最新刊期
卷 ， 期 6 ， 2020
- 摘要：In order to improve the decoding performance of the irregular Quasi Cyclic Low Density Parity Check（QC-LDPC） code and reduce the implementation difficulty of the decoder, this paper proposes a Based-Degree Normalized Min Sum（BD-NMS） algorithm and an improved decoding structure. The algorithm first analyzes the changing rule of the optimal normalization factor, and obtains its distribution characteristics in different degrees. According to the distribution characteristics, the degrees can be layered. Finally, the normalization factors of each layer are obtained by density evolution and weighted vector. In the proposed structure, the verification nodes are grouped with the lifting value as the unit, and each group is divided by the integral power of 2 as the unit molecular layer. The sub-layers are then updated in sequence. Simulation results and complexity analysis show that the proposed decoding structure consumes less resources and has lower complexity. It can be seen that the BD-NMS algorithm has better decoding performance with faster convergence speed. The decoding performance is 0.19 dB higher than that of Density Evolution Min-Sum（DE-MS） when the bit error rate is 10-6. It is also concluded that the increased complexity only includes comparison operation, which is easy to implement in hardware.关键词：QC-LDPC;normalized min-sum algorithm;decoding structure
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发布时间： - 摘要：Aiming at the problems of high hardware cost of streaming service node and insufficient development and utilization of streaming server hardware capability, we propose a software method to optimize the performance of streaming servers. Firstly, based on the results of performance testing and analysis, the performance bottleneck of streaming server is that the load of disk groups is unbalanced, and the overall throughput of disk groups is not fully utilized. Secondly, the Input/Output（I/O） access method of the Linux file system is analyzed, and a method combining direct I/O and asynchronous I/O is proposed to improve the file reading speed. Thirdly, according to the characteristics of streaming media files, shard storage technology is proposed to support concurrent reading and balance the load of hard disk groups. Finally, a dynamic replication strategy based on content popularity is proposed to support massive concurrent access to hot contents. After testing and verification, using these technologies to optimize streaming application software can greatly improve the performance of streaming servers.关键词：streaming server;direct I/O;asynchronous I/O;shard storage;dynamic multiple copies
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发布时间： - 摘要：The Internet of Things（IoT） of fiber-optic sensing has the characteristics of measurement perception and data transmission. In order to realize the fast positioning of any node in the network, a fast node positioning technology is investigated, which uses the method of boundary box optimizing the Artificial Bee Colony（ABC） algorithm. Experiments are performed on multiple unknown nodes in fiber-optic sensor networks. The performances of the proposed algorithm, the unoptimized ABC algorithm and the traditional Particle Swarm Optimization（PSO） algorithm are compared. The results show that as the population increases, the positioning accuracy of the three algorithms improves. When the population is greater than 20, it will stabilize, and the positioning accuracy is 2.2, 3.0 and 3.3 m, respectively. It can be known from the number of iterations and positioning accuracy interval that the convergence speed and positioning stability of this algorithm are better than the latter two algorithms. It can be seen that the positioning technology based on this algorithm is more suitable for node positioning applications of the optical fiber sensing IoT.关键词：fiber optic sensor network;ABC algorithm;bounding box;positioning accuracy;IOT
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发布时间： - 摘要：Aiming at the problem of spectral data aliasing in multi-band laser interference images, this paper proposes an autocorrelation extraction classification algorithm based on associated feature information. First, the auto-correlation calculation mode is used to complete the data attribute classification. Then, an autoregressive average model based on feature data mining is designed by using attribute membership function as a criterion. Finally, the data mining is completed by cyclic iteration of time-decay weight coefficients. In the experiment, a mixed laser light source is tested. The algorithm is compared with traditional mean classification algorithm and least square method classification algorithm. Experimental results show that the classification error of the algorithm is 0.110, which is better than the other two algorithms（0.191 and 0.167）. And under the condition of the same total amount of data, the proposed algorithm takes the least time. It can be seen that this algorithm has a very good effect on the effective separation of aliasing data in multi-band laser interference images. It has certain practical value in the application of aliasing data classification.关键词：multi-band spectral data;feature extraction;data mining;autocorrelation calculation model
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发布时间： - 摘要：Aiming at the problem of high latency and low throughput in electric Data Center Network（DCN）, two kinds of passive optical DCN architecture are proposed, one for small DCN and the other for large DCN. Using passive optical devices such as Arrayed Waveguide Grating Router（AWGR）, coupler and demultiplexer, wavelength assignment and packet transmission algorithms are proposed for each scale architecture. The results show that the proposed method has lower latency and higher throughput compared with electric DCN, such as Fat-tree and Flat Butterfly（FBFLY） networks. It is also shown that the performances of proposed optical DCN architectures are similar to those of other optical interconnection architectures（such as Datacenter Optical Switch（DOS） and Petabit）. The packet delay is less than 18 μs with lower cost.关键词：DCN;AWGR;wavelength assignment;latency;throughput
