A near-field integrated sensing, positioning, and communication (ISPAC) framework is proposed, where a base station (BS) simultaneously serves multiple communication users and carries out target sensing and positioning. A novel double-array structure is proposed to enable the near-field ISPAC at the BS. Specifically, a small-scale assisting transceiver (AT) is attached to the large-scale main transceiver (MT) to empower the communication system with the ability of sensing and positioning. Based on the proposed framework, the joint angle and distance Cramér-Rao bound (CRB) is first derived. Then, the CRB is minimized subject to the minimum communication rate requirement in both downlink and uplink ISPAC scenarios: 1) For downlink ISPAC, a downlink target positioning algorithm is proposed and a penalty dual decomposition (PDD)-based double-loop algorithm is developed to tackle the non-convex optimization problem. 2) For uplink ISPAC, an uplink target positioning algorithm is proposed and an efficient alternating optimization algorithm is conceived to solve the non-convex CRB minimization problem with coupled user communication and target probing design. Both proposed optimization algorithms can converge to a stationary point of the CRB minimization problem. Numerical results show that: 1) The proposed ISPAC system can locate the target in both angle and distance domains merely relying on single BS and limited bandwidths; and 2) the positioning performance achieved by the hybrid-analog-and-digital ISPAC approaches that achieved by fully digital ISPAC when the communication rate requirement is not stringent.

中文翻译：

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近场集成传感、定位和通信：下行链路和上行链路框架


提出了近场综合感知、定位和通信（ISPAC）框架，其中基站（BS）同时服务多个通信用户并进行目标感知和定位。提出了一种新颖的双阵列结构来实现基站的近场 ISPAC。具体来说，在大型主收发器（MT）上附加一个小型辅助收发器（AT），以赋予通信系统感知和定位的能力。基于所提出的框架，首先推导了关节角度和距离 Cramér-Rao 界限（CRB）。然后，在下行链路和上行链路ISPAC场景下，根据最小通信速率要求最小化CRB： 1）对于下行链路ISPAC，提出下行链路目标定位算法，并开发基于惩罚对偶分解（PDD）的双环算法来解决非凸优化问题。 2)针对上行ISPAC，提出了一种上行目标定位算法，并提出了一种有效的交替优化算法，以解决耦合用户通信和目标探测设计的非凸CRB最小化问题。两种提出的优化算法都可以收敛到 CRB 最小化问题的驻点。数值结果表明：1）所提出的ISPAC系统仅依靠单个基站和有限的带宽就可以在角度和距离域对目标进行定位； 2）当通信速率要求不严格时，通过全数字ISPAC实现的模拟和数字混合ISPAC方法所实现的定位性能。