Showing papers on "Redundancy (engineering) published in 2001"

Chaos-based random number generators. Part II: practical realization

Abstract: This paper and its companion (see ibid., vol. 48, p. 281-88, 2001) are devoted to to the analysis of the application of a chaotic piecewise-linear one-dimensional (PL1D) map as Random Number Generator (RNG). In Part I, me have mathematically analyzed the information generation process of a class of PL1D maps. In this paper, we find optimum parameters that give an RNG with lowest redundancy and maximum margin against parasitic attractors. Further, the map is implemented in a 0.8 /spl mu/m standard CMOS process utilizing switched current techniques. Post-layout circuit simulations of the RNG indicate no periodic attractors over variations in temperature, power supply and process conditions, and maximum redundancy of 0.4%. We estimate that the output bit rate of our RNG is 1 Mbit/s, which is substantially higher than the output bit rate of RNGs available on the market.

Sabotage-tolerance mechanisms for volunteer computing systems

Abstract: We address the new problem of protecting volunteer computing systems from malicious volunteers who submit erroneous results by presenting sabotage-tolerance mechanisms that work without depending on checksums or cryptographic techniques. We first analyze the traditional technique of voting, and show how it reduces error rates exponentially with redundancy, but requires all work to be done at least twice, and does not work well when there are many saboteurs. We then present a new technique called spot-checking which reduces the error rate linearly (i.e., inversely) with the amount of work to be done, while only costing an extra function of the original time. We then integrate these mechanisms by presenting the new idea of credibility-based fault-tolerance, which uses probability estimates to efficiently limit and direct the use of redundancy. By using voting and spot-checking together credibility-based fault-tolerance effectively allows us to exponentially shrink an already linearly-reduced error rate, and thus achieve error-rates that are orders-of-magnitude smaller than those offered by voting or spot-checking alone. We validate this new idea with Monte Carlo simulations, and discuss how credibility-based fault tolerance can be used with other mechanisms and in other applications.

Compact and transparent fuzzy models and classifiers through iterative complexity reduction

Abstract: In our previous work (2000) we showed that genetic algorithms (GAs) provide a powerful tool to increase the accuracy of fuzzy models for both systems modeling and classification. In addition to these results, we explore the GA to find redundancy in the fuzzy model for the purpose of model reduction. An aggregated similarity measure is applied to search for redundancy in the rule base description. As a result, we propose an iterative fuzzy identification technique starting with data-based fuzzy clustering with an overestimated number of local models. The GA is then applied to find redundancy among the local models with a criterion based on maximal accuracy and maximal set similarity. After the reduction steps, the GA is applied with another criterion searching for minimal set similarity and maximal accuracy. This results in an automatic identification scheme with fuzzy clustering, rule base simplification and constrained genetic optimization with low-human intervention. The proposed modeling approach is then demonstrated for a system identification and a classification problem.

Method and system for achieving high availability in a networked computer system

Abstract: The present invention describes a method and system for achieving high availability in a networked computer system. In particular, the method for achieving high-availability is executed in a networked computer system. The networked computer system includes nodes connected by a network. The method includes using high-availability-aware components to represent hardware and software in the networked computer system, managing the components to achieve a desired level of redundancy, and monitoring health of the networked computer system, including health of components and nodes. The method further includes detecting a failure in the networked computer system. Failures detected by the method include failures of a component and/or node. Finally, the method includes recovering from the failure by performing an appropriate failure recovery procedure.

Motion-compensated highly scalable video compression using an adaptive 3D wavelet transform based on lifting

Abstract: This paper proposes a new framework for the construction of motion compensated wavelet transforms, with application to efficient highly scalable video compression. Motion compensated transform techniques, as distinct from motion compensated predictive coding, represent a key tool in the development of highly scalable video compression algorithms. The proposed framework overcomes a variety of limitations exhibited by existing approaches. This new method overcomes the failure of frame warping techniques to preserve perfect reconstruction when tracking complex scene motion. It also overcomes some of the limitations of block displacement methods. Specifically, the lifting framework allows the transform to exploit inter-frame redundancy without any dependence on the model selected for estimating and representing motion. A preliminary implementation of the proposed approach was tested in the context of a scalable video compression system, yielding PSNR performance competitive with other results reported in the literature.

