks. In this paper, we propose a novel Interference Graph based MAC protocol (IG-MAC) to improve the throughput of ad hoc wireless networks. The key point is to model the interference information by means of Interference Graph and send busy tone with encoded communication information to prevent the potentially interfering nodes from initiating new transmissions. Through the simulation, our protocol can solve the above two problems caused by 802.11 and improve the network performance substantially.

Smart path-finding with local information in a sensory field

Abstract: Field surveillance is one of the most important applications for wireless sensor networks. Many sensors are deployed in a region of concern to detect any potential targets. On the contrary, intelligent target looks for the best path to traverse the sensing field for fear of being detected and leads to defunct surveillance. In this paper, we focus on how an intelligent target traverses the sensing field. We model this traversing problem, design, implement and evaluate a number of path-finding algorithms. Different from previous works which assume complete information of the sensing field, we assume that the target only can detect part of the sensor network in its detection radius. This makes the proposed methods more practical. Extensive experiments with a target and a sensor network confirm the validity of the approach.

Model-Aided metadata management for wireless sensor networks

Abstract: Metadata are abstraction and knowledge of wireless sensor networks and are used to provide adequate information for query processing. The purpose of metadata management is to provide adequate information for query processing, while at the same time to make the cost of maintaining the metadata as low as possible. In this paper, we discuss new issues about metadata management in wireless sensor networks; and propose a metadata management solution which includes an architecture and a model-aided approach for the base station to collect meta-data from sensor nodes. Experimental results show the effectiveness of our solution.

Smart Path-Finding with Local Information in a Sensory Field

Abstract: Field surveillance is one of the most important applications for wireless sensor networks. Many sensors are deployed in a region of concern to detect any potential targets. On the contrary, intelligent target looks for the best path to traverse the sensing field for fear of being detected and leads to defunct surveillance. In this paper, we focus on how an intelligent target traverses the sensing field. We model this traversing problem, design, implement and evaluate a number of path-finding algorithms. Different from previous works which assume complete information of the sensing field, we assume that the target only can detect part of the sensor network in its detection radius. This makes the proposed methods more practical. Extensive experiments with a target and a sensor network confirm the validity of the approach.

Towards building intelligent transportation information service system on grid

Abstract: Poor interpretability of current transportation systems has become an obstacle to further develop the intelligent transportation systems (ITS). Our design and implementation of intelligent transportation information service systems (ITIS) focuses on integrating heterogeneous data, transportation systems, and resources by using the grid technique. The ITIS project will refine and summarize the business model in Shanghai transportation information service system, design and set up open standards for intelligent transportation information service and simulation, develop grid supporting platform for transportation information service, integrate and fuse massive dynamic transportation data and legacy transportation systems, construct high performance computing (HPC) platform and dynamic parallel transportation simulation platform. ITIS will provide various high-level transportation information services for both citizens and government, which include optimal dynamic bus riding planning service, dynamic on-board navigation service, bus arrival-time prediction service, network optimization and simulation system, large-scale traffic-flow simulation system. Using these services will help to reduce the traffic congestion and other traffic problems, enhancing the transportation intelligence.

Model-Aided data collecting for wireless sensor networks

Abstract: In this paper, we address the problem of collecting data from sensor nodes using a model-aided approach. In our approach, a model is maintained by a node and a replica of the model is maintained the base station. The base station uses the replica model to estimate the actual measurement data of the sensor node in usual time, and an actual measurement datum is sent to the base station only when the error of the model's corresponding estimation exceeds allowable error bound. In such a way, energy can be saved by reducing the transmission of actual measurement data. Experimental results show the effectiveness of our approach.

History-sensitive based approach to optimizing top-k queries in sensor networks

Abstract: Sensor networks generate a large amount of data during monitoring process. These data must be sparingly exacted to conserve energy. There are two methods to obtain data: push and pull. When the sensory data satisfied a preset condition, they are pushed towards the base station. The pull method is to actively query the sensor networks for any interesting sensory data. The problem is how to plan the query and save the energy. When a query has been executed, there are some hints that can be kept to optimize the subsequent query processing. Energy consumption can be reduced by not contacting nodes whose values either can be predicted or are unlikely to be used. In this paper, we propose a history-sensitive based method to optimize top-k query processing in sensor networks. The top-k query looks for and utilizes the historical data in each sensor node. Subsequent top-k queries are guided by these historical data, therefore, to improve the entire query process. Simulation results show that the number of query hops can be reduced and the delays in response are improved.

An area-based collaborative sleeping protocol for wireless sensor networks

Abstract: An effective approach for energy conservation in wireless sensor networks is putting redundant sensor nodes to sleep while the active nodes provide certain degree of coverage. This paper presents an Area-based Collaborative Sleeping protocol (ACOS) that can control the degree of coverage for diverse applications. The ACOS protocol, based on the net sensing area of a sensor, controls the mode of sensors to maximize the coverage, minimize the energy consumption, and to extend the lifetime of the sensor network. The net sensing area of a sensor is the area of the region exclusively covered by the sensor itself. We study the parameter tuning in ACOS to guide to configure the network for diverse applications. The simulation shows that our protocol has better coverage of the surveillance area while waking fewer sensors than other sleeping protocols. It extends the lifetime of sensor networks significantly

ShanghaiGrid: an Information Service Grid: Research Articles

Abstract: The goal of the ShanghaiGrid is to provide information services to the people. It aims to construct a metropolitan-area information service infrastructure and establish an open standard for widespread upper-layer applications from both communities and the government. The Information Service Grid Toolkit and a typical application called the Traffic Information Grid are discussed in detail. Copyright © 2005 John Wiley & Sons, Ltd.

