Due to the research paradigm of the conventional Visible Light Communications (VLC), researchers usually assume that the optical sources follow the Lambertian spatial radiation characteristics. Objectively, this assumption ignores that the potential heterogeneous optical beams based on distinct beams, and the essential exploration for the coverage of the VLC based on the above heterogeneous optical beams. To address the issue, we comprehensively consider the distinct non-Lambertian optical beams characteristics of commercial light emitting diodes, and provide several potential heterogeneous optical beams configuration. Simultaneously, in typical indoor scenario, the coverage characteristics are compared between the conventional Lambertian beam based transmitter configuration and the proposed heterogeneous optical beams configuration. Numerical results show that, compared with the well-known Lambertian transmitter design, the proposed heterogeneous optical beams configuration could provide up to 1.97 dB minimum Signal-to-Noise Ratio (SNR) gain, and modify the SNR fluctuation extent from about 22.75 dB of original design to about 15.33 dB in the heterogeneous configuration. Moreover, via the heterogeneous configuration, the weak coverage proportion with lower than 30 dB SNR, is reduced to about 7.23 % from original proportion of about 13.2 %. Therefore, to indoor spatial coverage, the effects induced by the heterogeneous optical beams are verified preliminarily.

Aiming at the problems of low positioning accuracy and high computational complexity of the traditional location fingerprint algorithm, this paper proposes a single Light Emitting Diode (LED) indoor positioning algorithm based on Back Propagation Neural Network and Multiple Linear Regression (MLR). First, three horizontal PhotoDetectors (PD) are used at the receiver side to receive optical power, and the point to be measured is located at the center of the receivers. Then, according to the received optical power vector, the BP neural network is used to obtain the coarse location range of the point to be measured. Finally, the location range is used as a constraint, and multiple linear regression is used to achieve more accurate positioning of the point. The experimental results demonstrate that in an indoor space of 2.0 m × 2.0 m × 2.5 m, the average positioning error of the algorithm is 5.04 cm, and the average positioning time is 0.002 83 s. Compared with the traditional location fingerprint algorithm, the average positioning accuracy of the algorithm is improved by 41.53%, and the average positioning time is reduced by 56.60%, which achieves more accurate positioning under the requirement of lower computational complexity.

To improve the decoding speed and performance of Weighted Bit Flipping (WBF) decoding algorithm for Low Density Parity Check (LDPC) codes, a two-stage WBF algorithm with a multi-/single-bit switching mechanism is proposed. It first performs multi-bit flipping decoding in the first-stage decoder. When cyclic flipping is detected or the maximum flipping function value is less than zero, it switches to the second-stage decoder. Simulation results show that the proposed algorithm obtains gains both in average decoding iteration number and in decoding performance compared with the Sum of the Magnitude based WBF (SMWBF) and the Variable node updating based SMWBF (VSMWBF).

For the problem of system timing synchronization inaccuracy caused by impulsive noise in Multiple-Input Multiple-Output (MIMO) Power Line Communication (PLC), an Orthogonal Frequency Division Multiplexing (OFDM) symbol timing synchronization algorithm based on MIMO PLC system is proposed in this paper, which uses differential correlation and Maximum Ratio Combining (MRC) to improve the synchronization performance. Under 2×2 MIMO PLC channel model, the two transmitting ports send preamble sequences with good autocorrelation and cross-correlation characteristics. At the receiving end, the impulse noise in the power line is filtered by setting the threshold, and the timing coarse synchronization is realized by using the improved delay autocorrelation algorithm. Next, the window summation method is used to reduce the estimation range of fine synchronization. Then, a combined differential correlation and MRC algorithm is used in the timing fine synchronization stage, which has 2 dB improvement compared with the previous method. The simulation shows that the synchronization performance of the proposed method is obviously superior to the traditional cross-correlation method.

