Anchor Points Assisted Uplink Sensing in Perceptive Mobile Networks

Uplink sensing in integrated sensing and communications (ISAC) systems, such as Perceptive Mobile Networks, is challenging due to the clock asynchronism between transmitter and receiver. Existing solutions typically require the presence of a line-of-sight path and the knowledge of the transmitter’s location. In this paper, these requirements, we propose a novel uplink sensing scheme to relieve these requirements by introducing static anchor points for the first time. The scheme consists of two efficient algorithms. The first algorithm estimates the relative timing and carrier frequency offsets, with respect to a randomly selected reference snapshot. Its estimation performance is analyzed with closed-form bias and root mean squared error derived. The estimates from the first algorithm are then used to eliminate clock offsets, enabling the construction of angle-Doppler maps. Using the maps, the second algorithm is developed to identify anchor points and then locate the transmitter and dynamic targets. The impact of the locations of the transmitter and anchor points is also analytically illustrated. Extensive simulation results are provided, demonstrating the effectiveness of the proposed sensing scheme in practical 5G communication setups and its superiority over prior art in terms of noise resilience and asymptotic performances.