通信工程专业英语结课论文(中英)
通信工程英文论文
英文原文RESEARCH OF CELLULAR WIRELESSCOMMUNATION SYSTEMAbstractCellular communication systems allow a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed base stations using a limited amount of radio frequency （RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband，or to a wideband microwave link，and relayed to mobile switching centers （MSC), which connect the mobile transmissions with the Public Switched Telephone Network （PSTN）. Similarly，communications from the PSTN are sent to the base station, where they are transmitted to the mobile。
Cellular systems employ either frequency division multiple access (FDMA），time division multiple access (TDMA）, code division multiple access (CDMA）, or spatial division multiple access （SDMA)。
通信工程毕业设计 外文翻译
东华理工大学长江学院毕业设计外文翻译学生姓名：张伟学号：09323119专业：信息工程系别：信息工程指导教师：谌洪茂职称：讲师二0一三年六月五日OriginalOptical Fiber CommunicationsThe General System Communication may be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance a communication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information onto an electromagnetic wave which acts as a carrier for the information signal. This modulated carrier is then transmitted to the required destination where it is received and the original information signal is obtained by demodulation. Sophisticated techniques have been developed for this process by using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter w ave frequencies. However, ‘communication’ may also be achieved by using an electromagnetic carrier which is selected from the optical range of frequencies.An optical fiber communication system is similar in basic concept to any type of communication system.The communication system therefore consists of a transmitter or modulator linked to the information source, the transmission medium,and a receiver or demodulator at the destination point. In electrical communications the information source provides an electrical signal, usually derived from a message signal which is not electrical (e.g. sound), to a transmitter comprising electrical and electronic components which converts the signal into a suitable form for propagation over the trans-mission medium. This is often achieved by modulating a carrier, which, as mentioned previously, may be an electromagnetic wave. The transmission medium can consist of a pair of wires, a coaxial cable or a radio link through free space down which the signal is transmitted to the receiver, where it is transformed into the original electrical information signal (demodulated) before being passed to the destination.However, it must be noted that in any transmission medium the signal is attenuated, or suffers loss, and is subject to degradations due to contamination by random signals and noise, as well as possible distortions imposed by mechanisms within the medium itself. Therefore, in any communication system there is a maximum permitted distance between the transmitter and the receiver beyond which the system effectively ceases to give intelligible communication. For long-haul applications these factors necessitate the installation of repeaters or line amplifiers atintervals,both to remove signal distortion and to increase signal level before transmission is continued down the link.For optical fiber communications system shown in Figure (a) may be considered in slightly greater detail, as given in Figure (b).Fig(a) The general communication system(b)The optical fiber communication systemIn this case the information source provides an electrical signal to a transmitter comprising an electrical stage which drives an optical source to give modulation of the light wave carrier. The optical source which provides the electrical–optical conversion may be either a semiconductor laser or light-emitting diode (LED). The transmission medium consists of an optical fiber cable and the receiver consists of an optical detector which drives a further electrical stage and hence provides demodulation of the optical carrier. Photodiodes (p–n, p–i–n or avalanche) and, in some instances, phototransistors and photoconductors are utilized for the detection of the optical signal and the optical–electrical conversion. Thus there is a requirement for electrical interfacing at either end of the optical link and at present the signal processing is usually performed electrically.The optical carrier may be modulated using either an analog or digital information signal. In the system shown in Figure (b) analog modulation involves the variation of the light emitted from the optical source in a continuous manner. Withdigital modulation,however, discrete changes in the light intensity are obtained (i.e. on–off pulses).Although often simpler to implement, analog modulation with an optical fiber communication system is less efficient, requiring a far higher signal-to-noise ratio at the receiver than digital modulation. Also, the linearity needed for analog modulation is not always provided by semiconductor optical sources, especially at high modulation frequencies. For these reasons,analog optical fiber communication links are generally limited to shorter distances and lower bandwidth operation than digital links.Figure (c) shows a block schematic of a typical digital optical fiber link. Initially, the input digital signal from the information source is suitably encoded for optical transmission. The laser drive circuit directly modulates the intensity of the semiconductor laser with the encoded digital signal. Hence a digital optical signal is launched into the optical fiber cable. The avalanche photodiode (APD) detector is followed by a front-end amplifier equalizer or filter to provide gain as well as linear signal processing and noise bandwidth reduction.Fig(c)A digital optical fiber link using a semiconductor laser source and an avalanche photodiode(APD) detectorFinally, the signal obtained is decoded to give the original digital information. However, at this stage it is instructive to consider the advantages provided by light wave communication via optical fibers in com-parison with other forms of line and radio communication which have brought about the extensive use of such systems in many areas throughout the world.译文光纤通信一般来说把信息从一点传送到另一点就称为通信。
作文范文之通信专业英语作文
通信专业英语作文【篇一：通信工程专业外语介绍二极管作文】? 1、there are two types of standard transistors,npn and pnp,with different circuit symbols. the letters refer to the layers of semiconductor material used to make the transistor.2、the leads are labelled base(b),collector(c)and emitter(e).these terms refer to the internal operation of a transistor.3、transistors amplify currents,for example they can be used to amplify the small output current from a logic chip so that it can operate a lamp,relay or other high current device.in many circuits a resistor is used to convert the changing current to a changing voltage,so the transistor is being used to amplify voltage.4、a transistor may be used as a switch (either fully on with maximum current,or fully off with no current)and as an amplifier(always partly on).【篇二：通信工程-专业英语论文】《专业英语》课程论文论文题目：wireless sensor network node 学院(系)：信息工程学院专业：电子科学与技术班级：学生姓名：胡剑学号：1049721303194 教师：徐文君2014年 5月 16 日wireless sensor network node positioningalgorithmhu jianschool of information engineering,wuhan university of technology, wuhan, chinaabstract- wireless sensor networks as a new type of data node localization algorithm to complete. targeting the acquisition technology, combined with microelectronics, location of the network nodes is known as the reference wireless communications and wireless networks, such as node, the destination node determines that the event or multi-discipline, have broad application prospects in the field of the location in the network.industrialcontrol,military,medicalassistance,andenvironmental monitoring. in most applications, the physical location of the guide to the sensor node is a basic requirement, however, due to the large number of sensor nodes, randomly distributed, and the software and hardware resources are limited, so study effective positioning algorithm to determine the location of each node has an important theoretical significance and practical value.access to large amounts of literature on the basis of the lessons do an overview of the wireless sensor network-based positioning technology, wireless sensor networks, highlights several typical distributed positioning algorithm principle and characteristics, including amorphous , apit, centroid, dv-hop, rssi, etc., its matlab simulation environment simulation analysis, and compare the positioning accuracy of the various algorithms and error.keywords: wireless sensor algorithm, matlab, simulation analysisnetworks, localizationii. system designtin sensor networks, most existing node localizationalgorithms, reference anchor nodes are positioned to take advantage of the way place. a large number of sensor nodes in the target area in the layout: a portion called the particular node, also called anchor node (beacon), which themselves can be obtained by carrying the exact location of the gps positioning apparatus or artificial means, and have more than node powerful capabilities, but such a small proportion of nodes; node other unknown