The roots of this book were planted about a decade ago. At that time, I became increasingly convinced that wide-area and metropolitan-area networks, where much of my group’s research has been centered at that time, were in good shape. Although research in these fields was (and still is) needed, that’s not where the networking bottleneck seemed to be. Rather, the bottleneck was (and still is in many places) in the access networks, which choked users’ access to information and services. It was clear to me that the long-term solution to that problem has to involve optical fiber access networks.
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The ever-increasing demand for private and sensitive data transmission over wireless net- works has made security a crucial concern in the current and future large-scale, dynamic, and heterogeneous wireless communication systems. To address this challenge, computer scientists and engineers have tried hard to continuously come up with improved crypto- graphic algorithms. But typically we do not need to wait too long to find an efficient way to crack these algorithms. With the rapid progress of computational devices, the current cryptographic methods are already becoming more unreliable. In recent years, wireless re- searchers have sought a new security paradigm termed physical layer security. Unlike the traditional cryptographic approach which ignores the effect of the wireless medium, physi- cal layer security exploits the important characteristics of wireless channel, such as fading, interference, and noise, for improving the communication security against eavesdropping attacks. This new security paradigm is expected to complement and significantly increase the overall communication security of future wireless networks.
标签： Communications Physical Security Wireless Layer in
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Wireless means different things to different people. For this book, it refers to the radio systems that provide point-to-point, point-to-multipoint, and Earth-space communications over transmission links that propagate outside buildings through the lower atmosphere. Wireless systems are being built that provide data transmission between computers and other devices on one’s own desk. These are part of the wireless world but not the part where, except for interference perhaps, the atmosphere has any influence. The intent of this book is to provide a description of the physical phenomena that can affect propagation through the atmosphere, present sample measurements and statistics, and provide models that system designers can use to calculate their link budgets and estimate the limitations the atmosphere may place on their design.
标签： Communication Propagation Handbook Wireless for
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This book was born from the perception that there is much more to spectrum use and sharing than one sees reflected in publications, whether academic, commercial or political. the former – in good research style – tend towards reductionism and concentrate on specific, detailed aspects. commercial publications tend to empha- size the positive aspects and they tend to put promise above practice. Given the ever increasing pace of technology development and recent successes of new wireless technologies, some pundits predict large-scale spectrum scarcity, potentially lead- ing to economic catastrophe. Although economic theory has a hard time explaining recent events that shook the world economy, the notion of spectrum scarcity is intui- tively acceptable, even if not correct or immediately relevant.
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Until the mid-1990s most readers would probably not have even come across the term soft- ware defined radio (SDR), let alone had an idea what it referred to. Since then SDR has made the transition from obscurity to mainstream, albeit still with many different understandings of the terms – software radio, software defined radio, software based radio, reconfigurable radio.
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Radio frequency spectrum is a scarce and critical natural resource that is utilized for many services including surveillance, navigation, communication, and broadcast- ing. Recent years have seen tremendous growth in the use of spectrum especially by commercial cellular operators. Ubiquitous use of smartphones and tablets is one of the reasons behind an all-time high utilization of spectrum. As a result, cellular operators are experiencing a shortage of radio spectrum to meet bandwidth demands of users. On the other hand, spectrum measurements have shown that much spectrum not held by cellular operators is underutilized even in dense urban areas. This has motivated shared access to spectrum by secondary systems with no or minimal impact on incumbent systems. Spectrum sharing is a promising approach to solve the problem of spectrum congestion as it allows cellular operators access to more spectrum in order to satisfy the ever-growing bandwidth demands of commercial users.
标签： Spectrum Sharing Between Radars
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The idea for this book was born during one of my project-related trips to the beautiful city of Hangzhou in China, where in the role of Chief Architect I had to guide a team of very young, very smart and extremely dedicated software developers and verification engineers. Soon it became clear that as eager as the team was to jump into the coding, it did not have any experience in system architecture and design and if I did not want to spend all my time in constant travel between San Francisco and Hangzhou, the only option was to groom a number of local junior architects. Logically, one of the first questions being asked by these carefully selected future architects was whether I could recommend a book or other learning material that could speed up the learning cycle. I could not. Of course, there were many books on various related topics, but many of them were too old and most of the updated information was either somewhere on the Internet dispersed between many sites and online magazines, or buried in my brain along with many years of experience of system architecture.
标签： Telecommunication Gateways System Design for
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In Helsinki during a visiting lecture, an internationally well-known professor in communica- tionssaid,‘Inthecommunicationssocietywehavemanagedtoconvertourproposalsandideas to real products, not like in the control engineering society. They have very nice papers and strong mathematics but most of the real systems still use the old PID controllers!’. As our background is mainly in control as well as communications engineering, we know that this thought is not very accurate. We agree that most of the practical controllers are analog and digital PID controllers, simply because they are very reliable and able to achieve the required control goals successfully. Most of the controllers can be explained in terms of PID. The reasons behind this impressive performance of PID will be explained in Chapter 2.
标签： Communications Engineering Wireless Systems in
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Before I can present design concepts or tactical wireless communications and network challenges, I feel the need to mention the challenges of writing for a field where some information is not available for public domain and cannot be included in this book’s context. Another challenge is the use of military jargon and the extensive number of abbreviations (and abbreviations of abbreviations!) in the field. Engineering books are naturally dry, and I have attempted to make it light by presenting the concepts in layman’s terms before diving into the technical details. I am structuring this book in such a way as to make it useful for a specialized graduate course in tactical communications and networking, or as a reference book in the field.
标签： Communications Tactical Networks Wireless and
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The first edition of this book was published in 1992. Nine years later it had become clear that a second edition was required because of the rapidly changing nature of telecommunication. In 1992, the Internet was in existence but it was not the household word that it is in the year 2001. Cellular telephones were also in use but they had not yet achieved the popularity that they enjoy today. In the current edition, Chapter 1 has been revised to include a section on the Internet. Chapter 10 is new and it covers the facsimile machine; I had overlooked this important tele- communication device in the first edition. Chapter 11 is also new and it describes the pager, the cordless telephone and the cellular telephone system. These are examples of a growing trend in telecommunications to go ‘‘wireless’’.
标签： Telecommunication Circuit Design 2nd
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