The design of electromagnetic interference (EMI) filters needs to fulfill the EMI standards. Designing a filter is a time-consuming process for new engineers as well as for those experienced engineers. This paper measures and compares the noise spectrum of the wireless base station power prototype with and without the original filter. The ideal insertion loss (IL) of the original filter is obtained by combining calculation and simulation. It is pointed out that the effect of the original filter is not good. Based on the improved insertion-loss method, the source impedance model of the prototype is established by combining measurement and theory. A procedure for designing EMI filters for switch power supply will be presented. The filter design procedure makes it possible to design filters quickly and easily. Finally, the proposed filter design method is proved to be effective by the EMI measurement of the wireless base station power supply prototype.

The transformer is the key circuit component of the common-mode noise current when an isolated converter is working. The high-frequency characteristics of the transformer have an important influence on the common-mode noise of the converter. Traditionally, the measurement method is used for transformer modeling, and a single lumped device is used to establish the transformer model, which cannot be predicted in the transformer design stage. Based on the transformer common-mode noise transmission mechanism, this paper derives the transformer common-mode equivalent capacitance under ideal conditions. According to the principle of experimental measurement of the network analyzer, the electromagnetic field finite element simulation software three-dimensional (3D) modeling and simulation method is used to obtain the two-port parameters of the transformer, extract the high-frequency parameters of the transformer, and establish its electromagnetic compatibility equivalent circuit model. Finally, an experimental prototype is used to verify the correctness of the model by comparing the experimental measurement results with the simulation prediction results.

The further integration of telecommunications and industry has been considerable and is expected to bring significant benefits to society and economics in 6G. It also forms some evolution trends for next-generation communication systems, including further rises in machine-type communications (MTC), uplink-dominated systems, and decentralized structures. However, the existing access protocols are not friendly to these trends. This paper analyzes the problems of existing access protocols and provides novel access technologies to solve them. These technologies include contention-based non-orthogonal multiple access (NOMA), data features, enhanced pilot design and successive interference cancellation (SIC) of diversity. With these key enablers, truly grant-free access can be realized, and some potential modifications of protocols are then analyzed. Finally, this paper uses massive and critical scenarios in digital transformations to show the great necessity of introducing novel access technologies into future communication protocols.

Crowd counting is a challenging task in computer vision as realistic scenes are always filled with unfavourable factors such as severe occlusions, perspective distortions and diverse distributions. Recent state-of-the-art methods based on convolutional neural network (CNN) weaken these factors via multi-scale feature fusion or optimal feature selection through a front switch-net. L2 regression is used to regress the density map of the crowd, which is known to lead to an average and blurry result, and affects the accuracy of crowd count and position distribution. To tackle these problems, we take full advantage of the application of generative adversarial networks (GANs) in image generation and propose a novel crowd counting model based on conditional GANs to predict high-quality density maps from crowd images. Furthermore, we innovatively put forward a new regularizer so as to help boost the accuracy of processing extremely crowded scenes. Extensive experiments on four major crowd counting datasets are conducted to demonstrate the better performance of the proposed approach compared with recent state-of-the-art methods.

Multiple access scheme is one of the key techniques in wireless communication systems. Each generation of wireless communication is featured by a new multiple access scheme from 1G to 4G. In this article we review several non?orthogonal multiple access schemes for 5G. Their principles, advantages and disadvantages are discussed, and followed by a comprehensive comparison of these solutions from the perspective of user overload, receiver type, receiver complexity and so on. We also discuss the application challenges of non?orthogonal multiple access schemes in 5G.

The merging of optical communication and wireless communication is a tendency in the development of future communication. Orthogonal Frequency Division Multiplexing (OFDM ) technology is becoming a core technology in the physical layer of next generation wireless communication system. Taking advantages of both wireless communication and optical communication, OFDM Radio over Fiber (OFDM-RoF ) system is characterized by high speed, large capacity and high spectral efficiency. However, it still has some problems to be addressed, including dispersion and nonlinearity effects. The nonlinearity effect of fiber and modulator can be mitigated by PAPR reduction algorithms, the dispersion effect can be eliminated using Cyclic Prefix (CP ) and channel estimation, and the fiber nonlinearity can be reduced by techniques such as digital phase conjugation, Partial Carrier Filling (PCF ), nonlinearity precompensation and serial correlation reduction.