通信工程专业英语论文设计

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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。

通信专业发展前景英文作文

通信专业发展前景英文作文英文回答：The field of communication is constantly evolving and expanding, and the future prospects for professionals inthis industry are quite promising. With the rapid advancement of technology and the increasing reliance on digital communication, there is a growing demand for individuals with expertise in various areas of communication, such as journalism, public relations, advertising, and digital media.One of the key factors driving the growth of the communication industry is the increasing integration of technology into our daily lives. This has created new opportunities for communication professionals to leverage digital platforms and social media to reach and engage with audiences in innovative ways. As a result, there is a high demand for individuals who are skilled in digital marketing, content creation, and social media management.Furthermore, the globalization of businesses and the interconnectedness of the global economy have also contributed to the demand for communication professionals who are proficient in cross-cultural communication and international media relations. Companies are seeking individuals who can effectively navigate the complexities of communicating with diverse audiences across different cultural and linguistic backgrounds.In addition, the rise of data analytics and the emphasis on measuring the impact of communication efforts have created a need for professionals who are adept at interpreting and utilizing data to inform communication strategies. This has led to a growing demand forindividuals with skills in data analysis, market research, and consumer behavior insights.Overall, the future of the communication industry looks bright, with ample opportunities for professionals to make a meaningful impact in various sectors, including business, media, government, and non-profit organizations.中文回答：通信专业的发展前景十分广阔，随着科技的不断进步和数字通信的日益普及，对于在这一领域有专业知识的人才需求量不断增加。

通信工程毕业设计外文翻译中英文空间多路复用与信道建模

南京邮电大学毕业设计(论文)外文资料翻译学院通信与信息工程学院专业通信工程学生姓名班级学号B070210 B07021021外文出处无线通信基础(Fundamentals ofwireless communications byDavid Tse)附件：1.外文资料翻译译文；2.外文原文附件1：外文资料翻译译文7．mimo：空间多路复用与信道建模本书我们已经看到多天线在无线通信中的几种不同应用。

在第3章中，多天线用于提供分集增益，增益无线链路的可靠性，并同时研究了接受分解和发射分解，而且，接受天线还能提供功率增益。

在第5章中，我们看到了如果发射机已知信道，那么多采用多幅发射天线通过发射波束成形还可以提供功率增益。

在第6章中，多副发射天线用于生产信道波动，满足机会通信技术的需要，改方案可以解释为机会波束成形，同时也能够提供功率增益。

章以及接下来的几章将研究一种利用多天线的新方法。

我们将会看到在合适的信道衰落条件下，同时采用多幅发射天线和多幅接收天线可以提供用于通信的额外的空间维数并产生自由度增益，利用这些额外的自由度可以将若干数据流在空间上多路复用至MIMO信道中，从而带来容量的增加：采用n副发射天线和接受天线的这类MIMO信道的容量正比于n。

过去一度认为在基站采用多幅天线的多址接入系统允许若干个用户同时与基站通信，多幅天线可以实现不同用户信号的空间隔离。

20世纪90年代中期，研究人员发现采用多幅发射天线和接收天线的点对点信道也会出现类似的效应，即使当发射天线相距不远时也是如此。

只要散射环境足够丰富，使得接受天线能够将来自不同发射天线的信号分离开，该结论就成立。

我们已经了解到了机会通信技术如何利用信道衰落，本章还会看到信道衰落对通信有益的另一例子。

将机会通信与MIMO技术提供的性能增益的本质进行比较和对比是非常的有远见的。

机会通信技术主要提供功率增益，改功率增益在功率受限系统的低信噪比情况下相当明显，但在宽带受限系统的高信噪比情况下则很不明显。

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.。

通信专业英语作文模板

通信专业英语作文模板英文回答：1. What is the definition of communication?Communication is the process of effectively conveying a message from one person or group to another, with theintent of creating shared understanding. It involves the exchange of information, thoughts, feelings, and ideas through various channels, such as speaking, writing, gestures, and visual cues.2. What are the different types of communication?Verbal communication: Spoken or written words used to convey a message.Nonverbal communication: Body language, facial expressions, tone of voice, and eye contact that convey messages without words.Intrapersonal communication: Communication with oneself, involving internal thoughts, feelings, and self-reflection.Interpersonal communication: Communication between individuals, including conversations, discussions, and relationships.Mass communication: Dissemination of a message to alarge audience through media such as television, radio, and print.3. What are the key elements of effective communication?Clarity: The message is easy to understand and unambiguous.Accuracy: The message is truthful and represents the intended meaning.Relevance: The message is pertinent to the recipient's needs and interests.Timeliness: The message is delivered at an appropriate time.Completeness: The message includes all necessary information.Conciseness: The message is brief and to the point.Empathy: The message demonstrates understanding of the recipient's perspective.Feedback: The sender receives feedback to ensure the message has been received and understood.4. What are the barriers to effective communication?Language differences: Misunderstandings due to linguistic barriers.Cultural differences: Varying communication styles and protocols across cultures.Personal biases: Preconceived notions or prejudices that influence perception.Noise: Distractions that interfere with the transmission or reception of the message.Lack of attention: The recipient is not paying enough attention to the message.Emotional barriers: Strong emotions that hinder clear thinking and communication.5. What are the strategies for improving communication skills?Active listening: Paying full attention to the speaker and demonstrating comprehension.Effective speaking: Clearly and confidently expressing oneself with appropriate tone and body language.Feedback and clarification: Seeking and providing feedback to ensure understanding.Cultural sensitivity: Being aware of and adapting to different communication styles across cultures.Emotional management: Controlling emotions and maintaining a professional demeanor.Written communication skills: Writing emails, reports, and other documents effectively and clearly.中文回答：1. 什么是沟通？沟通是有效地将信息从一个人或群体传达给另一个人或群体，以期达成共同理解的过程。