locations themselves, through their neighbor nodes to communicate to get information of each anchor nodes, these nodes using the locationinformation as a reference, and use some calculations to get their position known to the unknown is called a node (node)in wireless sensor networks usually used only two-dimensional coordinate system of .so long as we know from the unknown node with three anchor nodescan calculate the position of the unknown node.i. introductionpositioning of wireless sensor networks is the wireless, self-organizing network to provide location information of nodes in the network in some way, self-organizing network localization process can be divided into self-positioning and targeting node node positioning itself to determine the coordinates of the information network node . the targeting information is needed to determine the coordinates of a target within the network coverage or an event. node itself is the process of determining the positioning properties of the network itself, or you can use the manual calibration of variousfigure 1. schematic trilateral positioningassuming three anchor node coordinates are (x1,y1), (x2, y2), (x3, y3), the coordinates of the unknown node (xu, yu), unknown node distances from three anchor nodes are r1, r2 , r3, shown in figure 3-2, the distance formula based on a two-dimensional coordinate system of equations can be obtained asfollows:(1)the above equations are usually solved using the maximum likelihood method estimates the unknown node coordinate multilateral used (xu, yu)：(2)in summary, it may obtain a plurality of unknown nodes as long as the anchor node that the unknown distance from the node to the anchor node 3 may be positioned on the practical application of the unknown node, this calculation can be different for each selected three points, and finally the results were averaged for several times and thus improve the positioning accuracy.iii. specific positioning algorithma. apit algorithmapit algorithm theoretical basis is the best point inside the triangle test method pit. pit test principle is that if there is a direction unknown nodes simultaneously moving along this direction away from or close to three beacon nodes, then the unknown nodes located in three beacon nodes outside the triangle; otherwise unknown nodes located within the triangle. point test using the network in a relatively high density ofnodes to simulate the mobile nodes using wireless signal propagation characteristics to determine whether far or near beacon nodes within the approximate triangle, usually in a given direction, a node from another node the farther the received signal strength is weaker. neighbor nodes exchange their received signal strength determination of a distance of beacon nodes, the nodes to move mimic pit. b.centroid positioning algorithmcentroid algorithm, the beacon node to a neighboringnode periodically broadcasts a beacon packet, a beacon packet contains the identification number and the location information of beacon nodes. when the node receives the unknown number of different beacon beacon packet from a node or reception exceeds a certain threshold time, the position of which determines its beacon nodes consisting of the centroid of the polygon.centroid algorithm based solely on network connectivity, and therefore relatively easy to implement. however, this method is affected by the density of the beacon nodes. centroid algorithm for improved algorithm, density adaptive heap algorithm, by increasing the beacon beacon nodes nodes in a low density area in order to improve the positioning accuracy.c. dv-hop positioning algorithman advantage of the proposed method of ideological distance vector routing and gps positioning. consists of three phases: first, all nodes in the network to obtain the number of hops from a beacon node; secondly, when obtaining the position and the other beacon nodes hop distance apart, the beacon nodes calculate the average hop distance of the network, giving their survival period, then the survival of the school with a positive value in the webcast. unknown node receives only record the first correction, and forwarded to the neighbors.this strategy ensures that the vast majority of node receives an average hop distance from the nearest beacon node. according unknown node hops records to calculate distance to jump beacon nodes.... d. rssi algorithmrssi measurement model and the theoretical model of general experience using the signal propagation. for empirical model before the actual positioning, first select a number of test points, records the received signal strength at these points ofthe base stations, to establish the relationship between position and signal strength line database (x, y, ss1, ss2 respective points, ss3 ). in the actual positioning, based on the measured signal strength (ss1 , ss2, ss3 ) and the signal strength recorded in the database by comparing the variance of the coordinates of the minimum signal strength that are used as the coordinates of the node point.iv. the simulation resultsa.apit algorithmfigure 4. figure positioning error（red * indicates anchor nodes, blue o represents an estimate offigure 2. node distribution（300 nodes, including 60 anchor nodes, red * indicates anchornodes, blue o represents the unknown node）the position of the unknown node, black o that they can not be positioned unknown nodes, blue - shows the positioning error of unknown nodes (nodes connected to an unknown location and estimate the true position), a total of 300 node: 60 anchor nodes, 240 unknown nodes, 0 unknown nodes can not be located, the positioning error of 0.29857）v. conclusionsfive algorithms are square_random selected node distribution, gps errors are 30m, communication radius comm-r are 200 unified communication model for the same communication model regular model folder, a list of error will be calculated by the five algorithms，as shown in figure 5:figure 3. neighbor relationship diagram（300 nodes, including 60 anchor nodes, red * indicates anchornodes, red o indicates unknown node communication radius: 200m, anchor node communication radius:200m, communication model: regular model, the average connectivity of the network is: 31.1133, the average number of neighbor nodes of the network anchor is: 6.18）figure 5. positioning deviationseen from the table, the maximum error and the centroid apit algorithm followed dv-hop algorithm then amorphous algorithm is the smallest error rssi algorithm.references[1] ou dexiang, wang zhizhong. “the design for intelligent node o f dcs based can bus”. electronic computer design world, vol 19,2002.[2] sun huixian, zhang yuhua, luo feilu. “data collection system for power monitor based on usb and can bus”. proceedings of the csu–epsa, vol 21, pp: 99-103, 2009.[3] zhang zhen-wei, huang shi-hong, “the design of vibration signal acquisition system,” turbine technology, 49 (3), pp.187-188, march 2007.[4] xu huazhong, “feng bo. design of usb module based on pdiusbd12.”.journal of wuhan university oftechnology(informationmanagement engineering), vol 02, 2008.[5] li jinbo. “design and realization of usb2．0 interface in equipment condition monitoring instrument”. process automation instrumentation. vol 29, pp: 14-17, 2008.【篇三：通信英语专业论文】the development trend of modernmobile communicationabstractrecalling the development history of the mobile communication,development of mobile communications has gone through several stages of development.the first generation of mobile communication technology mainly refers analog cellular mobile communication ,technical characteristics of a cellular network architecture to overcome the large district system capacity is low, the problem of limited range of activities.the second generation mobile communications is a cellular digital mobile communication, the cellular system can be provided with digital transmission and various advantages of integrated services.the third generation mobile communications also known as modern mobile communications.it is in addition to the main features of a second-generation mobile communication systems have various advantages and overcome its shortcomings, but also able to provide broadband multimedia services, can providehigh-quality video broadband multimedia integrated services, and to achieve global roaming.third generation technology is not too successful today,but it has great prospects for development.so lets talk about development trend of modern mobile communication.in the information technology support, market competition and demand together, the development of mobile communication technology is leaps and bounds, showing the following major trends:network traffic data, packet; broadband network technologies; intelligent network technology; higher frequency bands; more effective use of frequencies; various networks to converge. understand and master these trends on mobile operators and equipment manufacturers have important practical significance.work traffic data, packetmobile wireless data communications are considered the main direction of development. in recent years there are mainly two kinds of mobile data communications, one is circuit-switched mobile data services, the other