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Performance Analysis of One- and Two-way DV-QKD with MIMO FSO Communication Systems

Sushil Kumar, Soumya P. Dash, George C. Alexandropoulos

TL;DR

The paper addresses secure key distribution over MIMO FSO channels by developing one- and two-way DV-QKD protocols that employ decoy states to mitigate photon-number-splitting attacks. It constructs a detailed channel model with beam spreading, pointing errors, and turbulence, and analyzes SKR and QBER for both BB84 with decoys (one-way) and LM05 (two-way) using SVD-based MIMO decomposition. The authors derive closed-form bounds and estimators for per-channel yields, single-photon contributions, and error rates, then aggregate across the MIMO sub-channels to obtain overall SKR and QBER as functions of distance and antenna count. Numerical results show clear SKR gains with larger MIMO configurations, and reveal a crossover distance where the two-way protocol outperforms the one-way scheme for tall MIMO, which increases with the number of antennas. The work demonstrates the practical viability of DV-QKD over realistic MIMO FSO links for secure 6G/NTN networks with decoy-state techniques.

Abstract

This paper considers a multiple-input multiple-output (MIMO) wireless system wherein two legitimate users attempt to exchange secret keys over free-space optical (FSO) channels. Novel frameworks for the use of the one- and two-way discrete-variable quantum key distribution (DV-QKD) protocols, employing weak coherent pulses and decoy states, are presented. Focusing on the case where a photon-number-splitting attack is adopted by the eavesdropper and the legitimate multi-antenna receiver using threshold detection for the key extraction, novel expressions for the secret key rate and quantum bit error rate for both one- and two-way protocols are derived. The performance gain with larger MIMO configurations and the tradeoff between the performances with the one- and the two-way protocols with respect to the transmission distance of the legitimate FSO link are numerically assessed.

Performance Analysis of One- and Two-way DV-QKD with MIMO FSO Communication Systems

TL;DR

The paper addresses secure key distribution over MIMO FSO channels by developing one- and two-way DV-QKD protocols that employ decoy states to mitigate photon-number-splitting attacks. It constructs a detailed channel model with beam spreading, pointing errors, and turbulence, and analyzes SKR and QBER for both BB84 with decoys (one-way) and LM05 (two-way) using SVD-based MIMO decomposition. The authors derive closed-form bounds and estimators for per-channel yields, single-photon contributions, and error rates, then aggregate across the MIMO sub-channels to obtain overall SKR and QBER as functions of distance and antenna count. Numerical results show clear SKR gains with larger MIMO configurations, and reveal a crossover distance where the two-way protocol outperforms the one-way scheme for tall MIMO, which increases with the number of antennas. The work demonstrates the practical viability of DV-QKD over realistic MIMO FSO links for secure 6G/NTN networks with decoy-state techniques.

Abstract

This paper considers a multiple-input multiple-output (MIMO) wireless system wherein two legitimate users attempt to exchange secret keys over free-space optical (FSO) channels. Novel frameworks for the use of the one- and two-way discrete-variable quantum key distribution (DV-QKD) protocols, employing weak coherent pulses and decoy states, are presented. Focusing on the case where a photon-number-splitting attack is adopted by the eavesdropper and the legitimate multi-antenna receiver using threshold detection for the key extraction, novel expressions for the secret key rate and quantum bit error rate for both one- and two-way protocols are derived. The performance gain with larger MIMO configurations and the tradeoff between the performances with the one- and the two-way protocols with respect to the transmission distance of the legitimate FSO link are numerically assessed.

Paper Structure

This paper contains 10 sections, 28 equations, 3 figures.

Table of Contents

  1. Introduction
  2. System and Channel Models
  3. One-Way DV-QKD MIMO FSO System
  4. One-Way Protocol
  5. Analysis of QBER and SKR
  6. Two-Way DV-QKD MIMO FSO System
  7. Two-Way protocol
  8. Analysis of QBER and SKR
  9. Numerical Results and Discussion
  10. Conclusion

Figures (3)

  • Figure 1: Model of the one-way DV-QKD MIMO FSO system.
  • Figure 2: Model of the two-way MIMO FSO DV-QKD system.
  • Figure 3: SKR versus distance between Alice and Bob for the one-way and two-way protocols with $N = 8,16,32$, $\eta_d = 0.12$ and (a) $p_m=0.50$, (b) $p_m=0.95$; (c) QBER versus distance between Alice and Bob for the one-way and two-way protocols with $N=8,16,32$, $\eta_d=0.12$, and $p_m=0.50$; (d) Crossover distance $\left( \text{where } \text{SKR}_{\text{MIMO}}^{\text{2-way}} = \text{SKR}_{\text{MIMO}}^{\text{1-way}}\right)$ versus $N$ for $\eta_d=0.12,0.5,0.8$ and $p_m=0.5,0.95$.