短波电台车载适配器测试系统设计与实现

通过分析一种短波电台车载适配器的测试需求,提出简洁有效的自动测试系统实现方式,包括自动测试系统的搭建,配套开关矩阵的设计实现,测试软件的开发等,并重点对自动测试过程中的校准手段等进行论述,本文所述短波电台车载适配器测试系统通过在某型电台车载适配器的生产线测试过程中得到充分应用,大幅提升了测试效率,取得了良好的效益.     

Home Energy Management System Using NILM and Low-Cost HAN

Home energy management systems(HEMs) are used to provide comfortable life for consumers as well as to save energy. An essential component of HEMs is a home area network(HAN) that is used to remotely control the electric devices at homes and buildings. Although HAN prices have dropped in recent years but they are still expensive enough to prohibit a mass scale deployments. In this paper, a very low cost alternative to the expensive HANs is presented. We have applied a combination of non-intrusive load monitoring(NILM) and very low cost one-way HAN to develop a HEM. By using NILM and machine learning algorithms we find the status of devices and their energy consumption from a central meter and communicate with devices through the one-way HAN. The evaluations show that the proposed machine learning algorithm for NILM achieves up to 99% accuracy in certain cases. On the other hand our radio frequency(RF)-based one-way HAN achieves a range of 80 feet in all settings.     

Optimal Cooperative Inactive Secondary Sensing Order Using Users in Cognitive Radio Networks

A novel cooperative spectrum sensing or- der which utilizes inactive Secondary users （SUs） efficiently based on maximum throughput has been proposed in Cog- nitive radio networks （CRNs）. In order to predict the states of Primary users （PUs）, we build the PU＇s traffic pattern as a Continuous-time Markov chain （CTMC） pro- cess. CRNs obtain the maximum throughput while SUs sense the licensed channels with the optimal order. The numerical simulation results show that the proposed or- der based on spectrum sensing scheme can achieve larger channel utilization and lower sensing overhead as compared with the spectrum sensing scheme without using the opti- mal order sensing. After considering the report overhead of SUs, the optimal number of inactive SUs for the maxi- mum throughput can be found.     

Self-Organization Approaches for Optimization in Cognitive Radio Networks

Cognitive radio （CR） is regarded as a promising technology for providing a high spectral efficiency to mobile users by using heterogeneous wireless network architectures and dynamic spectrum access techniques. However, cognitive radio networks （CRNs） may also impose some challenges due to the ever increasing complexity of network architecture, the increasing complexity with configuration and management of large-scale networks, fluctuating nature of the available spectrum, diverse Quality-of-Service （QoS） requirements of various applications, and the intensifying difficulties of centralized control, etc. Spectrum management functions with self-organization features can be used to address these challenges and realize this new network paradigm. In this paper, fundamentals of CR, including spectrum sensing, spectrum management, spectrum mobility and spectrum sharing, have been surveyed, with their paradigms of self-organization being emphasized. Variant aspects of self- organization paradigms in CRNs, including critical functionalities of Media Access Control （MAC）- and network-layer operations, are surveyed and compared. Furthermore, new directions and open problems in CRNs are also identified in this survey.     

基于短波自适应技术的快速建链设备实现方案

因具有以较低功率实现远距离无线电信号传输的特点,短波通信技术已成为通信领域不可或缺的一门重要技术。近年来,随着计算机数字信号处理、扩频通信、自适应通信等现代电子信息技术在短波通信领域的广泛应用,短波自适应技术进入快速发展时期,可在短波通信中自动选频、自动设置信道的短波快速建链技术也由此兴起。基于此,提出了一种基于短波快速建链技术的设备设计及实现方法,可作为该技术在实际应用中的设备级解决方案。     

Time Agility Optimization for Dual-stage Collaborative Spectrum Sensing

Cooperative spectrum sensing has been shown to be an effective method to mitigate the impact of hidden terminal and shadow fading in cognitive radio networks. Currently most works focused on either coop- erative sensing or sensing scheduling as a viable means to improve the detection performance without studying their interactions. This paper proposed a dynamic and variable time-division multiple-access scheduling mechanism that was incorporated into a Dual-stage collaborative spectrum sensing （DCSS） model in a less ideal radio environment. Moreover, this paper derived closed-form expressions of sensing time for DCSS, and addressed the critical range of timeslot length. An optimized algorithm to minimize sens- ing time was deduced and verified. The simulation results indicate that average sensing time with DCSS is shortened by 11.5~V0 when compared with that of the Single collabora- tive spectrum sensing （SCSS） while guaranteeing detection error rate requirement of less than 1%.     

