多载波蜂窝移动通信系统中的多业务切换算法

提出一种用于多载波蜂窝移动通信系统的子信道合并切换算法。采用多维Markov链对子信道合并切换算法进行系统建模分析,得到了呼叫阻塞率、切换阻塞率等关键系统性能参数的解析结果。与切换保护信道算法相比,子信道合并切换算法在对其他类型呼叫性能影响很小的前提下,改善了对带宽要求较高的业务的切换性能。该算法还可以与其他资源预留切换算法相结合,改善其性能。     

An implanted spherical head model exposed to electromagnetic fields at a mobile communication frequency

Can cellular phones and personal communication systems base station antennas affect the active or passive implantable medical devices adversely? Concerns over the possible harmful effects of nonionizing irradiaton upon implanted medical devices have been present for many years. Key issues to address are the questions of whether mobile phones have a detrimental effect on implants, and how the interaction of the handset with the body can be minimized in order to both alleviate public fears and improve handset antenna performance and new implant designs. This paper presents a thorough investigation of the scattering of an electromagnetic (EM) wave from a perfectly conducting implant (a cylindrical wire and a very thin cylindrical disk) of electrically small radius (of resonant length), embedded eccentrically into a dielectric spherical head model by a dipole antenna (0.4 wavelength) at 900 MHz. The dyadic Green's function (DGF) for spherical vector wave functions is employed. Analytical expressions for the scattered fields of an implant embedded head model is obtained. Numerical results from analytical expressions are computed for this problem and then compared with the results from the same model using the finite-difference time-domain, EMU-FDTD electromagnetic simulator. Good agreement is observed between the analytical results on the proposed method in comparison with the FDTD method.     

高速无线通信中的正交多载波调制技术OFDM

本文介绍了无线信道的特征,进而引出多载波调制技术,着重介绍了正交频分复用(OFDM)的原理,优缺点及其在无线通信中的广泛应用。     

On using peer-to-peer communication in cellular wireless data networks

A recent class of approaches for enhancing the performance of cellular wireless data networks has focused on improving the underlying network model. It has been shown that using the peer-to-peer network model, a mode of communication typically seen in ad hoc wireless networks, can result in performance improvements such as increased data rate, reduced transmission power, better load balancing, and enhanced network coverage. However, the true impact of adopting the peer-to-peer network model in such an environment is yet to be fully understood. In this paper, we investigate the performance benefits and drawbacks of using the peer-to-peer network model for Internet access in cellular wireless data networks. We find that, although the peer-to-peer network model has significantly better spatial reuse characteristics, the improved spatial reuse does not translate into better throughput performance. Instead, we observe that using the peer-to-peer network model as-is might actually degrade the throughput performance of the network. We identify and discuss the reasons behind these observations. Using the insights gained through the performance evaluations, we then propose two categories of approaches to improve the performance of the peer-to-peer network model: approaches that leverage assistance from the base station and approaches that leverage the relaying capability of multihomed hosts. Through simulation results, we show that using the peer-to-peer network model in cellular wireless data networks is a promising approach when the network model is complemented with appropriate mechanisms.     

蜂窝无线通信网络呼叫允许控制分析

无线网络中由于用户的移动性、频谱资源的缺乏以及信道的衰落,使无线网络的服务质量的供给成为一个日益严峻的问题。呼叫允许控制(CAC)是无线资源管理中的重要组成部分,是一种保证服务质量和网络资源利用率的重要机制。总结了CAC领域的研究成果,对蜂窝无线通信网络的CAC方案进行了分析,指出了目前CAC研究中存在的问题,并探讨了今后的研究方向。     

电磁脉冲下通信偶极天线的时域响应快速计算

针对电磁脉冲作用下通信系统受扰的场路结合计算过程较为复杂的问题,提出了基于等效电路的偶极子天线端口时域响应的计算方法.通过分别建立天线的等效电路模型以及电磁脉冲照射下的等效干扰源模型,快速求解天线端口的时域电流响应.选取电磁辐照条件下两个不同尺寸的偶极子天线进行验证,并与采用全波电磁数值软件计算的结果进行了对比.结果表明：提出的等效电路方法不仅速度快而且元件参数易调整,等效电路模型还可以直接应用于通信系统内部电路的电磁受扰评估计算.     

