| 摘要 |
<p>An improved system for transmitting a coded orthogonal frequency division multiplex (COFDM) signal is proposed wherein bits of data of most importance are coded into portions of the signal with greatest ruggedness, e.g. a QPSK signal. Bits of data of lesser importance are coded onto portions of the signal with less ruggedness, e.g. a 16 QAM signal. The resultant signal is transmitted. The peak to mean ratio of a signal for transmission is minimised by varying the amplitudes of carriers making up each COFDM symbol from symbol to symbol. At a receiver the thresholds for decoding anything of a higher order than a QPSK signal are computed by averaging the amplitudes of carriers in each quadrant of a phase diagram. In order to minimise interference to other transmissions the amplitudes of carriers within each symbol are varied such that the interfering contributions from each are equal.</p> |