is packet-switched mobile data industry.wireless data services is the main driving force of the users application , and other areas of communication, wireless data services one of the most important driving force from the internet.quest for voice communication anytime, anywhere mobile communications success so early. mobile communications business value and user market has been proved that the global mobile market with extraordinary pace. the next phase of the evolution of mobile communications is to provide mobile multimedia wireless data transfer and even individuals, this progress has already begun, andwill be an important future growth. personal mobile multimedia will provide people based on location can not imagine, perfect service and wireless personal information will people work and all aspects of life impact.2.broadband network technologiesin the history of the telecommunications industry, mobile communications technology and the market may be the fastest growing areas. business, technology and market interaction among a relationship, along with the user data and multimedia services demand increases, the data network service, packetdevelopment of broadband mobile networks will inevitably move toward.the third-generation mobile systems, namely imt-2000, is a true broadband multimedia system that can provide high-quality broadband integrated services and achieve seamless global coverage. after 2000, the narrow-band mobile phone business needs will remain large, but with the internet and other high-speed data communications and multimedia communications demand-driven, integrated broadband multimedia services will gradually increase, and the construction of the future information superhighway seamless coverage in terms of , broadband mobile communications as a whole, a subset of the mobile market share will become increasingly important.3.intelligent network technologygrowing demand for mobile communications and new technologies in mobile communication widely used, prompting the mobile network has been developing rapidly. mobile network consists simply transfer and exchange of information, and gradually to store and process information, the development of intelligent, mobile intelligent network as a result.along with the mobile network evolution to third generation systems, intelligent networks are constantly improved. intelligent network and its intelligence services constitute the basic conditions for future personal communications.4.higher frequency bandsfrom the first generation analog mobile phone, to the second generation of digital mobile networks, to the future of the third generation mobile communication systems, networks using wireless spectrum from low to high to follow a trend. born in 1981, the first international roaming nmt analog systems use frequency band 450mhz, 1986 年 nmt changes to the 900mhz band. chinas current band analog tacs system is used for 900 mhz. in the second generation networks, gsm systems use frequency band is started 900mhz, is-95 cdma system is800mhz. in order to from the fundamentally improve the gsm system the capacity of the,1997 appeared in 1800mhz system, gsm 900/1800 dual-band network rapid popularization. 2002 will be put into commercialthird generation systems imt-2000 is positioned in the 2ghz band.5.more effective use of frequenciesradio frequency is a valuable resource. with the rapid development of mobile communications, spectrum resources are limited and the dramatic increase in mobile subscribers increasingly acute contradictions, a frequency of severe shortage phenomenon. frequency congestion problem solving way is to use various frequency effective use of technology and development of new bands.as the future mainstream of the third generation mobile communication systems wireless access technology wcdma (wideband code division multiple access) to more efficient use of radio frequencies. it uses hierarchical cell structure, adaptive antenna array and coherent demodulation (bidirectional) technology, a substantial increase in network capacity available that can better meet the requirements of the development of future mobile communication.6.various networks to convergetechnological developments, changes in market demand, market competition and market control policies will relax computer。
数据通信 毕业论文外文文献英文翻译
郑州轻工业学院本科毕业设计（论文）——英文翻译题目差错控制编码解决加性噪声的仿真学生姓名专业班级通信工程05-2 学号 12院（系）计算机与通信工程学院指导教师完成时间 2009年4月26日英文原文:Data communicationsGildas Avoine and Philippe OechslinEPFL, Lausanne, Switzerlandfgildas.avoine, philippe.oechsling@ep.chAbstractData communications are communications and computer technology resulting from the combination of a new means of communication. To transfer information between the two places must have transmission channel, according to the different transmission media, there is wired data communications and wireless data communications division. But they are through the transmission channel data link terminals and computers, different locations of implementation of the data terminal software and hardware and the sharing of information resources.1 The development of data communicationsThe first phase: the main language, through the human, horsepower, war and other means of transmission of original information.Phase II: Letter Post. (An increase means the dissemination of information)The third stage: printing. (Expand the scope of information dissemination)Phase IV: telegraph, telephone, radio. (Electric to enter the time)Fifth stage: the information age, with the exception of language information, there are data, images, text and so on.1.1 The history of modern data communicationsCommunication as a Telecommunications are from the 19th century, the beginning Year 30. Faraday discovered electromagnetic induction in 1831. Morse invented telegraph in 1837. Maxwell's electromagnetic theory in 1833. Bell invented the telephone in 1876. Marconi invented radio in 1895. Telecom has opened up in the new era. Tube invented in 1906 in order to simulate the development of communications.Sampling theorem of Nyquist criteria In 1928. Shannong theorem in 1948. The invention of the 20th century, thesemiconductor 50, thereby the development of digital communications. During the 20th century, the invention of integrated circuits 60. Made during the 20th century, 40 the concept of geostationary satellites, but can not be achieved. During the 20th century, space technology 50. Implementation in 1963 first synchronized satellite communications. The invention of the 20th century, 60 laser, intended to be used for communications, was not successful. 70 The invention of the 20th century, optical fiber, optical fiber communications can be developed.1.2 Key figuresBell (1847-1922), English, job in London in 1868. In 1871 to work in Boston. In 1873, he was appointed professor at Boston University. In 1875, invented many Telegram Rd. In 1876, invented the telephone. Lot of patents have been life. Yes, a deaf wife.Marconi (1874-1937), Italian people, in 1894, the pilot at his father's estate. 1896, to London. In 1897, the company set up the radio reported. In 1899, the first time the British and French wireless communications. 1916, implementation of short-wave radio communications. 1929, set up a global wireless communications network. Kim won the Nobel Prize. Took part in the Fascist Party.1.3 Classification of Communication SystemsAccording to type of information: Telephone communication system, Cable television system ,Data communication systems.Modulation by sub: Baseband transmission,Modulation transfer.Characteristics of transmission signals in accordance with sub: Analog Communication System ,Digital communication system.Transmission means of communication system: Cable Communications,Twisted pair, coaxial cable and so on.And long-distance telephone communication. Modulation: SSB / FDM. Based on the PCM time division multiple coaxial digital base-band transmission technology. Will gradually replace the coaxial fiber.Microwave relay communications:Comparison of coaxial and easy to set up, low investment, short-cycle. Analog phone microwave communications mainly SSB / FM /FDM modulation, communication capacity of 6,000 road / Channel. Digital microwave using BPSK, QPSK and QAM modulation techniques. The use of 64QAM, 256QAM such as multi-level modulation technique enhance the capacity of microwave communications can be transmitted at 40M Channel 1920 ~ 7680 Telephone Rd PCM figure.Optical Fiber Communication: Optical fiber communication is the use of lasers in optical fiber transmission characteristics of long-distance with a large communication capacity, communication, long distance and strong anti-interference characteristics. Currently used for local, long distance, trunk transmission, and progressive development of fiber-optic communications network users. At present, based on the long-wave lasers and single-mode optical fiber, each fiber road approach more than 10,000 calls, optical fiber communication itself is very strong force. Over the past decades, optical fiber communication technology develops very quickly, and there is a variety of applications, access devices, photoelectric conversion equipment, transmission equipment, switching equipment, network equipment and so on. Fiber-optic communications equipment has photoelectric conversion module and digital signal processing unit is composed of two parts.Satellite communications: Distance communications, transmission capacity, coverage, and not subject to geographical constraints and high reliability. At present, the use of sophisticated techniques Analog modulation, frequency division multiplexing and frequency division multiple access. Digital satellite communication using digital modulation, time division multiple road in time division multiple access.Mobile Communications: GSM, CDMA. Number of key technologies for mobile communications: modulation techniques, error correction coding and digital voice encoding. Data Communication Systems.1.4 Five basic types of data communication system:（1）Off-line data transmission is simply the use of a telephone or similar link to transmit data without involving a computer system.The equipment used at both ends of such a link is not part of a computer, or at least does not immediately make the data available for computer process, that is, the data when sent and / or received are 'off-line'.This type of data communication is relatively cheap and simple.