The torsion behavior of composite submarine cables often occurs due to external load during the laying and operation. A 3 dimension numerical simulation model of composite submarine cable is established using the finite element software. The clockwise-anticlockwise torsion characteristics of the steel armor, copper conductor and optical fiber of cables are mainly studied. The results show that the stress of each structure along the twisted direction of the steel armor, copper conductor and optical fiber is greater than that in the opposite direction, which leads to a wide range of stress concentration in the copper conductor. The torsion angle of the internal structure of the marine cable along the axial direction has a good consistency and shows linear variation characteristics. In the case of small angle torsion, the stress of each structure increases first and then decreases. When the torsion angle increases, the stress of each structure increases gradually, and the growth rate increases. The materials successively yield during the torsion.

Under the influence of internal and external conditions during the peration of Optical Fiber Composite Overhead Ground Wire (OPGW), the performance of metal strand, ointment, optical unit tube and optical fiber in the structure will degrade to a certain extent, resulting in the deterioration of the overall health of optical cable. How to evaluate the health status of OPGW optical cable according to different parameters and repair or replace it before failure is the main problem. In this paper, a health evaluation method of OPGW optical cable based on subjective and objective weight assignment method and Principal Component Analysis (PCA) method is proposed with detailed case analysis. The data analysis results show that this method can effectively reflect the health status of OPGW optical cable.

As a product with the characteristics of low cost, convenient construction and reliable performance, Bow-type drop cable has been widely used in Fiber To The Home (FTTH) project. However, the emergence of a variety of new application scenarios has brought new development in technologies for Bow-type drop cable. According to the revision of the standard YD/T 1997.1 for Bow-type drop cable, this paper comprehensively describes some new developments in new structure, new material and product performance of Bow-type drop cable in recent years.

Pipeline cable in southwest mountainous areas goes through many complex areas (mountains, rivers, tunnels, farmland, etc.). By geological deformation, man-made damage often leads to fiber core broken, and seriously affects the safety of pipeline production and transportation. Based on the Rayleigh scattering principle of light, the return time of scattered light can be detected, and the position of fault points can be judged. Finally, the vibration signal characteristics around the cable can be collected and analyzed. Due to the difference of surface structure and background noise in different areas, the collected signals are different. In this paper, after processing and analyzing the optical cable signals with different terrain, the external signal characteristics received by the optical cable in different regions are summarized, which helps to perceive the status of the pipeline optical cable line in a complex environment. The results in this paper can provide decision support for the safe operation of the pipeline, and achieve the purpose of early warning, which facilitates the construction of the pipeline safety early warning system in the future.

The Minimum Mean-Square Error (MMSE) detector can achieve excellent Bit Error Rate (BER) performance in massive Multiple-Input Multiple-Output (MIMO) systems. However, it involves high complexity large-scale matrix inversion operation with high degree, resulting in very high hardware requirements. To solve this problem, the article proposes a Generalized Weighted-Preconditioned Gauss-Seide (GS) (GW-PGS) iterative algorithm. In this algorithm, an initialization scheme based on preprocessing is first proposed, which speeds up the convergence speed without adding additional complexity. In addition, this paper proposes an adaptive weighting factor scheme. The experimental results show that compared with the traditional GS algorithm, the algorithm proposed in this paper can effectively reduce the BER and computational complexity.

The diversity and complexity of 5G network services make the Poisson distribution-based reliability test confidence analysis method of traditional products no longer applicable. In order to solve this problem, this paper proposes a confidence analysis method based on application failure distribution statistics. In the early stage of the reliability test, it is designed to conduct a pre-test. Two methods for statistically fitting the pre-tested application failure data are described to obtain the failure distribution law of the 5G network applications. The confidence analysis is then applied in order to get the required duration of the test and the confidence interval of the test result. Case verification shows that this method can help 5G network test designers to obtain credible test results.

