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frame synchronization for Passive Continuous-Variable Quantum Key Distribution with a Local Local Oscillator

ADVANCED QUANTUM TECHNOLOGIES 2025年

作者： Wang, Dong Zhou, Liang-Jiang Zhao, Yi-Bo Chinese Acad Sci Aerosp Informat Res Inst Natl Key Lab Microwave Imaging Beijing 100190 Peoples R China Zhejiang Univ Huzhou Inst Huzhou 313000 Peoples R China Zhejiang Univ Coll Control Sci & Engn Hangzhou 310027 Peoples R China

frame synchronization is essential in continuous-variable quantum key distribution (CVQKD), typically relying on active modulation to establish a specific frame structure. In passive CVQKD systems, however, the elimination of modulation requirements poses a significant challenge for frame synchronization, especially in local-local-oscillator (LLO) configurations. This paper introduces a robust, modulation-free frame synchronization method tailored for passive LLO CVQKD systems. This method leverages the complex cross-correlation of quantum signals exchanged between Alice and Bob for synchronization purposes. Validated through an analytical model and numerical simulations, this approach demonstrates high synchronization success rates, robustness to noise, and resilience to both slow phase drifts between local oscillators and quantum signals and fast phase drifts stemming from two independent lasers. These results underscore the viability of the proposed method for implementing long-distance CVQKD in real-world scenarios.

关键词： continuous-variable frame synchronization passive state preparation quantum key distribution

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frame synchronization for pulsed jammed satellite telecommand links

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INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING 2020年第1期38卷 16-30页

作者： Noels, Nele Moeneclaey, Marc UGent Telecommun & Informat Proc Dept Ghent Belgium

A new issue of the satellite telecommand synchronization and channel coding sublayer protocol includes LDPC-coded communication link transmission units (CLTUs) that contain a 64-bit start sequence. The novel data structures allow operation at lower signal-to-noise ratios than before and offer improved protection against jamming attacks. This paper considers the corresponding CLTU frame synchronization process. We derive practical algorithms to locate the start sequence in the presence of high noise levels and pulsed jamming. The different algorithms are compared in terms of implementation complexity and performance under various jamming conditions. It is shown that among the considered frame synchronizers, those involving a full search over the entire observation window provide the desired accuracy, ie, they guarantee a frame synchronization error probability that is significantly smaller than the codeword error rate, for codeword error rates near a target value of 10(-4). Among these synchronizers, the full-search hard-decision-directed correlation-based algorithm has the lowest complexity.

关键词： frame synchronization pulsed jamming satellite telecommand system

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frame synchronization FOR OPTICAL OVERLAPPING PULSE-POSITION MODULATION SYSTEMS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第4期40卷 783-794页

作者： PATARASEN, S GEORGHIADES, CN Department of Electrical Engineering Texas A and M University College Station TX USA

The maximum-likelihood rules for locating data frames in direct-detection optical communication systems utilizing overlapping pulse-position modulation (OPPM) are derived under two distinct assumptions of symbol and chip synchronization, respectively. Various approximations to the optimal rules are identified, as well as upper and lower bounds on the probability of correct synchronization. Further, the problem of sequence design based on a maximum peak-to-sidelobe distance criterion is studied, and upper bounds on peak-to-sidelobe distance for sequences of OPPM symbols are derived. Some good sequences are obtained through a computer search.

关键词： .optical communication maximum-likelihood Overlapping frame synchronization direct-detection sequence design chip synchronization peak-to-sidelobe sequences of OPPM good sequences obtained through computer pulse-positions

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frame synchronization in Frequency Uncertainty

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IEEE TRANSACTIONS ON COMMUNICATIONS 2010年第4期58卷 1235-1246页

作者： Pedone, Raffaella Villanti, Marco Vanelli-Coralli, Alessandro Corazza, Giovanni Emanuele Mathiopoulos, P. Takis Univ Bologna DEIS Dept Elect Comp Sci & Syst ARCES I-40136 Bologna Italy Natl Observ Athens Metaxa & V Pavlou ISARS Athens 14536 Greece

