Quantum-secured Free-space Optical Communication for disaster management: a QPSK-Based system with hybrid atmospheric modelling and advanced mitigation strategies
Abstract This investigation examines the use of a Quadrature Phase Shift Keying (QPSK)-based Free-space Optical (FSO) Communication system combined with Quantum Key Distribution (QKD) for improved security and dependability in disaster management situations. We tackle the problems caused by atmospheric turbulence by utilizing a hybrid gamma–gamma and log–normal channel model to precisely characterize the FSO link. The proposed system’s purpose is to offer secure, high-bandwidth communication for emergency response coordination, telemedicine, and data transmission in environments affected by disasters. We present a system design and performance evaluation based on the hybrid atmospheric model, discuss the potential advantages, drawbacks, and countermeasures of the approach, and propose future research avenues, encompassing real-time adjustment, modulation variability, and field testing. Our implementation of real-time adaptation mechanisms lowers the BER by about 30 % under conditions affected by turbulence, while hybrid FSO/RF switching maintains uninterrupted connectivity during severe atmospheric attenuation.
Abstract This investigation examines the use of a Quadrature Phase Shift Keying (QPSK)-based Free-space Optical (FSO) Communication system combined with Quantum Key Distribution (QKD) for improved security and dependability in disaster management situations. We tackle the problems caused by atmospheric turbulence by utilizing a hybrid gamma–gamma and log–normal channel model to precisely characterize the FSO link. The proposed system’s purpose is to offer secure, high-bandwidth communication for emergency response coordination, telemedicine, and data transmission in environments affected by disasters. We present a system design and performance evaluation based on the hybrid atmospheric model, discuss the potential advantages, drawbacks, and countermeasures of the approach, and propose future research avenues, encompassing real-time adjustment, modulation variability, and field testing. Our implementation of real-time adaptation mechanisms lowers the BER by about 30 % under conditions affected by turbulence, while hybrid FSO/RF switching maintains uninterrupted connectivity during severe atmospheric attenuation.
Abstract Quantum Key Distribution (QKD) provides information-theoretic security for future communication networks by exploiting the fundamental principles of quantum mechanics. However, satellite-to-ground QKD links suffer significant performance degradation due to atmospheric turbulence, absorption, scattering, and satellite-induced pointing errors. This paper investigates the BB84 QKD protocol over a Free-Space Optical (FSO) channel modeled using the Gamma–Gamma distribution, which accurately captures both small-scale and large-scale atmospheric irradiance fluctuations. Closed-form and numerical results for outage probability and Quantum Bit Error Rate (QBER) are presented under weak, moderate, and strong turbulence regimes. The Secure Key Rate (SKR) is analyzed as a function of link distance under clear and foggy weather conditions. Additionally, the impact of satellite vibration is evaluated using a jitter-dependent pointing error model, demonstrating that misalignment significantly reduces link reliability. Simulation results show that strong turbulence conditions introduce more than 15 dB SNR penalty compared to clear-sky operation, while haze conditions limit QKD range to under 8–10 km. These findings provide practical performance benchmarks for Low-Earth Orbit (LEO) quantum downlinks in realistic atmospheric environments. The results provide practical insights for electronic receiver design and system implementation of satellite quantum communication links.
Unmanned aerial vehicles (UAV) based on free-space optical (FSO) systems combine the benefits of both the high data rate of the FSO and the mobility of UAV. However, cumulative effects of laser beam divergence and turbulence-induced fading on the received irradiance in the FSO link might allow an external eavesdropper located near the authorized receiver to break the transmission under certain conditions. Quantum key distribution (QKD) is a technique of secure communication that employs quantum mechanics-based cryptography principles. A combination of a continuous-variable quantum key distribution (CV-QKD) and Gaussian modulation of quantum coherent states (GMCS) enables a relatively secure communication system against collective attacks over FSO transmission links. However, the performance is restricted and degraded due to the influence of atmospheric turbulence and excess noise. This paper aims to evaluate the performance of a secured UAV-based FSO system utilizing prepare and measure CV-QKD protocol based on GMCS under collective attack in terms of quantum bit error rate (QBER), outage probability, and secret key rate (SKR) considering the impairments of the FSO channel, link budget, deviations in the position and attitude angles of the UAV, channel fluctuating transmittance, and excess noise. The system parameters, including transmit power, receiver’s field-of-view, and beam divergence angle, are optimized to satisfy the system’s design criteria of threshold-QBER=10−3and threshold outage probability=10−2. The proposed system tolerates boresight displacement up to 7 cm with the optimized values. The Closed-form expressions and analytical results are confirmed by Monte-Carlo simulations.