电信工程专业英语本科毕业论文

A Hybrid ASIC and FPGA ArchitectureApplications Emerge for Hybrid DevicesImplementation using an ASIC approach typically yields a faster, smaller, and lower power design than implementation in FPGA technology. The growing requirements in the marketplace for design flexibility however, are driving the need for hybrid ASIC/FPGA devices. The potential to change hardware configuration in real time, to support multiple design options with a single mask set, and to product’s usable life, all compel designers to look for a blending of high density ASIC circuits along with the inherent FPGA circuit flexibility.The ability to create a “base design” and then reuse the base with minimal changes for subsequent devices helps reduce design time and encourages standardization. Since many consumer and office products are offered with a range of low to high-end options, this base design concept can be effectively used - with features added to each successive model. Printers, fax machines, PC's and digital imaging equipment are examples where this concept can be useful.DSP applications are also well suited to FPGA because of the FPGAs fast multiply and accumulate (MAC) processing capability. When building a DSP system, the design can take advantage of parallel structures and arithmetic algorithms to minimize resources and exceed performance of single or multiple purpose DSP devices. DSP designers using both ASIC and FPGA within the same design can optimize a system for performance beyond the capabilities of either separate circuit technology.Other applications that lend themselves to the hybrid ASIC/FPGA approach are designs that support multiple standards such as USB, FireWire and CameraLink, in a single device. Similarly, designs that are finalized, with the exception of any undefined features or emerging standards , are excellent candidates for this technology. Without the benefit of programmable logic, the designer must decide between taping-out the chip knowing that the PCI logic has a high probability for change, or waiting until the design requirements are firm –potentially impacting the end product’s schedule. With both programmable logic and ASIC working together on a single device, some situations like these can be accommodated. Other similar issues like differing geographic or I/O standards could also be incorporated within the FPGA cores, without requiring mask and fabrication updates for each change.Economics Play a Role in Using Hybrid DevicesWhile technical applications are emerging for the hybrid architecture, it is unlikely that design teams would utilize this new capability unless it is also economically viable. We will now explore the economics behind this new architecture.To realize the performance and density advantages of an ASIC, design teams must accept higher NREs and longer TATs than FPGAs. Unlike off-the-shelf FPGAs, each ASIC design requires a custom set of masks for silicon fabrication. The custom mask set allows circuitry and interconnections to be tailored to the requirements of eachunique application - yielding high performance and density. However, the cost of the mask sets is rapidly increasing (nearly doubling with each successive technology node). As a result, mask costs are becoming a significant portion of the per-die cost in many cases .For example, consider the case where a mask set costs $1,000,000. For applications where only 1,000 chips are required, each chip will cost well over $1000, since the mask cost (plus many other expenses) must be amortized over the volume of chips sold. As the volume requirements for this same ASIC rise, the effective cost of each die decreases.Conversely, FPGAs are standard products, where the mask charges for a small number of design passes are amortized over a large number of customers and chips, so the mask cost per chip sold is minimal. As a result, for each technology node there is a volume threshold, below which it’s more cost-effective to buy an FPGA chip vs. a smaller ASIC chip.TAT is another primary economic driver, having a direct impact on time -to-market for many applications. The time required for ASIC layout and fabrication is typically in the range 2-5 months - much longer than FPGAs, which generally require 1-4 weeks once a customer’s RTL is firm.These NRE and TAT issues are compounded by customers’needs for multiple design passes. Since each ASIC design requires a unique mask set, if a customer discovers logic errors or needs to add features after tape out, they must initiate another ASIC design pass, requiring additional NRE charges and silicon fabrication time. As silicon technologies progress and chip designs become more complex, design verification becomes increasingly difficult, and the chance for logic errors grows. In many cases, time to market pressures drive design teams to continue verification well into layout and sometimes beyond chip tape out. This increases the risk that logic updates will be required, and therefore cost per chip will increase.In summary, ASICs to date have offered higher performance in smaller chip sizes than FPGAs. However, the NRE for current technology nodes has rendered them very expensive for applications that require low quantities of chips - particularly when multiple designs or design passes are required.The Hybrid ASIC/FPGA SolutionEnter the hybrid ASIC/FPGA. Like an ASIC, the initial mask set must be purchased. But with the incorporation of FPGA cores into the ASIC, it is now possible to use the programmable circuitry to enable a single physical chip design to satisfy several different