Communication System Performance Analysis of Satellite-to-Ground BB84 Quantum Key Distribution over Gamma–Gamma Turbulence Channels with Pointing Errors.
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.
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.
Abstract In this paper, we analyze the performance of free-space optical quantum key distribution (FSO-QKD) using the BB84 protocol with BPSK modulation under realistic channel conditions. The Málaga distribution is employed to model the composite atmospheric turbulence, considering pointing errors. We derive closed-form expressions for the average quantum bit error rate (QBER) and the secure key rate (SKR), incorporating both turbulence and misalignment effects. Numerical results demonstrate the impact of turbulence parameters and beam misalignment on system performance. The findings provide insights for the robust design of FSO-QKD systems under practical deployment conditions.
Satellite-based free-space quantum key distribution (QKD) provides a practical framework for achieving secure global communication beyond the limitations of optical fibers. In this work, the quantum bit error rate (QBER) and secure key rate of four representative protocols-BB84, B92, BBM92, and E91 are investigated over low earth orbit (LEO) links in both uplink and downlink configurations. The optical link is modeled using a Gaussian beam formalism, incorporating the effects of diffraction, pointing errors, atmospheric turbulence, and background noise contributions. The protocols are examined under day and night-time operating conditions, and their dependence on the zenith angle is analyzed. The findings show that downlink links generally exhibit lower QBER and higher secure key rates than uplinks, and among prepare-and-measure schemes, BB84 consistently outperforms B92, while in entanglement-based approaches, BBM92 achieves higher key rates than E91.
Quantum Key Distribution (QKD) has emerged as a fundamentally secure approach to communication in the era of quantum computing, offering protection against threats posed to classical cryptographic schemes such as RSA and Diffie-Hellman. This thesis presents a comprehensive performance analysis of satellite-based QKD protocols, focusing on both prepare-and-measure and entanglement-based schemes under realistic atmospheric and operational conditions. The study begins by introducing the theoretical foundations of quantum communication, including qubits, entanglement, and quantum entropy, and motivates the need for satellite-based QKD to overcome the distance limitations of fiber-based systems. Subsequently, the thesis evaluates four prominent QKD protocols-BB84, B92, BBM92, and E91-using a circular beam propagation model that incorporates atmospheric effects such as diffraction, turbulence, attenuation, and pointing errors, along with environmental noise contributions for uplink and downlink. Comparative numerical simulations reveal that protocol performance is strongly influenced by channel asymmetries, beam propagation characteristics, and noise, providing guidance on optimal protocol selection for low Earth orbit (LEO) satellite links. The research further investigates high-dimensional (HD) QKD protocols, specifically HD-BB84 and HD-Extended B92, using the elliptic-beam approximation to account for turbulence-induced distortions for both uplink and downlink. Simulations under vary ing system dimensions, weather conditions, and zenith angles demonstrate that HD-BB84 achieves higher key rates, superior noise tolerance, and more favorable probability distributions of the key rate compared to HD-Extended B92, highlighting the advantages of high-dimensional encoding for robust satellite-based QKD.
Nowadays, a high level of security is required for the transmission of critical information. Quantum Key Distribution (QKD) systems are considered the best option to protect such information. Many studies have shown the efficiency of the QKD optical fiber inspired by M-ary pulse position modulation (MPPM). Free-Space Optical (FSO) links provide an efficient and effective data transmission system. However, cumulative effects of laser beam divergence, misalignment, 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. This paper introduces the development of an FSO system based on the MPPM and the BB84 protocol (MPPM-BB84) over the Gamma-Gamma (GG) turbulence channel with pointing errors. Time Binning is implemented using MPPM to increase system security and reduce the quantum bit error rate (QBER). The system security is investigated under photon number splitting attack and excess noise. Closed-form expressions for asymptotic expressions of the average symbol error probability (SER), raw key rate (RKR), and secret key rate (SKR) are introduced. Moreover, the Monte-Carlo simulations are then used to prove the validity of the analytical results. The optimal values for the average photon number per pulse (to achieve the maximum RKR and SKR) for each symbol length can guarantee the stability of the FSO system under different weather conditions. Smaller symbol lengths are more tolerant of detector loss. The proposed system supports linking distances from 1 km to 3 km while keeping the SKR almost constant.
We devoted to analyzing information transfer in quantum channels in terms of the performance of quantum key distribution (QKD) free-space optical (FSO) communication systems through Bennett and Brassard 84 (BB84) protocol by taking into account the combined effect of attenuation, turbulence, pointing error, and angle of arrival (AOA) fluctuations. Path loss is modeled by Beer-Lambert law, and the turbulent channel is assumed to be Fisher-Snedecor F distributed. The pointing error and AOA fluctuations are modeled by Hoyt and Rayleigh distributions, respectively. The error and sift probabilities, quantum bit error rate, and secret key rate of a QKD FSO system are obtained in analytical form, and results are presented depending on various parameters. It is shown that increased beam waist, beam deviation, AOA fluctuations, and propagation distance cause performance degradation and less secure information transmission. However, an increase in the ratio of horizontal and vertical beam misalignments, field of view, average photon number per pulse, visibility of the atmospheric environment, and optical beam wavelength impact the performance of QKD FSO systems positively. The effect of the turbulence structure constant is observed to be modest on the performance of the QKD FSO system.
Satellite-based quantum key distribution (QKD) offers a pathway to secure global communications, yet its performance is fundamentally constrained by atmospheric turbulence. This paper presents a detailed analysis of the BBM92 entanglement-based protocol under realistic satellite-to-ground conditions using the Hufnagel-Valley turbulence model. We examine the role of key atmospheric factors, including wind speed, ground station altitude, and diurnal variations, on quantum performance metrics across a mean photon number (MPN) range of 0.001-0.3. Results reveal that turbulence strength, captured via the refractive index structure constant, governs channel transmittance through Rytov variance and scintillation index, directly impacting quantum bit error rate (QBER) and secret key rate (SKR). Simulations show that elevated ground stations improve SKR by15−25%, nighttime operation yields40 - 80 %gains compared with daytime, and wind speeds of30m/scan reduce SKR by up to 60% relative to10m/sconditions. Optimal operation lies in the MPN range of 0.1-0.2, beyond which multiphoton noise degrades security as QBER approaches the 9% threshold.