| 摘要 |
<p>Data, especially when it is source-coded multimedia information (video, speech, audio), often should be protected differently, since the effects of errors would lead to disturbances of different susceptibility. Thus, unequal error protection (UEP) should be provided by the physical transport. Multicarrier modulation (DMT: Discrete MultiTone, OFDM: Orthogonal Frequency Division Multiplex) allows to implement unequal error protection already when allocating the bits (signal alphabets) to the carriers. UEP coding is a well-known alternative, which may be additionally used. Implementing it in multicarrier transmission is a very low-complex and efficient realization. The solution in this application allows to arbitrarily select the number of bits in the different protection classes with arbitrary spacing in the signal-noise ratio margin or, equivalently, with an arbitrary separation in bit-error ratios. The invention includes an SNR sorting scheme ensuring robustness in the sense that high-protected bits will still be better protected even under non-stationary noise. The bit-allocation can also be allowed to be mixed with bits from different protection classes leading to hierarchical modulation schemes.</p> |
