A near-field integrated sensing and communications (ISAC) framework is proposed, which introduces an additional distance dimension for both sensing and communications compared to the conventional far-field system. In particular, the Cramer-Rao bound for the near-field joint distance and angle sensing is derived, which is minimized subject to the minimum communication rate requirement of each user. Both fully digital antennas and hybrid digital and analog antennas are investigated. For fully digital antennas, a globally optimal solution of the ISAC waveform is obtained via semidefinite relaxation. For hybrid antennas, a high-quality solution is obtained through two-stage optimization. Numerical results demonstrate the performance gain introduced by the additional distance dimension of the near-field ISAC over the far-field ISAC.

翻译：本文提出了一种近场集成感知与通信（ISAC）框架，相较于传统远场系统，该框架在感知与通信中引入额外的距离维度。具体而言，推导了近场联合距离与角度感知的克拉美-罗下界，并在满足各用户最低通信速率需求的前提下对其进行最小化。研究中分别考察了全数字天线与混合数字-模拟天线架构。针对全数字天线，通过半定松弛方法获得ISAC波形的全局最优解；针对混合天线，采用两阶段优化得到高质量解。数值结果表明，近场ISAC因额外距离维度带来的性能增益优于远场ISAC。