In response to the urgent need for the development of low-orbit 5th Generation Mobile Networks (5G) protocol standards, R16 protocol standards and terminal baseband chips based on 5G low-orbit broadband satellite communication systems, a Primary Synchronization Signal (PSS) detection algorithm of "two blocks combined and divided into two cross-correlation" is proposed for coarse frequency offset estimation based on the analysis of the Low Earth Orbit (LEO)-5G system's PBCH link structure and downlink time-frequency synchronization overall architecture. The frequency offset is further estimated through Secondary Synchronization Signal (SSS) correlation, and combined with Cell-Specific Reference Signal (CRS) pilot signal to determine the precise synchronization LEO-5G downlink synchronization algorithm with Field Programmable Gate Array (FPGA). The feasibility and effectiveness of the algorithm were verified by simulation using Vivado and Matlab. The results show that the synchronization algorithm has good real-time performance and high stability. The accuracy rate of the downstream time-frequency synchronization FPGA module with Management Information Base (MIB) parsing is about 83.07%. The chip storage resource consumption for the evaluation of timing and resource consumption is only 11.7%. All indicators meet the indicator requirements.

The linear Minimum Mean Square Error (MMSE) signal detection algorithm in the massive Multiple-Input Multiple-Output (MIMO) system is difficult to use in practical engineering due to the complex inversion of the high-dimensional matrix of the signal detection algorithm. In order to solve this problem, the article proposes a low-complexity hybrid iterative algorithm based on the idea of matrix block and combined with Neumann series expansion algorithm. Using the Neumann series second-order expansion of the inverse matrix of the weighted matrix in the MMSE algorithm as the initial value of the iterative inversion of the block matrix can effectively improve the convergence speed of the algorithm. The simulation results show that this method can have similar performance as the traditional MMSE algorithm with fewer iterations and lower complexity.

The Common Public Radio Interface (CPRI) used in mobile fronthaul has low spectrum efficiency. In this paper, we propose to use Delta-Sigma Modulation (DSM) technology as a new fronthaul interface. In addition, to solve the problem of high computational complexity in the parameter searching of high-order stable Delta-Sigma modulator, Genetic Algorithm (GA) is used to search and optimize the structural parameters of the fourth-order Delta-Sigma modulator. The simulation results under the optimized structural parameters are compared with those under the original structural parameters. Under the condition of 1 bit quantization, the Delta-Sigma modulator with optimized parameters increases the transmission capacity of the system while the average Error Vector Magnitude (EVM) decreases from 0.031 to 0.028. In the case of 2 bit quantization, the average EVM decreases from 0.013 to 0.011.

Narrow Band Internet of Things (NB-IoT) has many kinds of secondary synchronization signals, which need a lot of space to store. Therefore, the requirement of low power consumption is difficult to be satisfied. In order to solve this problem, we propose a low complexity cell Identity (ID) detection algorithm. Firstly, the algorithm splits the secondary synchronization signal, and reduces the multiplication operation by using the law of phase offset changing with frame number. Then it uses the symmetry of Zadoff-Chu (ZC) sequence in the secondary synchronization signal to calculate the autocorrelation value of the received signal. Combined with the cross-correlation between the local signal and the received signal, the secondary synchronization signal can be detected and the cell ID number can be calculated. By comparing with other algorithms, the proposed algorithm can greatly reduce the complexity of the algorithm while maintaining the acceptable performance.

This paper briefly introduces the technical architecture of the 5th Generation Mobile Communication (5G) forward transmission network,analyzes the 5G forward transmission requirement under the 5G co-construction of China Telecom and China Unicom, and gives the implementation scheme of 5G forward transmission. Combined with the 5G co-construction engineering practices of China Telecom and China Unicom, the article gives 5G fronthaul network construction planning, engineering design and construction plan suggestions. Based on the passive wavelength division multiplexing technology, the operator can effectively reduce the consumption of optical fiber resources and reduce the cost of network construction, which provides guidance on how to achieve 5G fronthaul network coverage quickly and economically.