applications. This has the potential to eliminate multiple designs and in some cases, avoid costly respins. In the case where a customer requires several similar ASICs for a family of products, FPGA circuitry can be added to the base ASIC logic and be configured as needed to satisfy the multiple applications. Similarly, logic updates required to correct bugs discovered late in the verification process, or to accommodate changing market needs, can be handled with appropriately placed FPGA cores.The question must be asked; why embed FPGA into an ASIC if a two chip solutioncould achieve the same results? The answer is both technical and economic. Technically, for a certain class of applications, the embedded solution offers greater performance with lower power dissipation. By embedding the FPGA into the ASIC, signals that must propagate from the ASIC through the FPGA, then back to the ASIC can avoid four chip boundary delays, two card crossings, and the associated power dissipation. By keeping the ASIC to FPGA interconnections on the die, valuable ASIC I/O pins are also conserved.Economically, the embedded solution can be the less expensive option. As we will discuss, the FPGA fabric does not require any unique semiconductor processing above and beyond the base ASIC (unlike embedded flash or embedded DRAM). The resulting increase in ASIC cost is associated with the area occupied by the embedded FPGA core. In addition, the cost of assembly, test and packaging of a second chip are eliminated.In certain cases, it can be advantageous to include embedded FPGA on an ASIC if that FPGA eliminates the need for additional design passes. For example, at volumes of up to 250,000 pieces, 50K gates of embedded FPGA are cost effective. Similarly, 10K gates of embedded FPGA are cost effective versus a 2 pass ASIC design at volume of up to 1M. In general, if mask costs rise, volumes decrease, or more design passes are avoided, then the embedded FPGA approach becomes progressively more cost-effective compared to the ASIC approach. This is because at low volumes, the mask costs (and NRE) for additional design passes becomes a significant adder to per-chip cost, and this can outweigh the cost impact of the larger die area required by the embedded FPGA circuitry. This analysis leads us to conclude that technology and market trends have created a need for the development of the hybrid ASIC/FPGA product. Mask costs for advanced technologies are growing - making multiple design passes too costly for many applications. Fortunately, the technology advancements that have driven this trend have also opened up the potential to embed significant amounts of FPGA gates onto an ASIC die - enough to handle some of the design updates that would otherwise require additional design passes.Hybrid Offering OverviewThe IBM/Xilinx hybrid will first be available in IBM’s Cu-08 90nm ASIC offering, and will consist of three FPGA block sizes. Multiple blocks can be used on the same die and the sizes of blocks used can be mixed and matched. Table 1 shows the features of the various blocks.Table 1 Hybrid offeringEstimated Equivalent ASIC Gate Estimated Size Signal IO10K 3 mm238420K 5 mm251240K 7 mm2640Physically, the FPGA cores are being ported to the same semiconductor process that the ASIC product uses . The issues encountered in doing this porting are similar to those of other 3rd party IP ports. One of the largest challenges is full chip physical verification. Common design rules and transistor design points are critical in blending of IP between suppliers. Minor differences in design rules can be accommodated, assuming that checking decks and other verification software are able to handle the mixture of design rules. Designing these tools for increased flexibility will likely be needed as more companies share IP.To ensure that the FPGA can be integrated with the rest of the ASIC, agreements must be reached on metal stack options. In the case of the Cu-08 hybrid offering, 5 levels of metal were allocated to the FPGA blocks. This requires a re-layout of the FPGA cores, which were originally designed for a standard product with 9 levels of metal.As part of the re-layout, the power distribution of the FPGA blocks will be designed to integrate easily into the ASIC power distribution methodology. Care needs to be taken to ensure the power density required by the FPGA blocks are within the capability of the ASIC power supply routing. Due to extensive use of pass-gate structures, the FPGA blocks require standard 1.2V power supply levels, and are not operable below 1.0 Volt. For low-power applications, the FPGA blocks will make use of IBM’s Voltage Island capability, allowing them to operate at typical 1.2V levels, while the bulk of the chip operates at lower levels .The embedded FPGA blocks consist of programmable logic blocks, configuration logic, test interface logic, and simplified IO buffers for use in driving and receiving on-chip nets. Multiple end user configuration modes are supported including JTAG, serial and parallel modes. Individual cores can be configured asynchronously, allowing for “on-the-fly” reconfiguration.To design the new hybrid chips, a modified design methodology is being developed as shown in Figure 1. This hybrid design flow incorporates two proven design methodologies, the IBM ASIC flow and the XILINX FPGA flow, including several third party vendor synthesis options. The ASIC methodology integrates the embedded FPGA as a hard core with appropriate ASIC level models. The FPGA flow, including timing closure of the FPGA configuration, is done using