History-sensitive based approach to optimizing top-k queries in sensor networks

Abstract: Sensor networks generate a large amount of data during monitoring process. These data must be sparingly exacted to conserve energy. There are two methods to obtain data: “push” and “pull”. When the sensory data satisfied a preset condition, they are “push”ed towards the base station. The “pull” method is to actively query the sensor networks for any interesting sensory data. The problem is how to plan the query and save the energy. When a query has been executed, there are some hints that can be kept to optimize the subsequent query processing. Energy consumption can be reduced by not contacting nodes whose values either can be predicted or are unlikely to be used. In this paper, we propose a history-sensitive based method to optimize top-k query processing in sensor networks. The top-k query looks for and utilizes the historical data in each sensor node. Subsequent top-k queries are guided by these historical data, therefore, to improve the entire query process. Simulation results show that the number of query hops can be reduced and the delays in response are improved.

Context-Aware adaptation for media delivery in pervasive computing environment

Abstract: A robust solution for context-aware multimedia delivery in the pervasive computing environment remains a challenging problem. Its heterogeneous and dynamic nature demands a more flexible and intelligent framework than Internet does. We propose an adaptive middleware solution to address this issue. The system responds to the condition of the network to offer extensibility and efficiency. Furthermore, we propose an active controlling scheme, in which the multimedia delivery is able to adapt to the environment variation in a timely fashion. In addition, we describe an application scenario of our framework, which opens out a wide prospect.

Blocking Vulnerable Paths of Wireless Sensor Networks

Abstract: In this work, we study the topology enhancement problem of wireless sensor networks. Our research focuses on reducing the path-based vulnerability. The objective is to get as much information as possible for any target moving out of the surveillance area. We study intelligent targets that have the knowledge of existing sensor distribution. Under such assumption, we find the vulnerable paths that rational targets would like to take and block these paths to enhance the network detection performance. Simulation shows that by adding only a few numbers of new sensors on specific positions, we can greatly decrease the vulnerability of a randomly deployed sensor network.

Model-aided data collecting for wireless sensor networks

Abstract: In this paper, we address the problem of collecting data from sensor nodes using a model-aided approach. In our approach, a model is maintained by a node and a replica of the model is maintained the base station. The base station uses the replica model to estimate the actual measurement data of the sensor node in usual time, and an actual measurement datum is sent to the base station only when the error of the model's corresponding estimation exceeds allowable error bound. In such a way, energy can be saved by reducing the transmission of actual measurement data. Experimental results show the effectiveness of our approach.

Monitoring wireless sensor networks using a model-aided approach

Abstract: A wireless sensor network may consist of a large number of small, battery-powered, wireless sensor nodes and works in an unattended way. In order to manage the sensor network and collect data from the network efficiently, we need to know the state of the WSN. In this paper, we propose a model-aided approach to support the monitoring of the state of WSNs. In this approach, models are created on base station to support the monitoring of the network, and mobile agents are injected into the network to collect state information. Experimental results show the effectiveness of our approach.

WSN09-6: Blocking Vulnerable Paths of Wireless Sensor Networks

Abstract: In this work, we study the topology enhancement problem of wireless sensor networks. Our research focuses on reducing the path-based vulnerability. The objective is to get as much information as possible for any target moving out of the surveillance area. We study intelligent targets that have the knowledge of existing sensor distribution. Under such assumption, we find the vulnerable paths that rational targets would like to take and block these paths to enhance the network detection performance. Simulation shows that by adding only a few numbers of new sensors on specific positions, we can greatly decrease the vulnerability of a randomly deployed sensor network.

Extended List Scheduling for Optical Grid Applications

Abstract: We propose a more practical resource model for optical grid applications by extending the classic list scheduling algorithm to achieve communication contention aware scheduling of optical grid applications. An effective adaptive routing scheme is also proposed to improve the performance of the extended list scheduling. The impacts of different routing schemes on the extended list scheduling are comparatively investigated by simulations.

Scalable backbone for wireless metropolitan grid

Abstract: Wireless metropolitan grid promises to offer various broadband services to citizens anywhere with low cost The problem of throughput and scalability are still critical challenges for the success In this paper, we propose and evaluate scalable backbone architecture which employs super nodes with asymmetric capability to reduce the hop count as well as increase the scalability Multi-channel multi-radio approach is utilized to increase the throughput A detailed performance evaluation shows that the deployment of about 20% super nodes can increase the network throughput by a factor of up to 5 compared with the conventional single channel multi hop architecture