🤖 AI Summary
To address tag identification failure caused by signal collisions in RFID systems, this paper proposes a novel pilot-free signal recovery method leveraging antenna arrays and blind source separation. The method introduces a hybrid objective function that jointly incorporates the Zero-Forcing Constant-Modulus (ZFCM) criterion and a newly designed ambiguity suppression criterion, effectively mitigating phase and amplitude ambiguities inherent in conventional ZFCM-based beamformer estimation; gradient descent optimization ensures efficient solution convergence. By fully exploiting the spatial resolution of antenna arrays, the approach achieves high-precision and robust separation of concurrent tag signals—without requiring channel state information, tag location knowledge, or pilot symbols. Experimental results demonstrate substantial improvements in identification accuracy under high-density tag scenarios, establishing a scalable physical-layer multiple-access solution for passive RFID systems.
📝 Abstract
In this letter, we propose an efficient mix source separation (MSS) algorithm for collision resolution in radio frequency identification (RFID) systems equipped with an antenna array at the reader. We first introduce an approach that exploits the zero constant modulus (ZCM) criterion to separate colliding tags through gradient descent, without using pilot symbols. We show that the ZCM characteristic, considered alone, in the design of the objective function can lead to significant ambiguities in the determination of the beamformers used in the recovery of tag messages. To address this limitation, we propose a more sophisticated approach, relying on a hybrid objective function, incorporating a new ambiguity-raising criterion in addition to the ZCM criterion.