XILINX tools. The designer has the choice of using constraints or detailed timing from the XILINX tool flow to close the ASIC timing at the FPGA core interfaces. If an FPGA configuration is known prior to the design of the ASIC, actual timing information can be passed to the ASIC tools from the FPGA tools. If the logic content of the embedded FPGA is unknown, the ASIC design can be completed using timing assertions and the embedded FPGA design can be completed later. If the embedded FPGA design is being reconfigured after the ASIC is in manufacturing, the final timing constraints from the completed ASIC can be passed to the FPGA tools for timing closure of the new FPGA design.ASIC DesignASIC RTL FPGA RTLThe logical design of the chip must be partitioned prior to final synthesis . The logic destined for an FPGA block is processed independently of the logic destined for ASIC logic. When multiple FPGA logic blocks are used, each must be designed and optimized independently.The ASIC physical design process treats the FPGA macro similarly to other large placeable objects, except for port assignment. During the initial ASIC design, the port assignment of each embedded FPGA block can be modified to accommodate floor planning or timing requirements. Once the final ASIC design is taped-out, the port assignments are fixed for subsequent FPGA configurations.The IBM ASIC methodology has been described in references, and the Xilinx FPGA methodology is described in reference . As to be expected, most of the issues in creating the hybrid methodology occur at the boundary between the two methodologies. The mechanics of the communications between the two systems can be accomplished by creating data translators, however, optimization between the two systems can be difficult, due to the significant architectural differences between traditional ASIC flows and traditional FPGA flows.Planning for future reconfigurationIn addition to partitioning, designers will face several other challenges in using embedded FPGAs. The basic question of how many FPGA gates to include is fundamental. Not only must the FPGA be sized sufficiently for the initial application, but enough unused FPGA resources must be left to support future logic configurations. This is a critical design-planning consideration, since once the hybrid chip has been implemented in silicon, a second (costly) mask set is required if the FPGA capacity is insufficient to handle the future configurations. To prevent this ASIC FLOW FPGA FLOW ASIC MASK DATA Bitstream Constraints Final Constreainsunfortunate situation, the design team must anticipate the potential growth in the logic which is to be implemented in the FPGA, as well as correctly estimate the embedded FPGA utilization that can be achieved. In addition, because the interconnect between the embedded FPGA and the ASIC is fixed in the mask set, any future interconnect requirements must be accounted for during the initial ASIC design. These are difficult architectural and design planning challenges that will require enhanced CAD tools to help in the design of tomorrow’s hybrid SOCs.For optimization tools to effectively partition hybrid designs, they must be able to correctly model the area, power and performance capabilities of both ASIC and FPGA circuit architectures. Since the architectures are so different in these characteristics, tools that are capable of efficiently and quickly assessing these tradeoffs will be needed to help the designers choose the best logic partition and specific circuit options for each portion of the design.Floorplanning and Physical DesignOnce the initial design is partitioned, the next step is to plan the physical layout of the chip. The hybrid architecture presents thedesign tools with some interesting challenges in this area. First, by their nature, the embedded FPGA cores are very metalintensive. The floorplan of the ASIC design must consider the global chip interconnect requirements when choosing the location for each core, to prevent chip wiring congestion. Similarly, the size of the FPGA s can have an impact on signal routing over the core itself, due to RC delays and noise considerations. The large cores may also interfere with pad buffer placement and routing in flip chip architectures. These present additional dimensions that floorplanning tools and designers need to consider and optimize.Next, the problem of port assignment must be solved. In traditional hierarchical design, the port assignment of a block involves simultaneously solving an optimization problem between two levels of hierarchy within the same circuit architecture. In the hybrid architecture, this optimization problem is more complex; spanning two tool sets and two circuit architectures.Proper port assignment is necessary at the ASIC level to remove routing congestion and also to aid in timing closure. However, this port assignment can have a significant impact on the optimal configuration of the FPGA. In today’s environment, this leads to a “chicken and egg problem”. Is the ASIC optimized first and then the resulting port assignment used in the FPGA, or is the FPGA optimized first, resulting in a potential impact to the ASIC design? A third option is to perform multiple iterations through each tool set, evaluating the results and identifying the best solution. What is needed is a port assignment algorithm that can find an optimum solution, by considering the congestion and timing issues at the ASIC design level as well as the configuration complexities of the FPGA .ASIC和FPGA架构的混合混合设计应用的出现通常使用ASIC方案的实施产生了更快，更小，功耗更低的FPGA技术设计，比实施。

