Polar Codes with Enhanced Weight Distribution.

This paper aims to improve the error-correcting performance of polar codes and polarization-adjusted convolutional (PAC) codes, by reducing the number of the low-weight codewords. The proposed codes are implemented via repeating message bits at frozen indices for polar codes or re-freezing the bits at frozen indices to zeros after convolution operation for PAC codes. The operations of repeating and re-freezing can be designed by simply analyzing a subset of row indices of polar transform, and can be directly incorporated into the existing encoding chain of polar codes and PAC codes. The proposed codes consistently outperform or at least perform similarly than the 5G polar and PAC codes. Up to 0.2 dB and 0.1 dB improvements have been observed over the respective codes.