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24
Rendezvous Planning in Wireless Sensor Networks with Mobile Elements
, 2008
"... Recent research shows that significant energy saving can be achieved in wireless sensor networks by using mobile elements (MEs) capable of carrying data mechanically. However, the low movement speed of MEs hinders their use in data-intensive sensing applications with temporal constraints. To addres ..."
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Cited by 26 (2 self)
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Recent research shows that significant energy saving can be achieved in wireless sensor networks by using mobile elements (MEs) capable of carrying data mechanically. However, the low movement speed of MEs hinders their use in data-intensive sensing applications with temporal constraints. To address this issue, we propose a rendezvous-based approach in which a subset of nodes serves as the rendezvous points (RPs) that buffer data originated from sources and transfer to MEs when they arrive. RPs enable MEs to collect a large volume of data at a time without traveling long distances, which can achieve a desirable balance between network energy saving and data collection delay. We develop two rendezvous planning algorithms: RP-CP and RP-UG. RP-CP finds the optimal RPs when MEs move along the data routing tree, while RP-UG greedily chooses the RPs with maximum energy saving to travel distance ratios. We design the Rendezvous-based Data Collection protocol that facilitates reliable data transfers from RPs to MEs in presence of significant unexpected delays in ME movement and network communication. Our approach is validated through extensive simulations.
TASA: Tag-free Activity Sensing using RFID Tag Arrays
- IEEE Transactions on Parallel and Distributed Systems
, 2011
"... Abstract—Radio Frequency IDentification (RFID) has attracted considerable attention in recent years for its low cost, general availability, and location sensing functionality. Most existing schemes require the tracked persons to be labeled with RFID tags. This requirement may not be satisfied for so ..."
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Cited by 17 (5 self)
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Abstract—Radio Frequency IDentification (RFID) has attracted considerable attention in recent years for its low cost, general availability, and location sensing functionality. Most existing schemes require the tracked persons to be labeled with RFID tags. This requirement may not be satisfied for some activity sensing applications due to privacy and security concerns and uncertainty of objects to be monitored, e.g., group behavior monitoring in warehouses with privacy limitations, and abnormal customers in banks. In this paper, we propose TASA—Tag-free Activity Sensing using RFID tag Arrays for location sensing and frequent route detection. TASA relaxes the monitored objects from attaching RFID tags, online recovers and checks frequent trajectories by capturing the Received Signal Strength Indicator (RSSI) series for passive RFID tag arrays where objects traverse. In order to improve the accuracy for estimated trajectories and accelerate location sensing, TASA introduces reference tags with known positions. With the readings from reference tags, TASA can locate objects more accurately. Extensive experiment shows that TASA is an effective approach for certain activity sensing applications. Index Terms—RFID, activity sensing, tag-free localization, object tracking, frequent trajectories. Ç 1
A New Storage Scheme for Approximate Location Queries in Object Tracking Sensor Networks
- IEEE Trans. Parallel and Distributed Systems
, 2008
"... Abstract—Energy efficiency is one of the most critical issues in the design of wireless sensor networks. Observing that many sensor applications for object tracking can tolerate a certain degree of imprecision in the location data of tracked objects, this paper studies precision-constrained approxim ..."
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Cited by 11 (2 self)
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Abstract—Energy efficiency is one of the most critical issues in the design of wireless sensor networks. Observing that many sensor applications for object tracking can tolerate a certain degree of imprecision in the location data of tracked objects, this paper studies precision-constrained approximate queries that trade answer precision for energy efficiency. We develop an Energy-conserving Approximate StoragE (EASE) scheme to efficiently answer approximate location queries by keeping error-bounded imprecise location data at some designated storage node. The data impreciseness is captured by a system parameter called the approximation radius. We derive the optimal setting of the approximation radius for our storage scheme based on the mobility pattern and devise an adaptive algorithm to adjust the setting when the mobility pattern is not available a priori or is dynamically changing. Simulation experiments are conducted to validate our theoretical analysis of the optimal approximation setting. The simulation results show that the proposed EASE scheme reduces the network traffic from a conventional approach by up to 96 percent and, in most cases, prolongs the network lifetime by a factor of 2-5. Index Terms—Energy efficiency, data dissemination, data storage, location query, wireless sensor network. 1
1 Exploiting Reactive Mobility for Collaborative Target Detection in Wireless Sensor Networks
"... Abstract—Recent years have witnessed the deployments of wireless sensor networks in a class of mission-critical applications such as object detection and tracking. These applications often impose stringent Quality of Service (QoS) requirements including high detection probability, low false alarm ra ..."