（2）Remote batch is the term used for the way in which data communication technology is used geographically to separate the input and / or output of data from the computer on which they are processed in batch mode.（3）On-line data collection is the method of using communications technology to provide input data to a computer as such input arises-the data are then stored in the computer (say on a magnetic disk) and processed either at predetermined intervals or as required.（4）Enquiry-response systems provide, as the term suggests, the facility for a user to extract information from a computer.The enquiry facility is passive, that is, does not modify the information stored.The interrogation may be simple, for example, 'RETRIEVE THE RECORD FOR EMPLOYEE NUMBER 1234 'or complex.Such systems may use terminals producing hard copy and / or visual displays.（5）Real-time systems are those in which information is made available to and processed by a computer system in a dynamic manner so that either the computer may cause action to be taken to influence events as they occur (for example as in a process control application) or human operators may be influenced by the accurate and up-to-date information stored in the computer, for example as in reservation systems.2 Signal spectrum with bandwidthElectromagnetic data signals are encoded, the signal to be included in the data transmission. Signal in time for the general argument to show the message (or data) as a parameter (amplitude, frequency or phase) as the dependent variable. Signal of their value since the time variables are or not continuous, can be divided into continuous signals and discrete signals; according to whether the values of the dependent variable continuous, can be divided into analog signals and digital Signal.Signals with time-domain and frequency domain performance of the two most basic forms and features. Time-domain signal over time to reflect changing circumstances. Frequency domain characteristics of signals not only contain the same information domain, and the spectrum of signal analysis, can also be a clear understanding of the distribution ofthe signal spectrum and share the bandwidth. In order to receive the signal transmission and receiving equipment on the request channel, Only know the time-domain characteristics of the signal is not enough, it is also necessary to know the distribution of the signal spectrum. Time-domain characteristics of signals to show the letter .It’s changes over time. Because most of the signal energy is concentrated in a relatively narrow band, so most of our energy focused on the signal that Paragraph referred to as the effective band Bandwidth, or bandwidth. Have any signal bandwidth. In general, the greater the bandwidth of the signal using this signal to send data Rate on the higher bandwidth requirements of transmission medium greater. We will introduce the following simple common signal and bandwidth of the spectrum.More or less the voice signal spectrum at 20 Hz ~ 2000 kHz range (below 20 Hz infrasound signals for higher than 2000 KHz. For the ultrasonic signal), but with a much narrower bandwidth of the voice can produce an acceptable return, and the standard voice-frequency signal gnal 0 ~ 4 MHz, so the bandwidth of 4 MHz.As a special example of the monostable pulse infinite bandwidth. As for the binary signal, the bandwidth depends on the generalThe exact shape of the signal waveform, as well as the order of 0,1. The greater the bandwidth of the signal, it more faithfully express the number of sequences.3 The cut-off frequency channel with bandwidthAccording to Fourier series we know that if a signal for all frequency components can be completely the same through the transmission channel to the receiving end, then at the receiving frequency components of these formed by stacking up the signal and send the signal side are exactly the same, That is fully recovered from the receiving end of the send-side signals. But on the real world, there is no channel to no wear and tear through all the Frequency components. If all the Fourier components are equivalent attenuation, then the signal reception while Receive termination at an amplitude up Attenuation, but the distortion did not happen. However, all the transmission channel and equipment for different frequency components of the degree of attenuation is differentSome frequency components almost no attenuation, and attenuation of some frequency components by anumber, that is to say, channel also has a certain amount of vibrationIncrease the frequency characteristics, resulting in output signal distortion. Usually are frequency of 0 Hz to fc-wide channel at Chuan harmonic lost during the attenuation does not occur (or are a very small attenuation constant), whereas in the fc frequency harmonics at all above the transmission cross Decay process a lot, we put the signal in the transmission channel of the amplitude attenuation of a component to the original 0.707(that is, the output signal Reduce by half the power) when the frequency of the corresponding channel known as the cut-off frequency (cut - off frequency).Cut-off frequency transmission medium reflects the inherent physical properties. Other cases, it is because people interested in Line filter is installed to limit the bandwidth used by each user. In some cases, because of the add channel Two-pass filter, which corresponds to two-channel cut-off frequency f1 and f2, they were called up under the cut-off frequency and the cut-off frequency.This difference between the two cut-off frequency f2-f1 is called the channel bandwidth. If the input signal bandwidth is less than the bandwidth of channel, then the entire input signal Frequency components can be adopted by the Department of channels, which the letter Road to be the output of the output waveform will be true yet. However, if the input signal bandwidth greater than the channel bandwidth, the signal of a Frequency components can not be more on the channel, so that the signal output will be sent with the sending end of the signal is somewhat different, that is produced Distortion. In order to ensure the accuracy of data transmission, we must limit the signal bandwidth.4 Data transfer rateChannel maximum data transfer rate Unit time to be able to transfer binary data transfer rate as the median. Improve data transfer rate means that the space occupied by each Reduce the time that the sequence of binary digital pulse will reduce the cycle time, of course, will also reduce the pulse width.The previous section we already know, even if the binary digital pulse signal through a limited bandwidth channel will also be the ideal generated wave Shape distortion, and when must the input signal bandwidth, the smaller channel bandwidth, output waveformdistortion will be greater. Another angle Degree that when a certain channel bandwidth, the greater the bandwidth of the input signal, the output signal the greater the distortion, so when the data transmissionRate to a certain degree (signal bandwidth increases to a certain extent), in the on-channel output signal from the receiver could not have been Distortion of the output signal sent to recover a number of sequences. That is to say, even for an ideal channel, the limited bandwidth limit System of channel data transfer rate.At early 1924, H. Nyquist (Nyquist) to recognize the basic limitations of this existence, and deduced that the noise-free Limited bandwidth channel maximum data transfer rate formula. In 1948, C. Shannon (Shannon) put into the work of Nyquist 1 Step-by-step expansion of the channel by the random noise interference. Here we do not add on to prove to those now seen as the result of a classic.Nyquist proved that any continuous signal f (t) through a noise-free bandwidth for channel B, its output signal as a Time bandwidth of B continuous signal g (t). If you want to output digital signal, it must be the rate of g (t) for interval Sample. 