无线通信技术在数字化发展中的应用

随着我国经济的发展和科技的进步,推动着我国数字化发展进程的不断加快,促进了我国数字化的管理和应用,提高了我国的经济效益和社会效益。然而,数字化在发展的过程中出现了许多的问题,严重阻碍了我国数字化的发展进程。无线通信技术作为新时期的科技力量,在人们生活和工作之中应用越来越广泛,引起了我国的生活方式和工作方式巨大的转变,对我国经济和科技的发展发挥了重要的作用。文章对无线通信技术在数字化发展中的应用进行了研究。     

探究无线通信技术的发展

近些年以来,无线通信技术在军事、商务等一系列的行业被普遍地应用,对当前我国无线通信技术的发展现状以及发展趋势进行正确地认知,有助于我国更好地发展无线通信技术.     

Minimum-value distribution of random electromagnetic fields for modeling deep fading in wireless communications

In this work, we presented a theoretical investigation of the minimum-value distribution inside complex electromagnetic environments. In particular, a statistical model for characterizing the minimum value of the complex-value field or power inside a dynamic mode-tuned or mode-stirred reverberation chamber is presented and discussed. Such an EM environment serves as an emulator of multipath radiowave propagation for indoor/outdoor wireless communication channels. It is found that, for both overmoded and undermoded regimes, the generalized extreme value distribution leads to the reverse Fréchet and Weibull types for complex-value (Cartesian and total) fields and for the total energy (or intensity). These distributions are stable and follow from the convergent behavior of the lower tail for their corresponding parent distribution of the Cartesian field magnitude, namely a χ ². On the other hand, received power exhibits a Pareto-type distribution because of the unbounded left tail of the negative exponential parent distribution.     

5G无线通信技术的应用前景分析

经历过2G追赶,也经历过3G突破,社会正处在4G同台竞技的高峰期,马上迎来新一代无所不在的移动信息网络—5G无线通线技术。随着我国ICT产业的进一步融合,我国已经进入到了现代化的网络信息时代,移动通信技术在各个方面影响着人们的生活。5G无线通信技术被认为是当前最具有应用前景的技术,可满足用户对移动网络技术的使用需要。文章就5G无线通信技术的优点、5G无线通信的关键技术以及5G无线通信技术的研究意义这几个方面一一进行了阐述。     

一种用于无线通信DOA估计的改进MUSIC算法研究

MUSIC算法是一种空间谱估计算法,在对宽带信号进行空间谱估计时,该算法需要较长的观测时间来估计协方差矩阵,不利于高速运动目标的定位。提出了基于驾驶协方差矩阵(STCM)的MUSIC算法,该算法首先对每个频带的CSDM进行特征分解,然后利用各频带的噪声子空间求得噪声空间的STCM,进而利用噪声空间的STCM直接得到整个宽带信号的空间谱估计结果。仿真表明该算法在保证高分辨率的同时,需要较短观测时间,适用于较低信噪比、具有较小观测方差。     

一种用于无线通信的数字语音识别系统设计

数字语音录制过程中存在的环境、用户口音和非目标词汇等干扰,使以往开发出的无线通信数字语音识别系统准确性较低、可移植性较差。因此,对无线通信的数字语音识别系统进行优化设计,设计系统的核心元件为C6727DSP芯片、QGDH710语音识别芯片和CC2520射频收发器。C6727DSP芯片进行数字语音的前期处理工作;QGDH710语音识别芯片对处理后的数字语音进行识别,并将其识别出的指令反馈到CC2520射频收发器;CC2520射频收发器进行指令的格式转换工作,并将指令传输到用户无线通信设备中,最终实现数字语音识别系统在无线通信中的有效利用。为了方便用户进行系统操作,软件给出用户无线通信设备虚拟功能图。经实验验证可知,该设计系统准确性较高,具有高度可移植性。     

我国宽带无线接入应用前景广阔

宽带无线接入加快我国信息化过程宽带无线接入系统可以加快我国信息化进程,而且可以节省资金,解决现在的电信网解决不了的一些问题.作为个人用户用到56K或许就足够了,但是宽带接入主要用于大的企业、集团用户、小区或者政府机关,这些部门需要一个总的宽带出口.没有这个宽带出口,内部的计算机就联不起来,上不了互联网,而且一个一个上网费用也昂贵.……     

