A time-hopping modulation format employing impulse signal technology has several features which may make it attractive for multiple-access communications. These features are outlined, an estimate of the multiple-access capability of a communication system employing this format under ideal propagation conditions is presented, and emerging design issues are described. >

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Multiple access with time-hopping impulse modulation

A new class of fast-converging timing recovery methods for synchronous digital data receivers is investigated. Starting with a worst-case timing offset, convergence with random binary data will typically occur within 10-20 symbols. The input signal is sampled at the baud rate; these samples are then processed to derive a suitable control signal to adjust the timing phase. A general method is outlined to obtain near-minimum-variance estimates of the timing offset with respect to a given steady-state sampling criterion. Although we make certain independence assumptions between successive samples and postulate ideal decisions to obtain convenient analytical results, our simulations with a decision-directed reference and baud-to-baud adjustments yield very similar results. Convergence is exponential, and for small loop gains the residual jitter is proportional and convergence time is inversely proportional to the loop gain. The proposed algorithms are simple and economic to implement. They apply to binary or multilevel PAM signals as well as to partial response signals.

Timing Recovery in Digital Synchronous Data Receivers

Developments in the theory of linear least-squares estimation in the last thirty years or so are outlined. Particular attention is paid to early mathematica[ work in the field and to more modern developments showing some of the many connections between least-squares filtering and other fields.

A view of three decades of linear filtering theory

This paperd escribes a byte-oriented binary transmission code and its implementation. This code is particularly well suited for high-speed local area networks and similar data links, where the information format consists of packets, variable in length, from about a dozen up to several hundred 8-bit bytes. The proposed transmission code translates each source byte into a constrained 10-bit binary sequence which hase excellent performance parameters near the theoretical limits for 8B/10B codes. The maximum run length is 5 and the maximum digital sum variation is 6. A single error in the encoded bits can, at most, generate an error burst of length 5 in the decoded domain. A very simple implementation of the code has been accomplished by partitioning the coder into 5B/6B and 3B/4B subordinate coders.

A DC-balanced, partitioned-block, 8B/10B transmission code

This paper surveys a variety of data compression methods spanning almost 40 years of research, from the work of Shannon, Fano, and Huffman in the late 1940s to a technique developed in 1986. The aim of data compression is to reduce redundancy in stored or communicated data, thus increasing effective data density. Data compression has important application in the areas of file storage and distributed systems. Concepts from information theory as they relate to the goals and evaluation of data compression methods are discussed briefly. A framework for evaluation and comparison of methods is constructed and applied to the algorithms presented. Comparisons of both theoretical and empirical natures are reported, and possibilities for future research are suggested.

Data compression

Optimal cyclic group codes obtained by deleting or puncturing certain coordinates of maximal length shift register code

Algebraically punctured cyclic codes

Theory of synchronous communications

This chapter provides an overview of fault-tolerant computing. Fault-tolerant computing can be defined as the process by which a computing system continues to perform its specified tasks correctly in the presence of faults with the goal of improving the dependability of the system. Principles of fault-tolerant computing as well as various fault-tolerant architectures are discussed. The article concludes by observing trends in the fault-tolerant computing.


Keywords:

fault tolerance;
reliability;
availability;
coverage;
dependability;
redundancy

Jack J. Stiffler

Papers

Algebraically punctured cyclic codes

Theory of synchronous communications

Fault-Tolerant Computing

Error correcting codes