The Chirp signal parameter estimation has the problems of high computational complexity and low precision under low Signal-to-Noise Ratio (SNR). In order to solve these issues, an improved Chirp parameter estimation algorithm is proposed. According to the Chirp signal energy and the signal period, the square of the signal spectrum amplitude is inversely proportional to the frequency modulation slope. The Chirp signal is multiplied by the unknown Chirp signal to find the known Chirp signal with the largest square of the spectral amplitude. In order to achieve the parameter estimation with high accuracy, the Modified Rife (M-Rife) is used to estimate the center frequency and correct the amplitude of the multiplied signal. The algorithm is combined with the Short-Time Fourier Transform (STFT). First, STFT is used to estimate the approximate range and signal period of Chirp. The dichotomy is used instead of the equal step size to allow the improved Chirp signal parameter estimation algorithm to search within this approximate range, resulting in significant complexity reduction. The experimental results show that when the SNR is not less than -10 dB, the Normalized Mean Square Error (NMSE) of modulation frequency estimated by our proposed algorithm is better than Fractional Fourier Transform (FRFT) by 1~2 dB. When the signal-to-noise ratio is not less than -10 dB, the NMSE of center frequency estimated by our proposed algorithm is significantly better than FRFT and close to the Cramer-Rao Low Bound (CRLB) line.

Underwater Visible Light Communication (UVLC), as an important branch of underwater wireless communication technology, is widely used in the field of marine environmental monitoring and underwater military struggle. This paper first briefly introduces the research background, significance and difficulties of UVLC. Then we summarize the underwater visible light channel modeling technology from three aspects including optical attenuation modeling, vertical channel modeling and turbulence channel modeling. Finally, we investigate the research results related to different underwater visible light modulation technologies. It can be seen from the analysis that the modeling of optical attenuation in the horizontal direction of UVLC tends to be perfect. At present, there is no accurate and complete model of underwater visible light turbulence and vertical channel. On the other hand, intensity modulation is the mainstream in underwater visible light modulation technology, while coherent modulation is usually used to improve the reliability of the system. The possible development direction of UVLC in the future is also discussed from the perspective of constructing UVLC network and adaptive modulation coding.

Screen communication is a near-field communication mode using dynamic bar code as the information carrier and visible light as the media. Due to its strong anti-interference ability, spectrum resources free, and simple deployment, it has a wide range of application scenarios and great development potential. We have proposed a screen communication location tracking algorithm based on the method of deep learning. The information area is processed by Faster Region with Convolutional Neural Networks Feature (Faster R-CNN) algorithm which makes the optical camera can intelligently locate the carrier area without relying on the traditional positioning finder pattern, resulting in the improvement of the single frame carrying. The Lucas-Kanade (LK) optical flow is used for position change estimation of the subsequent frame information region introduced by the jitter, which improves the continuous frame processing rate and the system communication rate. Experimental results show that the mean Average Precision (mAP) of the Faster R-CNN is reached up to 90.91% while the LK optical flow was introduced to improve the processing efficiency of the system, and overcome the bottleneck of the processing power of the terminal system. The processing time was shortened by 59.5% compared with the Faster R-CNN algorithm.

The key links of power optical networks play an important role in the security and reliable protection of quality of service. Research on the key link identification method helps to improve the efficiency and accuracy of the identification process. In this paper, we first measure the shortest path sensitivity in the network. Then the shortest path length between network nodes is calculated to study the effect of link state deterioration on network performance. Next, based on three different targets, such as minimum hop count, shortest delay and highest reliability, we conduct a statistical analysis on the link state change and the correlation relationship on the shortest path sensitivity to obtain key link indicators. Finally, the actual provincial power communication network is taken as an example to verify the feasibility and correctness of the method. The research conclusion has reference value for the planning, design and operation maintenance of power optical network.

In order to solve the problem of service blocking caused by Inter Core Crosstalk (ICXT) in Space Division Multiplexing Elastic Optical Network (SDM-EONs), a dynamic routing and crosstalk sensing algorithm is proposed. Firstly, in the routing stage, a candidate path sorting formula combining the shortest path and path loading is designed to dynamically select a more appropriate path for business requests according to the system load. For the problem of inter core crosstalk in multi-core fiber, a crosstalk sensing strategy is proposed to minimize the impact of inter core crosstalk, with improvement of the probability of successful transmission and reduction of the blocking rate. In order to evaluate the performance of this algorithm, the ICXT improvement index is defined to evaluate the performance difference between this algorithm and the comparison algorithm. Simulation results show that the algorithm in this paper has a significant improvement in blocking rate performance and inter core crosstalk compared with many comparative literatures.

