The digital dilemma: Telecoms fi rms prepare for the future is an Economist Intelligence Unit (EIU) report commissioned by WIPRO. The report strives to identify the key issues that companies within the telecoms sector are facing as they attempt to reshape their businesses to compete in a more digitised world.
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Wireless communication has become increasingly important not only for professional appli- cations but also for many fields in our daily routine and in consumer electronics. In 1990, a mobile telephone was still quite expensive, whereas today most teenagers have one, and they use it not only for calls but also for data transmission. More and more computers use wireless local area networks (WLANs), and audio and television broadcasting has become digital.
标签： Applications and Theory OFDM CDMA of
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Wireless communications has become a field of enormous scientific and economic interest. Recent success stories include 2G and 3G cellular voice and data services (e.g., GSM and UMTS), wireless local area networks (WiFi/IEEE 802.11x), wireless broadband access (WiMAX/IEEE 802.16x), and digital broadcast systems (DVB, DAB, DRM). On the physical layer side, traditional designs typically assume that the radio channel remains constant for the duration of a data block. However, researchers and system designers are increasingly shifting their attention to channels that may vary within a block. In addition to time dispersion caused by multipath propagation, these rapidly time-varying channels feature frequency dispersion resulting from the Doppler effect. they are, thus, often referred to as being “doubly dispersive.”
标签： Time-Varying Channels
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The information age is exploding around us, giving us access to dizzying amounts of data the instant it becomes available. Smart phones and tablets provide an untethered experience that offers stream- ing video, audio, and other media formats to just about any place on the planet. Even people who are not “computer literate” use Facebook to catch up with friends and family, use Google to research a new restaurant choice and print directions to get there, or Tweet their reactions once they have sampled the fare. The budding Internet-of-things will only catalyze this data eruption. The infrastructure supporting these services is also growing exponentially, and the technology that facilitates this rapid growth is virtualization.
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Wavelength division multiplexing (WDM) refers to a multiplexing and transmission scheme in optical telecommunications fibers where different wavelengths, typically emitted by several lasers, are modulated independently (i.e., they carry independent information from the transmitters to the receivers). These wavelengths are then multiplexed in the transmitter by means of passive WDM filters, and likewise they are separated or demultiplexed in the receiver by means of the same filters or coherent detection that usually involves a tunable local oscillator (laser).
标签： Multiplexing Wavelength Division
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The use of optical free-space emissions to provide indoor wireless commu- nications has been studied extensively since the pioneering work of Gfeller and Bapst in 1979 [1]. These studies have been invariably interdisciplinary in- volving such far flung areas such as optics design‚ indoor propagation studies‚ electronics design‚ communications systems design among others. The focus of this text is on the design of communications systems for indoor wireless optical channels. Signalling techniques developed for wired fibre optic net- works are seldom efficient since they do not consider the bandwidth restricted nature of the wireless optical channel.
标签： Communication Wireless Optical Systems
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A wireless ad-hoc network is a wireless network deployed without any infrastructure. In such a network, there is no access point or wireless router to forward messages among the computing devices. Instead, these devices depend on the ad-hoc mode of their wireless net‐ work interface cards to communicate with each other. If the nodes are within the transmis‐ sion range of the wireless signal, they can send messages to each other directly. Otherwise, the nodes in between will forward the messages for them. Thus, each node is both an end system and a router simultaneously.
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Digital radios have undergone an astonishing evolution in the last century. Born as a set of simple and power-hungry electrical and electromechanical devices for low data rate transmission of telegraph data in the Marconi age, they have transformed, thanks to substantial advances in electronic technology, into a set of small, reliable and sophisticated integrated devices supporting broadband multimedia communications. This, however, would not have been possible unless significant progress had been made in recent decades in the field of signal processing algorithms for baseband and passband signals. In fact, the core of any modern digital radio consists of a set of algorithms running over programmable electronic hardware. This book stems from the research and teaching activities of its co-authors in the field of algorithmic techniques for wireless communications. A huge body of technical literature has accumulated in the last four decades in this area, and an extensive coverage of all its important aspects in a single textbook is impossible. For this reason, we have selected a few important topics and, for ease of reading, organized them into two parts.
标签： Communications Algorithmic Techniques Wireless
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Static electricity is the most ancient form of electricity known to humans. More than 2000 years ago, the Greeks recognized the attraction between certain mate- rials when they were rubbed together; indeed, the word electricity comes from the Greek elektron, which means amber. During the seventeenth and eighteenth centuries, several key experiments were conducted to understand and measure static electricity. But the discovery of electromagnetism and its formidable break- through has rapidly outgrown interest in static electricity. Even today, where the industrial applications of static electricity are not insignificant, they cannot compare with those of electromagnetism and electrodynamics.
标签： Understand Discharge Electro Static
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Recent advancements in nanotechnology (NT) materials and growth of micro/ nanotechnology have opened the door for potential applications of microelectro- mechanical systems (MEMS)- and NT-based sensors and devices. Such sensors and devices are best suited for communications, medical diagnosis, commercial, military, aerospace, and satellite applications. This book comes at a time when the future and well-being of Western industrial nations in the twenty-first century’s global eco- nomy increasingly depend on the quality and depth of the technological innovations they can commercialize at a rapid pace.
标签： MEMS
上传时间： 2020-06-06
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