11369157
Statistical model of lossy links in wireless sensor networks
Recently, several wireless sensor network studies demonstrated large discrepancies between experimentally observed communication properties and properties produced by widely used simulation models. Our first goal is to provide sound foundations for conclusions drawn from these studies by extracting relationships between location (e.g. distance) and communication properties (e.g. reception rate) using non-parametric statistical techniques. The objective is to provide a probability density function that completely characterizes the relationship. Furthermore, we study individual link properties and their correlation with respect to common transmitters, receivers and geometrical location. The second objective is to develop a series of wireless network models that produce networks of arbitrary sizes with realistic properties. We use an iterative improvement-based optimization procedure to generate network instances that are statistically similar to empirically observed networks. We evaluate the accuracy of our conclusions using our models on a set of standard communication tasks, like connectivity maintenance and routing.
195861616
Optimization-intensive watermarking techniques for decision problems
Recently, a number of watermarking-based intellectual property protection techniques have been proposed. Although they have been applied to different stages in the design process and have a great variety of technical and theoretical features, all of them share two common properties: they all have been applied solely to optimization problems and do not involve any optimization during the watermarking process. In this paper we propose the first set of optimization-intensive watermarking techniques for decision problems. In particular we demonstrate how one can select a subset of superimposed watermarking constraints so that the uniqueness of the signature and the likelihood of satisfying an instance of the satisfiability problem are simultaneously maximized. We have developed three watermarking SAT techniques: adding clauses, deleting literals, push-out and pull-back. Each technique targets different types of signature induced constraint superimposition on an instance of the SAT problem. In addition to comprehensive experimental validation, we theoretically analyze the potentials and limitations of the proposed watermarking techniques. Furthermore, we analyze the three proposed optimization-intensive watermarking SAT techniques in terms of their suitability for copy detection.
2985827
Flexible ASIC: shared masking for multiple media processors
ASIC provides more than an order of magnitude advantage in terms of density, speed, and power requirement per gate. However, economic (cost of masks) and technological (deep micron manufacturability) trends favor FPGA as an implementation platform. In order to combine the advantages of both platforms and alleviate their disadvantages, recently a number of approaches, such as structured ASIC/regular fabrics, have been proposed. Our goal is to introduce an approach that has the same objective, but is orthogonal to those already proposed. The idea is to implement several ASIC designs in such a way that they share the datapath, memory structure, and several bottom layers of interconnect, while each design has only a few unique metal layers. We identified and addressed two main problems in our quest to develop a CAD flow for realization of such designs. They are: (i) the creation of the datapath, and (ii) the identification of common and unique interconnect for each design. Both problems are solved optimally using ILP formulations. We assembled a design flow platform using two new programs and the Trimaran and Shade tools. We quantitatively analyzed the advantages and disadvantages of the approach using the Mediabench benchmark suite.
1973000
Gateway placement for latency and energy efficient data aggregation [wireless sensor networks]
We propose the use of multiple gateways to significantly reduce latency and energy consumption in multi-hop wireless sensor networks during data aggregation. We have derived efficient integer linear programming formulations as well as a novel negative selection statistically-tuned heuristics. The heuristics are based on newly developed relaxation based lower bounds that are also used to quantify the effectiveness of the proposed heuristics. Our simulation study indicates that the use of gateways can often reduce latency and energy consumption by several times.
1532971
Relative Generic Computational Forensic Techniques
Computational forensic engineering is the process of identification of the tool or algorithm that was used to produce a particular output or solution by examining the structural properties of the output. We introduce a new Relative Generic Forensic Engineering (RGFE) technique that has several advantages over the previously proposed approaches. The new RGFE technique not only performs more accurate identification of the tool used but also provides the identification with a level of confidence. Additionally, we introduce a generic formulation (integer linear programming formulation) which enables rapid application of the RGFE approach to a variety of problems that can be formulated as 0-1 integer linear programs. 
 
The key innovations of the RGFE technique include the development of a simulated annealing-based (SA) CART classification technique and a generic property formulation technique that facilitates property reuse. We introduce instance properties which enable an enhanced classification of problem instances leading to a higher accuracy of algorithm identification. Finally, the single most important innovation, property calibration, interprets the value for a given algorithm for a given property relative to the values for other algorithms. We demonstrated the effectiveness of the RGFE technique on the boolean satisfiability (SAT) and graph coloring (GC) problems.
