The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 13, 1991
Filed:
Jul. 10, 1990
G D Forney, Jr, Cambridge, MA (US);
Vedat M Eyuboglu, Boston, MA (US);
Codex Corporation, Mansfield, MA (US);
Abstract
Apparatus for generating a (running digital sum) sequence of digital signals X.sub.k and/or a (partial response coded) sequence of digital signals Y.sub.k, K=1, 2, . . . , such that Y.sub.k =X.sub.k .+-.X.sub.k-l, L and integer, in which the Y.sub.x signals are a sequence in a given modulation code. In one aspect, the signals Y.sub.k are chosen to be congruent to coset representatives specified in accordance with a modulation code, a plurality of code constellations are used, and at least one constellation includes both a point with a positive sum of coordinates and one with a negative sum of coordinates. In another aspect, the signals X.sub.k are chosen to be congruent to a sequence of alternate (precoded) coset representatives. In other aspects, the Y.sub.k alphabet signals are evenly spaced, and a selectable, e.g., an optimal, tradeoff between S.sub.x and S.sub.y is made. An N-dimentional modulation code is generated as a sequence of one-dimensional signals. A maximum likelihood sequence estimation decoder reconstructs the estimated running digital sum, and generates a signal whenever the estimated running digital sum is outside a permissible range. In another aspect, the decoder includes a modified maximum likelihood sequence estimator adapted to find MQ partial decoded sequences, where Q is the number of encoder states, and M is an integer.