通信专业的英文作文

通信专业的英文作文I chose to study communication because I've always been fascinated by how people connect with each other. From verbal communication to nonverbal cues, there's so much to learn about how we interact and share information.One of the things that drew me to this field is the ever-evolving nature of communication technology. From the invention of the telephone to the rise of social media,it's incredible to see how these advancements have changed the way we communicate.In my studies, I've learned about the power of storytelling and how it can be used to convey messages and evoke emotions. Whether it's through advertising, public speaking, or film, storytelling is a powerful tool that can bring people together and inspire action.Another aspect of communication that I find fascinating is the role of culture in shaping how we communicate.Different cultures have their own unique communication styles and norms, and understanding these differences is crucial for effective cross-cultural communication.I'm also interested in the impact of communication on relationships, both personal and professional. Effective communication is essential for building trust, resolving conflicts, and fostering collaboration, and I'm eager to explore how communication strategies can be used to strengthen relationships.Overall, the study of communication is a rich and diverse field that offers endless opportunities for learning and growth. I'm excited to continue exploring the many facets of communication and applying my knowledge to make a positive impact in the world.。

通信工程论文

Telecommunication is the transmission of signals over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, drums, semaphore, flags or heliograph. In modern times, telecommunication typically involves the use of electronic devices such as telephones, television, radio or computers. Early inventors in the field of telecommunication include Alexander Graham Bell, Guglielmo Marconi and John Logie Baird. Telecommunication is an important part of the world economy and the telecommunication industry's revenue was estimated to be $3.85 trillion in 2008.[1]Contents[hide]• 1 Historyo 1.1 Early telecommunicationso 1.2 Telegraph and telephoneo 1.3 Radio and televisiono 1.4 Computer networks and the Internet• 2 Key conceptso 2.1 Basic elementso 2.2 Analogue or digitalo 2.3 Networkso 2.4 Channelso 2.5 Modulation• 3 Society and telecommunicationo 3.1 Economic impact▪ 3.1.1 Microeconomics▪ 3.1.2 Macroeconomicso 3.2 Social impacto 3.3 Other impacts• 4 Telecommunication and government• 5 Modern operationo 5.1 Telephoneo 5.2 Radio and televisiono 5.3 The Interneto 5.4 Local area networks• 6 Telecommunication by region•7 See also•8 References•9 Further reading•10 External links[edit] HistoryFor more details on this topic, see History of telecommunication. [edit] Early telecommunicationsA replica of one of Chappe's semaphore towers in NalbachIn the Middle Ages, chains of beacons were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London signalling the arrival of Spanish ships.[2]In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system (or semaphore line) between Lille and Paris.[3]However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres (six to nineteen miles). As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880.[4][edit] Telegraph and telephoneThe first commercial electrical telegraph was constructed by Sir Charles Wheatstone and Sir William Fothergill Cooke and opened on 9 April 1839. Both Wheatstone and Cooke viewed their device as "an improvement to the [existing] electromagnetic telegraph" not as a new device.[5]Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837. His code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was successfully completed on 27 July 1866, allowing transatlantic telecommunication for the first time.[6]The conventional telephone now used worldwide was first patented by Alexander Graham Bell in March 1876.[7] That first patent by Bell was the master patent of the telephone, from which all other patents for electric telephone devices and features flowed. Credit for the invention of the electric telephone has been frequently disputed, and new controversies over the issue have arisen from time-to-time. As with other great inventions such as radio, television, light bulb, and computer, there were several inventors who did pioneering experimental work on voice transmission over a wire and improved on each other's ideas.The first commercial telephone services were set up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London.[8][9][edit] Radio and televisionIn 1832, James Lindsay gave a classroom demonstration of wireless telegraphy to his students. By 1854, he was able to demonstrate a transmission across the Firth of Tay from Dundee, Scotland to Woodhaven, a distance of two miles (3 km), using water as the transmission medium.[10] In December 1901, Guglielmo Marconi established wireless communication between St. John's, Newfoundland(Canada) and Poldhu, Cornwall(England), earning him the 1909 Nobel Prize in physics (which he shared with Karl Braun).[11] However small-scale radio communication had already been demonstrated in 1893 by Nikola Tesla in a presentation to the National Electric Light Association.[12]On 25 March 1925, John Logie Baird was able to demonstrate the transmission of moving pictures at the London department store Selfridges. Baird's device relied upon the Nipkow disk and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning 30 September 1929.[13]However, for most of the twentieth century televisions depended upon the cathode ray tube invented by Karl Braun. The first version of such a televisionto show promise was produced by Philo Farnsworth and demonstrated to his family on 7 September 1927.[14][edit] Computer networks and the InternetOn 11 September 1940, George Stibitz was able to transmit problems using teletype to his Complex Number Calculator in New York and receive the computed results back at Dartmouth College in New Hampshire.[15] This configuration of a centralized computer or mainframe with remote dumb terminals remained popular throughout the 1950s. However, it was not until the 1960s that researchers started to investigate packet switching— a technology that would allow chunks of data to be sent to different computers without first passing through a centralized mainframe. A four-node network emerged on 5 December 1969; this network would become ARPANET, which by 1981 would consist of 213 nodes.