电力线接入技术与接入网的发展

随着IP业务的急剧增长,接入网已成为全网带宽的最后瓶颈,宽带化和IP化将成为接入网发展的大趋势。论文从有线接入和无线接入两方面出发,对现有的接入方式进行了详细的分析和比较,还论述了有线接入和无线接入的各种方式。其中,尤其在对电力线接入等技术作了详细的介绍,并指出了接入网的发展前景。     

局域网技术与发展

介绍了局域网的概念和基本构成,并以目前使用最广泛的以太网为核心,介绍了10Mbit/s以太网的基本技术和100Mbit/s,1Gbit/s以太网技术的发展,以及近几年来出现的新技术和新进展。预计局域网在未来几年内仍然会有较快的发展,尤其在虚拟局域网,无线局域网以及千兆以太网技术等方面。     

Gigabit Ethernet‐based time transfer system

We suggest a gigibit Ethernet (GbE)‐based time transfer technique. In this technique, timing signals used for clock error measurements are inserted into interframe gaps and transmitted. We developed the GbE‐based time transfer system and evaluated the phase stability and precision. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(3): 39–44, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20383     

Channel Characterization for Indoor Power-Line Networks

Power-line networks are promising mediums by which broadband services can be offered, such as Internet services, voice over Internet protocol, digital entertainment, etc. In this paper, an analysis of delay spread, coherence bandwidth, channel capacity, and averaged delay in the frequency bands up to 100 MHz for typical indoor power-line networks are studied. Earlier studies for indoor power-line networks considered frequencies up to 30 MHz only and earlier works have shown that at these frequency bands, the data rates are generally low and are inefficient for digital entertainment in comparison with wireless local-area networks standards, such as IEEE 802.11 n. In this paper, it is shown that at 100 MHz, the average channel capacity for typical indoor power-line networks can be up to 2 Gb/s and it is found that by increasing the number of branches in the link between transmitting and receiving ends, the average channel capacity decreases from 2 Gb/s to 1 Gb/s (when the number of branches was increased by four times for a power spectral density of -60 dBm/Hz). At the same time, the coherence bandwidth decreased from 209.45 kHz to 137.41 kHz, which is much better than the coherence bandwidths corresponding to 30-MHz systems. It is therefore recommended to operate the indoor power-line networks at 100-MHz bandwidths for a wide variety of broadband services.     

Beyond 3G

Beyond 3G is the official IEEE designation for the next stage of wireless technology that some people call 4G or fourth-generation radio. Over the years, every conceptual shift in wireless technology has been characterized as a generational change. Third generation includes wideband mobile multimedia networks and broadband mixed wireless systems. The mobile systems support variable data rates depending on demand and the level of mobility. Typically 144 kb/s is supported for full vehicular mobility and higher bandwidths for pedestrian levels of mobility. Switched packet radio techniques and wideband CDMA-like systems (as the physical channel is) rather than assigned physical channel schemes (referred to as circuit switched) are required to support this bandwidth-on-demand environment. There are two essential concepts beyond 3G. One of these is the provision of data transmission at rates of 100 Mb/s while mobile and 1 Gb/s while stationary. The other concept is that of pervasive networks where a handset supports many access technologies (e.g., cellular, UMTS, and WiFi) perhaps simultaneously and smoothly transitions between them     

HDTV-what's going on?

The economic and signal environment into which high-definition television (HDTV) must fit is described, and the resulting technology requirements are examined. These include advanced signal processing, image processing, communications, and display technology. The two factors dictating these requirements are examined: the need for compatibility with existing National Television Standards Committee (NTSC) broadcasts and home receivers and the finite available broadcast spectrum. The discussion is focused on the video aspects of HDTV, but HDTV is generally expected to include improved audio, probably some form of compressed digital audio requiring a data rate no greater than 500 kb/s per stereo pair     

5 GHz goes the distance for home networkng

Today, there are a number of basic networking technologies that can support data-centric home networking, including 802.11b, HomeRF, and Bluetooth. As with most new markets and technologies, what users want their home network to do is rapidly changing and evolving. Today's early-adopters want more from their home networks than just sharing PC peripherals; they want to be able to send their digital entertainment content (digital pictures, MP3 audio, and DV-based video) throughout their homes. As this "early-adopter market" rapidly changes into a mass market, today's home network must evolve to where it supports not only TCP/IP-based data, but also audio and video data that require QoS. This evolution will require changes in the architecture and implementation of wireless networks. Air5 is a solution for handling the demands of wireless home networking. Based on the lEEE802.11a PHY-layer specification, it includes enhancements for delivering range and throughput levels. Air5 also delivers triple-DES security and guaranteed QoS performance through its TDMA-based synchronous MAC. There are over 40 companies developing 5-GHz based networking technologies today, so this will be a highly competitive technology evolution.     

