Pulse or digital communications – Repeaters – Testing
Patent
1983-01-04
1985-08-06
Krass, Errol A.
Pulse or digital communications
Repeaters
Testing
340347DD, 375 59, H04L 300
Patent
active
045340404
ABSTRACT:
An input bit sequence is encoded for transmission on a QAM carrier by dividing a scrambled version of the input sequence into groups of N consecutive bits. Each group is then subdivided into first and second subsets of r and r.sup.1 bits, where r+r.sup.1 =N. At least one of the bits in the first subset is applied to a finite state machine (such as a convolution encoder) which is arranged to expand the applied bits by at least one additional bit, in accordance with a prescribed logic arrangement. At least one bit in the second subset is processed similarly but independently, using a different finite state machine, or by time sharing a single finite state encoder. The expanded bit subsets, which include at least r+1 and r.sup.1 +1 bits, respectively, are then mapped into in-phase and quadrature symbols such that the minimum euclidean distance for an error event is larger than that obtained from an uncoded system. The symbols to be transmitted are then filtered and the filter output is modulated using conventional QAM methods.
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AT&T Information Systems
Black Thomas G.
Freedman Barry H.
Krass Errol A.
Slusky Ronald D.
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