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Sixteen-State Feedback Convolutional Encoder

IP.com Disclosure Number: IPCOM000060129D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Maddens, F: AUTHOR

Abstract

A preference has been established for trellis-coded modulation for use in data modems which transmit data at a rate of 9,600 bits/s. over the Public Switched Networks, and those which transmit data at a rate higher than 9,600 bits/s. over leased voice grade telephone lines. This article describes a 16-state feedback convolutional encoder which is a feedback version of the 16-state forward convolutional encoder described in the IBM Technical Disclosure Bulletin 28, 6, 2466-2468 (November 1985). The feedback encoder is as much insensitive to 90Πphase jumps of the carrier as the forward encoder, thus allowing carrier phase to relock in any one of four phase positions after a temporary loss of carrier phase synchronization.

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Sixteen-State Feedback Convolutional Encoder

A preference has been established for trellis-coded modulation for use in data modems which transmit data at a rate of 9,600 bits/s. over the Public Switched Networks, and those which transmit data at a rate higher than 9,600 bits/s. over leased voice grade telephone lines. This article describes a 16-state feedback convolutional encoder which is a feedback version of the 16-state forward convolutional encoder described in the IBM Technical Disclosure Bulletin 28, 6, 2466-2468 (November 1985). The feedback encoder is as much insensitive to 90OE phase jumps of the carrier as the forward encoder, thus allowing carrier phase to relock in any one of four phase positions after a temporary loss of carrier phase synchronization. The figure illustrates a feedback encoder for trellis-coded modulation that transforms six parallel information bits (In,1-In,6) into sequences of seven parallel bits (Yn,0-Yn,6) which are then mapped into complex channel signals of the 128-state signal constellation shown in the above-referenced article. The 128 states are partitioned into 8 subsets: A = (ai), B = (bi), C = (ci), D = (di), E = (ei), F = (fi), G = (gi), and H = (hi). The association of these subsets with state transitions of the convolutional encoder is similar to that shown in the above-referenced article, but the state of the convolutional encoder is defined by bits Wn,1, Wn,2, Wn,3, and Wn,4. A transition at time n is uniquely asso...