2B samples per second times faster than are meaningless, because the signal bandwidth B is higher than the high-frequency component other than a letter has been Road decay away. If g (t) by V of discrete levels, namely, the likely outcome of each sample for the V level of a discrete one, The biggest channel data rate Rm ax as follows:Rmax = 2Blog 2 V (bit / s)For example, a 3000 Hz noise bandwidth of the channel should not transmit rate of more than 6,000 bits / second binary digital signal.In front of us considered only the ideal noise-free channel. There is noise in the channel, the situation will rapidly deteriorate. Channel Thermal noise with signal power and noise power ratio to measure the signal power and noise power as the signal-to-noise ratio (S ignal - to -- Noise Ratio). If we express the signal power S, and N express the noise power, while signal to noise ratio should be expressed as S / N. However, people Usually do not use the absolute value of signal to noise ratio, but the use of 10 lo g1 0S / N to indicate the units are decibels (d B). For the S / N equal 10 Channel, said its signal to noise ratio for the 1 0 d B; the same token, if the channel S / N equal to one hundred, then the signal to noiseratio for the 2 0 d B; And so on. S hannon noise channel has about the maximum data rate of the conclusions are: The bandwidth for the BH z, signal to noise ratio for the S / N Channel, the maximum data rate Rm ax as follows:Rmax = Blog 2 (1 + S / N) (bits / second)For example, for a bandwidth of 3 kHz, signal to noise ratio of 30 dB for the channel, regardless of their use to quantify the number of levels, nor Fast sampling rate control, the data transfer rate can not be greater than 30,000 bits / second. S h a n n o n the conclusions are derived based on information theory Out for a very wide scope, in order to go beyond this conclusion, like you want to invent perpetual motion machine, as it is almost impossible.It is worth noting that, S hannon conclusions give only a theoretical limit, and in fact, we should be pretty near the limit Difficult.SUMMARYMessage signals are (or data) of a magnetic encoder, the signal contains the message to be transmitted. Signal according to the dependent variable Whether or not a row of values, can be classified into analog signals and digital signals, the corresponding communication can be divided into analog communication and digital communication.Fourier has proven: any signal (either analog or digital signal) are different types of harmonic frequencies Composed of any signal has a corresponding bandwidth. And any transmission channel signal attenuation signals will, therefore, Channel transmission of any signal at all, there is a data transfer rate limitations, and this is Chengkui N yquist (Nyquist) theorem and S hannon (Shannon) theorem tells us to conclusions.Transmission medium of computer networks and communication are the most basic part of it at the cost of the entire computer network in a very Large proportion. In order to improve the utilization of transmission medium, we can use multiplexing. Frequency division multiplexing technology has many Road multiplexing, wave division multiplexing and TDM three that they use on different occasions.Data exchange technologies such as circuit switching, packet switching and packetswitching three have their respective advantages and disadvantages. M odem are at Analog phone line for the computer's binary data transmission equipment. Modem AM modulation methods have, FM, phase modulation and quadrature amplitude modulation, and M odem also supports data compression and error control. The concept of data communications Data communication is based on "data" for business communications systems, data are pre-agreed with a good meaning of numbers, letters or symbols and their combinations.参考文献[1]C.Y.Huang and A.Polydoros,“Two small SNR classification rules for CPM,”inProc.IEEE Milcom,vol.3,San Diego,CA,USA,Oct.1992,pp.1236–1240.[2]“Envelope-based classification schemes for continuous-phase binary Frequency-shift-keyed modulations,”in Pr oc.IEEE Milcom,vol.3,Fort Monmouth,NJ,USA,Oct.1994,pp. 796–800.[3]A.E.El-Mahdy and N.M.Namazi,“Classification of multiple M-ary frequency-shift keying over a rayleigh fading channel,”IEEE m.,vol.50,no.6,pp.967–974,June 2002.[4]Consulative Committee for Space Data Systems(CCSDS),Radio Frequency and Modulation SDS,2001,no.401.[5]E.E.Azzouz and A.K.Nandi,“Procedure for automatic recognition of analogue and digital modulations,”IEE mun,vol.143,no.5,pp.259–266,Oct.1996.[6]A.Puengn im,T.Robert,N.Thomas,and J.Vidal,“Hidden Markov models for digital modulation classification in unknown ISI channels,”in Eusipco2007,Poznan,Poland, September 2007,pp.1882–1885.[7]E.Vassalo and M.Visintin,“Carrier phase synchronization for GMSK signals,”I nt.J.Satell. Commun.,vol.20,no.6,pp.391–415,Nov.2002.[8]J.G.Proakis,Digital Communications.Mc Graw Hill,2001.[9]L.Rabiner,“A tutorial on hidden Markov models and selected applications in speechrecognition,”Proc.IEEE,vol.77,no.2,pp.257–286,1989.英文译文：数据通信Gildas Avoine and Philippe OechslinEPFL, Lausanne, Switzerlandfgildas.avoine, philippe.oechsling@ep.ch摘要数据通信是通信技术和计算机技术相结合而产生的一种新的通信方式。
现代移动通信 毕业论文外文翻译 (2)
一、英文原文Modern mobile communication technologyIn now highly the information society, the information and the correspondence have become the modern society “the life”. The information exchange mainly relies on the computer correspondence, but corresponds takes the transmission method, with the sensing technology, the computer technology fuses mutually, has become in the 21st century the international society and the world economic development powerful engine. In order to of adapt the time request, the new generation of mobile communication technology seasonable and lives, the new generation of mobile communication technology is the people said that third generation's core characteristic is the wide band addressing turns on non-gap roaming between the rigid network and numerous different communications system's, gains the multimedia communication services.Along with the time progress, the technical innovation, people's life request's enhancement, the mobile communication technology renewal speed is quite astonishing, almost every other ten year mobile communication technology has a transformation update, from the 1980s “the mobile phone” to present's 3G handset, during has had two mobile communication technology transformation, transits from 1G AMPS to 2G GSM, from GSM to IMT-2000 (i.e. 3G technology). Knows modern on me the mobile communication technology to have the following several aspect important technology:1. wideband modulation and multiple access techniqueThe wireless high speed data transmission cannot only depend on the frequency spectrum constantly the expansion, should be higher than the present number magnitude at least in the frequency spectrum efficiency, may use three technologies in the physical level, namely OFDM, UWB and free time modulation code. OFDM with other encoding method's union, nimbly OFDM and TDMA, FDMA, CDMA, SDMA combines the multiple access technique.In the 1960s the OFDM multi-channel data transmission has succeeded uses in complex and the Kathryn high frequency military channels. OFDM has used in 1.6 M bit/s high bit rate digital subscriber line (HDSL), 6 M bit/s asymmetrical digital subscriber line (ADSL), 100 M bit/s really high speed figure subscriber's line (VDSL), digital audio frequency broadcast and digital video broadcast and so on. OFDM applies on 5 GHz provides 54 M bit/s wireless local network IEEE 802.11 a and IEEE 802.11g, high performance this region network Hi per LAN/2 and ETSI-BRAN, but also takes metropolitan area network IEEE 802.16 and the integrated service digit broadcast (ISDB-T) the standard. Compares with the single load frequency modulation system service pattern, the OFDM modulation service pattern needs to solve the relatively big peak even power ratio (PAPR, Peak to Average Power Ratio) and to the frequency shifting and the phase noise sensitive question.High speed mobile communication's another request is under the wide noise bandwidth, must demodulate the signal-to-noise ratio to reduce as far as possible, thus increases the cover area. May adopt the anti-fading the full start power control and the pilot frequency auxiliary fast track demodulation technology, like the frequency range anti-fading's Rake receive and the track technology, the OFDMA technology which declines from the time domain and the frequencyrange resistance time and the frequency selectivity, the link auto-adapted technology, the union coding technique.2. frequency spectrum use factor lift techniqueThe fundamental research pointed out: In the independent Rayleigh scattering channel, the data rate and the antenna several tenth linear relationships, the capacity may reach Shannon 90%. Is launching and the receiving end may obtain the capacity and the frequency spectrum efficiency gain by the multi-antenna development channel space. The MIMO technology mainly includes the spatial multiplying and the space diversity technology, concurrent or the salvo same information enhances the transmission reliability on the independent