Cold-standby redundancy optimization for nonrepairable systems

Abstract: A solution methodology is described and demonstrated to determine optimal design configurations for nonrepairable series–parallel systems with cold-standby redundancy. This problem formulation considers non-constant component hazard functions and imperfect switching. The objective of the redundancy allocation problem is to select from available components and to determine an optimal design configuration to maximize system reliability. For cold-standby redundancy, other formulations have generally required exponential component time-to-failure and perfect switching assumptions. For this paper, there are multiple component choices available for each subsystem and component time-to-failure is distributed according to an Erlang distribution. Optimal solutions are determined based on an equivalent problem formulation and integer programming. Compared to other available algorithms, the methodology presented here more accurately models many engineering design problems with cold-standby redundancy. Previously, it has been difficult to determine optimal solutions for this class of problems or even to efficiently calculate system reliability. The methodology is successfully demonstrated on a large problem with 14 subsystems.

Method for creating circuit redundancy in programmable logic devices

Abstract: In a field programmable gate array (FPGA) allowing dynamic reconfiguration in time multiplexing fashion, duplicate copies are configured in a time multiplexing manner which are functionally identical to a primary circuit specified for a predetermined FPGA's application. The primary and duplicate circuits are interrogated by a voting circuit which determines the existence of a faulted circuit in order to eliminate the faulted circuit from the operation of the FPGA. In this manner, without physical addition of redundant circuits, fault tolerancy for the FPGA is provided to minimize the cost, weight, volume, heat and energy associated issues of conventional redundance techniques.

System and method of addressing and configuring a remote device

Abstract: A system and method of addressing and configuring a remote device implement a dynamic device addressing and configuration protocol. Equipment such as industrial automation devices may be dynamically coupled to a communications network, providing flexibility and redundancy in network device configuration. Industrial automation devices may be assigned both network address information as well as operational parameters according to a dynamic protocol.

Disk drive employing sector-reconstruction-interleave sectors each storing redundancy data generated in response to an interleave of data sectors

Abstract: A disk drive is disclosed comprising a disk, a head, and an actuator for actuating the head radially over the disk. The disk comprises a plurality of tracks, each track comprises a plurality of data sectors for storing data and a plurality of sector-reconstruction-interleave (SRI) sectors for storing redundancy data. The redundancy data stored in a selected one of the SRI sectors is generated in response to the data stored in an interleave of the data sectors corresponding to the selected one of the SRI sectors.

Disk drive for storing sector-reconstruction sectors and for storing a sector-reconstruction status in sectors distributed around a disk

Abstract: A disk drive is disclosed comprising a disk, a head, and an actuator for actuating the head radially over the disk. The disk comprises a plurality of tracks, wherein each track comprises a plurality of sectors. The plurality of sectors comprise a plurality of data sectors for storing data and at least one sector-reconstruction (SR) sector for storing redundancy data generated in response to the data stored in at least one of the data sectors. At least two of the plurality of sectors of a track are for storing a SR status indicating a validity of the SR sector stored on the track.

Functional redundancy in heterogeneous environments: implications for conservation

Abstract: It has been argued that one of the best ways to conserve biological diversity is to maintain the integrity of functional processes within communities, and this can be accomplished by assessing how much ecological redundancy exists in communities. Evidence suggests, however, that the functional roles species play are subject to the influences of local environmental conditions. Species may appear to perform the same function (i.e. be redundant) under a restricted set of conditions, yet their functional roles may vary in naturally heterogeneous environments. Incorporating the environmental context into ecological experiments would provide a critical perspective for examining functional redundancy among species.

Partial-Order Reduction in Symbolic State-Space Exploration

Abstract: State-space explosion is a fundamental obstacle in the formal verification of designs and protocols. Several techniques for combating this problem have emerged in the past few years, among which two are significant: partial-order reduction and symbolic state-space search. In asynchronous systems, interleavings of independent concurrent events are equivalent, and only a representative interleaving needs to be explored to verify local properties. Partial-order methods exploit this redundancy and visit only a subset of the reachable states. Symbolic techniques, on the other hand, capture the transition relation of a system and the set of reachable states as boolean functions. In many cases, these functions can be represented compactly using binary decision diagrams (BDDs). Traditionally, the two techniques have been practiced by two different schools—partial-order methods with enumerative depth-first search for the analysis of asynchronous network protocols, and symbolic breadth-first search for the analysis of synchronous hardware designs. We combine both approaches and develop a method for using partial-order reduction techniques in symbolic BDD-based invariant checking. We present theoretical results to prove the correctness of the method, and experimental results to demonstrate its efficacy.