Occupational exposure to radio-frequency electromagnetic fields

Occupational exposure to radio-frequency (RF) electro-magnetic (EM) fields occurs in various industrial processes. The exposure usually takes place in the near field, i.e., within one free space wavelength from the RF source. When a survey of a workplace is performed from a leakage radiation point of view, the near-field situation implies that the electric as well as the magnetic field strengths have to be monitored in order to assess the health hazard. This paper discusses the field strengths typically encountered in some of these occupational situations. Thin sheets of plastic materials can be joined or sealed by application of RF energy. The plastic welding machine, using for this purpose, usually does not have shielded electrodes and this may lead to high levels of RF fields in the immediate vicinity of the machines. The ANSI standard is exceeded in several cases near the plastic welding machines. In medicine, for instance, RF energy is used in shortwave therapy. Due to the construction of the apparatus (i.e. presence of electrodes and cables) the physiotherapist as well as the maintenance personnel may be exposed to very high levels of both E and H fields. The results of measurements of these fields in the vicinity of shortwave diathermy apparatus are discussed. The maintenance personnel working in FM/TV broadcast towers are another group of workers subject to occupational exposure of intense RF fields, and some recent studies of the exposure are presented.     

浅议车载无线通讯技术的应用和发展前景

随着集成电路、专用芯片等科学技术的飞速发展,无线通讯技术也开始在汽车设备领域获得了广泛应用。目前,车载无线通讯技术不但是现代汽车安全的重要组成部分之一,而且大量应用在车内、外通讯等方面。简要介绍了车载无线通讯技术的应用,并探讨车载无线通讯技术的发展前景。     

A review of analytically determined electric fields and currents induced in the human body when exposed to 50-60-Hz electromagnetic fields

In this review paper, analytical methods are used to determine the electric field and current induced in the conducting human body when this is exposed to an electromagnetic field at extremely low frequencies (ELFs) or very low frequencies (VLFs). This is done by treating it as a parasitic antenna when this is modeled successively as a sphere, an ellipsoid, and a cylinder. Because the body is electrically very short at ELF and VLF, the axial current depends primarily on the length of the body. Comparison with the ellipsoidal shape shows that the induced current is virtually independent of the cross-sectional shape. It is concluded that the axial current induced in the cylinder is a good approximation of the current induced in an actual body with the same length and mean cross sectional area. References to persons standing on the earth and with the arms raised are given. The significance of the accurate knowledge of induced currents and fields for biomedical purposes is discussed.     

Bluetooth in wireless communication

Bluetooth is a method for data communication that uses short-range radio links to replace cables between computers and their connected units. Industry-wide Bluetooth promises very substantial benefits for wireless network operators, end workers, and content developers of exciting new applications. This article delves into the implementation and architecture of Bluetooth. It also describes the functional overview and applications of Bluetooth, and deals with the development of a model for recording, printing, monitoring, and controlling of eight process variables at the same time, using a distributed control system. We explain industrial automation via Bluetooth using IISS. Industrial automation is one of the major applications of Bluetooth technology. Industrial automation, in terms of controlling or monitoring a factory, office, or industrial process, means to install machines that can do the work instead of human workers. Industrial plants consists of many devices interconnected in different ways ranging from simple data collection units (I/O) to more intelligent devices such as sensors, one-loop controllers, or programmable controllers, and a supervisory system used as a human-machine interface (HMI) for data logging and supervisory control. An IISS is a controlling device that monitors the devices in a company. It basically communicates via the interface card in the PC; the hardware is connected parallel across the device, and it is interfaced with the PC via a transceiver. The device can be accessed both manually via the switches and remotely via the PC. A simulation of connecting a PC with the machines in a company was executed. Also, we wrote a software program using C language; we will show how the remote monitoring takes place between the control room and the PC. These details in the article establish the growing need for Bluetooth technology     

自主创新导向下的宽带无线通信网络优化及发展策略思考

历经“．COM”泡沫及全球电信产业低迷之后，人们对“宽带”、“宽带无线”及“3G”、“WiMAX”等技术已开始持较理性的态度进行分析、思考与处理。当今，围绕NGN问题的讨论，人们探索了一系列以IP为基础的新一代网络的重要课题，包括：QoS性能、安全性、智能网管改进、可赢利商业模式及向FMCIMS／SIP多业务网络平滑演进的务实途径，这是一种前后向兼容、有效创造增值效益的演进。而下一代或新一代宽带无线移动（NGBWM）亦将按这一概念向前发展，特别是从个性化与个体化含义上看，未来NGN及GII的接入与应用层面，必将是包括卫星通信及其应用在内的无线通信的世界。     

动中通无线激光通信系统研制

通过对动中通无线激光通信系统关键技术的分析,提出了针对不同关键技术的解决方法.研制了一套动中通无线激光通信系统,通过试验验证了动中通无线激光通信系统的可行性.