This paper addresses the problem of robust frame synchronization for TDM/TDMA systems in the presence of frequency errors, accomplished through data-aided recognition of the Unique Word (UW) preamble in the transmission flow. Robust detection design is performed applying, through approximations, the Maximum Likelihood (ML) criterion coupled to Post Detection Integration (PDI), to obtain a novel detector identified as Balanced-GPDI (B-GPDI). This new approach considerably outperforms other schemes available in the literature, at the cost of a moderate complexity increase. This is possible thanks to an optimized use of coherent accumulation, which enhances the correlation term in the decision variable, along with highly accurate modeling of the energy correction factor. To limit complexity increase and memory requirements, several approximations of the exact B-GPDI are proposed and discussed in the paper, to provide the designer with practical solutions that are still able to outperform other approaches in specific application scenarios. In particular, approximations for low and high Signal-to-Noise Ratio (SNR) are presented. Different application scenarios are considered in the paper for numerical analysis. In particular, the cases of forward link Continuous Transmission (CTX) and return link Burst Transmission (BTX) are addressed.

关键词： frame synchronization time division multiple access frequency error post detection integration

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frame synchronization for coded systems over AWGN channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2004年第3期52卷 484-489页

作者： Cassaro, TM Georghiades, CN Microwave Networks Stafford TX 77477 USA Texas A&M Univ Dept Elect Engn College Stn TX 77843 USA

For the additive white Gaussian noise channel, we consider the problem of frame synchronization for coded systems. We present an algorithm that takes advantage of soft information provided by a soft decoder to produce an enhanced estimate of the frame boundary. To reduce complexity, a companion algorithm is introduced that is a hybrid of the optimal uncoded frame synchronizer introduced by Massey and the list synchronizer introduced by Robertson. The high-complexity coded maximum-likelihood frame synchronizer used by Robertson will accordingly be replaced by our algorithm, which operates on decoder-provided soft decisions. The algorithm begins by obtaining a list of high-probability starting positions via the log-likelihood function of the optimal uncoded frame synchronizer. Then, a test delta is used to decide if the decision of the optimal uncoded frame synchronizer is sufficient, or whether list synchronization is required. If the test chooses in favor of using the optimal uncoded synchronizer, the estimate is obtained with relative ease. Otherwise, list synchronization is performed, and statistics provided by the decoder are used to resolve the frame boundary. Monte Carlo simulations demonstrate that the frame-synchronization-error rate (the probability of the synchronizer making an error) achieves the lower bound for signal-to-noise ratio values exceeding 1 dB.

关键词： coded systems frame boundary frame recovery frame synchronization preamble

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frame synchronization using distributed sequences

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IEEE TRANSACTIONS ON COMMUNICATIONS 2000年第12期48卷 2127-2138页

作者： van Wijngaarden, AJD Willink, TJ Univ Essen Inst Expt Math Digital Commun Dept Essen Germany Commun Res Ctr Ottawa ON K2H 8S2 Canada

frame synchronization is traditionally achieved by inserting a given sequence periodically into the data stream. Here, a new method of synchronization is introduced in which the synchronization sequence is not contiguous, but is interleaved with the data symbols. The properties of these distributed sequences are investigated, and requirements are specified for detectibility of these sequences when inserted in random data. Methods for constructing and searching for good sequences are presented. It is demonstrated that this new method reduces the probability of false synchronization over traditional methods in the presence of additive white Gaussian noise.

关键词： correlation frame synchronization Gaussian channels maximum-likelihood detection sequences signal detection synchronization

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frame synchronization for variable-length packets

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2008年第1期26卷 52-69页

作者： Suwansantisuk, Watcharapan Chiani, Marco Win, Moe Z. MIT Informat & Decis Syst Lab Cambridge MA 02139 USA Univ Bologna Dipartimento Elettr Informat & Sistemist I-40136 Bologna Italy

A cognitive radio can sense its environment and adapt some of its features, such as carrier frequency, transmission bandwidth, transmission power, and modulation, thus allowing dynamic reuse of the available spectrum. Due to their high degree of adaptability to environmental variations, cognitive radios are expected to utilize packet-based transmission with variable-length frames. Packet-based transmission requires the receiver to perform frame synchronization, an important enabling step that allows adaptation in cognitive radios. However, proper metrics to characterize the performance of frame synchronization for transmission of variable-length frames are currently unavailable. To address this issue, we put forth two performance metrics, namely the expected duration to complete frame synchronization and the probability of correct acquisition within a given duration. We then develop analytical expressions for these important metrics. This paper advances our understanding of frame synchronization for the continuous transmission of variable-length frames and for bursty transmission.