[16]ARPANET's development centred around the Request for Comment process and on 7 April 1969, RFC 1 was published. This process is important because ARPANET would eventually merge with other networks to form the Internet and many of the protocols the Internet relies upon today were specified through the Request for Comment process. In September 1981, RFC 791 introduced the Internet Protocol v4 (IPv4) and RFC 793 introduced the Transmission Control Protocol(TCP) —thus creating the TCP/IP protocol that much of the Internet relies upon today.However, not all important developments were made through the Request for Comment process. Two popular link protocols for local area networks(LANs) also appeared in the 1970s. A patent for the token ring protocol was filed by Olof Soderblom on 29 October 1974 and a paper on the Ethernet protocol was published by Robert Metcalfe and David Boggs in the July 1976 issue of Communications of the ACM.[17][18][edit] Key conceptsA number of key concepts reoccur throughout the literature on modern telecommunication systems. Some of these concepts are discussed below.[edit] Basic elementsA basic telecommunication system consists of three elements:• a transmitter that takes information and converts it to a signal;• a transmission medium that carries the signal; and,• a receiver that receives the signal and converts it back into usable information.For example, in a radio broadcast the broadcast tower is the transmitter, free space is the transmission medium and the radio is the receiver. Often telecommunication systems are two-way with a single device acting as both a transmitter and receiver or transceiver. For example, a mobile phone is a transceiver.[21]Telecommunication over a telephone line is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous receivers.[21][edit] Analogue or digitalSignals can be either analogue or digital. In an analogue signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values (for example ones and zeros). During transmission the information contained in analogue signals will be degraded by noise. Conversely, unless the noise exceeds a certain threshold, the information contained in digital signals will remain intact. Noise resistance represents a key advantage of digital signals over analogue signals.[22][edit] NetworksA network is a collection of transmitters, receivers and transceivers that communicate with each other. Digital networks consist of one or more routers that work together to transmit information to the correct user. An analogue network consists of one or more switches that establish a connection between two or more users. For both types of network, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from noise.[23][edit] ChannelsA channel is a division in a transmission medium so that it can be used to send multiple streams of information. For example, a radio station may broadcast at 96.1 MHz while another radio station may broadcast at 94.5 MHz. In this case, the medium has been divided by frequency and each channel has received a separate frequency to broadcast on. Alternatively, one could allocate each channel a recurring segment of time over which to broadcast—this is known as time-division multiplexing and is used in optic fibre communication.[24][23][edit] ModulationThe shaping of a signal to convey information is known as modulation. Modulation can be used to represent a digital message as an analogue waveform. This is known as keying and several keying techniques exist (these include phase-shift keying, frequency-shift keying and amplitude-shift keying). Bluetooth, for example, uses phase-shift keying to exchange information between devices.[25][26]Modulation can also be used to transmit the information of analogue signals at higher frequencies. This is helpful because low-frequency analogue signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analogue signal must be superimposed on a higher-frequency signal (known as the carrier wave) before transmission. There are several different modulation schemes available to achieve this (two of the most basic being amplitude modulation and frequency modulation). An example of this process is a DJ's voice being superimposed on a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel "96 FM").[27][edit] Society and telecommunicationTelecommunication has a significant social, cultural and economic impact on modern society. In 2006, estimates placed the telecommunication industry's revenue at $1.2 trillion (USD) or just under 3% of the gross world product(official exchange rate).[28]The following sections discuss the impact of telecommunication on society.[edit] Economic impact[edit] MicroeconomicsOn the microeconomic scale, companies have used telecommunication to help build global empires. This is self-evident in the case of online retailer but, according to academic Edward Lenert, even the conventional retailer Wal-Mart has benefited from better telecommunication infrastructure compared to its competitors.[29] In cities throughout the world, home owners use their telephones to organize many home services ranging from pizza deliveries to electricians. Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh's Narshingdi district, isolated villagers use cell phones to speak directly to wholesalers and arrange a better price for their goods. In Cote d'Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price.[30][edit] MacroeconomicsOn the macroeconomic scale, Lars-Hendrik Röll er and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth.[31] Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal.[32]Because of the economic benefits of good telecommunication infrastructure, there is increasing worry about the inequitable access to telecommunication services amongst various countries of the world—this is known as the digital divide. A 2003 survey by the International Telecommunication Union (ITU) revealed that roughly one-third of countries have less than 1 mobile subscription for every 20 people and one-third of countries have less than 1 fixed line subscription for every 20 people. In terms of Internet access, roughly half of all countries have less than 1 in 20 people with Internet access. From this information, as well as educational data, the ITU was able to compile an index that measures the overall ability of citizens to access and use information and communication technologies.[33]Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Nigeria, Burkina Faso and Mali received the lowest.[34][edit] Social impactTelecommunication has played a significant role in social relationships. Nevertheless devices like the telephone were originally advertised with an emphasis on the practical dimensions of the device (such as the ability to conduct business or order home services) as opposed to the social dimensions. It was not until the late 1920s and 1930s that the social dimensions of the device became a prominent theme in telephone advertisements. New promotions started appealing to consumers' emotions, stressing the importance of social conversations and staying connected to family and friends.