One of the prerequisites for the development of telecommunication services is the
understanding of the propagation of the waves, eIther acoustic, electromagnetic,
radio or light waves, which are used for the transmission of information.
In this work, we shall limit ourselves to the study of radio waves: this term
apply to the electromagnetic waves used in radio communications. Their
frequency spectrum is very broad, and is divided into the following frequency
bands : ELF waves (f < 3 kHz), VLF (3-30 kHz), LF waves (30-300 kHz), MF
waves (300-3000 kHz), HF (3-30 MHz), VHF waves (30-300 MHz), UHF waves
(300-3000 MHz), SHF waves (3-30 GHz), EHF waves (30-300 GHz) and sub-
EHF waves (300-3000 GHz).
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.
Notwithstanding its infancy, wireless mesh networking (WMN) is a hot and
growing field. Wireless mesh networks began in the military, but have since
become of great interest for commercial use in the last decade, both in local
area networks and metropolitan area networks. The attractiveness of mesh
networks comes from their ability to interconnect eIther mobile or fixed
devices with radio interfaces, to share information dynamically, or simply to
extend range through multi-hopping.
Welcome to the world of wireless communications and the logical extension
to the broadband architectures that are emerging as the future of the
industry. No aspect of communications will be untouched by the wireless
interfaces;no part of our working environment will be left untouched eIther.
As the world changes and the newer technologies emerge, we can expect to
see more in the line of untethered communications than in the wired inter-
faces.
n the first part of this book, we give an introduction to the basic applications of wireless com-
munications, as well as the technical problems inherent in this communication paradigm. After a
brief history of wireless, Chapter 1 describes the different types of wireless services, and works
out their fundamental differences. The subsequent Section 1.3 looks at the same problem from
a different angle: what data rates, ranges, etc., occur in practical systems, and especially, what
combination of performance measures are demanded (e.g., what data rates need to be transmitted
over short distances; what data rates are required over long distances?) Chapter 2 then describes
the technical challenges of communicating without wires, putting special emphasis on fading and
co-channel interference. Chapter 3 describes the most elementary problem of designing a wireless
system, namely to set up a link budget in eIther a noise-limited or an interference-limited system.
After studying this part of the book, the reader should have an overview of different types of
wireless services, and understand the technical challenges involved in each of them. The solutions
to those challenges are described in the later parts of this book.
This chapter provides extensive coverage of existing mobile wireless technologies. Much of the
emphasis is on the highly anticipated 3G cellular networks and widely deployed wireless local
area networks (LANs), as the next-generation smart phones are likely to offer at least these two
types of connectivity. Other wireless technologies that eIther have already been commercialized or
are undergoing active research and standardization are introduced as well. Because standardization
plays a crucial role in developing a new technology and a market, throughout the discussion
standards organizations and industry forums or consortiums of some technologies are introduced.
In addition, the last section of this chapter presents a list of standards in the wireless arena.
There’s a story (it’s eIther an old vaudeville joke
or a Zen koan) in which a fisherman asks a fish,
“What’s the water like down there?” and the
fish replies “What is water?” If the story is just
a joke, the point is to make us laugh; but if it’s
a koan, the point is that the most obvious and
ubiquitous parts of our immediate environ-
ment are, paradoxically, often the easiest to
overlook.
This book is eIther ambitious, brave, or reckless approaching
a topic as rapidly evolving as industrial control system (ICS)
security. From the advent of ICS-targeted malicious software
such as Stuxnet to the advanced persistent threats posed by
organized crime and state-sponsored entities, ICS is in the
crosshairs and practices and controls considered safe today
may be obsolete tomorrow. Possibly more so than in more
traditional IT security, because of the differences inherent in
ICS.
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If register should be written or read.This value is passed to the calback functions which support eIther reading or writing register values. Writing means that the application registers should be updated and reading means that the modbus protocol stack needs to know the current register values.See also: eMBRegHoldingCB(), eMBRegCoilsCB(), eMBRegDiscreteCB() and eMBReglnputCB().Enumeration values: MB_REG_READ Read register values and pass to protocol stack.MB_REG_WRITE Update register values.Note: Note all ports implement this function.A port which wants to get an callback must define the macro MB_PORT_HAS_CLOSE to 1.Returns: If the resources where released it return eMBErrorCode:: MB_ENOERR. If the protocol stack is not in the disabled state it returns eMBErrorCode:: MB_EILLSTATE.Examples: LINUX/demo.c, MCF5235TCP/demo.c, STR71XTCP/demo.c, WIN32/demo. cpp, and WIN32TCP/demo. cpp.his function disables processing of Modbus frames.Returns: If the protocol stack has been disabled
