| 摘要 |
A transmitter for transmitting a sequence of octets over a digital network which digital network converts the octets into a sequence of levels for transmission over an analog channel to a receiver, the levels producing an analog signal having a predefined spectral shape, the transmitter including: a mapping device which receives at its input groups of data bits to be transmitted and outputs for each group an equivalence class of one or more levels, wherein at least one equivalence class contains more than one level; a level selector, operably coupled to the mapping device, for selecting the level in the equivalence class to represent the group of data bits to be transmitted; a filter device, operably coupled to the level selector and having a filter response corresponding to the predefined spectral shape, which receives at its input previously selected levels and provides its output to the level selector, wherein the level selector selects the level to be transmitted based on the output of the filter device; and an octet converter, operably coupled to the level selector, which receives the selected level at its input and transmits over the digital network an octet corresponding to the selected level to produce the analog signal having the predefined spectral shape when the transmitted octets are converted to levels in the digital network.
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