HF Communications: Past, Present, and Future

High frequency(HF) communication, commonly covering frequency range between 3 and 30 MHz, is an important wireless communication paradigm to offer over-thehorizon or even global communications with ranges up to thousands of kilometers via skywave propagation with ionospheric refraction. It has widespread applications in fields such as emergency communications in disaster areas, remote communications with aircrafts or ships and non-light-of-the-sight military operations. This tutorial article overviews the history of HF communication, demystifies the recent advances, and provides a preview of the next few years, which the authors believe will see fruitful outputs towards wideband, intelligent and integrated HF communications. Specifically, we first present brief preliminaries on the unique features of HF communications to facilitate general readers in the communication community. Then, we provide a historical review to show the technical evolution on the three generations of HF communication systems. Further, we highlight the key challenges and research directions. We hope that this article will stimulate more interests in addressing the technical challenges on the research and development of future HF radio communication systems.

A Heterogeneous Information Fusion Deep Reinforcement Learning for Intelligent Frequency Selection of HF Communication

The high-frequency(HF) communication is one of essential communication methods for military and emergency application. However, the selection of communication frequency channel is always a difficult problem as the crowded spectrum, the time-varying channels, and the malicious intelligent jamming. The existing frequency hopping, automatic link establishment and some new anti-jamming technologies can not completely solve the above problems. In this article, we adopt deep reinforcement learning to solve this intractable challenge. First, the combination of the spectrum state and the channel gain state is defined as the complex environmental state, and the Markov characteristic of defined state is analyzed and proved. Then, considering that the spectrum state and channel gain state are heterogeneous information, a new deep Q network(DQN) framework is designed, which contains multiple sub-networks to process different kinds of information. Finally, aiming to improve the learning speed and efficiency, the optimization targets of corresponding sub-networks are reasonably designed, and a heterogeneous information fusion deep reinforcement learning(HIF-DRL) algorithm is designed for the specific frequency selection. Simulation results show that the proposed algorithm performs well in channel prediction, jamming avoidance and frequency channel selection.

Exploring Channel Diversity in HF Communication Systems： A Matching-Potential Game Approach

This paper investigates the channel diversity problem in high frequency(HF) communication systems. Due to the limited HF spectrum resources, a HF communication system with shared channels is considered, where each user equipment(UE) has individual communication demand. In order to maximize the communication probability of the whole system, a matching-potential game framework is designed. In detail, the channel diversity problem is decomposed into two sub-problems. One is channel-transmitter matching problem, which can be formulated as a many-to-one matching game. The other is the transmitter allocation problem which decides the transmission object that each transmitter communicates with under channel-transmitter matching result, and this sub-problem can be modeled as a potential game. A multiple round stable matching algorithm(MRSMA) is proposed, which obtains a stable matching result for the first sub-problem, and a distributed BR-based transmitter allocation algorithm(DBRTAA) is designed to reach Nash Equilibrium(NE) of the second sub-problem. Simulation results verify the effectiveness and superiority of the proposed method.

System-Level EMC Assessment for Military Vehicular Communication Systems Based on a Modified Four-Level Assessment Model

With the development of EMC technology, EMC assessment has become increasingly important in EMC design. Although numerous EMC assessment models are available today, few of them can provide a tradeoff between efficiency and accuracy for the specific case of military vehicular communication systems. Face to this situation, a modified four-level assessment model is proposed in the paper. First, the development of EMC assessment technology is briefly reviewed, and the theoretical mechanism of EMI environment is introduced. Then, the architecture of the proposed model is outlined, and the assessment methods are explored. To demonstrate the application of it, an example involving a communication system in a military vehicle is presented. From the physical layer to the signal layer, a hierarchical assessment on the entire system is successfully performed based on the proposed model, and we can make a qualitative EMC assessment on the EMC performance of the system. Based on a comparison with the traditional model, we conclude that the proposed model is more accurate, more efficient and less time-consuming, which is suitable for the EMC assessment on militaryvehicular communication systems. We hope that the proposed model will serve as a useful reference for system-level EMC assessments for other systems.

Deep Spectrum Prediction in High Frequency Communication Based on Temporal-Spectral Residual Network

High frequency(HF) communication is widely spread due to some merits like easy deployment and wide communication coverage. Spectrum prediction is a promising technique to facilitate the working frequency selection and enhance the function of automatic link establishment. Most of the existing spectrum prediction algorithms focus on predicting spectrum values in a slot-by-slot manner and therefore are lack of timeliness. Deep learning based spectrum prediction is developed in this paper by simultaneously predicting multi-slot ahead states of multiple spectrum points within a period of time. Specifically, we first employ supervised learning and construct samples depending on longterm and short-term HF spectrum data. Then, advanced residual units are introduced to build multiple residual network modules to respectively capture characteristics in these data with diverse time scales. Further, convolution neural network fuses the outputs of residual network modules above for temporal-spectral prediction, which is combined with residual network modules to construct the deep temporal-spectral residual network. Experiments have demonstrated that the approach proposed in this paper has a significant advantage over the benchmark schemes.

Research on Multi-Layer Distributed HF Radio Network Structure

High frequency（HF）transmission is an important communication techniques.However,conven-tional point-to-point transmission can be easily destroyed,which limits its utilization in practice.HF networking communication has the capability against demolishment.The network structure is one of the key factors for HF networking communication.In this paper,a novel analysis method of the network connectedness based on the eigenvalue is derived,and a multi-layer distributed HF radio network structure is proposed.Both the theore-tical analysis and the computer simulation results verify that the application of the proposed network structure in the HF radio communication can improve the anti-demolishment ability of the HF network efficiently.

