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You searched for +publisher:"University of Arizona" +contributor:("Leonard, John"). Showing records 1 – 3 of 3 total matches.

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University of Arizona

1. Hay, Karen June. A proof methodology for verification of real-time and fault-tolerance properties of distributed programs.

Degree: 1993, University of Arizona

From the early days of programming, the dependability of software has been a concern. The development of distributed systems that must respond in real-time and continue to function correctly in spite of hardware failure have increased the concern while making the task of ensuring dependability more complex. This dissertation presents a technique for improving confidence in software designed to execute on a distributed system of fail-stop processors. The methodology presented is based on a temporal logic augmented with time intervals and probability distributions. A temporal logic augmented with time intervals, Bounded Time Temporal Logic (BTTL), supports the specification and verification of real-time properties such as, "The program will poll the sensor every t to T time units." Analogously, a temporal logic augmented with probability distributions, Probabilistic Bounded Time Temporal Logic (PBTTL), supports reasoning about fault-tolerant properties such as, "The program will complete with probability less than or equal to p", and a combination of these properties such as, "The program will complete within t and T time units with probability less than or equal to p." The syntax and semantics of the two logics, BTTL and PBTTL, are carefully developed. This includes development of a program state model, state transition model, message passing system model and failure system model. An axiomatic program model is then presented and used for the development of a set of inference rules. The inference rules are designed to simplify use of the logic for reasoning about typical programming language constructs and commonly occurring programming scenarios. In addition to offering a systematic approach for verifying typical behaviors, the inference rules are intended to support the derivation of formulas expressing timing and probabilistic relationships between the execution times and probabilities of individual statements, groups of statements, message passing and failure recovery. Use of the methodology is demonstrated in examples of varying complexity, including five real-time examples and four combined real-time and fault-tolerant examples. Advisors/Committee Members: Downey, Peter J. (committeemember), Debray, Saumya (committeemember), Leonard, John (committeemember).

Subjects/Keywords: Fault-tolerant computing.; Computer science.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hay, K. J. (1993). A proof methodology for verification of real-time and fault-tolerance properties of distributed programs. (Doctoral Dissertation). University of Arizona. Retrieved from http://hdl.handle.net/10150/186261

Chicago Manual of Style (16th Edition):

Hay, Karen June. “A proof methodology for verification of real-time and fault-tolerance properties of distributed programs. ” 1993. Doctoral Dissertation, University of Arizona. Accessed January 16, 2021. http://hdl.handle.net/10150/186261.

MLA Handbook (7th Edition):

Hay, Karen June. “A proof methodology for verification of real-time and fault-tolerance properties of distributed programs. ” 1993. Web. 16 Jan 2021.

Vancouver:

Hay KJ. A proof methodology for verification of real-time and fault-tolerance properties of distributed programs. [Internet] [Doctoral dissertation]. University of Arizona; 1993. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/10150/186261.

Council of Science Editors:

Hay KJ. A proof methodology for verification of real-time and fault-tolerance properties of distributed programs. [Doctoral Dissertation]. University of Arizona; 1993. Available from: http://hdl.handle.net/10150/186261


University of Arizona

2. Tang, Zuqiang. THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS .

Degree: 2005, University of Arizona

This dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations.Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver.Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated.We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading.Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies. Advisors/Committee Members: Ryan, William E (advisor), Ryan, William E. (committeemember), Marcellin, Michael W. (committeemember), Goodman, Nathan (committeemember), Leonard, John L. (committeemember).

Subjects/Keywords: DS-CDMA; LDPC; Coding-Spreading Tradeoff

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Tang, Z. (2005). THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS . (Doctoral Dissertation). University of Arizona. Retrieved from http://hdl.handle.net/10150/194932

Chicago Manual of Style (16th Edition):

Tang, Zuqiang. “THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS .” 2005. Doctoral Dissertation, University of Arizona. Accessed January 16, 2021. http://hdl.handle.net/10150/194932.

