Information decoder for polar codes

An information decoder for decoding an encoded sequence into a decoded sequence, the information decoder comprising processing circuitry, the processing circuitry being configured to cause the information decoder to:

• obtain a channel output, the channel output representing the encoded sequence as passed through a communications channel, the encoded sequence having been encoded using a polar code, wherein the polar code is representable by a code diagram;
• successively decode the channel output into the decoded sequence by traversing the code diagram, and while doing so:
• compute soft values for encoded bits, decided encoded bits and soft values for intermediate bits, decided intermediate bits, and decided input bits;
• determine a bit score term for each potential decoding decision on one or more bits being decoded;
• and
• add an adjustment term to each bit score term to form a candidate score for said each potential decoding decision;
• wherein the successive decoding is repeated until all bits of the channel output have been decoded, resulting in at least two candidate decoded sequences;
• and
• discard all but one of the at least two candidate decoded sequences, resulting in one single decoded sequence,
• wherein each potential decoding decision on said one or more bits being decoded results in a respective candidate decoded sequence for said one or more bits being decoded, each with its own candidate score, and wherein which candidate decoded sequence to represent said one or more bits being decoded is selected based on which candidate score is highest for said one or more bits being decoded.

A non-transitory computer readable medium storing a computer program product for decoding an encoded sequence into a decoded sequence, the computer program product comprising computer code which, when run on processing circuitry of an information decoder, causes the information decoder to:

• obtain a channel output, the channel output representing the encoded sequence as passed through a communications channel, the encoded sequence having been encoded using a polar code, wherein the polar code is representable by a code diagram;
• successively decode the channel output into the decoded sequence by traversing the code diagram, and while doing so:
• compute soft values for encoded bits, decided encoded bits and soft values for intermediate bits, decided intermediate bits, and decided input bits;
• determine a bit score term for each potential decoding decision on one or more bits being decoded;
• and
• add an adjustment term to each bit score term to form a candidate score for said each potential decoding decision;
• wherein the successive decoding is repeated until all bits of the channel output have been decoded, resulting in at least two candidate decoded sequences;
• and
• discard all but one of the at least two candidate decoded sequences, resulting in one single decoded sequence,
• wherein each potential decoding decision on said one or more bits being decoded results in a respective candidate decoded sequence for said one or more bits being decoded, each with its own candidate score, and wherein which candidate decoded sequence to represent said one or more bits being decoded is selected based on which candidate score is highest for said one or more bits being decoded.