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Cited by 10 (7 self)
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Abstract—Recent years have witnessed the deployments of wireless sensor networks in a class of mission-critical applications such as object detection and tracking. These applications often impose stringent Quality of Service (QoS) requirements including high detection probability, low false alarm rate and bounded detection delay. Although a dense all-static network may initially meet these QoS requirements, it does not adapt to unpredictable dynamics in network conditions (e.g., coverage holes caused by death of nodes) or physical environments (e.g., changed spatial distribution of events). This paper exploits reactive mobility to improve the target detection performance of wireless sensor networks. In our approach, mobile sensors collaborate with static sensors and move reactively to achieve the required detection performance. Specifically, mobile sensors initially remain stationary and are directed to move toward a possible target only when a detection consensus is reached by a group of sensors. The accuracy of final detection result is then improved as the measurements of mobile sensors have higher Signal-to-Noise Ratios after the movement. We develop a sensor movement scheduling algorithm that achieves near-optimal system detection performance under a given detection delay bound. The effectiveness of our approach is validated by extensive simulations using the real data traces collected by 23 sensor nodes. Index Terms—Data fusion, Algorithm/protocol design and analysis, Wireless sensor networks. 1
Collaborative Target Detection in Wireless Sensor Networks with Reactive Mobility
"... Abstract—Recent years have witnessed the deployments of wireless sensor networks in a class of mission-critical applications such as object detection and tracking. These applications often impose stringent QoS requirements including high detection probability, low false alarm rate and bounded detect ..."
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Cited by 9 (2 self)
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Abstract—Recent years have witnessed the deployments of wireless sensor networks in a class of mission-critical applications such as object detection and tracking. These applications often impose stringent QoS requirements including high detection probability, low false alarm rate and bounded detection delay. Although a dense all-static network may initially meet these QoS requirements, it does not adapt to unpredictable dynamics in network conditions (e.g., coverage holes caused by death of nodes) or physical environments (e.g., changed spatial distribution of events). This paper exploits reactive mobility to improve the target detection performance of wireless sensor networks. In our approach, mobile sensors collaborate with static sensors and move reactively to achieve the required detection performance. Specifically, mobile sensors initially remain stationary and are directed to move toward a possible target only when a detection consensus is reached by a group of sensors. The accuracy of final detection result is then improved as the measurements of mobile sensors have higher signal-to-noise ratios after the movement. We develop a sensor movement scheduling algorithm that achieves near-optimal system detection performance within a given detection delay bound. The effectiveness of our approach is validated by extensive simulations using the real data traces collected by 23 sensor nodes. I.
The k-angle object coverage problem in a wireless sensor network. technical report, National Tsing Hua Univ
, 2010
"... Abstract — One of the fundamental issues in sensor networks is the coverage problem, which reflects how well a field is monitored or tracked by sensors. Various versions of this problem have been studied, such as object, area, barrier, and hole coverage problems. In this paper, we define a new k-ang ..."
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Cited by 6 (1 self)
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Abstract — One of the fundamental issues in sensor networks is the coverage problem, which reflects how well a field is monitored or tracked by sensors. Various versions of this problem have been studied, such as object, area, barrier, and hole coverage problems. In this paper, we define a new k-angle object coverage problem in a wireless sensor network. Each sensor can only cover a limited angle and range, but can freely rotate to any direction to cover a particular angle. Given a set of sensors and a set of objects at known locations, the goal is to use the least number of sensors to k-angle-cover the largest number of objects such that each object is monitored by at least k sensors satisfying some angle constraint. We propose centralized and distributed polynomial-time algorithms to solve this problem. Simulation results show that our algorithms can be effective in maximizing coverage of objects. A prototype system is developed to demonstrate the usefulness of angle coverage. Index Terms — Coverage problem, pervasive computing, sensor network, video surveillance, wireless network.