[35]Since then the role that telecommunications has played in social relations has become increasingly important. In recent years, the popularity of social networking sites has increased dramatically. These sites allow users to communicate with each other as well as post photographs, events and profiles for others to see. The profiles can list a person's age, interests, sexuality and relationship status. In this way, these sites can play important role in everything from organising social engagements to courtship.[36]Prior to social networking sites, technologies like SMS and the telephone also had a significant impact on social interactions. In 2000, market research group Ipsos MORI reported that 81% of 15 to 24 year-old SMS users in the United Kingdom had used the service to coordinate social arrangements and 42% to flirt.[37][edit] Other impactsIn cultural terms, telecommunication has increased the public's ability to access to music and film. With television, people can watch films they have not seen before in their own home without having to travel to the video store or cinema. With radio and the Internet, people can listen to music they have not heard before without having to travel to the music store.Telecommunication has also transformed the way people receive their news.A survey by the non-profit Pew Internet and American Life Project found that when just over 3,000 people living in the United States were asked where they got their news "yesterday", more people said television or radio than newspapers. The results are summarised in the following table (the percentages add up to more than 100% because people were able to specify more than one source).[38]Telecommunication has had an equally significant impact on advertising. TNS Media Intelligence reported that in 2007, 58% of advertising expenditure in the United States was spent on mediums that depend upon telecommunication.[39] The results are summarised in the following table.[edit] Telecommunication and governmentMany countries have enacted legislation which conform to the International Telecommunication Regulations establish by the International Telecommunication Union(ITU), which is the "leading United Nations agency for information and communication technology issues."[40] In 1947, at the Atlantic City Conference, the ITU decided to "afford international protection to all frequencies registered in a new international frequency list and used in conformity with the Radio Regulation." According to the ITU's Radio Regulations adopted in Atlantic City, all frequencies referenced in the International Frequency Registration Board, examined by the board and registered on the International Frequency List "shall have the right to international protection from harmful interference."[41]From a global perspective, there have been political debates and legislation regarding the management of telecommunication andbroadcasting. The history of broadcasting discusses some of debates in relation to balancing conventional communication such as printing and telecommunication such as radio broadcasting.[42] The onset of World War II brought on the first explosion of international broadcasting propaganda.[42]Countries, their governments, insurgents, terrorists, and militiamen have all used telecommunication and broadcasting techniques to promote propaganda.[42][43]Patriotic propaganda for political movements and colonization started the mid 1930s. In 1936 the BBC would broadcast propaganda to the Arab World to partly counteract similar broadcasts from Italy, which also had colonial interests in the region.[42]Modern insurgents, such as those in the latest Iraq war, often use intimidating telephone calls, SMSs and the distribution of sophisticated videos of an attack on coalition troops within hours of the operation. "The Sunni insurgents even have their own television station, Al-Zawraa, which while banned by the Iraqi government, still broadcasts from Erbil, Iraqi Kurdistan, even as coalition pressure has forced it to switch satellite hosts several times." [43][edit] Modern operation[edit] TelephoneOptical fibre provides cheaper bandwidth for long distance communicationIn an analogue telephone network, the caller is connected to the person he wants to talk to by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the callerdials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. This electrical signal is then sent through the network to the user at the other end where it is transformed back into sound by a small speaker in that person's handset. There is a separate electrical connection that works in reverse, allowing the users to converse.[44][45]The fixed-line telephones in most residential homes are analogue —that is, the speaker's voice directly determines the signal's voltage. Although short-distance calls may be handled from end-to-end as analogue signals, increasingly telephone service providers are transparently converting the signals to digital for transmission before converting them back to analogue for reception. The advantage of this is that digitized voice data can travel side-by-side with data from the Internet and can be perfectly reproduced in long distance communication (as opposed to analogue signals that are inevitably impacted by noise).Mobile phones have had a significant impact on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile phones in 2005 totalled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m).[46] In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2% growth.[47]Increasingly these phones are being serviced by systems where the voice content is transmitted digitally such as GSM or W-CDMA with many markets choosing to depreciate analogue systems such as AMPS.[48]There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT-8 in 1988, the 1990s saw the widespread adoption of systems based on optic fibres. The benefit of communicating with optic fibers is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid at that time and today's optic fibre cables are able to carry 25 times as many telephone calls as TAT-8.[49]This increase in data capacity is due to several factors: First, optic fibres are physically much smaller than competing technologies. Second, they do not suffer from crosstalk which means several hundred of them can be easily bundled together in a single cable.[50] Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre.[51][52]Assisting communication across many modern optic fibre networks is a protocol known as Asynchronous Transfer Mode (ATM). The ATM protocolallows for the side-by-side data transmission mentioned in the second paragraph. It is suitable for public telephone networks because it establishes a pathway for data through the network and associates a traffic contract with that pathway. The traffic contract is essentially an agreement between the client and the network about how the network is to handle the data; if the network cannot meet the conditions of the traffic contract it does not accept the connection. This is important because telephone calls can negotiate a contract so as to guarantee themselves a constant bit rate, something that will ensure a caller's voice is not delayed in parts or cut-off completely.