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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 r1 bits, where r+r1=N. At least one of the bits in the first subset is appl

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 r1 bits, where r+r1=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 r1+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.

대표청구항 ▼

Apparatus for encoding a sequence of input bits for transmission via a quadrature amplitude modulated carrier signal, comprising: means responsive to first and second subsets of selected bits in each group of N consecutive ones of said input bits for forming first and second expanded versions of the

Apparatus for encoding a sequence of input bits for transmission via a quadrature amplitude modulated carrier signal, comprising: means responsive to first and second subsets of selected bits in each group of N consecutive ones of said input bits for forming first and second expanded versions of the bits in each of said first and second subsets, respectively, each of said expanded versions having at least one more bit than the subset from which it is formed, and means individually responsive to said first and second expanded versions for modulating in-phase and quadrature components of said carrier signal to generate an individual one of a predetermined constellation of signal points, wherein said forming means includes means for combining at least one bit in said first subset with at least one bit in the first subset of a preceding one of saidn N-bit groups and means for combining at least one bit in said second subset with at least one bit in the second subset of a preceding one of said N-bit groups, said combining and modulating means being arranged such that less than all possible sequences of said signal points is generated.