Soft List Decoding of Polar Codes

Soft-output (SO) decoding is proposed for the Logarithmic Successive Cancellation List (Log-SCL) polar decoder for the first time, by exploiting the left-to-right propagation of the Belief Propagation (BP) decoder, which opens new avenues for its employment in powerful turbo-receivers. In the case of decoding a half-rate polar code having a block length of 1024 bits, the proposed soft list polar decoder achieves a 1.5 dB Block Error Ratio (BLER) performance gain, <inline-formula><tex-math notation="LaTeX">$50\%$</tex-math></inline-formula> latency improvement and <inline-formula><tex-math notation="LaTeX">$26\%$</tex-math></inline-formula> complexity reduction, compared to the state-of-the-art SO Soft Cancellation (SCAN) polar decoder in a polar-coded Multiple-Input Multiple-Output (MIMO) system. Furthermore, we conceive a Memory-Efficient (ME) soft list polar decoder, which requires only <inline-formula><tex-math notation="LaTeX">$16\%$</tex-math></inline-formula> of the soft list polar decoder's memory, at the cost of slightly increased latency and complexity.