MLA Handbook (7th Edition):

Tang, Zuqiang. “THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS .” 2005. Web. 16 Jan 2021.

Vancouver:

Tang Z. THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS . [Internet] [Doctoral dissertation]. University of Arizona; 2005. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/10150/194932.

Council of Science Editors:

Tang Z. THE CODING-SPREADING TRADEOFF PROBLEM IN FINITE-SIZED SYNCHRONOUS DS-CDMA SYSTEMS . [Doctoral Dissertation]. University of Arizona; 2005. Available from: http://hdl.handle.net/10150/194932


University of Arizona

3. Mishra, Shivakant. Consul: A communication substrate for fault-tolerant distributed programs.

Degree: 1992, University of Arizona

As human dependence on computing technology increases, so does the need for computer system dependability. This dissertation introduces Consul, a communication substrate designed to help improve system dependability by providing a platform for building fault-tolerant, distributed systems based on the replicated state machine approach. The key issues in this approach – ensuring replica consistency and reintegrating recovering replicas – are addressed in Consul by providing abstractions called fault-tolerant services. These include a broadcast service to deliver messages to a collection of processes reliably and in some consistent order, a membership service to maintain a consistent system-wide view of which processes are functioning and which have failed, and a recovery service to recover a failed process. Fault-tolerant services are implemented in Consul by a unified collection of protocols that provide support for managing communication, redundancy, failures, and recovery in a distributed system. At the heart of Consul is Psync, a protocol that provides for multicast communication based on a context graph that explicitly records the partial (or causal) order of messages. This graph also serves as the basis for novel algorithms used in the ordering, membership, and recovery protocols. The ordering protocol combines the semantics of the operations encoded in messages with the partial order provided by Psync to increase the concurrency of the application. Similarly, the membership protocol exploits the partial ordering to allow different processes to conclude that a failure has occurred at different times relative to the sequence of messages received, thereby reducing the amount of synchronization required. The recovery protocol combines checkpointing with the replay of messages stored in the context graph to recover the state of a failed process. Moreover, this collection of protocols is implemented in a highly-configurable manner, thus allowing a system builder to easily tailor an instance of Consul from this collection of building-block protocols. Consul is built in the x-Kernel and executes standalone on a collection of Sun 3 work-stations. Initial testing and performance studies have been done using two applications: a replicated directory and a distributed wordgame. These studies show that the semantic based order is more efficient than a total order in many situations, and that the overhead imposed by the checkpointing, membership, and recovery protocols is insignificant. Advisors/Committee Members: Schlichting, Richard D (advisor), Peterson, Larry L. (committeemember), Snodgrass, Richard T. (committeemember), Gay, David (committeemember), Leonard, John (committeemember).

Subjects/Keywords: Fault-tolerant computing.; Computer network protocols.; Software engineering.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Mishra, S. (1992). Consul: A communication substrate for fault-tolerant distributed programs. (Doctoral Dissertation). University of Arizona. Retrieved from http://hdl.handle.net/10150/185824

Chicago Manual of Style (16th Edition):

Mishra, Shivakant. “Consul: A communication substrate for fault-tolerant distributed programs. ” 1992. Doctoral Dissertation, University of Arizona. Accessed January 16, 2021. http://hdl.handle.net/10150/185824.

MLA Handbook (7th Edition):

Mishra, Shivakant. “Consul: A communication substrate for fault-tolerant distributed programs. ” 1992. Web. 16 Jan 2021.

Vancouver:

Mishra S. Consul: A communication substrate for fault-tolerant distributed programs. [Internet] [Doctoral dissertation]. University of Arizona; 1992. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/10150/185824.

Council of Science Editors:

Mishra S. Consul: A communication substrate for fault-tolerant distributed programs. [Doctoral Dissertation]. University of Arizona; 1992. Available from: http://hdl.handle.net/10150/185824

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