Digital encoder and method of encoding

A method of encoding UF-OFDM signals, said method comprising:

• segmenting a series of input symbols in a sequence of respective segments each segment of said sequence of respective segments comprising a first plurality of symbols, said first plurality of symbols corresponding in number to the number of said input symbols being assigned to each sub-band;
• processing each said first plurality of symbols to obtain a corresponding first plurality of samples,
• sorting said first plurality of samples in a predetermined sequence of respective processed segments, wherein each processed segment of the respective processed segments comprises a second plurality of samples corresponding in number to the number of the series of the input symbols being assigned to each sub-carrier so as to interleave the processed outputs for each sub-band across the sub-carriers;
• and
• processing each said second plurality of samples to obtain a UF-OFDM data stream.

A method of defining a set of filter coefficients, comprising:

• sampling a frequency shifted UF-OFDM filter to obtain a first plurality of core filter coefficients,
• zero padding said first plurality of core filter coefficients to obtain a set of padded core filter coefficients, said set of padded core filter coefficients comprising a number of coefficients equal to a total number of sub-carriers across sub-bands,
• performing a Fast Fourier Transform of size equal to a total number of sub-carriers across the sub-bands, to obtain a second plurality of core filter coefficients being equal in number to the total number of sub-carriers across the sub-bands,
• extracting a third plurality of core filter coefficients from first outputs of the Fast Fourier Transform performed in the preceding step, said third plurality of core filter coefficients being equal in number to a number of input symbols being assigned to each sub-carrier for a given sub-band index,
• repeating said extracted core filter coefficients until a fourth plurality of core filter coefficients equal in number to the total number of sub-carriers across the sub-bands is obtained, and
• subjecting said fourth plurality of core filter coefficients to a linear phase rotation.

A method of defining a set of filter coefficients, comprising:

• sampling a frequency shifted UF-OFDM filter to obtain a first plurality of filter tail coefficients;
• in a case where no value is available for a preceding iteration, setting an iterated coefficient value to 0, or otherwise
• in a case where a value is available for a preceding iteration, multiplying a cumulative iterated coefficient value by a linear phase rotation term;
• adding a respective coefficient from first plurality of filter tail coefficient to the iterated coefficient number determined in the preceding iteration to obtain a cumulative iterated coefficient value;
• repeating for each successive iterated coefficient until a second plurality of filter tail coefficients have been determined, said second plurality of filter tail coefficients being equal in number to the number of coefficients defining the UF-OFDM filter repeating for each sub-carrier until all values have been determined.