channel.Receives and dispatches the bilateral space diversity is the high-capacity wireless communication system uses one of technical. Bell Lab free time's opposite angle BLAST (D-BLAST) capacity increase to receive and dispatch the bilateral smallest antenna number in administrative levels the function. The cross time domain which and the air zone expansion signal constitutes using MIMO may also resist the multi-diameter disturbance. V-BLAST system when indoor 24~34 dB, the frequency spectrum use factor is 20~40 bit/s/Hz. But launches and the receiving end uses 16 antennas, when 30 dB, the frequency spectrum use factor increases to 60~70 bit/s/Hz.The smart antenna automatic tracking needs the signal and the auto-adapted free time processing algorithm, produces the dimensional orientation wave beam using the antenna array, causes the main wave beam alignment subscriber signal direction of arrival through the digital signal processing technology, the side lobe or zero falls the alignment unwanted signal direction of arrival. The auto-adapted array antennas (AAA, Adaptive Array Antennas) disturbs the counter-balance balancer (ICE, Interference Canceling Equalizer) to be possible to reduce disturbs and cuts the emissive power.3. software radio technologyThe software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Processing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut.UWB is also called the pulse to be radio, the modulation uses the pulse width in the nanosecond level fast rise and the drop pulse, the pulse cover frequency spectrum from the current to the lucky hertz, does not need in the radio frequency which the convention narrow band frequency modulation needs to transform, after pulse formation, may deliver directly to the antenna launch.4. software radio technologyThe software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Processing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut.5. network security and QoSQoS divides into wireless and the wired side two parts, wireless side's QoS involves theradio resource management and the dispatch, the admission control and the mobility management and so on, the mobility management mainly includes the terminal mobility, individual mobility and service mobility. Wired side's QoS involves based on the IP differ discrimination service and the RSVP end-to-end resources reservation mechanism. Mechanism maps the wireless side IP differ IP the QoS. Network security including network turning on security, core network security, application security, safety mechanism visibility and configurable.In the above modern mobile communication key technologies' foundation, has had the land honeycomb mobile communication, the satellite communication as well as the wireless Internet communication, these mailing address caused the correspondence appearance to have the huge change, used the digital technique the modern wireless communication already to permeate the national economy each domain and people's daily life, for this reason, we needed to care that its trend of development, hoped it developed toward more and more convenient people's life's direction, will let now us have a look at the modern mobile communication the future trend of development.modern mobile communication technological development seven new tendencies :First, mobility management already from terminal management to individual management and intelligent management developmentSecond, network already from synchronized digital circuit to asynchronous digital grouping and asynchronous transfer mode (ATM) development;the three, software's developments actuated from the algorithm to the procedure-oriented and face the goal tendency development;the four, information processing have developed from the voice to the data and the image;five, wireless frequency spectrum processing already from narrow band simulation to the narrow band CDMA development;the six, computers have developed from central processing to the distributional server and intellectualized processing;the seven, semiconductor devices have developed from each chip 16,000,000,000,000 /150MHz speed VLSI to 0.5 /350MHz speed VLSI and 2,000,000,000,000,000 /550MHz speed VLSI.Under this tendency's guidance, the mobile service rapid development, it satisfied the people in any time, any place to carry on the correspondence with any individual the desire. The mobile communication realizes in the future the ideal person-to-person communication service way that must be taken. In the information support technology, the market competition and under the demand combined action, the mobile communication technology's development is progresses by leaps and bounds, presents the following several general trends: work service digitization, grouping; 2. networking wide band; working intellectualization; 4.higher frequency band; 5. more effective use frequency; 6.each kind of network tends the fusion. The understanding, grasps these tendencies has the vital practical significance to the mobile communication operator and the equipment manufacturer.二、英文翻译现代移动通信在当今高度信息化的社会，信息和通信已成为现代社会的“命脉”。
对移动通信专业课的英文作文
对移动通信专业课的英文作文Mobile communication has become an integral part of our daily lives, revolutionizing the way we interact, access information, and conduct business. As a field of study, mobile communications encompasses a vast array of technological advancements, innovative applications, and evolving industry trends. In this essay, we will delve into the significance of mobile communications as a professional discipline, exploring its key aspects, the skills and knowledge required, and the exciting career prospects it offers.At the core of mobile communications lies the seamless integration of various technologies, including wireless networks, cellular systems, and mobile devices. The rapid development of 4G and 5G networks, coupled with the widespread adoption of smartphones and tablets, has transformed the way we communicate, access information, and engage with the digital world. Mobile communication professionals play a crucial role in designing, implementing, and optimizing these complex systems, ensuring reliable and efficient connectivity for users.One of the fundamental aspects of mobile communications is the understanding of wireless network architectures. Students in this field must grasp the principles of radio frequency (RF) propagation, antenna design, and cellular network topologies. They learn to analyze and address the challenges posed by factors such as signal interference, coverage, and capacity optimization. Additionally, they delve into the intricacies of network protocols, such as GSM, CDMA, and LTE, and their role in enabling seamless voice, data, and multimedia communication.Beyond the technical foundations, mobile communications professionals must also possess a strong understanding of mobile device technologies. This includes the hardware components, operating systems, and software applications that power modern smartphones and tablets. They need to stay abreast of the latest advancements in mobile processors, memory, sensors, and display technologies, as well as the evolving user interface designs and mobile app development frameworks.Another crucial aspect of mobile communications is the study of mobile data and services. Students in this field explore the various mobile data transmission techniques, such as packet switching and circuit switching, and learn to optimize data throughput and minimize latency. They also examine the role of mobile internet protocols, such as WAP and GPRS, and their integration withtraditional internet technologies.The field of mobile communications also encompasses the study of mobile applications and services. Students delve into the development of mobile apps, exploring user experience design, cross-platform compatibility, and the integration of advanced features like location-based services, augmented reality, and mobile payments. They also learn to navigate the complex ecosystem of mobile app stores, distribution channels, and monetization strategies.In addition to the technical aspects, mobile communications professionals must also possess strong analytical and problem-solving skills. They must be adept at data analysis, network optimization, and performance monitoring to ensure the smooth operation of mobile systems. Furthermore, they need to understand the regulatory frameworks and industry standards that govern the mobile communications landscape, adapting to the ever-evolving landscape of policies and regulations.The career prospects in mobile communications are vast and diverse. Graduates can find employment in a wide range of industries, including telecommunications companies, mobile device manufacturers, software development firms, and IT consulting agencies. They may take on roles such as network engineers, mobile app developers, data analysts, project managers, and technical salesrepresentatives, contributing to the development and deployment of cutting-edge mobile technologies.Moreover, the field of mobile communications is constantly evolving, presenting professionals with opportunities for continuous learning and growth. As new technologies, such as 5G, the Internet of Things (IoT), and edge computing, continue to emerge, mobile communication experts must stay ahead of the curve, constantly updating their skills and knowledge to remain competitive in the job market.In conclusion, mobile communications is a dynamic and multifaceted field that offers a wealth of opportunities for aspiring professionals. By mastering the technical aspects of wireless networks, mobile devices, and data services, as well as developing strong analytical and problem-solving skills, students in this discipline can position themselves for rewarding careers in a rapidly advancing industry. As the world becomes increasingly interconnected and reliant on mobile technologies, the demand for skilled mobile communication professionals will only continue to grow, making it an exciting and promising career path.。