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发布时间： - 摘要：In BB84 quantum key distribution protocol, the security key is usually extracted from the measurement results of the system, but the actual system is vulnerable to attack. In basis encoding quantum key distribution protocol, the security key is based on the basis information, which does not need to be extracted by the measurement results. Compared with BB84 protocol, the basis encoding protocol does not change the hardware, and only needs to adjust the post-processing of the data. Therefore, the actual system is easy to implement. Aiming at the photon number splitting attack and the intercept-resend attack in the actual system, we analyze the actual security of basis coding protocol, BB84 protocol and B92 protocol. The results indicate that the basis coding protocol has better performance in fighting against the photon number splitting attack and the intercept-resend attack.关键词：basis encoding;quantum key distribution;photon number splitting attack;post-processing
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发布时间： - 摘要：A large-scale and high-precision Chromatic Dispersion（CD） monitoring technique for high-speed coherent optical communication system is proposed, which combines the signal power waveform with amplitude and phase histograms characteristics. We conduct a simulation for 112 Gbit/s（28 GBaud） Polarization Division Multiplexing Quadrature Phase Shift Keying（PDM-QPSK） coherent optical communication system. In the simulation, the feasibility of this method is proved and the monitoring error is further analyzed. The maximum absolute estimation error of 62.1 ps/nm and the average relative error of 0.002 7 are achieved in the range of 6.4 to 48.0 ns/nm.关键词：CD monitoring;deep-neural networks;coherent optical communication;optical performance monitoring;CD compensation
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发布时间： - 摘要：A K-Nearest Neighbors（KNN） based fiber nonlinearity compensation technique for Polarization Division Multiplexing-Quadrature Phase Shift Keying（PDM-QPSK） unrepeartered Raman amplification system is studied. The nonlinearity compensation of optical fiber is realized by classifying the test data by calculating the distance from the test data to all the training data. All the simulation results show that the KNN-based fiber nonlinearity compensation technique can alleviate the fiber nonlinearity in 112 Gbit/s PDM-QPSK 350 km dispersion compensated unrepeartered Raman amplification system. Especially, the input optical power can increase by 1 dBm at the bit error rate of 10-3 after KNN-based nonlinearity compensation.关键词：unrepeatered fiber transmission system;PDM-QPSK;KNN;nonlinearity compensation
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发布时间： - 摘要：In the Software Defined Optical Network（SDON）, control plane may encounter various intrusion threat, which may affect the stable and reliable service provisioning in the network. Aiming at control plane security problems in SDON, machine learning based intrusion detection strategy is proposed, which utilizes Isolation Forest algorithm to detect point anomalies and Exponentially Weighted Moving Average（EWMA） algorithm to detect sequence anomalies. Theoretical analysis and simulation experimental results show that the proposed SDON detection technology based on machine learning can achieve 90% accuracy of point anomaly detection and 85% accuracy of sequence anomaly detection.关键词：SDON;control plane;abnormal detection;machine learning
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发布时间： - 摘要：Because the manufacturing technology of commercial optical fiber device and polarization-maintaining fiber fusion splicing technology based on 40 μm polarization-maintaining fiber are not mature, general polarization-maintaining fiber parameter measurement methods are difficult to directly apply. In this paper, a simple polarization interference device is constructed by accomplishing Superluminescent Diode（SLD） source coupling and making optical fiber polarizer online on a 40 μm polarization-maintaining fiber. The beating length and refractive index temperature coefficient of polarization-maintaining fiber can be both measured using the modulated spectrum. The measuring method is elaborated in theory and verified via the experiment, which is also applicable for polarization-maintaining fibers with other diameters.关键词：40 μm polarization-maintaining fiber;modulated spectrum;beatlength;refractive index temperature coefficient
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发布时间： - 摘要：In view of the complexity and bulkiness of most current random number generation schemes, we theoretically propose and demonstrate an all-optical physical random number generation method based on Vertical-Cavity Surface-Emitting Laser（VCSEL） mode hopping. Through periodically restarting a VCSEL operating in a bistable regime with a square-wave modulation signal, and balancing the asymmetry between two polarization modes utilizing spontaneous emission noise, a random number stream can be directly generated. Numerical results show that 2.5 Gbit/s physical random numbers can be obtained with verified randomness. This scheme can be simply implemented by only a solitary VCSEL and provide a new solution for photonic integrated random number generator.关键词：optical communications;all-optical physical random number;mode hopping;VCSEL
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发布时间： - 摘要：Here we propose a new scheme to testify the half-wave loss through both theory and experimental demonstration. The scheme uses Jones matrix to analyze the transforming of optical state and calculates the outputs of two different kinds of Sagnac interferometers after light propagation. The results clearly show a π phase shift in a Faraday mirror. It is noted that the structure is simple since the structure is based on a developed Sagnac interferometer and some commercial optical components such as X type coupler, polarization beam splinter, Faraday mirror. The experimental results also indicate that the interference phenomenon is obvious, with interference contrast as high as 99%.关键词：half-wave loss;Sagnac interferometer;Jones matrix;polarization beam splinter;Faraday mirror
