Showing papers by "Kenneth Steiglitz published in 1991"

Optimization of signal sets for partial-response channels. I. Numerical techniques

Abstract: Given a linear, time-invariant, discrete-time channel, the problem of constructing N input signals of finite length K that maximize minimum l/sub 2/ distance between pairs of outputs is considered. Two constraints on the input signals are considered: a power constraint on each of the N inputs (hard constraint) and an average power constraint over the entire set of inputs (soft constraint). The hard constraint, problem is equivalent to packing N points in an ellipsoid in min(K,N-1) dimensions to maximize the minimum Euclidean distance between pairs of points. Gradient-based numerical algorithms and a constructive technique based on dense lattices are used to find locally optimal solutions to the preceding signal design problems. Two numerical examples are shown for which the average spectrum of an optimized signal set resembles the water pouring spectrum that achieves Shannon capacity, assuming additive white Gaussian noise. >

Comparison of tree and straight-line clocking for long systolic arrays

Abstract: Achieving efficient and reliable synchronization is a critical problem in building long systolic arrays. This problem is addressed in the context of synchronous systems by introducing probabilistic models for two alternative clock distribution schemes: tree and straight-line clocking. Analytic bounds are presented for the probability of failure, and an examination is made of the tradeoffs between reliability and throughput in both schemes. The basic conclusion is that as the one-dimensional systolic array gets very long, tree clocking becomes preferable to straight-line clocking. >

Reconfigurability and reliability of systolic/wavefront arrays

Abstract: Fault-tolerant redundant structures for maintaining reliable arrays are studied. It is assumed that the desired array (application graph) is embedded in a certain class of regular, bounded-degree graphs called dynamic graphs. The authors define the degree of reconfigurability (DR), and DR with distance DR/sup d/ of a redundant graph. When DR (respectively DR/sup d/) is independent of the size of the application graph, it is said that the graph is finitely reconfigurable, FR (resp. locally reconfigurable, LR). It is shown that DR provides a natural lower bound on the time complexity of any distributed reconfiguration algorithm, and that there is no difference between being FR and LR on dynamic graphs. It is then shown that if one wishes to maintain both local reconfigurability and a fixed level of reliability, a dynamic graph must be of dimension at least one greater than the application graph. >