The frequency offset estimation method for chirp signal has the problem of limited resolution and low estimation accuracy. A Frequency Offset Estimation based on Matched Filter Interpolation (MFI-FOE) method is proposed. Firstly, the received signal is filtering matched with the corresponding matching signal. Then, the peak value of the waveform at the output of the matched filter is searched. Finally, we calculate the relative deviation and interpolate between the peak and the left or right point of the immediately adjacent peak to obtain an accurate frequency offset estimation. The simulation results show that the signal-noise ratio threshold of MFI-FOE method is reduced by 2~4 dB compared with the traditional frequency offset estimation method, and the performance is stable in the whole range of relative frequency offset estimation. The Normalized Mean Square Error (NMSE) of the frequency offset estimation is closer to the Cramer-Rao Bound. Therefore, MFI-FOE method can significantly improve the accuracy of estimation and anti-noise ability, which verifies the effectiveness of the method.

The strategy of electricity internet of things is recently proposed by State Grid, which attracts much attention. In this paper, we focus on the base station deployment schemes in electricity internet of things. Different from the traditional schemes without considering the user behavior, a new aggregation coefficient indicator is proposed to measure the traffic and spatial aggregation phenomena in this paper. On this basis, the energy efficient base station deployment strategy is studied. Simulation results show that Poisson cluster process scheme is more suitable for the higher aggregation coefficient environment. However, the energy efficiency of our proposed scheme is lower than other schemes. Poisson point process scheme has higher energy efficiency but only be suitable for lower aggregation coefficient environment.

High voltage submarine cable laying is the key link of offshore wind farm development. In order to improve the simulation accuracy of submarine cable laying and landing, the paper uses the hydrodynamic analysis method to apply viscous damping in SESAM/HydroD to obtain the Response Amplitude Operator (RAO) of cable laying vessel. The coupling model of cable-laying vessel-submarine cable-mooring system is established in Orcaflex to analyze the effect of viscous damping on the response of the coupling system. Through the comparative evaluation of the position, tension and curvature of the submarine cable, the maximum allowable operating sea state of the submarine cable landing is given. The results show that the heave amplitude of the hull decreases by about 55% after considering viscous damping. The effective tension and curvature during laying and the offset during landing of the submarine cable are significantly reduced. Taking the analysis results of vessel viscous damping into account as engineering guidance can effectively reduce the expropriation area of submarine cable landing in the sea area, and increase the operation window period with improvement of the efficiency of submarine cable laying.

This paper mainly studies several factors, which may affect the temperature measurement result when the Distributed Optical Fiber Temperature Sensor System (DTS) based on Raman scattering is used to monitor the cable temperature, and provides some feasible suggestions on how to improve the accuracy of DTS in temperature measurement under the actual monitoring. Firstly, the comparative experiment is developed by measuring the temperature of bare fiber and optical cable using the DTS at the same time. The result shows that if the calibration parameters obtained by bare fiber are directly applied to the optical cable in the field, the measured temperatures of optical cable and bare fiber are different. Therefore, higher temperature accuracy can be obtained by correcting the bare fiber calibration parameters or directly using the optical cable for calibration. Secondly, the influence of the sag and vibration of the aerial optical cable under the actual working conditions on the temperature measurement accuracy is investigated by experiment, and the result shows that the influence of sag and vibration on the temperature measurement accuracy is small. While compared with vibration, the influence of sag on the temperature measurement result is more obvious, which means that the influence on the temperature measurement result by the dynamic strain of the cable is more obvious than that by the static strain of the cable.

Polarization control with fast response speed is highly desired in optical communication systems, such as in related studies of polarization scrambling and polarization stabilization. However, due to the influence of materials and structure, current polarization controller can only reach nanoseconds at the fastest, which becomes the main bottleneck of polarization-related research. In this paper, a novel optical structure based on low-speed electronic polarization controller and high-speed phase modulator is introduced to realize ultrafast polarization control. The changing trajectory of polarization state on Poincare Sphere caused by slow amplitude difference change and simultaneous fast phase difference change of two orthogonal projects is demonstrated and analyzed experimentally. This method greatly improves the response speed of polarization control and provides strong support for better performance of the polarization scrambling and polarization stabilization.

