Probabilistic Constellation Shaping for OFDM-Based ISAC Signaling

• Main Authors: Du, Zhen, Liu, Fan, Xiong, Yifeng, Han, Tony Xiao, Yuan, Weijie, Cui, Yuanhao, Yao, Changhua, Eldar, Yonina C
• Format: Journal Article
• Language: English
• Published: 27.10.2023
• DOI: 10.48550/arxiv.2310.18090

Integrated Sensing and Communications (ISAC) has garnered significant attention as a promising technology for the upcoming sixth-generation wireless communication systems (6G). In pursuit of this goal, a common strategy is that a unified waveform, such as Orthogonal Frequency Division Multiplexing (OFDM), should serve dual-functional roles by enabling simultaneous sensing and communications (S&C) operations. However, the sensing performance of an OFDM communication signal is substantially affected by the randomness of the data symbols mapped from bit streams. Therefore, achieving a balance between preserving communication capability (i.e., the randomness) while improving sensing performance remains a challenging task. To cope with this issue, in this paper we analyze the ambiguity function of the OFDM communication signal modulated by random data. Subsequently, a probabilistic constellation shaping (PCS) method is proposed to devise the probability distributions of constellation points, which is able to strike a scalable S&C tradeoff of the random transmitted signal. Finally, the superiority of the proposed PCS method over conventional uniformly distributed constellations is validated through numerical simulations.