| 摘要 |
An HDTV transmission system includes a Tomlinson precoder (17) in the transmitter in order to compensate for the forced intersymbol interference introduced by an NTSC rejection filter used in the receiver. The system employs one of a family of four-dimensional coded modulation schemes based on a six-signal-point, one dimensional base constellation. The various schemes exhibit different amounts of so-called shaping gain and support respective different payload data rates. The characteristics of the Tomlinson precoder are such as to preserve a substantial portion of the shaping gain. The system may switch its operation among the various coded modulation schemes to account for changes in channel conditions and/or to accommodate different source signal bit rates.
|