Block FIR decision-feedback equalizers for filterbank precoded transmissions with blind channel estimation capabilities

Abstract: In block transmission systems, transmitter-induced redundancy using finite-impulse response (FIR) filterbanks can be used to suppress intersymbol interference and equalize FIR channels irrespective of channel zeros. At the receiver end, linear or decision-feedback (DF) FIR filterbanks can be applied to recover the transmitted data. Closed-form expressions are derived for the FIR linear or DF filterbank receivers corresponding to varying amounts of transmission redundancy. Our framework encompasses existing block transmission schemes and offers low implementation-cost equalization techniques both when interblock interference is eliminated, and when IBI is present as, e.g., in orthogonal frequency-division multiplexing with insufficient cyclic prefix. By applying blind channel estimation methods, our filterbank transmitters-receivers (transceivers) dispense with bandwidth consuming training sequences. Extensive simulations illustrate the merits of our designs.

Architectures for reliable computing with unreliable nanodevices

Abstract: As electronic devices get smaller and smaller, so the probability of errors in manufacturing increases, and the need to use fault-tolerant techniques. This paper compares the relative performance of four such techniques: R-fold multiple redundancy; cascaded triple modular redundancy; von Neumann's multiplexing method; and a reconfigurable computer technique. It is shown that manufacturing defect rates of the order of 0.01 to 0.1 will require enormous amounts of redundancy, of the order of 10/sup 3/ to 10/sup 5/.

Memory built-in self-repair using redundant words

Abstract: A word oriented memory Built-In Self-Repair (BISR) methodology is described without modifying the memory module. Faulty addresses and its data are stored in the redundancy logic immediately after its detection during test. Fuse boxes can be connected via scan registers to the redundancy logic.

A redundancy-based iterative approach for avoiding joint limits: application to visual servoing

Abstract: We propose new redundancy-based solutions to avoid robot joint limits of a manipulator. We use a control scheme based on the task function approach. We first recall the classical gradient projection approach and then present a far more efficient method that relies on the iterative computation of motion that does not affect the task achievement and ensures the avoidance problem. We apply this new method in a visual servoing application. We demonstrate the validity of the approach on various real experiments as well as on the control of a virtual humanoid.

System and method for adaptive streaming of predictive coded video data

Abstract: This invention provides an adaptive transcoder which streams predictive coded video data over variable bandwidth networks and to devices having varying processing capabilities. The invention dynamically and continuously determines an available network bandwidth and a client device's processing capabilities. This invention uses bit stream transcoding of video data to reduce the bandwidth required to stream the video. Certain frames of a bit stream are replaced with Pseudo-P frames according to the results of rate control feedback and frame ranking. The invention thus transmits a single MPEG stream to multiple devices having varying capabilities and does not add redundancy into the network.

Iterative source-channel decoder using extrinsic information from softbit-source decoding

Abstract: In digital mobile communications, efficient compression algorithms are needed to encode speech or audio signals. As the determined source parameters are highly sensitive to transmission errors, robust source and channel decoding schemes are required. This contribution deals with an iterative source-channel decoding approach where a simple channel decoder and a softbit-source decoder are concatenated. We mainly focus on softbit-source decoding which can be considered as an error concealment technique. This technique utilizes residual redundancy remaining after source coding. We derive a new formula that shows how the residual redundancy transforms into extrinsic information utilizable for iterative decoding. The derived formula opens several starting points for optimizations, e.g. it helps to find a robust index assignment. Furthermore, it allows the conclusion that softbit-source decoding is the limiting factor if applied to iterative decoding processes. Therefore, no significant gain will be obtainable by more than two iterations. This will be demonstrated by simulation.

System and method for comprehensive availability management in a high-availability computer system

Abstract: A system and method for availability management coordinates operational states of components to implement a desired redundancy model within a high-availability computing system. Within the availability management system, an availability manager monitors various reports on the status of components and nodes within the system. The availability manager uses these reports to direct components to change states if necessary, in order to maintain the desired system redundancy model. The availability management system includes a health monitor for performing component status audits upon individual components and reporting component status changes. The system also includes a watch-dog timer, which monitors the health monitor and reboots the entire node containing the health monitor if it becomes non-responsive. Each node within the system also includes a cluster membership monitor, which monitors nodes becoming non-responsive and reports node non-responsive errors.

Apparatus and method for spare capacity allocation

Abstract: A method is given for deriving a backup path routing spare capacity template that is feasible, scalable, adaptive, much faster, and near global optimal in redundancy reduction. The method includes determining working paths, aggregating the working paths into a first matrix, determining backup paths, aggregating the backup paths into a second matrix, and deriving the template from the first and second matrices. A method is also given for successively approximating the optimal spare capacity allocation needed for a network. The method includes, determining the link cost associated with a selected traffic flow's backup path, determining an updated link cost that is less than the current link cost, determining a backup path with the updated link cost, and notifying the rest of the network of the backup path.