Energy Efficient Monitoring in Sensor Networks
, 2008
"... In this paper we study a set of problems related to efficient energy management for monitoring applications in wireless sensor networks. We study several generalizations of a basic problem called Set k-Cover. The problem can be described as follows: we are given a set of sensors, and a set of regi ..."
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Cited by 4 (0 self)
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In this paper we study a set of problems related to efficient energy management for monitoring applications in wireless sensor networks. We study several generalizations of a basic problem called Set k-Cover. The problem can be described as follows: we are given a set of sensors, and a set of regions to be monitored. Each region can be monitored by a subset of the sensors. To increase the lifetime of the sensor network, we would like to partition the sensors into k sets (or time-slots), and activate each set of sensors in a different time-slot, thus extending the battery life of the sensors by a factor of k. The goal is to find a partitioning that maximizes the total coverage of the regions for a given k. This problem is known to be NP-hard. We develop an improved approximation algorithm for this problem using a reduction to Max k-Cut. Moreover, we are able to demonstrate that this algorithm is practical, and yields almost optimal solutions in practice. We also consider generalizations of this problem in several different directions. First, we allow each sensor to be active in α different sets (time-slots). This means that the battery life is extended by a factor of k α, and allows for a richer space of solutions. We also consider different coverage requirements, such as requiring that all regions, or at least a certain number of regions, be covered in each time slot. In the Set k-Cover formulation, there is no requirement that a region be monitored at all, or in any number of time slots. We develop a randomized rounding algorithm for this problem. We also consider extensions where each sensor can monitor only a bounded number of regions in any time-slot, and not all the regions adjacent to it. This kind of problem may arise when a sensor has a directional camera, or some other physical constraint might prevent it from monitoring all adjacent regions even when it is active. We develop the first approximation algorithms for this problem.
Dynamic Multi-resolution Data Dissemination in Wireless Sensor Networks
- MSWIM 2007
, 2007
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General Maximal Lifetime Sensor-Target Surveillance Problem and Its Solution
"... Abstract—We address a new and general maximal lifetime problem in sensor-target surveillance. We assume that each sensor can watch at most k targets (k 1) and each target should be watched by h sensors (h 1) at any time. The problem is to schedule sensors to watch targets and forward the sensed data ..."
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Cited by 3 (0 self)
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Abstract—We address a new and general maximal lifetime problem in sensor-target surveillance. We assume that each sensor can watch at most k targets (k 1) and each target should be watched by h sensors (h 1) at any time. The problem is to schedule sensors to watch targets and forward the sensed data to a base station such that the lifetime of the surveillance network is maximized. This general problem includes the existing ones as its special cases (k 1 and h 1 in [12] and k 1 and h 2 in [13]). It is also important in practice because some sensors can monitor multiple or all targets within their surveillance ranges and multisensor fusion (i.e., watching a target by multiple sensors) gives better surveillance results. The problem involves several subproblems and one of them is a new matching problem called ðk; hÞ-matching. The ðk; hÞ-matching problem is a generalized version of the classic bipartite matching problem (when k h 1, ðk; hÞ-matching becomes bipartite matching). We design an efficient (k, h)-matching algorithm to solve the ðk; hÞ-matching problem and then solve the general maximal lifetime problem. As a byproduct of this study, the ðk; hÞ-matching problem and the proposed ðk; hÞ-matching algorithm can potentially be applied to other problems in computer science and operations research.
Novel Algorithms for Complete Targets Coverage in Energy Harvesting Wireless Sensor Networks
, 2015
"... Novel algorithms for complete targets coverage in energy harvesting wireless sensor networks ..."
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Cited by 3 (2 self)
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Novel algorithms for complete targets coverage in energy harvesting wireless sensor networks