100-Gb/s optical communications

Optical communications is a quickly evolving field, driven by the ever increasing need for communication bandwidth. Over the next decade, the field is expected to mature substantially as high-speed components enable more advanced modulation and digital signal processing. With the standardization of 100-Gb/s Ethernet well in progress, terabit Ethernet is just over the horizon. As data rates continue to increase above 100 Gb/s, the role of the microwave engineer will become more and more critical to the success of next-generation optical communications gear. There is a tremendous opportunity for the radio engineer to migrate his or her skills to work in the field of microwave signal integrity. This is an up-and-coming field with lots of room for innovative research. In this article, the current state of the art and the research frontiers of 100 G optical communication systems is explained, and various optical modulation approaches are illustrated. Furthermore, comparison with traditional microwave communication systems is presented as well as the increasing role of the microwave engineer in high-speed optical communication design.     

Feasibility study on a highly mobile microwave-band broad-bandtelecommunication system

A prototype of a wireless transmission system has been developed that can transmit multimedia-information data at a maximum rate of 4.608 Mb/s in the 5.2-GHz carrier frequency band. It is based on a multicode transmission scheme that uses cyclic shifted-and-extended M-sequences and is designed for applications such as intelligent transport systems (ITS) and future broadband mobile communication systems. The proposed scheme is highly robust against high-speed multipath fading. The transmission performance of the prototype system was measured in field trials at an outdoor ITS experimental course. The real-time data-transmission rate between the base and mobile stations was 4.608 Mb/s at a vehicle speed of 80 km/h     

High-capacity undersea long-haul systems

This paper reviews technologies and techniques that have been used in deployed long-haul wavelength division multiplexing (WDM) systems and emerging technologies that could be used for the next generation of cost-reduced systems. The overview of current generation technologies starts with a discussion of modulation formats, focusing on the superior properties of the chirped return to zero on-off shift keying (CRZ-OOK) modulation format. The use of 10-Gb/s CRZ-OOK modulation format together with advanced fiber types, more powerful forward error correction (FEC), and broadband erbium-doped fiber amplifiers resulted in the deployment of dense WDM systems with capacities per fiber in terabits per second range and trans-Pacific reach. Demand for the systems with large design capacity led to further development of broadband optical amplifiers. Laboratory demonstrations successfully expanded transmission into the full C-band and later in the C and L transmission bands. The current market conditions dictate the need for reducing the first cost of an installed system rather than reaching record capacity per fiber. Reducing first cost can be achieved by reducing the amount of optical amplifiers in the cable by utilizing an excess performance margin provided by available RZ-OOK technology. Further improvements would be possible if more powerful FEC and modulation formats with better receiver sensitivity are used. For example, the RZ differential phase-shift keying (RZ-DPSK) modulation format with 3-dB better receiver sensitivity and better nonlinear tolerance to large amounts of accumulated dispersion is a very promising technology. This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ-DPSK signals versus RZ-OOK signals. Due to superior receiver sensitivity, the RZ-DPSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission.     

Wide bandgap semiconductor transistors for microwave poweramplifiers

Explores the RF power performance of microwave amplifiers fabricated from wide bandgap semiconductor transistors and demonstrates that microwave power amplifiers fabricated from 4H-SiC and AlGaN/GaN transistors offer superior RF power performance, particularly at elevated temperatures. Theoretical models predict room temperature RF output power on the order of 4-6 W/mm and 10-12 W/mm, with power-added efficiency (PAE) approaching the ideal values for class A and B operation, available from 4H-SiC MESFETs and AlGaN/GaN HFETs, respectively. All calculations were thoroughly calibrated against dc and RF experimental data. The simulations indicate operation at elevated temperature at least up to 5000°C is possible. The RF output power capability of these devices compares very favorably with the 1 W/mm available from GaAs MESFETs. The wide bandgap semiconductor devices will find application in power amplifiers for base station transmitters for wireless telephone systems, HDTV transmitters, power modules for phased-array radars, and other applications. The devices are particularly attractive for applications that require operation at elevated temperature     

Analysis of high frequency performance of TO‐46 header through three‐dimensional full wave electromagnetic model and circuit model

The TO‐46 header has been commonly used for vertical cavity surface emitting laser (VCSEL) and photodetector package. The high‐frequency characteristics of a TO‐46 header were measured using our special K‐type adaptors and simulated through a three‐dimensional full wave electromagnetic simulator. The measurement and simulation results show the TO‐46 header provides a resonance‐free transmission bandwidth over 40‐GHz and reflection loss below −10‐dB within 31‐GHz, with an ideal 50‐Ω terminal. The 25‐Gb/s and 40‐Gb/s eye diagrams through a TO‐46 header were measured using our measurement setup, and the eye diagrams are clear enough. In addition, the single‐end and differential‐end equivalent circuit models of a TO‐46 header were established and verified. The TO‐46 header provides a low‐cost and high‐speed package solution and can be applied in 21‐Gb/s fiber channel technology and 100‐Gb/s (4 × 25‐Gb/s) Ethernet (100 GbE) network. Copyright © 2015 John Wiley & Sons, Ltd.     

