Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Patent
1997-10-30
1999-10-26
Pham, Chi H.
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
371 431, 371 438, H04L 512, H04L 2302
Patent
active
059740914
ABSTRACT:
This invention provides means for processing a received digitally-modulated carrier signal to coherently demodulate or, for some applications, coherently demodulate and decode said signal when the signal's phase has an undesired component and/or to generate successive estimated values of said undesired phase of the received signal. The signal processed is partially represented by a composite trellis diagram formed by combining multiple component trellis diagrams which are phase-displaced versions of a root trellis diagram. Desired variations in signal parameter values that result from modulating the signal effect transitions between states within the root trellis diagram. For some embodiments of this invention, transitions between states within different component trellis diagrams for which phase values are proximate, trellis coupling transitions, are incorporated into the composite trellis diagram in a periodic manner to accommodate undesired variations in the received signal's phase for which the rate of change in phase is adequately small relative to the modulation rate but not otherwise restricted. The received signal is processed in accord with the composite trellis diagram through appropriate application of the Viterbi maximum likelihood processing algorithm or any sub-optimum variant, derivative or counterpart thereof. A demodulated data sequence and/or a sequence of estimated values of the received signal's phase are derived from appropriately structured path history values generated for the multiple states in the composite trellis diagram. The received signal processed may have a continuous envelope or may be comprised of a succession of non-overlapping signal bursts which originate at one or more transmit locations as in a TDMA system.
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Communication Network Systems
Pham Chi H.
Webster Bryan
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