铝电解多功能天车电气控制系统的设计改进

铝电解多功能天车是铝冶炼工艺过程中的关键设备,电解车间的高温、强磁场、多粉尘及HF气体的恶劣环境对电气控制系统的影响非常大。对此,本文从电气控制系统的设计、选型以及后期的安装布线等方面着重进行分析和改进,PLC采用XT系列的高温防腐型模块,主从站之间设计无线通过冗余,变频器选用IP55高防护等级套件,柜体内部元器件安装及电缆敷设考虑EMC设计,从设计端解决了可能出现的故障,有力地保障了电解铝的稳定生产。

电路辐射干扰机理诊断与特性估计

针对远场测试无法准确获取电路辐射机理且电磁测量过程复杂问题,提出基于近场测量的高频电路辐射机理快速诊断和基于电路射频参数测量的空间场辐射特性快速预估方法。首先,通过近场电磁场天线测量得到波阻抗及与测试点空间位置关系,分别根据共模和差模辐射的近场特性进行机理诊断;其次,根据共模辐射电流与空间总辐射场之间关系,得到基于射频共模电流分析的辐射EMI估计方法;最后,完成了针对不同无线通信设备和高速数字PCB的辐射干扰诊断与抑制实验,结果验证了文中方法的有效性。此外还利用美国ETS-Lindgren公司3m法标准电波暗室做了对比测试,结果吻合较好且误差小于5.13%。

安装FACTS的变电站高频电磁干扰测试系统

应用屏蔽移动车、高频电压电流探头、电磁场天线、光纤传输和频谱分析仪等设备与技术 ,设计了安装FACTS设备的变电站中高频电磁干扰的测试系统并实现了传导干扰与辐射干扰的同步触发测量。 4个安装不同类型SVC的变电站的现场测试和分析表明 ,SVC的高频电磁辐射集中在 10kHz～ 3.5MHz,最大辐射强度为磁场 0 .87A/m和电场 114V/m。将测量数据与IEC6 10 0 0 4系列电磁兼容标准比较后 ,针对基于SVC的电磁辐射干扰提出了两项抗扰性试验的具体改进建议。

FACTS设备的电磁兼容问题展望

大容量FACTS(柔性交流输电系统)设备在现代高压变电站中的广泛应用,将产生大量的宽带电磁干扰,对电网和环境造成严重的电磁污染,威胁到其本身的正常运行甚至可能影响附近二次电子设备的正常工作.通过分析近年来国内外的研究现状,提出了FACTS变电站电磁兼容研究的主要课题和内容,对具体的研究方法和目标进行了详细论述,为下一步开展深入研究提供参考.

Simulation analysis on co-site interference of vehicular digital communication system based on IM prediction method by BER

The co-site interference exists in kinds of communication systems, especially in digital communication systems, also is one of the biggest threats ＂in electromagnetic compatibility （EMC） designation of the systems. Analyzing the co-site interference is an important process in achieving EMC performance of the system. Under the situation, the co-site interference simulation analysis of a vehicular digital communication system based on interference margin （IM） prediction method by bit error ratio （BER） was proposed in the paper. In the simulation analysis, some physical models of the vehicular communication system were established on SIMULINK environment, the upper limit of BER level for audio signals was defined as the IM, three different types of co-site interference was analyzed respectively, and the simulation results were obtained in the form of system interference bandwidth. From these results, the EMC performance evaluation of the vehicular communication system was predicted based on the IM prediction method. By comparing with the actual test results, the correctness of the simulation results was validated and the simulation analysis method can be used for reference by other communication systems was indicated.

EDA软件在通信设备中的应用及重要性

通过对电子设计自动化(EDA)软件的功能、性能分析,结合通信电台的仿真设计,阐述了在通信设备中使用EDA设计工具来提高设计质量和可靠性的重要性。

直接序列扩频通信侦察技术实验模型

直接序列扩频通信侦察技术实验模型主研人员：郭伟余敬东洪福明李牧张国平三超时冯天久蒋明该研究成果直接应用于＂直接序列扩频通信对抗系统＂中，为直扩通信对抗装备和直扩通信侦收提供技术支撑，同时本项目成果所突破的关键技术可应用于ＣＤＭＡ通信系统的开发和管理。...

基于VXI总线技术的短波多通道调谐器设计

主要介绍基于VXI总线技术的短波多通道调谐器的组成及基本原理，对主要技术指标和关键技术实现进行详尽的分析论证，并针对VXI设备的特点对电路进行了小型化、一体化、及电磁兼容性优化设计。

A Novel Device for Real-Time Monitoring of High Frequency Phenomena in CENELEC PLC Band

This paper proposes the design and development of a novel, portable and low-cost intelligent electronic device (IED) for real-time monitoring of high frequency phenomena in CENELEC PLC band. A high speed floating-point digital signal processor (DSP) along with 4 MSPS analog-to-digital converter (ADC) is used to develop the intelligent electronic device. An optimized algorithm to process the analog signal in real-time and to extract the meaningful result using signal processing techniques has been implemented on the device. A laboratory environment has setup with all the necessary equipment including the development of the load model to evaluate the performance of the IED. Smart meter and concentrator is also connected to the low voltage (LV) network to monitor the PLC communication using the IED. The device has been tested in the laboratory and it has produced very promising results for time domain as well as frequency domain analysis. Those results imply that the IED is fully capable of monitoring high frequency disturbances in CENELEC PLC band.