电子与通信专业英语作文
电子与通信专业英语作文Electronic and Communication Engineering。
Electronic and Communication Engineering is a field that combines electrical engineering and communication systems. It deals with the design, development, and maintenance of electronic devices, circuits, and communication systems. In this article, we will explore the various aspects of this discipline and its importance in today's world.Firstly, let us understand the basics of electronic engineering. It involves the study of electronic circuits, which are the building blocks of any electronic device. These circuits consist of various components such as resistors, capacitors, transistors, and integrated circuits. Electronic engineers are responsible for designing and analyzing these circuits, ensuring their proper functioning.Communication engineering, on the other hand, focuses on the transmission and reception of information through various communication systems. This includes wired and wireless communication systems, such as telecommunication networks, satellite communication, and mobile communication. Communication engineers work on designing and optimizing these systems to ensure efficient and reliable communication.The integration of electronic and communication engineering has revolutionized the way we communicate and interact with the world. It has played a crucial role in the development of advanced technologies like smartphones, the internet, and satellite communication. These technologies have made communication faster, easier, and more accessible to people across the globe.One of the key areas where electronic and communication engineering has made significant contributions is in the field of telecommunication. Telecommunication networks are the backbone of modern communication systems. They enable voice, data, and video transmission over long distances. Electronic and communication engineers are involved in the design, deployment, and maintenance of these networks, ensuring seamless communication between individuals and organizations.Another area where this discipline is making a difference is in the development of wireless communication systems. Wireless technologies like Wi-Fi, Bluetooth, and 5G have revolutionized the way we connect and communicate. Electronic and communication engineers are at the forefront of developing and improving these technologies, enhancing our connectivity and enabling the Internet of Things (IoT) revolution.Moreover, electronic and communication engineering plays a vital role in the defense and security sector. It involves the development of advanced communication systems for military applications, including secure communication networks and surveillance systems. These technologies are essential for national security and defense operations.In conclusion, electronic and communication engineering is a dynamic and rapidly evolving field. It encompasses the design, development, and maintenance of electronic devices, circuits, and communication systems. This discipline has revolutionized the way we communicate and has contributed to the development of advanced technologies. From telecommunication networks to wireless communication systems, electronic and communication engineers play a crucial role in shaping our connected world. As technology continues to advance, the importance of this field will only grow, making it an exciting and promising career choice for aspiring engineers.。
通信工程专业英语论文
通信工程专业英语论文 Document serial number【UU89WT-UU98YT-UU8CB-UUUT-UUT108】The General Situation of AT89C51The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM) and 128 bytes RAM. The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51instruction set and pin out. The chip combines a versatile 8-bit CPU with Flash on a monolithic chip; the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.Features:Compatible with MCS-51Products4K Bytes of In-System Reprogrammable Flash MemoryEndurance: 1,000 Write/Erase CyclesFully Static Operation: 0 Hz to 24 MHzThree-Level Program Memory Lock128 x 8-Bit Internal RAM32 Programmable I/O LinesTwo 16-Bit Timer/CountersSix Interrupt SourcesProgrammable Serial ChannelLow Power Idle and Power Down ModesThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Block DiagramPin Description:VCC Supply voltage.GND Ground.Port 0：Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. (Sink/flow)Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull-ups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during programverification. External pull-ups are required during program verification.Port 1：Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally beingpulled low will source current (IIL) because of the internal pull-ups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2：Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally beingpulled low will source current (IIL) because of the internal pull-ups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when emitting 1s. During accesses to external data memories that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3：Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/sourcefour TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups.Port 3 also serves the functions of various special features of the AT89C51 as listed below:Port 3alsoreceives some control signals for Flash programming and verification.RST：Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROG：Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALEpulse is skipped during each access to external Data Memory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSEN：Program Store Enable is the read strobe to external program memory.When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPP：External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1(LB1) is programmed, EA will be internally latched (fasten with a latch) on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage（VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1：Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2：Output from the inverting oscillator amplifier.Oscillator Characteristics：XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source,XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low times specifications must be observed.Idle Mode：In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabledinterrupt or by a hardware reset.It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Status of External Pins During Idle and Power Down ModesPower Down ModeIn the power down mode the oscillator is stopped, and the instruction that invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. The only exit from power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below:When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.Programming the Flash：The AT89C51 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH) and ready to be programmed.The programming interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal.The low voltage programming mode provides a convenient way to program theAT89C51 inside the user’s system, while the high-voltage programming mode is compatible with conventional third party Flash or EPROM programmers.The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled. The respective top-side marking and device signature codes are listed in theThe AT89C51 code memory array is programmed byte-bybytein either programming mode. To program any nonblank byte in the on-chip Flash Programmable and Erasable Read Only Memory, the entire memory must be erased using the Chip Erase Mode.Programming Algorithm: Before programming the AT89C51,the address, data and control signals should be set up according to the Flash programming mode table and Figures 3 and 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines.3. Activate the correct combination of control signals.4. Raise EA/VPP to 12V for the high-voltage programming mode.5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timed and typically takes no more than ms. Repeat steps 1 through 5, changing the address and data for the entire array oruntil the end of the object file is reached.Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on . Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy:The progress of byte programming can also be monitored by the RDY/BSY output signal. is pulled low after ALE goes high during programming to indicate BUSY. is pulled high again when programming is done to indicate READY.Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.Chip Erase: The entire Flash Programmable and Erasable Read Only Memory array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that and must be pulled to a logic low. The values returned are as follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programmingProgramming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to completion.AT89C51的概况AT89C51是美国ATMEL公司生产的低电压，高性能CMOS8位单片机，片内含4Kbytes的快速可擦写的只读程序存储器（PEROM）和128 bytes 的随机存取数据存储器（RAM），器件采用ATMEL公司的高密度、非易失性存储技术生产，兼容标准MCS-51产品指令系统，片内置通用8位中央处理器（CPU）和flish存储单元，功能强大AT89C51单片机可为您提供许多高性价比的应用场合，可灵活应用于各种控制领域。
