Wideband Polarimetric Directional Propagation Channel Analysis Inside an Arched Tunnel

A wideband directional measurement campaign was managed inside an arched highway tunnel to analyze the radio propagation channel inside such tunnel for future cellular systems in terms of coverage, delay spread and dominant scatterers. Measurements were performed in 3 rounds with different transmitter positions. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver, the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The extracted paths using this super-resolution algorithm constitute 88% of the total received power. It was also observed that the line-of-sight component (53%) plus single-bounce scattering (26%) comprise up to 79% of the total received power. In other words, more than 90% (i.e. 79% in 88%) of the extracted paths consists of the line-of-sight component and single-bounce scatterings. The strong contribution from single-bounce scattering paths causes the path gain exponent along the tunnel to be larger than -2 which is the value for free space. This validates that there is wave guiding effect in the tunnel and coverage is extended relative to open space. The rms delay spreads are generally less than 20 ns and increase when influenced by scattering objects such as jetfans. The dominant scatterers are identified and classified into 6 classes based on the structure of the tunnel and existing objects such as ground, wall, light-frame, ceiling, jetfan and cleaner-parking. It was observed that scattering from ground was dominant among all classified scatterers in all scenarios.     

Performance enhancement of the DSRC system using frequency-domain equalization for 5.9 GHz DSRC applications

This paper proposes the use of equalization concepts in frequency domain that exploit the frequency domain channel matrix to combat inter-carrier interference (ICI) instead of inter-symbol interference (ISI) in 5.9 GHz Dedicated Short Range Communications (DSRC) systems. The physical layer (PHY) of DSRC is currently being developed by work group of IEEE 802.11p. The conventional system currently assumes static channel characteristics. Channel tracking schemes were investigated and the Viterbi-aided channel estimation scheme was proposed for DSRC systems that did not explicitly exploit the ICI components caused by the time-varying channels. The performance of the DSRC system is investigated for a time-varying channel using a conventional DSRC model, a decision-directed (Viterbi-aided) channel estimation model, and the frequency-domain equalization design. It is shown that the DSRC system with the frequency-domain equalization achieves a considerable performance enhancement compared to both the conventional and the Viterbi-aided channel estimation schemes in terms of both packet error rate (PER) and bit error rate (BER) at relatively high and low velocities.     

Analysis on effectiveness of wave absorbers to improve DSRC electromagnetic environment on express highway

Electromagnetic (EM) wave absorbers have been used for improving the EM environment of an electronic toll collection system on an express highway or a wireless local area network system in an indoor environment. In this paper, an efficient multiray propagation model, which uses three-dimensional geometry and image techniques to trace multiple signal rays from transmitter to receiver, is employed to analyze the EM environment of a dedicated short-range communication (DSRC) system on an express highway. The validity of the model employed is discussed by a comparison with the results obtained by an experiment on the highways when a right-circular polarized transmitter and receiver are used. The analysis shows that the possible undesired communications between onboard equipment that acts as a receiver and DSRC beacon, which transmits the radio signals, is improved by increasing the EM wave-absorption capability of the sidewalls and the pavement of the highway. Another advantage of the employed model is that it is effective for investigating the location of wave absorbers to be set up on the highway, and it takes only a fraction of a minute for computation.     

ITS智能交通中的DSRC技术

DSRC专用短程通信技术是随着IT智能交通的发展和EFC[1]电子(自动)收费应用的要求而提出发展起来的,本文主要介绍DSRC技术和其在EFC 领域的应用.     

弧面电流探头传输阻抗的校准

利用内圆外方同轴传输线理论,提出弧面电流探头传输阻抗的校准方法.详细介绍了校准装置的设计制作、测试及校准应用.     

应用于DSRC系统的5.8GHz CMOS LNA设计

基于TSMC 0.18μm CMOS RF工艺,完成了一个全集成共源-共栅低噪声放大器设计。版图后仿真结果表明:1.8V电源电压下,电路静态功耗约为17mW;在DSRC系统工作频段上,电路实现了良好的综合性能指标,输入反射系数(S11)和输出反射系数(S22)小于-15dB,增益(S21)大于14.0dB,反向隔离度(S12)达到32dB,噪声系数小于2dB,并且工作稳定。     

DSRC系统中微波信号源相位噪声分析

在专用短程通信系统中采用M-PSK调制通信方式,以适应多种速率要求.给出了射频信道模型和微波数字锁相本振信号源的相位噪声模型,分析了微波本振信号源相位噪声的影响,仿真给出了相位噪声功率谱密度与系统误码率之间的关系.利用该结果,有助于无线通信系统的设计.     

现场服务管理信息系统分析与设计

近年来,为应对激烈的市场竞争,具有现场服务类业务的企业迫切需要提升现场服务人员的利用效率及市场信息反馈的及时率,而移动通信技术、定位技术、电子地图等新技术的迅猛发展也为其提供了技术上的可能。本文使用GPS定位、电子地图、移动终端等技术,介绍现场服务管理信息系统的分析与设计,主要包括:行业特性分析、业务功能和软件架构设计、电子地图选型、移动终端适配等内容。     

Performance of DSRC systems using conventional channel estimation at high velocities

In this paper, we present a study of the dedicated short range communications (DSRC) receiver performance under varying signal to noise ratio, velocity, symbol durations and packet lengths. Conventional channel estimation, which is used in IEEE 802.11a, assumes static channel characteristics for the entire packet duration. That is found to be infeasible for high velocity DSRC applications. Simulation results show that the packet-error-rate increases with the increase in relative velocity. Viterbi decoding substantially improves the performance, but the sensitivity to Doppler shift still exists. Analysis and simulation results show that extending the symbol duration or increasing packet length results in an increase of the packet-error-rate. These results may serve as benchmarks for future DSRC channel estimation methods.     

