13581814
All-optical network demonstrator program centered around a testbed for verifying and validating next generation optical networks
The all-optical network (AON) demonstrator program is centered around a long-term trial testbed for the validation and verification of key network building blocks, scalable architectures, control and management solutions for next generation wavelength division multiplexing networks. The AON testbed has already validated certain system level concepts in both physical (performance characterization) and upper layers (network management). Performance characterization of optical signals was used to develop real-time monitoring techniques of the key network parameters for detection, identification and localization of signal degradations. Upper layer proof of concepts verified network level management approaches and optimizations for large and challenging applications. A prototype of a network management system was developed for customer-managed networks.
62540784
Customer-managed end-to-end lightpath provisioning
Customer-owned and managed optical networks bring new cost-saving benefits. Two types of such networks are becoming widely used: metro dark fiber networks and long-haul leased wavelength networks. Customers may invoke a special QoS mechanism where end-to-end (E2E) lightpaths are dynamically established across multiple independently managed customer domains. The cost of bandwidth is substantially reduced since it largely becomes a capital cost rather than an ongoing service charge. Customers can optimize the overall resource consumption by utilizing resources from different suppliers. Remote peering and transit reduce the Internet connectivity cost. Bandwidth and quality of service are guaranteed because customers directly peer with each other using transport networks. An architecture for a customer-managed E2E lightpath provisioning system is presented. Integration with Grid applications is discussed and a prototype demonstration is described.
59008197
A cycle-based rerouting scheme for wavelength-routed WDM networks
In this paper, we propose a cycle-based rerouting scheme (CRS) for link restoration in wavelength-routed WDM networks. The CRS is based on a scalable set of Pcycles covering a mesh network. Instead of using these Pcycles as enhanced self-healing rings as in traditional approaches, the CRS decomposes these P-cycles into rerouting paths for the links that the P-cycles cover. In this way, flexible and cost-effective link restoration is achieved. Simulation results show that the rerouting performance of the CRS can be very close to the theoretical upper bound.
11778170
Energy-efficient coverage problems in wireless ad-hoc sensor networks
Wireless sensor networks constitute the platform of a broad range of applications related to national security, surveillance, military, health care, and environmental monitoring. The sensor coverage problem has received increased attention recently, being considerably driven by recent advances in affordable and efficient integrated electronic devices. This problem is centered around a fundamental question: How well do the sensors observe the physical space? The coverage concept is subject to a wide range of interpretations due to a variety of sensors and their applications. Different coverage formulations have been proposed, based on the subject to be covered (area versus discrete points) and sensor deployment mechanism (random versus deterministic) as well as on other wireless sensor network properties (e.g. network connectivity and minimum energy consumption). In this article, we survey recent contributions addressing energy-efficient coverage problems in the context of static wireless sensor networks. We present various coverage formulations, their assumptions, as well as an overview of the solutions proposed.
46656
Reliable Unicasting in Faulty Hypercubes Using Safety Levels
We propose a unicasting algorithm for faulty hypercubes (including disconnected hypercubes) using the safety level concept. A faulty hypercube is a hypercube with faulty nodes and unicasting is a one-to-one communication between two nodes in the hypercube. Each node is associated with a safety level which is an approximated measure of the number and distribution of faulty nodes in the neighborhood. The safety level of each node in an n-dimensional hypercube (or n-cube) can be easily calculated through n-1 rounds of information exchange among neighboring nodes. Optimal unicasting between two nodes is guaranteed if the safety level of the source node is no less than the Hamming distance between the source and the destination. The proposed unicasting algorithm can also be used in disconnected hypercubes, where nodes in a hypercube are disjointed into two or more parts. The feasibility of an optimal or suboptimal unicasting can be easily determined at the source node by comparing its safety level, its neighbors' safety levels, and the Hamming distance between the source and the destination. The proposed scheme is the first attempt to address the unicasting problem in disconnected hypercubes. The safety level concept is also extended to be used in hypercubes with both faulty nodes and links and in generalized hypercubes.
14060490
Power-aware broadcasting and activity scheduling in ad hoc wireless networks using connected dominating sets
In ad hoc mobile wireless networks, owing to host mobility, broadcasting is expected to be more frequently used to find a route to a particular host, to page a host, and to alarm all hosts. A straightforward broadcasting by flooding is usually very costly and will result in substantial redundancy and more energy consumption. Power consumption is an important issue since most mobile hosts operate on battery. Broadcasting based on a connected dominating set is a promising approach, where only nodes in the dominating set need to relay the broadcast packet. A set is dominating if all the nodes in the system are either in the set or are neighbors of nodes in the set. Wu and Li proposed a simple and efficient distributed algorithm for calculating connected dominating set in ad hoc wireless networks, where connections of nodes are determined by their geographical distances. In general, nodes in the connected dominating set consume more energy to handle various bypass traffic than nodes outside the set. To prolong the life span of each node and, hence, the network by balancing the energy consumption in the system, nodes should be alternately chosen to form a connected dominating set. Activity scheduling deals with the way of rotating the role of each node among a set of given operation modes (e.g. dominating nodes versus dominated nodes). In this paper, we propose to apply the notion of power-aware connected dominating set to broadcasting and activity scheduling. The effectiveness of the proposed method in prolonging the life span of the network is confirmed through simulation. Copyright © 2003 John Wiley & Sons, Ltd.
6832021
Multiresolution Image Registration Based on Kullback-Leibler Distance
This paper extends our prior work on multi-modal image registration based on the a priori knowledge of the joint intensity dis- tribution that we expect to obtain, and Kullback-Leibler distance. This expected joint distribution can be estimated from pre-aligned training images. Experimental results show that, as compared with the Mutual Information and Approximate Maximum Likelihood based registration methods, the new method has longer capture range at different image resolutions, which can lead to a more robust image registration method. Moreover, with a simple interpolation algorithm based on non-grid point random sampling, the proposed method can avoid interpolation artifacts at the low resolution registration. Finally, it is experimentally demon- strated that our method is applicable to a variety of imaging modalities.
16399305
EECS: an energy efficient clustering scheme in wireless sensor networks
Data gathering is a common but critical operation in many applications of wireless sensor networks. Innovative techniques that improve energy efficiency to prolong the network lifetime are highly required. Clustering is an effective topology control approach in wireless sensor networks, which can increase network scalability and lifetime. In this paper, we propose a novel clustering schema EECS for wireless sensor networks, which better suits the periodical data gathering applications. Our approach elects cluster heads with more residual energy through local radio communication while achieving well cluster head distribution; further more it introduces a novel method to balance the load among the cluster heads. Simulation results show that EECS outperforms LEACH significantly with prolonging the network lifetime over 35%.