scispace - formally typeset
Search or ask a question

Showing papers by "Codex Corporation published in 1977"


Journal ArticleDOI
S. Qureshi1
TL;DR: The stability and convergence of the fast start-up algorithm with "stochastic" update in the presence of noise are examined and the one-shot method, which involves estimation of the inverse filter from one period of the received signal, proves to be robust in the absence of noise.
Abstract: Prior knowledge of the typical signal spectrum at the equalizer input can be used to speed up the convergence of a least mean-square error nonrecursivc equalizer by placing a weighting matrix in the path of the coefficient (tap gain) corrections. When the training sequence is periodic with period equal to the time-spread of the nonrecursive equalizer, the weighting matrix is not only symmetric and Toeplitz, but also circulant. Thus the fast update algorithm can be implemented by inserting a single nonrecursive filter in the path of the periodic input sequence before it is used for computing coefficient correction terms. The stability and convergence of the fast start-up algorithm with "stochastic" update in the presence of noise are examined. In the absence of prior information about the channel characteristics, this fast converging training procedure may be easily extended to a one-shot method of equalizer setup. The one-shot method, which involves estimation of the inverse filter from one period of the received signal, proves to be robust in the presence of noise. Simulation resuits are given for class I partial-response and Nyquist (20 percent roll-off raised cosine) data transmission systems with quadrature amplitude modulation over a dial-up telephone connection.

74 citations


Patent
07 Mar 1977
TL;DR: In this article, a data transmission system is described where data in a plurality of constituent streams are received at a multiplexer, processed to form a single composite stream comprising time slots each carrying data from one constituent stream, transmitted in the composite stream over a communication link, and demultiplexed in a demULTiplexer receiving the composite streams at the far end of the link.
Abstract: A data transmission system is described wherein data in a plurality of constituent streams are received at a multiplexer, processed to form a single composite stream comprising time slots each carrying data from one constituent stream, transmitted in the composite stream over a communication link, and demultiplexed in a demultiplexer receiving the composite stream at the far end of the link to recover the original plurality of constituent streams in separate form. The system implements a protocol according to which a plurality of queues, each associated with one of the constituent streams and arranged and connected to receive and store data therefrom, are serviced by a sequence of time slots corresponding to a defined service sequence, the data in any one slot being derived from an associated queue, and being formed into codewords from a codeword set, with framing apparatus emitting terminator codewords to mark the ends of at least some slots.

13 citations