直升机内部电缆抗干扰能力分析

在现代战争中,电磁干扰是制约直升机使用效能的重要因素之一。分析了直升机内部电缆对干扰信号的接收特性,计算电缆中产生干扰电流的最大值,并将之与负载电流相比较,从而得出直升机内部电缆具备很强的抗干扰能力的结论。     

专用短程通信协议描述方法的研究及应用

DSRC协议是为ITS中短距离间通信的系统专门开发的通信协议。通过应用SDL语言对DSRC协议的描述和验证,提出了建立抽象化模型、环境模块化、循环开发等方法,并进行了MAC子层的概要性设计和MAC子层中的transmission模块的过程化设计,重点论述了如何将上述方法应用到实际开发工作中去。     

基于DSRC协议的5.8 GHz收发电路设计与实现

提出了一种应用于专用短程通信(DSRC)协议的5.8 GHz收发电路的设计方案,给出了5.8 GHz收发电路的硬件设计方法,包括检波电路、接收电路、唤醒电路和发射电路的设计,最后列出了射频前端的测试方法。测试结果表明,该5.8 GHz收发电路的设计完全符合DSRC协议国家标准,并且验证了该设计方案的可行性与成功性,该系统性能稳定、实用性强,具有很好的市场推广价值。     

Analysis of the coupling of an incident wave with a wire inside a cavity using an FEM in frequency and time domains

This paper presents a numerical method based on finite elements in both the frequency and time domains for modeling the coupling of an incident wave with a conducting wire placed inside a metallic cavity having a small aperture. The method uses edge elements on tetrahedra for the electric field representation. The formulation can take into account thin wires as well as lumped elements. In the time-domain approach, the time derivatives are discretized by the Newmark method, which allows obtaining an unconditionally-stable scheme with second-order accuracy. Numerical results are provided to validate the presented method.     

Tunnel Diode Oscillator in an Open Structure

This paper describes a theoretical and experimental evaluation of the oscillation conditions of a microwave tunnel diode integrally mounted at the feed point of a semicircular loop antenna. The oscillation conditions are based on a quasi-linear equivalent circuit where the diode load impedance is the complex radiation impedance of the semicircular loop antenna. The results of a radiation impedance calculation based on a Fourier transform method are presented. Diode fabrication techniques are described and experimental results are reported to be consistent with the theory.     

WCDMA Uplink Capacity of a Long Tunnel Cigar-shaped Microcells for Underground Train Service

In this paper, the capacity and the interference statistics of the sectors of the cigar-shaped WCDMA microcells are studied using the hybrid model of propagation. A model of nine microcells in a metro tunnel is used to analyze the uplink capacity and the interference statistics. The capacity and the interference statistics of the microcells in metro tunnels are studied in this work for different propagation parameters, antenna side lobe levels, sector ranges and bends losses.

An empirical study of DSRC V2V performance in truck platooning scenarios

Among many safety applications enabled by Dedicated Short Range Communication (DSRC), truck platooning provides many incentives to commercial companies. This paper studies DSRC Vehicle-to-Vehicle (V2V) performance in truck platooning scenarios through real-world experiments. Commercial DSRC equipments and semi-trailer trucks are used in this study. We mount one DSRC antenna on each side of the truck. One set of dynamic tests and a few sets of static tests are conducted to explore DSRC behaviors under different situations. From the test results, we verified some of our speculations. For example, hilly roads can affect delivery ratio and antennas mounted on opposite sides of a truck can suffer from low delivery ratio at curved roads. In addition, we also found that antennas can sometimes suffer from low delivery ratio even when the trucks are on straight roads, possibly due to reflections from the nearby terrain. Fortunately, the delivery ratio can be greatly improved by using the two side antennas alternately.     

IMS业务体系架构中业务触发机制分析

分析了IP多媒体子系统(IMS)业务体系结构中的业务触发机制,包括业务触发数据、S-CSCF上的处理流程等,结果说明,该触发机制保证用户发起IMS呼叫时能够正常使用IMS业务体系结构中所提供的业务.     

彩信业务的风险性分析

多媒体消息业务(MMS)在国内俗称“彩信”。业内许多分析家认为，它是新型的短消息业务(SMS)，是“受激化”的文本信息业务，有望在全球电信经济走向低迷之际促进每用户平均收益(ARPU)大幅度增长。一些倡导者甚至颂扬道：“MMS是移动通信从文本信息业务走向未来3G多媒体业务的铺路石。”对此，笔者认为，尽管MMS拥有相当大的市场潜力，但人们所预期的MMS潜在市场与业者最终能够实现的MMS现实市场是两码事，业者必须当心MMS的市场风验。     

A Simplified Analysis of Scan Times in an Asymmetrical Newhall Loop with Exhaustive Service

A Newhall loop with exhaustive service, infinite buffer storage, and non-identical terminals is analyzed. A simple and computationally efficient procedure is demonstrated for determining first and second moments of queue lengths and scan times.     

TD-SCDMA系统的业务能力分析

本文通过IMT-2000规定的通用业务能力的描述,结合TD-SCDMA系统的承载技术特点,分析了TD-SCDMA系统的业务能力.TD-SCDMA系统的业务能力主要表现在业务种类、业务提供的方便性、业务质量和漫游能力等方面.