低压电力集抄上行通信信号盲区解决方案研究

为解决用电信息采集设备因安装在移动信号盲区,而导致GPRS/CDMA模块通信无法上线的问题,文中介绍了一种基于宽带载波通信技术的无线信号中继器设备——宽带电力线载波无线信号中继器。宽带电力线载波无线信号中继器由数据转换单元、本地单元和远程单元组成,本地单元与远程单元间通过宽带电力线载波通信技术进行通信。在使用原有终端与GPRS/CDMA远程通信模块的条件下,加装宽带电力线载波无线信号中继器,可使信号不良区域的终端实现与主站实时数据交互。通过试验测试表明,宽带电力线载波无线信号中继器具有良好的通信实时性和可靠性,能够较好地满足低压电力集抄系统上行通信对于通信技术的需求。     

MicroBusiness - Cellular Industry Competes for Broadband Business

Our previous column on WiMAX business prospects included a graph of the mobile WiMAX competitive environment. Many different versions of such graphs exist. What these graphs have in common is that they are all populated by a progression of cellular systems toward ever-higher broadband capabilities. The 4G target peak data rates agreed upon in ITU-R Working Party 8F for "Systems Beyond IMT-2000" (renamed "IMT-Advanced") are "up to approximately 100 Mb/s for high mobility such as mobile access and up to approximately 1 Gb/s for low mobility such as nomadic wireless access". The cellular industry is pursuing mobile broadband development toward these objectives along two distinct 3G/4G branches, one evolving from WCDMA and the other from CDMA2000. The former is spearheaded by the 3rd Generation Partnership Project (3GPP), and the latter by 3GPP2.     

基于以太数据的无线激光通信系统透明传输设计

以太网数据的透明传输是在传输过程中对外界透明,不用关心下层协议,只负责将需要传送的业务数据传送到目的节点,而不篡改数据内容、不改变数据属性的一种传输方式。采用以太数据透明传输的无线激光通信系统,可以方便的与现有工业以太网络无缝集成,提高设备可用性,扩大其应用范围。基于DE2-115教育开发平台,利用板载FPGA集成Nios Ⅱ软核作为控制单元,运行裁减后的NicheStack TCP/IP协议栈的μC/OS Ⅱ实时操作系统,实现了无线激光通信系统与千兆以太网在数据链路层上的数据透明传输。通过系统仿真、电路实验以及光路实验对本设计进行了数据一致性测试。测试结果表明,本设计具有良好的数据透明传输特性。     

High-speed and high-output InP-InGaAs unitraveling-carrier photodiodes

The unitraveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key for its ability to achieve excellent high-speed and high-output characteristics simultaneously. To date, a record 3-dB bandwidth of 310 GHz and a millimeter-wave output power of over 20 mW at 100 GHz have been achieved. The superior capability of the UTC-PD for generating very large high-bit-rate electrical signals as well as a very high RF output power in millimeter/submillimeter ranges can lead to innovations in various systems, such as broadband optical communications systems, wireless communications systems, and high-frequency measurement systems. Accomplishments include photoreceivers of up to 160 Gb/s, error-free DEMUX operations using an integrated UTC-PD driven optical gate of up to 320 Gb/s, a 10-Gb/s millimeter-wave wireless link at 120 GHz, submillimeter-wave generation at frequencies of up to 1.5 THz, and photonic frequency conversion with an efficiency of -8 dB at 60 GHz. For the practical use, various types of modules, such as a 1-mm coaxial connector module, a rectangular-waveguide output module, and a quasi-optic module, have been developed. The superior reliability and stability are also confirmed demonstrating usefulness of the UTC-PD for the system applications.     

Are Diamonds a MEMS' Best Friend?

Next-generation military and civilian communication systems will require technologies capable of handling data/ audio, and video simultaneously while supporting multiple RF systems operating in several different frequency bands from the MHz to the GHz range [1]. RF microelectromechani-cal/nanoelectromechanical (MEMS/NEMS) devices, such as resonators and switches, are attractive to industry as they offer a means by which performance can be greatly improved for wireless applications while at the same time potentially reducing overall size and weight as well as manufacturing costs.     

High-data-rate millimeter-wave radios

This article discusses millimeter-wave Gigabit-class radio systems operating at 1-10-Gb data rates, i.e., at fiberoptic speeds. Yet, we need to talk first about fiber optics. There has been stunning progress in high-speed fiber optic technology during the past 10-15 years. Systems operate 50-100 channels per fiber and with 50-100 fibers per communications bundle. Each wavelength channel operates at 10-40 Gb/s per channel [1]. Cost for hardware is decreasing rapidly, particularly for Ethernet optical equipment. Companies have begun transmitting radio signals over free-space optics links [2]. There is also an industry growing around the technology of transmitting radio signals over fiber optics [3]. As noted, the developments are absolutely stunning.     

基于ARM和以太网的振动信号采集器设计

介绍了一种振动信号采集硬件平台的设计。硬件以S3C2410ARM嵌入式处理器和10/100Mbit/s自适应的以太网接口DM9000为核心,主要包括信号调理、数据采集、嵌入式处理系统、以太网接口等部分。系统软件采用嵌入式Linux操作系统,使用伯克立软件研发组(BSD)套节字接口进行Linux操作系统下的网络应用程序的开发。通信软件的设计采用流式Socket、使用TCP协议。系统具有强大的网络支持功能,振动数据可通过以太网与远程故障诊断中心进行透明传输。