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Modern mobile communication technologyIn now highly the informationization society, the information and the correspondence have become the modern society “the life”. The information exchange mainly relies on the computer correspondence, but corresponds takes the transmission method, with the sensing technology, the computer technology fuses mutually, has become in the 21st century the international society and the world economic development powerful engine. In order to of adapt the time request, the new generation of mobile communication technology seasonable and lives, the new generation of mobile communication technology is the people said that third generation's core characteristic is the wide band addressing turns on non-gap roaming between the rigid network and numerous different communications system's, gains the multimedia communication services. the mobile communication technology to have the following several aspect important technology:1. wideband modulation and multiple access techniqueThe wireless high speed data transmission cannot only depend on the frequency spectrum constantly the expansion, should be higher than the present number magnitude at least in the frequency spectrum efficiency, may use three technologies in the physical level, namely OFDM, UWB and free time modulation code. OFDM with other encoding method's union, nimbly OFDM and TDMA, FDMA, CDMA, SDMA combines the multiple access technique.In the 1960s the OFDM multi-channel data transmission has succeeded uses in Kineplex and the Kathryn high frequency military channels. OFDM has used in 1.6 Mbit/s high bit rate digital subscriber line (HDSL), 6 Mbit/s asymmetrical digital subscriber line (ADSL), 100 Mbit/s really high speed figure subscriber's line (VDSL), digital audio frequency broadcast and digital video broadcast and so on. OFDM applies on 5 GHz provides 54 Mbit/s wirelesslocal network IEEE 802.11 a and IEEE 802.11g, high performance this region network Hiper LAN/2 and ETSI-BRAN, but also takes metropolitan area network IEEE 802.16 and the integrated service digit broadcast (ISDB-T) the standard. Compares with the single load frequency modulation system service pattern, the OFDM modulation service pattern needs to solve the relatively big peak even power ratio (PAPR, Peak to Average Power Ratio) and to the frequency shifting and the phase noise sensitive question.High speed mobile communication's another request is under the wide noise bandwidth, must demodulate the signal-to-noise ratio to reduce as far as possible, thus increases the cover area. May adopt the anti-fading the full start power control and the pilot frequency auxiliary fast track demodulation technology, like the frequency range anti-fading's Rake receive and the track technology, the OFDMA technology which declines from the time domain and the frequency range resistance time and the frequency selectivity, the link auto-adapted technology, the union coding technique.2. frequency spectrum use factor lift techniqueThe fundamental research pointed out: In the independent Rayleigh scattering channel, the data rate and the antenna several tenth linear relationships, the capacity may reach Shannon 90%. Is launching and the receiving end may obtain the capacity and the frequency spectrum efficiency gain by the multi-antenna development channel space. The MIMO technology mainly includes the spatial multiplying and the space diversity technology, concurrent or the salvo same information enhances the transmission reliability on the independent channel.Receives and dispatches the bilateral space diversity is the high-capacity wireless communication system uses one of technical. Bell Lab free time's opposite angle BLAST (D-BLAST) capacity increase to receive and dispatch the bilateral smallest antenna number in administrative levels the function. The cross time domain which and the air zone expansion signal constitutes using MIMO may also resist the multi-diameter disturbance. V-BLAST system whenindoor 24~34 dB, the frequency spectrum use factor is 20~40 bit/s/Hz. But launches and the receiving end uses 16 antennas, when 30 dB, the frequency spectrum use factor increases to 60~70 bit/s/Hz.The smart antenna automatic tracking needs the signal and the auto-adapted free time processing algorithm, produces the dimensional orientation wave beam using the antenna array, causes the main wave beam alignment subscriber signal direction of arrival through the digital signal processing technology, the side lobe or zero falls the alignment unwanted signal direction of arrival. The auto-adapted array antennas (AAA, Adaptive Array Antennas) disturbs the counter-balance balancer (ICE, Interference Canceling Equalizer) to be possible to reduce disturbs and cuts the emissive power.3. software radio technologyThe software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Pocessing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut.UWB is also called the pulse to be radio, the modulation uses the pulse width in the nanosecond level fast rise and the drop pulse, the pulse cover frequency spectrum from the cocurrent to the lucky hertz, does not need in the radio frequency which the convention narrow band frequency modulation needs to transform, after pulse formation, may deliver directly to the antenna launch.4. network security and QoSQoS divides into wireless and the wired side two parts, wireless side's QoS involves the radio resource management and the dispatch, the admissioncontrol and the mobility management and so on, the mobility management mainly includes the terminal mobility, individual mobility and service mobility. Wired side's QoS involves based on the IP diffSer discrimination service and the RSVP end-to-end resources reservation mechanism. Mechanism maps the wireless side IP diffSer IP the QoS. Network security including network turning on security, core network security, application security, safety mechanism visibility and configurable.In the above modern mobile communication key technologies's foundation, has had the land honeycomb mobile communication, the satellite communication as well as the wireless Internet communication, these mailing address caused the correspondence appearance to have the huge change, used the digital technique the modern wireless communication already to permeate the national economy each domain and people's daily life, for this reason, we needed to care that its trend of development, hoped it developed toward more and more convenient people's life's direction, will let now us have a look at the modern mobile communication the future trend of development.modern mobile communication technological development seven new tendencies :First, mobility management already from terminal management to individual management and intelligent management development Second, network already from synchronized digital circuit to asynchronous digital grouping and asynchronous transfer mode (ATM) development;the three, software's developments actuated from the algorithm to the procedure-oriented and face the goal tendency development;the four, information processing have developed from the voice to the data and the image;five, wireless frequency spectrum processing already from narrow band simulation to the narrow band CDMA development;the six, computers have developed from central processing to thedistributional server and intellectualized processing;the seven, semiconductor devices have developed from each chip 16,000,000,000,000 /150MHz speed VLSI to 0.5 /350MHz speed VLSI and 2,000,000,000,000,000 /550MHz speed VLSI.Under this tendency's guidance, the mobile service rapid development, it satisfied the people in any time, any place to carry on the correspondence with any individual the desire. The mobile communication realizes in the future the ideal person-to-person communication service way that must be taken. In the information support technology, the market competition and under the demand combined action, the mobile communication technology's development is progresses by leaps and bounds, presents the following several general trends: 1) network service digitization, grouping; 2) networking wide band; 3) networking intellectualization; 4) higher frequency band; 5) more effective use frequency; 6) each kind of network tends the fusion. The understanding, grasps these tendencies has the vital practical significance to the mobile communication operator and the equipment manufacturer.英译中：现代移动通信在当今高度信息化的社会，信息和通信已成为现代社会的“命脉”。