1221107
A probabilistic constructive approach to optimization problems
We propose a new optimization paradigm for solving intractable combinatorial problems. The technique, named Probabilistic Constructive (PC), combines the advantages of both constructive and probabilistic algorithms. The constructive aspect provides relatively short runtime and makes the technique amenable for the inclusion of insights through heuristic rules. The probabilistic nature facilitates a flexible trade-off between runtime and the quality of solution. In addition to presenting the generic technique, we apply it to the Maximal Independent Set problem. Extensive experimentation indicates that the new approach provides very attractive trade-offs between the quality of the solution and runtime, often outperforming the best previously published approaches.
3832041
Enabling Technology for Distributed Multimedia Applications
In September 1993, the Canadian Institute for Telecommunications Research, in collaboration with the IBM Toronto Laboratory Centre for Advanced Studies, initiated a major project on broadband services. The goal of this major project is to provide the software technologies required for the development of distributed multimedia applications. Of particular interest are “presentational“ applications where multimedia documents, stored in database servers, are retrieved by remote users over a broadband network. Emphasis is placed on efficiency and service flexibility. By efficiency, we mean the ability to support many users and many multimedia documents. By service flexibility, we mean that the application is able to support a wide range of quality-of-service requirements from the users, adapt to changing network conditions, and support multiple document types. The research program consists of six constituent projects: multimedia data management, continuous media file server, quality-of-service negotiation and adaptation, scalable video encoding, synchronization of multimedia data, and project integration. These projects are investigated by a multidisciplinary team from eight institutions across Canada. Multimedia news has been selected as a target application for development, and the results from the various projects have been integrated into a multimedia news prototype. In this paper, the system architecture, research results, and the prototyping effort are presented.
8690187
Distributed Simulation Using a Network of Processors
Abstract Simulation, particulary of networks of queues, is an application with a high degree of inherent parallelism and is of great practical interest. We hope to exploit this parallelism by performing simulations using a network of cheap, but slow, micro-processors. We define a taxonomy by which we classify a number of parameters of a distributed simulation method, and seek solutions to problems of synchronization, deadlock prevention and inter-process communication arising with various methods in each class of the taxonomy. We concentrate in particular on the class (loose, event-driven) which seems to possess the greatest potential parallelism, and on the class (scaled, tight, time-driven) which allows mock-up studies of real systems. We give algorithms for deadlock prevention and detection, and briefly discuss the design of a distributed operating system to support the simulation application. This research forms part of a joint program with the Dept. of Computer Sciences, University of Texas at Austin, directed by Prof. K.M. Chandy.
17359298
Queueing Network Modeling of Computer Communication Networks
The application of queueing network models to the performance analysis of messageswitched (or packet-switched) commumcatmn networks m surveyed. The main topics covered are the analysis of end-to-end delay and the analysis of buffer management schemes. A brief discussmn on flow control is also included. A queueing network model is developed for a simple user-resource network. The mean response time of a host computer m this network is illustrated by a numerical example.
206921648
DQMA and CRMA: new access schemes for Gbit/s LANs and MANs
Distributed-queue multiple-access (DQMA) and cyclic-reservation multiple-access (CRMA) access schemes for gigabit-per-second local and metropolitan area networks are described. These schemes are based on a slotted unidirectional bus structure, with both folded and dual-bus configurations. Like the distributed-queue dual-bus (DQDB) scheme, both the DQMA and the CRMA access schemes achieve full throughput independent of network speed and distance. They have two significant advantages over DQDB. They provide throughput fairness even at high speeds and large distances, where DQDB exhibits dramatic unfairness, and, by allowing reservation of multiple consecutive slots, they make segment labeling unnecessary and facilitate packet reassembly significantly.<<ETX>>
42047029
The effect of multiplexing, switching and other factors on the performance of broadband networks
A network model is developed for studying the effect of multiplexing and switching on broadband network performance. Emphasis is placed on the queuing behavior in the network and the impact of multiplexing and switching on the burstiness of the various traffic streams. The three parameters commonly used to characterize traffic (peak bit rate, mean bit rate, and mean burst length) are also considered, and the dependence of the queuing behavior on these parameters is investigated. The performance of three congestion control schemes based on the leaky bucket algorithm is evaluated. The results provide insight into how call acceptance, bandwidth allocation, and bandwidth enforcement should be implemented in a broadband integrated services digital network (BISDN).<<ETX>>