| 摘要 |
A decoder and an encoder for extracting a subset of symbols from, or inserting a subset of symbols into, a communication channel in which M symbols are transmitted as the amplitudes of M sinusoidal carriers. The decoder recovers K symbols, Sp . . . Sp+K-1, from an analog signal generated by modulating M sinusoidal carriers for a frame period. Each carrier is modulated with an amplitude proportional to the value of one of M symbols, the ith carrier being modulated by symbol Si. The K symbols are a contiguous subset of the M symbols. The decoder includes a down-converter for down-converting to the modulated signal on the communication channel to generate a down-converted signal in which the carriers corresponding to Sp . . . Sp+K-1 occupy frequencies starting from 0. An analog-digital converter generates K time-domain samples in each frame period from the down-converted signal. These time-domain samples are converted to K frequency-domain values representing the symbols Sp . . . Sp+k-1 by a time-domain to frequency-domain overlapped transform. The encoder encodes K symbols, S1 . . . SK, as the amplitudes of K sinusoidal carriers, the K sinusoidal carriers comprising a contiguous block of carriers in a signal comprising M sinusoidal carriers in which each of the carriers is modulated by a signal having an amplitude determined by the value of one of the symbols for a time equal to one frame period. The encoder includes a frequency-domain to time-domain overlapped transform for generating K time-domain samples from the K symbols, the time-domain samples representing a modulated carrier comprising K sinusoidal carriers, each the carrier being modulated by a signal having an amplitude determined by the value of one of the K symbols. A digital-to-analog converter converts the K time-domain samples to an analog signal. The analog signal is then up-converted such that the sinusoidal carrier modulated by S1 has a frequency equal to the pth carrier of the M sinusoidal carriers, wherein p>0.
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