Supporting Probabilistic Constellation Shaping in 5G-NR Evolution

It is known that probabilistic constellation shaping (PCS) can provide a shaping-gain of 1.53dB asymptotically as signal-to-noise (SNR) increases. This is however, under ideal assumptions that the system operates in optimal sense and can achieve the Shannon capacity. In practice, the system can operate well below the capacity. In this paper, we propose a PCS-transceiver for the fifth-generation new-radio (5G-NR) evolution that supports quadrature-amplitude-modulation (QAM) constellations shaped with PCS, namely, PCS-QAM, in comparison to conventional uniform QAM constellations, namely, Uniform-QAM. We put a special interest in the throughput achieved under a stringent block-error rate (BLER) constraint, and validate the effectiveness of PCS under practical detection and decoding algorithms. We also analyze the properties of power-gain, entropy-loss, and peak-to-average power-ratio (PAPR), in connections to PCS. As a lower BLER does not necessarily indicate a higher throughput due to entropy-loss from PCS, we further prove that a necessary and sufficient condition for PCS-QAM to outperform Uniform-QAM in throughput is that the normalized entropy-loss with PCS-QAM is less than the BLER obtained with Uniform-QAM. Furthermore, we demonstrate that the PCS-transceiver is flexible in rate-adaptation without impacting the encoder, and can yield a better throughput-envelope in 5G-NR system.