Fluid Antenna-assisted Unsourced ISAC Massive Access

2026-06-29

AI Summary

This work addresses the severe multi-user interference and pilot collision arising in ultra-dense passive integrated sensing and communication (ISAC) scenarios, where fixed antenna arrays are constrained by limited physical aperture and static spatial sampling. For the first time, fluid antenna systems (FAS) are introduced into the passive ISAC massive random access framework, leveraging their continuously reconfigurable spatial positions to dynamically optimize the channel environment. By integrating finite blocklength communication theory, angle-of-arrival (AOA)-aware algorithms, and joint communication-sensing signal processing, the proposed approach substantially exploits spatial diversity within compact spaces. Under a scenario with 1,000 active users, it achieves a 40 dB capacity gain over TDMA while significantly reducing the per-user probability of error (PUPE) and enhancing sensing accuracy.

Abstract

Unsourced integrated sensing and communication (UNISAC) has emerged as a promising paradigm for supporting massive connectivity in 6G networks. However, existing approaches predominantly rely on fixed-position antennas at the base station (BS) and user equipment (UE). In uplink transmission with huge access density and limited resource budgets (i.e., finite blocklength, FBL), the fixed arrays are constrained by their physical aperture and static spatial sampling, which lead to severe multi-user interference and an unavoidable pilot collision error floor. To conquer the bottleneck derived from fixed-position physical constraint and utilize the abundant spatial diversity within compact space, this paper proposes a novel unsourced ISAC framework incorporating a fluid antenna system (FAS) at the user side. The proposed scheme exploits the positional flexibility of FAS to reconfigure the channel environment by continuously adjusting antenna ports in the spatial domain. Numerical results demonstrate that the proposed FAS-aided approach significantly reduces the per-user probability of error (PUPE) and enhances angle-of-arrival (AOA) sensing accuracy. Specifically, the proposed scheme provides a 40 dB capacity gain over traditional TDMA at 1000 active users. It should be noted that the FAS considered in this paper is only deployed at the transmitter. In our future work, we will try deploying FAS at both the transmitter and receiver.

Problem

• unsourced ISAC
• massive access
• fixed-position antennas
• multi-user interference
• pilot collision

Innovation

• Fluid Antenna System
• Unsourced ISAC
• Massive Access
• Angle-of-Arrival Sensing
• Finite Blocklength