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Software Receiver Design : Build Your Own Digital Communications System in Five Easy Steps is structured like an onion. The first chapter presentsa sketch of a digital radio; the first layer of the onion. The second chapter peels back the onionto reveal another layer that fills in details and demystifies various pieces of the design.Successive chapters then revisit the same ideas, each layer adding depth and precision. The first functional(though idealized) receiver appears in [link] . Then the idealizing assumptions are stripped away one at a timethroughout the remaining chapters, culminating in a sophisticated receiver design in the final chapter. "The Complete Onion" outlines the five layers of the receiver onion and provides an overview of the orderin which topics are discussed.

The fundamental problem of communication is that of reproducing at one point either exactly or approximately a messageselected at another point.

—C. Shannon, “A Mathematical Theory of Communication,” Bell System Technical Journal , Vol. 27, 1948

A digital radio

The fundamental principles of telecommunications have remained much the same since Shannon's time.What has changed, and is continuing to change, is how those principles are deployed in technology.One of the major ongoing changes is the shift from hardware to software—and Software Receiver Design reflects this trend by focusing on the design of a digital software-defined radio that you will implement in M atlab .

“Radio” does not literally mean the AM/FM radio in your car, it represents any through-the-airtransmission such as television, cell phone, or wireless computer data, though many of the same ideas arealso relevant to wired systems such as modems, cable TV, and telephones. “Software defined” means that key elementsof the radio are implemented in software. Taking a “software defined” approach mirrorsthe trend in modern receiver design in which more and more of the system is designed and built in reconfigurablesoftware, rather than in fixed hardware. The fundamental concepts behind thetransmission are introduced, demonstrated, (and hopefully understood) through simulation. For example, when talking about how totranslate the frequency of a signal, the procedures are presented mathematicallyin equations, pictorially in block diagrams, and then concretely as short M atlab programs.

Our educational philosophy is that it is better to learn by doing: to motivate study withexperiments, to reinforce mathematics with simulated examples, to integrate concepts by “playing”with the pieces of the system. Accordingly, each of the later chapters is devotedto understanding one component of the transmission system, and each culminates in a series of tasks that askyou to “build” a particular version of that part of the communication system. In the final chapter,the parts are combined to form a full receiver.

We try to present the essence of each system component in the simplest possible form.We do not intend to show all the most recent innovations (though our presentation andviewpoint are modern), nor do we intend to provide a complete analysis of the various methods.Rather, we ask you to investigate the performance of the subsystems, partly through analysis and partlyusing the software code that you have created and that we have provided. We do offer insight into all piecesof a complete transmission system. We present the major ideas of communications via a small number ofunifying principles such as transforms to teach modulation, and recursive techniques to teach synchronization and equalization.We believe that these basic principles have application far beyond receiver design, and so the time spent mastering themis well worth the effort.

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Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
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