Optimal and Suboptimal Access and Transmission Polices for Dynamic Spectrum Access over Fading Channels in Cognitive Radio Networks

We propose a cross-layer optimal access and transmission framework for dynamic spectrum access to maximize expected long-term average throughput under power and collision constraints by a dynamic programming method namely Constrained Markov decision process （CMDP）. The optimal policy for CMDP is capable of guiding transmitter to choose an available channel and transmission rate at the beginning of each frame for its long-term goals according to current channel sensing results and prior channel fading information. The complexity of finding the optimal policy by Linear programming （LP） approach increases exponentially with the number of channels and fading levels, which incurs so-called curse of dimensionality. Therefore we propose two complexity- reduced suboptimal policies, namely, policy separation and heuristic algorithms. Finally, we compare the performances of policies by numerical results.     

Variable Persistence Sensing Schemes for Opportunistic Spectrum Access

Cognition technologies can significantly enhance spectrum utilization through secondary usage. Secondary users （SUs） search for spectrum holes which are not used by Primary users （PUs） and communicate through them. The design and analysis of simple opportunistic spectrum access schemes for maximizing utilization efficiency and minimizing delay of SUs under limited sensing bandwidth and energy is still at infancy. In this work, we consider PU＇s frequency occupancy patterns and propose three simple variable persistence sensing schemes for maximum exploitation of idle spectrum chunks by SUs, and perform their theoretical analysis. Numerical case studies are presented to verify the theoretical analysis and illustrate the performance of the schemes proposed.     

Applying System Thinking to Learn from Accident of Modern Automatic Control Systems

Modern societies increasingly rely on auto- matic control systems. These systems are hardly pure tech-nical systems; instead they are complex socio-technical sys- tems, which consist of technical elements and social components. It is necessary to have a systematic approach to analyze these systems because it is growing evidence that accidents from these systems usually have complex causal factors which form an interconnected network of events, rather than a simple cause-effect chain. We take railway Train control systems （TCS） as an example to demonstrate the importance of the socio-technical approach to analyze the system. The paper presents an investigation of recent high-speed railway accident by applying STAMP - one of the most notable socio-technical system analysis tech- niques, outlines improvements to the system which could avoid similar accidents in the future. We also provide our valuable feedback for the use of STAMP.     

Frequency bands for optimum propagation of complex signals through shortwave radio channels

A radio-engineering approach based on the dispersion characteristic and impulse response of a radio channel is proposed to describe the dispersion distortion of complex shortwave radio signals propagating through ionospheric radio channels. The impulse response of a wideband ionospheric radio channel is investigated using the polynomial representation of the dispersion characteristics, which are determined from oblique sounding of the radio channel by ultrawideband chirp signals. Frequency bands for optimal propagation of complex signals over radio links 3600 to 5700 km long are estimated.     

An Overview of Anti-Collision Protocols for Radio Frequency Identification Devices

Radio frequency identification （RFID） is a new type of non-contact automatic identification technology. Due to its low energy consumption, low cost, and its adaptability to harsh environments, it has been applied to many fields. In the RFID systems, data collision is inevitable when the reader sends a communication request and multiple tags respond with simultaneous data transmission. Data collision is prone to causing problems such as： identification delay, spectrum resource waste, a decreased system throughput rate, etc. Therefore, an efficient, stable anti-collision protocol is crucial for RFID systems. This research analysed the current research into RFID anticollision protocols and summarised means for its improvement through the mechanism of implementation of different types anticollision protocols. Finally, a new direction is proposed for the future development of RFID anti-collision protocol systems.     

