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Collision Resolution in RFID Systems Using Antenna Arrays and Mix Source Separation

Mohamed Siala, Noura Sellami

TL;DR

This work addresses collision resolution in RFID systems with antenna arrays by applying mix source separation (MSS) driven by a zero constant modulus (ZCM) criterion implemented via gradient descent, without pilot symbols. It identifies fundamental ambiguities when ZCM is used alone and introduces a new ambiguity-raising criterion to form a hybrid objective $J_{01}(\mathbf{w})=\lambda J_0(\mathbf{w})+(1-\lambda)J_1(\mathbf{w})$, enabling unambiguous beamformer estimation. The authors provide explicit gradient expressions and demonstrate, through simulations, that the hybrid objective outperforms prior AZCMA-based approaches, maintaining high success rates even under perfect frequency synchronization and in the presence of phase/frequency imperfections. The approach offers a robust, pilot-free method for resolving multi-tag collisions in RFID systems with antenna arrays, with potential impact on throughput and latency in RFID-enabled applications.

Abstract

In this letter, we propose an efficient mix source separation 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.

Collision Resolution in RFID Systems Using Antenna Arrays and Mix Source Separation

TL;DR

This work addresses collision resolution in RFID systems with antenna arrays by applying mix source separation (MSS) driven by a zero constant modulus (ZCM) criterion implemented via gradient descent, without pilot symbols. It identifies fundamental ambiguities when ZCM is used alone and introduces a new ambiguity-raising criterion to form a hybrid objective , enabling unambiguous beamformer estimation. The authors provide explicit gradient expressions and demonstrate, through simulations, that the hybrid objective outperforms prior AZCMA-based approaches, maintaining high success rates even under perfect frequency synchronization and in the presence of phase/frequency imperfections. The approach offers a robust, pilot-free method for resolving multi-tag collisions in RFID systems with antenna arrays, with potential impact on throughput and latency in RFID-enabled applications.

Abstract

In this letter, we propose an efficient mix source separation 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.

Paper Structure

This paper contains 8 sections, 21 equations, 1 figure, 2 tables.

Table of Contents

  1. Introduction
  2. System model
  3. AZCMA and Associated Ambiguities
  4. Gradient Descent Algorithm Minimizing a New Hybrid Objective Function
  5. New Criterion for Unambiguous Source Separation
  6. Gradient Descent Algorithm
  7. Simulation Results
  8. Conclusion

Figures (1)

  • Figure 1: Success rate vs. the weighting coefficient $\lambda$ : (a) impact of the number of iterations $L$ when the number of antennas $M=2$ and the number of tags $d=2$, (b) impact of $d$ and $M$ when $L=800$, and (c) impact of random phase or frequency deviations when $M=d=2$ and $L=800$.