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发布时间： - 摘要：In massive Machine Type Communications（mMTC） uplink grand-free Non Orthogonal Multiple Access（NOMA） systems, active users usually transmit data in consecutive time slots with high probability. In order to make full use of the time correlation between adjacent time slots, this paper proposes an Improved Dynamic Adaptive（IDA） multi-user detection algorithm, which combines the reconstruction idea of the existing compressed sensing algorithm with time correlation to achieve joint detection of active users and data. In the process of estimating the support set, an adaptive threshold-assisted strategy is added to select atoms, and the power function variable step size method is used to improve the accuracy of the sparsity estimation and optimize the iteration termination conditions. The simulation results show that compared with the greedy reconstruction algorithm and the Dynamic Compressed Sensing（DCS） algorithm, the IDA algorithm has better signal detection performance in the absence of a priori sparseness.关键词：mMTC;compressive sensing;time correlation;adaptive threshold
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发布时间： - 摘要：In order to improve the spectral efficiency of the system and increase the transmission reliability, it is necessary to establish a spatial fading channel model to analyze the performance of massive Multiple-Input and Multiple-Output（MIMO） systems. Assuming that the elevation and azimuth angles follow the Laplacian distribution and the Von-Mises distribution, the analytical expressions of the spatial correlation coefficients between the elements of the uniform planar array antenna are derived. The MIMO multi-antenna system model is established to analyze the system performance. The effects of different angle spread in elevation power spectrum on the fading correlation and channel capacity of uniform planar arrays, and the effects of different signal-to-noise ratios and antenna array elements on spectral efficiency are studied. Compared with the traditional uniform linear array, the analysis results show that the uniform planar array is more suitable for the massive MIMO system than the uniform linear array in the millimeter wave scene, which makes it possible for the future mobile network to work in different frequency bands and cells.关键词：wireless communication;massive MIMO;power spectrum;spatial fading correlation;channel capacity
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发布时间： - 摘要：The existing Multiple Input Multiple Output（MIMO） terahertz communication network dual-channel Medium Access Control（MAC） protocol works on the WiFi channel and the terahertz channel. If multiple pairs of nodes simultaneously transmit data in the terahertz channel, the problem of beam overlap interference occurs, which will reduce the message transmission success rate and network throughput. In addition, there is also a control overhead redundancy problem when the WiFi channel is exchanged for control messages, resulting in channel utilization low. Considering these two issues, the article proposes an Efficient Terahertz Dual-channel MAC Protocol to Avoid Beam Interference（E-ABIMAC）. E-ABIMAC is divided into beam interference pre-judgment mechanism, relay assistance mechanism and node information omission based Clear to Send frame/Acknowledgement frame（CTS/ACK） mechanism. The simulation results show that compared with the existing dual-channel MAC protocol for MIMO terahertz communication networks, the network throughput of the proposed protocol is increased by 10.1%, the channel utilization rate is increased by 11.7%, and the message transmission success rate is increased by 6.5%.关键词：beam interference;Terahertz;dual-channel;MAC protocol;efficient
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发布时间： - 摘要：Aiming at the problems of signal demodulation in 5 G downlink Orthogonal Frequency Division Multiplexing（OFDM） system due to Doppler frequency shift and frequency error caused by the non-synchronized transmitter and receiver crystal oscillators, a Primary Synchronization Signal（PSS） and Secondary Synchronization Signal（SSS） combined frequency offset estimation algorithm is proposed. Firstly, the cross correlation values of the PSS and SSS at the receiving end are calculated with the local PSS and SSS, respectively. Then, the PSS cross-correlation result of the first synchronization signal and Physical Broadcast Channel（PBC） block is used to calculate the initial frequency offset value with the SSS cross-correlation results of the second SSB block. Finally, we use the PSS cross-correlation results and SSS cross-correlation results in the same SSB block to perform cross-correlation calculations to calculate the new frequency offset value, and also use the initial frequency offset value to correct its polarity to obtain the final frequency offset. Compared with the PSS-based frequency offset estimation algorithm, this method uses PSS and SSS for joint frequency offset estimation to improve the accuracy of the algorithm, and expands the estimation range from [-3.5, 3.5] kHz to [-7.0,7.0] kHz.关键词：5G;OFDM;frequency offset estimation;PSS;SSS
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发布时间： - 摘要：Intelligent mine platform is able to increase mining production, among which communication, positioning and sensing system can guarantee miner and mineral safe. However, the lack of bandwidth of traditional redio frequency signal, serious attenuation and heavy communication equipment limit its application in mine. 5 G signals can be applied in mines, but electromagnetic interference is still existed. The wireless optical signal has the advantages of immune electromagnetic interference and high bandwidth, and the wireless optical communication, positioning and sensing can rely on the underground light source facilities, which reduce the cost and loss of communication equipment. This paper introduces the research status of mine wireless light from the aspects of wireless light propagation characteristics, wireless light communication scheme, wireless light positioning and wireless light sensing. Finally, we forecast the development of mine wireless light communication district layout, light source design, relay scheme and mine car collision prevention.关键词：intelligent mine;wireless optical technologies;wireless optical communications;person positioning;wireless optical sensing
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