Probabilistic Shaping Using 5G New Radio Polar Codes

An extension to the 5G New Radio polar coding chain is proposed by introducing a shaping encoder prior to the polar encoder that improves the performance with higher order modulation via probabilistic shaping. The method is based on attaching shaping bits to the data bits that force the resulting channel input symbols (after rate matching, scrambling, and symbol mapping) to have a desired non-uniform distribution, such that a shaping gain is obtained. The shaping encoder is realized by using a polar decoder so that no additional hardware is required. The extension does not change the structure of the existing blocks in the transmission chain but only modifies the input parameters. The required changes at the receiver are also very small and can be realized by simple operations without increasing the required computational power. The simulation results validate the performance improvements on the additive white Gaussian noise channels, which can be more than 1 dB for typical scenarios.