Dc-free or nyquist-free block-error correcting line encoders based on n-ask modulation

摘要

The invention relates to line encoding, in particular to DC free and/or Nyquist free encoding for terahertz communication. The encoded words are fed to a modulator that performs a weighted combination thereof. To improve DC free behaviour of an encoding scheme, the codebooks for the line encoders are built from an initial (11,15) Hamming code 405. A plurality of codebooks 415-465 are formed as sub-sets of this initial codebook, each coding codebook being associated with a mean absolute digital value corresponding to a mean of the absolute values of the digital sums of the codewords composing the sub-set. A target mean absolute digital value may be targeted when building the codebooks, said target being dependent on the modulation weights. The codebooks are then assigned to the sub-streams according to an inverse relationship between their mean absolute digital values and the weights applied to the sub-streams in the weighted combination for modulation.