| 摘要 |
<p>An orthogonal frequency division multiplexed (OFDM) signal is coded by dividing each OFDM symbol into a plurality of mini-symbols. Carriers (A, B, C, D) in each mini-symbol are formed from different portions of a plurality of signal sets (J, K, L, M). The most important data is coded on a signal set which provides a substantially constant contribution to the corresponding carriers in each mini-symbol and is thus conveyed most ruggedly. Less important data is coded on signal sets which vary between corresponding carriers from mini-symbol to mini-symbol in dependence on predetermined functions and is thus conveyed less ruggedly. The contributions from these signal sets sum substantially to zero across an OFDM symbol. Alternatively the signal sets coded with the most important data are assigned every rth carrier forming an OFDM symbol and signal sets coded with less important data are assigned to intermediate carriers wherein each intermediate carrier is coded with data derived from a plurality of signal sets. In each of these systems the most important data serves as a phase and amplitude reference for the signal sets carrying less important data.</p> |