Integrated millimeter-wave (mmWave) and free-space optical (FSO) communication systems offer a complementary solution for secure and high-speed data transmission. In this hybrid system, mmWave serves as the classical channel and FSO operates as a quantum channel for quantum key distribution (QKD), creating a multi-layered communication infrastructure. This dual channel faces significant challenges, including vulnerability to atmospheric attenuation, blockage, beam misalignment, and high sensitivity to environmental factors such as weather conditions, turbulence, and obstacles, which impact their reliability and performance. Taking into account these challenges, the integration of mmWave and FSO enables robust applications such as secure 6G networks, satellite-to-ground communications, and urban connectivity, where mmWave ensures reliability during FSO disturbances. By combining classical high-speed data transfer with the quantum security of QKD, this hybrid architecture opens the road for next-generation secure and high-capacity networks.
This paper proposes a novel quantum key distribution (QKD) set-up designed to enhance the security of a free-space optical (FSO) quantum communication system. By incorporating channel ordering information, the proposed QPSK-QKD (P-QPSK-QKD) system leverages the inherent randomness of FSO channels, providing dual protection against eavesdroppers (Eve). The first layer of security is achieved through the QPSK-QKD mechanism, while the second arises from the randomness of the FSO channels. To ensure a comprehensive investigation, the performance of P-QPSK-QKD and the existing QPSK-QKD (E-QPSK-QKD) system is analyzed using a Málaga distributed atmospheric turbulence channel model incorporating pointing errors. Novel closed-form expressions are derived for different performance metrics, including probability of sifted keys, quantum bit error rate, probability of Eve (Peve), and ergodic secret key rate (ESKR), under both perfect and imperfect feedback conditions. Intensive examination indicates that, unlike E-QPSK-QKD, wherePeveshows a water-falling trend with increasing signal-to-noise ratios (SNR) under dual thresholds, P-QPSK-QKD achieves a saturatedPeve, enhancing security. Moreover, under the single threshold,Peveof P-QPSK-QKD is twice that of E-QPSK-QKD. Additionally, due to channel randomness, the mutual information between Alice and Eve remains zero (for both single and dual thresholds), even at infinite SNR for P-QPSK-QKD, providing consistently higher ESKR than E-QPSK-QKD system under both perfect and imperfect feedback conditions.
Free-Space Optical (FSO) communication technology can cater to various types of connectivity requirements within optical networks, including core, edge, and access networks. However, the performance of FSO communication links can be adversely affected by severe atmospheric conditions, such as turbulence and weather-related factors. In this study, we have investigated the benefits of photon entangled 16-QAM- FSO link in improving the performance of FSO communication under diverse weather and atmospheric turbulence conditions. The efficient implementation of a practical secure quantum communication network may revolutionize the terrestrial and non-terrestrial communication both form speed and security point of view.
This work analyzes a terrestrial-based free-space quantum key distribution system employing quadrature-phase shift keying signaling (QKD-QPSK). An analytical framework is proposed to determine various joint probabilities under the gamma-gamma turbulence channel model without utilizing the Gaussian–Laguerre (GL) method. Although GL-based method provides ease of computation of integral forms, but it is not always stable. Using derived joint probabilities, novel analytical expressions for the probability of sifted keys (Psift), quantum bit error rate (QBER), error probability for the eavesdropper (Peve), and the ergodic secret-key rate (ESKR) are determined for QKD-QPSK system. This work also reveals that the QKD-QPSK system can be transformed into QKD-based binary phase-shift keying (QKD-BPSK) system. Furthermore, using the proposed analytical framework, all the considered performance metrics are also evaluated for the QKD-BPSK system. Finally, QKD-QPSK and QKD-BPSK systems are compared under moderate and strong turbulence regimes. Comparative results indicate that QKD-QPSK outperforms QKD-BPSK in terms of Peve. However, QKD-BPSK is superior to QKD-QPSK for Psiftand QBER. Furthermore, a positive ESKR can be achieved for both systems with the proper selection of threshold coefficient (ρ) and transmitted power (Pt).