COMMUNICATION SYSTEM, TRANSMISSION DEVICE, RECEIVING DEVICE, AND DIGITAL TRANSMISSION METHOD

摘要

A communication system is provided which uses hierarchical modulation and is capable of flexibly adjusting line quality. The communication system includes a transmission apparatus 1a that hierarchically modulates and transmits a plurality of signal sequences, a reception apparatus 2a that hierarchically demodulates a received signal, and a hierarchization-parameter setting unit 3 that sets hierarchization parameters. The transmission apparatus 1a includes a hierarchical modulation unit 11a that superimposes signals from a plurality of layers by using the hierarchical modulation while maintaining gray codes. The reception apparatus 2a includes a hierarchical demodulation unit 21a that demodulates and separates hierarchically modulated signals by using the hierarchical demodulation and detects signals from a plurality of layers. The hierarchization-parameter setting unit 3 sets, as the hierarchization parameters, a hierarchization ratio, which is a signal power ratio used for superimposing a higher layer and a lower layer, a mapping pattern capable of selecting two patterns from pattern candidates for bit mapping while allowing redundancy, and a mapping pattern mixing ratio indicating a ratio with which two mapping patterns are mixed in the signal sequences.