Pulse or digital communications – Pulse code modulation
Patent
1996-12-04
2000-06-27
Pham, Chi H.
Pulse or digital communications
Pulse code modulation
375295, 341 50, 371 43, H04B 1404, H04L 2704, H03M 700, G06F 1110
Patent
active
060815558
ABSTRACT:
An improved apparatus for implementing shell mapping in a PCM modem incorporates .mu.-law signal mapping points. An improved signal point encoding technique effectively employs ring indices that are generated in accordance with known principles. The ring indices are applied to a reordering module, which rearranges the ring indices produced by a conventional shell mapping algorithm. A preferred reordering scheme takes advantage of the non-uniform probability distribution provided by the conventional shell mapping algorithm. The rings are rearranged such that the sets of signal points having relatively small separation distances are assigned to rings with relatively low frequencies of occurrence, while the sets of signal points having relatively large separation distances are assigned to rings with relatively high frequencies of occurrence. The reordering scheme optimizes the signal point assignment while maintaining acceptable limits for average transmission power.
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Conexant Systems Inc.
Pham Chi H.
Tran Khai
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