The first practical examples of mobile communications were used in many countries like the USA, the UK and Germany in military services, and played a significant role in the First World War to transfer important information from the front to headquarters to take further actions. Good and secure wireless communications were an important need for all military services – army, navy and air force. In this respect, the Second World War was a big experimental battlefield for the development and evolution of mobile RADio. It was in the interests of governments that after the Second World War the military investment should be paid back by civilian use, and all western European countries started their so-called first generation of mobile communication networks.
标签： Multimedia Business Mobile The
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When thinking about mobile RADio engineers there is a tendency to assume that the engineering function relates solely to the technical aspects of the network, such as the equipment design or the network design. That is certainly a key part of the role of a mobile RADio engineer. However,increasinglyengineersarerequiredtointeractwithprofession- als from other divisions.
标签： Communications Professional Complete Wireless The
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Some tine ago it become apparent the the first edition of this book was rapidly approaching its sell-by date,since many aspects needed revise.There were two obvious courses of action : to forget the whole thing and concentrate my energies on other pursuits such as golf or fishing, or to embark on a new edition.For several reasons Iwas persuaded that a new edition was a worthwhile endeavour;many people had made complimentary remakrs or written complinentary letters about the first edition and I understood that it had become a recommended text for several postgraduate coures.
标签： TMobile RADio Propagation Channel
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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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Public telephone operators and new independent wireless operators through- out the world are deploying wireless access in an effort to drastically reduce delivery costs in the most expensive part of the network?the local loop. Available RADio technology enables both existing and new entrants to access subscribers in a rapid manner and deliver their basic telephony products and broadband-enhanced services.
标签： Transmission Handbooks Systems Design
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Recent advances in wireless communication technologies have had a transforma- tive impact on society and have directly contributed to several economic and social aspects of daily life. Increasingly, the untethered exchange of information between devices is becoming a prime requirement for further progress, which is placing an ever greater demand on wireless bandwidth. The ultra wideband (UWB) system marks a major milestone in this progress. Since 2002, when the FCC allowed the unlicensed use of low-power, UWB RADio signals in the 3.1–10.6GHz frequency band, there has been significant synergistic advance in this technology at the cir- cuits, architectural and communication systems levels. This technology allows for devices to communicate wirelessly, while coexisting with other users by ensuring that its power density is sufficiently low so that it is perceived as noise to other users.
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The continuing explosive growth in mobile communication is demanding more spectrally efficient RADio access technologies than the prevalent second generation (2G) systems such as GSM to handle just the voice traffic. We are already witnessing high levels of mobile penetration exceeding 70% in some countries. It is anticipated that by 2010 more than half of all communications will be carried out by mobile cellular networks. On the other hand, the information revolution and changing life habits are bringing the requirement of commu- nicating on a multimedia level to the mobile environment. But the data handling capabilities and flexibility of the 2G cellular systems are limited.
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An acronym for Multiple-In, Multiple-Out, MIMO communication sends the same data as several signals simultaneously through multiple antennas, while still utilizing a single RADio channel. This is a form of antenna diversity, which uses multiple antennas to improve signal quality and strength of an RF link. The data is split into multiple data streams at the transmission point and recombined on the receive side by another MIMO RADio configured with the same number of antennas. The receiver is designed to take into account the slight time difference between receptions of each signal, any additional noise or interference, and even lost signals.
标签： Understanding_the_Basics_of_MIMO
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As I have increasingly moved away from the world of research and into thatofmanagementandbusiness,ithasbecomeapparenttomethatthere are many people from a nontechnical background who need to under- standcellularsystemsinmoredetailinordertobeabletoperformtheir job,beitanalyzingfinancialinvestments,runningcallcenters,ormarket- ing cellular services.
标签： Understanding Cellular RADio
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Visible light communications (VLC) is the name given to an optical wireless communication system that carries information by modulating light in the visible spectrum (400–700 nm) that is principally used for illumination [1–3]. The communications signal is encoded on top of the illumination light. Interest in VLC has grown rapidly with the growth of high power light emitting diodes (LEDs) in the visible spectrum. The motivation to use the illumination light for communication is to save energy by exploiting the illumination to carry information and, at the same time, to use technology that is “green” in comparison to RADio frequency (RF) technology, while using the existing infrastructure of the lighting system.
标签： Communication Visible Light
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