关键词： frame synchronization cognitive radios hypothesis testing detection synchronization patterns

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frame synchronization Based on Multiple frame Observations

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2010年第3期9卷 1097-1107页

作者： Bastaki, Eesa M. Tan, Harry H. Shi, Yi Ben Letaief, Khaled United Arab Emirates Univ Fac Engn Elect & Engn Dept Al Ain U Arab Emirates Univ Calif Irvine Dept Elect Engn & Comp Sci Sch Engn Irvine CA USA Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Kowloon Hong Kong Peoples R China

We consider frame synchronization for fixed frame length communication system with periodically embedded sync words. In the past few decades, numerous researchers have made significant contributions in various aspects. However, it is almost surprising that a scrutinization over the literature reveals to us an important common assumption: frame synchronization decision-making through single-frame observation. Intuition tells us that an enlarged multiple-frame observation set bears the potential to reduce sync word identification ambiguities and also to combat multi-path fading through "frame diversity". The objective of this work is thus to characterize the performance improvement of using multiple-frame decision rules rather than the single-frame decision rules considered in the previous work. We select the work of Lui and Tan as our standing point, and have conducted a comparative study in a very comprehensive manner. In particular, we shall show that the benefits of multiple-frame based decision rules can be substantial. For example, in many cases, the performance of the correlation rule based on double-frame observation is superior to that of the optimum maximum likelihood rule with single-frame observation. While further enlarging the observation period beyond double frames was found to yield diminishing returns.

关键词： Correlation rule frame synchronization M-ary modulation maximum likelihood (ML) multiple frame observations

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frame synchronization Algorithm for LDPC Coded Burst Systems

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ETRI JOURNAL 2015年第5期37卷 940-944页

作者： Man, Xin Zhai, Haitao Zhang, Eryang Naval Univ Engn Coll Elect Engn Wuhan Hubei Peoples R China Natl Univ Def Technol Sch Elect Sci & Engn Changsha Hunan Peoples R China

We present a frame synchronization algorithm for low-density parity-check (LDPC) coded burst transmissions, which combines a conventional pilots-assisted frame synchronization algorithm and a code-aided algorithm based on the mean magnitude of the soft outputs from the LDPC decoder. With moderate computational complexity, the proposed algorithm is more efficient in bandwidth than conventional pilots-assisted algorithms. When compared with other code-aided algorithms, the proposed algorithm offers a better trade-off between complexity and performance. Simulation results in the case of an 8-PSK system with (1944, 972) LDPC code show that the proposed algorithm can achieve a performance equivalent to that of the perfect frame synchronization, with a bandwidth efficiency loss of 0.06 dB due to the use of pilot symbols.

关键词： Code-aided frame synchronization LDPC pilots-assisted bandwidth efficiency

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frame synchronization in the presence of frequency offset

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第7期50卷 1062-1065页

作者： Choi, ZY Lee, YH Korea Adv Inst Sci & Technol Div Elect Engn Dept Elect Engn & Comp Sci Taejon 305701 South Korea

A new frame synchronization technique, which is robust to carrier frequency and phase errors, is proposed for M-ary PSK systems. This technique is derived through modification of the procedure used for obtaining the maximum-likelihood (ML) rule in the paper by Gansman et al. The proposed rule is based on an operation called a double correlation which evaluates a correlation after properly multiplying the received signal with a sync pattern. It was shown through computer simulation that the proposed rule generally outperformed the existing rules when a frequency offset existed.

关键词： correlation frame synchronization frequency offset

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