Elastic Characteristic Extraction Method of Underwater Target Based on Adaptive Filtering

In this paper, a kind of elastic characteristic extraction method of underwater targets based on adaptive filtering is introduced. The kernel of the method is the recursive least square （RLS） algorithm. Firstly, the geometric scattering signal is fit by using the echo signal and the incident signal. Then, the frequency spectrum of the echo signal and the geometric scattering signal are calculated. At last, the frequency spectrum of the elastic scattering signal is obtained. The research of the simulation and lake experiment is carried on. As the results show, the formants of the elastic signal frequency spectrum can be precisely extracted by the algorithm, and the extraction algorithm can apply to extracting the elastic characteristic from the echo signal in a real underwater acoustics environment.     

基于OFDM的短波电台改进方案设计

短波电台作为远距离传输的重要载体,有着非常重要的作用。然而传统短波电台受短波信道固有缺点的限制,传输速率较低,频带利用率也不高。正交频分复用(OFDM)技术的各子载波之间的正交性使得其频谱可重叠从而提高了频带利用率,同时能有效对抗频率选择性衰落。为了有效提高短波电台的性能,可以采用OFDM技术。分析了OFDM的基本原理,提出了基于OFDM的短波电台性能增强方案。     

短波通信电台在人防通信中的重要作用初探

短波通信是无线电通信系统的基本组成,具有其它通信技术不可替代的抗损坏优势.因此,尽管短波通信是一种传统的无线电通信技术,依然被广泛应用于人防事业的发展进程中.鉴于此,本文主要探讨了短波通信电台在人防通信中的应用及其重要作用.     

A millimeter wave radio spectrometer for material analysis below T<1 K

A radio spectrometer set suggesting wide fuctional possibilities and operating in the shortwave part of the millimeter band at temperatures below 1 K is described. The set is intended for analyzing materials of polarized nuclear targets under the conditions close to actual operation, with the use of magnetic resonance methods. The potential of spectrometer allows employing it in semiconductor physics, physics of disordered media, biology, et.c.     

Optimal Spectrum Sensing in Energy Harvesting Cognitive Radio Systems

In this paper,we consider a cognitive radio system with energy harvesting,in which the secondary user operates in a saving-sensing-transmitting（SST） fashion.We investigate the tradeoff between energy harvesting,channel sensing and data transmission and focus on the optimal SST structure to maximize the SU＇s expected achievable throughput.We consider imperfect knowledge of energy harvesting rate,which cannot be exactly known and only its statistical information is available.By formulating the problem of expected achievable throughput optimization as a mixed-integer non-linear programming one,we derive the optimal saveratio and number of sensed channels with indepth analysis.Simulation results show that the optimal SST structure outperforms random one and performance gain can be enhanced by increasing the SU＇s energy harvesting rate.     

短波同步正交跳频网设计

常规短波跳频网由于自身的特性,常采用异步方式组网,限制了抗干扰能力的充分发挥。同步基准为设计性能优良的短波同步正交跳频网提供了条件。同步组网各跳频网络具有统一的时间基准,而异步组网时各跳频网络没有。为达到在任一瞬间,均不会发生频率碰撞,在总结常规跳频网络的特性的基础上,提出了基于同步基准的短波同步正交跳频组网的设计方法,并分析了短波同步正交跳频网的特性。     

A universal chart for use in relating ionospheric absorption to phase path and group path

The absorption of a radio wave in the ionosphere can be approximated byA = frac{omega}{c}frac{1}{2}intfrac{Z(mu' - mu)}{1 + g} cos alpha ds, where the integral is along the ray that exists when the normalized collision frequencyZ = 0, mu'andmuare the group and phase refractive indices, respectively, andalphathe angle between the wave normal and ray direction. Graphs are presented from whichgcan be obtained for any values of the ionospheric plasma parametersXandY.     

无线电短波天线的倾斜地面架设新技术

在无线电短波通信中,为了降低天线高度,节省人力、物力和经费,增加短波通信的隐蔽性,采用了面对通信方向的斜坡地面架设发射天线的新技术。本文经数学推导,给出了斜坡天线高度的数学算式,结合计算机辅助设计(CAD),提高了斜坡短波发射天线场的设计计算精度和速度。     

激光条形码识别技术的应用优势与面临的挑战

激光条形码自动识别技术是目前自动识别技术中应用最广泛的一种,探讨了该识别技术的特征与优势以及来自RFID无线射频识别新技术的挑战。