[53] There are competitors to ATM, such as Multiprotocol Label Switching (MPLS), that perform a similar task and are expected to supplant ATM in the future.[54][edit] Radio and televisionDigital television standards and their adoption worldwide.In a broadcast system, the central high-powered broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. The high-frequency wave sent by the tower is modulated with a signal containing visual or audio information. The receiver is then tuned so as to pick up the high-frequency wave and a demodulator is used to retrieve the signal containing the visual or audio information. The broadcast signal can be either analogue (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values).[21][55]The broadcast media industry is at a critical turning point in its development, with many countries moving from analogue to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. The chief advantage of digital broadcasts is that they prevent a number of complaints with traditional analogue broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. These occur because of the nature of analogue transmission,which means that perturbations due to noise will be evident in the final output. Digital transmission overcomes this problem because digital signals are reduced to discrete values upon reception and hence small perturbations do not affect the final output. In a simplified example, if a binary message 1011 was transmitted with signal amplitudes [1.0 0.0 1.0 1.0] and received with signal amplitudes [0.9 0.2 1.1 0.9] it would still decode to the binary message 1011 —a perfect reproduction of what was sent. From this example, a problem with digital transmissions can also be seen in that if the noise is great enough it can significantly alter the decoded message. Using forward error correction a receiver can correct a handful of bit errors in the resulting message but too much noise will lead to incomprehensible output and hence a breakdown of the transmission.[56][57]In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. All three standards use MPEG-2for video compression. ATSC uses Dolby Digital AC-3 for audio compression, ISDB uses Advanced Audio Coding (MPEG-2 Part 7) and DVB has no standard for audio compression but typically uses MPEG-1 Part 3 Layer 2.[58][59] The choice of modulation also varies between the schemes. In digital audio broadcasting, standards are much more unified with practically all countries choosing to adopt the Digital Audio Broadcasting standard (also known as the Eureka 147 standard). The exception being the United States which has chosen to adopt HD Radio. HD Radio, unlike Eureka 147, is based upon a transmission method known as in-band on-channel transmission that allows digital information to "piggyback" on normal AM or FM analogue transmissions.[60]However, despite the pending switch to digital, analogue television remains transmitted in most countries. An exception is the United States that ended analogue television transmission on the 12th of June 2009[61] after twice delaying the switch over deadline. For analogue television, there are three standards in use (see a map on adoption here). These are known as PAL, NTSC and SECAM. For analogue radio, the switch to digital is made more difficult by the fact that analogue receivers are a fraction of the cost of digital receivers.[62][63] The choice of modulation for analogue radio is typically between amplitude modulation (AM) or frequency modulation (FM). To achieve stereo playback, an amplitude modulated subcarrier is used for stereo FM.[edit] The InternetThe OSI reference modelThe Internet is a worldwide network of computers and computer networks that can communicate with each other using the Internet Protocol.[64] Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. Hence, any computer on the Internet can send a message to any other computer using its IP address. These messages carry with them the originating computer's IP address allowing for two-way communication. The Internet is thus an exchange of messages between computers.[65]As of 2008, an estimated 21.9% of the world population has access to the Internet with the highest access rates (measured as a percentage of the population) in North America (73.6%), Oceania/Australia (59.5%) and Europe (48.1%).[66] In terms of broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) led the world.[67]The Internet works in part because of protocols that govern how the computers and routers communicate with each other. The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more-or-less independently of other protocols. This allows lower-level protocols to be customized for the network situation while not changing the way higher-level protocols operate. A practical example of why this is important is because it allows an Internet browser to run the same code regardless of whether the computer it is running on is connected to the Internet through an Ethernet or Wi-Fi connection. Protocols are often talked about in terms of their place in the OSI reference model (pictured on the right), which emerged in 1983 as the first step in an unsuccessful attempt to build a universally adopted networking protocol suite.[68]。

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文档 The General Situation of AT89C51 The 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-51™ instruction 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-51™ Products • 4K Bytes of In-System Reprogrammable Flash Memory • Endurance: 1,000 Write/Erase Cycles • Fully Static Operation: 0 Hz to 24 MHz • Three-Level Program Memory Lock • 128 x 8-Bit Internal RAM • 32 Programmable I/O Lines • Two 16-Bit Timer/Counters • Six Interrupt Sources • Programmable Serial Channel • Low Power Idle and Power Down Modes The 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 文档 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 Diagram

Pin 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 文档 pull-ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. 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 being pulled 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 being pulled 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/source four 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 文档 listed below:

Port 3 also receives 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 ALE pulse 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