Modular uninterruptible power supply

Abstract: A modular uninterruptible power supply is disclosed, which provides complete redundancy for all components required for UPS operation. Novel aspects of the invention include design of the modules and their interconnection and interoperability, as well as improved operation techniques applicable to UPS systems generally.

Efficient Broadcast in Mobile Ad Hoc Networks Using Connected Dominating Sets

Abstract: Broadcast is a common operation in mobile ad hoc networks (MANETs). Many on demand ad hoc routing protocols resort to it to discover the route between any two nodes. It is also an important means to disseminate information in many MANET applications. An intuitive way for broadcast is flooding. However, without well designed control mechanisms, flooding will lead to serious message redundancy, contention and collision. This paper proposes an efficient broadcast scheme based on the concept of connected dominating set (CDS) in graph theory. The proposed scheme can reduce message redundancy significantly, while retaining the merits of flooding. Simulation results show that the proposed scheme outperforms a distributed CDS based algorithm and a cluster based approach.

Some results on reversed hazard rate ordering

Abstract: Recently, the reversed hazard rate (RHR) function, defined as the ratio of the density to the distribution function, has become a topic of interest having applications in actuarial sciences, forensic studies and similar other fields. Here we establish results with respect to RHR ordering between the exponentiated random variables. We also address the ordering results between component redundancy and system redundancy. Both the cases of matching spares and non-matching spares are discussed. In case of matching spares, a sufficient condition has been given for component redundancy to be superior to the system redundancy with respect to the reversed hazard rate ordering for any coherent system.

Redundancy strategies for a high splitting optically amplified passive optical network

Abstract: High splitting, optically amplified, passive optical networks (SuperPONs) are investigated in terms of redundancy provision and protection mechanisms. Options for redundancy, including the important special case of dual homing, are detailed, and it is determined as to which of these options (duplication of the feeder and first distribution section, and N+1 protection of the optical amplifiers in the amplified splitter) would be required to be provided to all attached users to facilitate appropriate availability of the basic telephony service. The distributed amplified splitter dual homing solution is found to outperform the single amplified splitter solution in terms of its survivability. The protection mechanisms necessary to automatically switch to the redundant provision are discussed and it is seen that with the aid of suitable regular precautionary procedures protection switching can generally be provided rapidly (<50 ms). Finally, an availability, and cost versus availability, study confirms the aforementioned redundancy assessment for fiber-to-the-home (FTTH) implementations, but shows fiber-to-the-curb (FTTC) as needing additional redundancy.

Remote mirroring in a switched environment

Abstract: A mechanism to support remote mirroring of storage devices by data storage systems in a one-to-many switched environment. Each data storage system includes a disk director that is adapted to control at least one device group that is supported in a mirrored configuration with a corresponding device group controlled by one of the other data storage systems. For each device group and corresponding device group, there are first ports associated with the device group and second ports associated with the corresponding device group. A switch element is adapted to connect one of the first ports to at least one of the second ports so that data may be exchanged between the ports for each device group and corresponding device group. The disk director selects which first port is to be connected to which second port via the switch element in the establishment of a logical link. Thus, each port connected to the switch is capable of achieving multiple connections to multiple destinations for increased connectivity, redundancy and performance (load balance) without additional hardware.

System and method of operating a programmable column fail counter for redundancy allocation

Abstract: The present invention includes a system and a methodology for eliminating faulty memory cells in a memory array with replacement columns of memory cells and replacement rows of memory cells. The individual memory cells are checked to ensure that each is operational. Non-operational cells are replaced by first replacing columns which contain a threshold number of non-operational cells with spare columns and second removing any remaining non-operational cells by replacing the rows containing those non-operational cells with spare rows.

Memory device and method for redundancy/self-repair

Abstract: The preferred embodiments described herein provide a memory device and method for redundancy/self-repair. In one preferred embodiment, a memory device is provided comprising a primary block of memory cells and a redundant block of memory cells. In response to an error in writing to the primary block, a flag is stored in a set of memory cells allocated to the primary block, and the redundant block is written into. In another preferred embodiment, an error in writing to a primary block is detected while an attempt is made to write to that block. In response to the error, the redundant block is written into. In yet another preferred embodiment, a memory device is provided comprising a three-dimensional memory array and redundancy circuitry. In still another preferred embodiment, a method for testing a memory array is provided. Other preferred embodiments are provided, and each of the preferred embodiments described herein can be used alone or in combination with one another.