Improved method for partially modulating and demodulating data in a multi-carrier transmission system

摘要

A decoder (200) and an encoder (300) for extracting a subset of symbols from, or inserting a subset of symbols into, a communication channel (333) in which M symbols are transmitted as the amplitudes of M sinusoidal carriers. The decoder (200) 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 i carrier being modulated by symbol Si. The K symbols are a contiguous subset of the M symbols. The decoder (200) includes a down-converter (201, 211, 202, 212) for down-converting 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 O. An analog-digital converter (203, 313) 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 (300) 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 (300) includes a frequency-domain to time-domain overlapped transform (302, 312) for generating K time-domain samples from the K symbols, the time-domain samples representing a modulated carrier comprising K sinusoidal carriers, each of the carriers being modulated by a signal having an amplitude determined by the value of one of the K symbols. A digital-to-analog converter (304, 314) 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 p carrier of the M sinusoidal carriers, wherein p>/=0.