Digital predistortion is an effective technical method to improve the nonlinearization of power amplifier. Based on the fractional-order memory polynomial model and the traditional bilinear polynomial model, an improved fractional-order bilinear polynomial model predistortion method for indirect learning structure is proposed. The model uses the indirect learning structure and Recursive Least Square (RLS) adaptive identification algorithm to simulate the adaptive predistortion system. The experimental results show that, compared with the traditional bilinear polynomial model, the Normalized Mean Square Error (NMSE) is improved by 2.6 dB with 34.3% reduction of the number of model coefficients and the improvement of Adjacent Channel Power Ratio (ACPR) of 5 dB. Therefore, the model can effectively compensate the distortion of the power amplifier.

In order to solve the problem that the water film and salt scale on the inner wall of the resonant cavity sensor could reduce the accuracy measurement of the wetness, a method for measuring the dielectric film thickness on the inner wall of cylindrical cavity is proposed in this paper. Based on the principle of dielectric perturbation method, this method uses the hyperbolic cosine-shaped slot resonator as a sensor, working at the TE111 mode to measure the dielectric film thickness. Taking the water film as an example, the relationship between the water film thickness and the resonant frequency is deduced theoretically, and the feasibility of measuring the water film by TE111 mode is analyzed through simulation. We establish the mathematical model of the current density distribution line of the cavity end face for the TE111 mode by the method of vector field equation, and design the hyperbolic cosine-shaped slot resonator sensor. The simulation results show that the performances of the electromagnetic characteristics, radiation characteristics and flow characteristics of the resonator are all relatively well. The electromagnetic leakage rate is basically 0, and the sampling error is -1.25%, which meet the design requirements. The water film thickness, salt scale, oil film, fouling and other dielectric films can be measured accurately. It is also shown that the film thickness is linearly related to the resonance frequency offset, which are consistent with the theory.

The Poisson Point Process (PPP) is widely used in wireless network modeling and analysis due to its theoretical analytic and random nature. However, the actual base station deployment is not completely random. In view of the mutual exclusion of base stations, we propose the Poisson Hard-Core Process (PHCP) to model the Homogeneous Cellular Network (HCN). We first choose a base station access scheme based on the Maximum Signal to Interference Ratio (SIR) criterion. Then per tier approximate SIR analysis based on PPP method is used to derive the approximate coverage of PHCP heterogeneous network. The simulation results show that the approximate coverage generated by this method is the lower bound of the actual coverage, and the coverage of the PHCP network is better than the PPP coverage, which is more suitable for the actual base station deployment with mutual exclusion.

Massive Multiple-Input Multiple-Output (MIMO) has been identified as a key technology for the upcoming Fifth Generation (5G) wireless communication systems. The original Message Passing Detection (MPD) algorithm utilizes channel hardening theory to achieve good detection performance in large-scale MIMO systems. However, the computational complexity of the MPD algorithm increases with the increase of the modulation order and the number of user antennas, which is difficult to implement effectively in an actual large-scale MIMO system. The Probabilistic Approximation-MPD (PA-MPD) algorithm can reduce the computational complexity of the original MPD algorithm. In this paper, the iterative process of terminating the iterative process and updating the partial symbol probability is applied in the iterative process of the MPD algorithm, a Selective Update-MPD (SU-MPD) algorithm is proposed, which reduces the computational complexity of the MPD algorithm. The simulation results show that the computational complexity of SU-MPD algorithm can be reduced to 19% of MPD algorithm and 50% of PA-MPD algorithm under various antenna configurations, without reducing the detection performance of the algorithm.

In order to improve the spectral efficiency of the index modulation scheme in Multiple Input Multiple Output (MIMO) systems, this paper combines Spatial Modulation (SM) with Code Index Modulation (CIM) and uses the idea of parallel transmission to convey the transmission information bits by two modulation symbols, two antenna indexes, and two Pseudo Noise (PN) code indexes in each time slot. In addition, the proposed scheme also uses the antenna selection technique and the rotational symmetry characteristics of the quadrature amplitude modulation symbols to improve the Bit Error Rate (BER) performance of the system and reduce the detection complexity of the receiver, respectively. The simulation results show that the BER performance of the proposed scheme is obviously better than other index modulation schemes, and the low complexity Maximum Likelihood (ML) detection algorithm proposed in this paper has the same BER performance compared with the optimal ML detection algorithm.