31-07-2012, 12:21 PM
Introduction to Digital Communications
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Preamble
Usage of the benefits of electrical communications in general and digital communications in particular, is an inseparable part of our daily experience now. Innumerable applications due to developments in digital communications have already started influencing our day-to-day activities directly or indirectly. Popularity of the Internet and television are only two of the most obvious examples to prove the point. In fact, it may not be an overstatement today that ‘information highways’ are considered as essential ingredients of national infrastructure in the march of a modern society. It is, however, pertinent to mention that isolated developments only in the field of electrical communications have not caused this phenomenon. Remarkable progresses and technical achievements in several related fields in electronics engineering and computer engineering have actually made applications of several principles and theories of communication engineering feasible for implementation and usage. The purpose of this web course, however, is narrow and specific to the principles of digital communications.
Block Schematic Description of a Digital Communication System
In the simplest form, a transmission-reception system is a three-block system, consisting of a) a transmitter, b) a transmission medium and c) a receiver. If we think of a combination of the transmission device and reception device in the form of a ‘transceiver’ and if (as is usually the case) the transmission medium allows signal both ways, we are in a position to think of a both-way (bi-directional) communication system. For ease of description, we will discuss about a one-way transmission-reception system with the implicit assumption that, once understood, the ideas can be utilized for developing / analyzing two-way communication systems. So, our representative communication system, in a simple form, again consists of three different entities, viz. a transmitter, a communication channel and a receiver.
A digital communication system has several distinguishing features when compared with an analog communication system. Both analog (such as voice signal) and digital signals (such as data generated by computers) can be communicated over a digital transmission system. When the signal is analog in nature, an equivalent discrete-time-discrete-amplitude representation is possible after the initial processing of sampling and quantization. So, both a digital signal and a quantized analog signal are of similar type, i.e. discrete-time-discrete-amplitude signals.
[attachment=29662]
Preamble
Usage of the benefits of electrical communications in general and digital communications in particular, is an inseparable part of our daily experience now. Innumerable applications due to developments in digital communications have already started influencing our day-to-day activities directly or indirectly. Popularity of the Internet and television are only two of the most obvious examples to prove the point. In fact, it may not be an overstatement today that ‘information highways’ are considered as essential ingredients of national infrastructure in the march of a modern society. It is, however, pertinent to mention that isolated developments only in the field of electrical communications have not caused this phenomenon. Remarkable progresses and technical achievements in several related fields in electronics engineering and computer engineering have actually made applications of several principles and theories of communication engineering feasible for implementation and usage. The purpose of this web course, however, is narrow and specific to the principles of digital communications.
Block Schematic Description of a Digital Communication System
In the simplest form, a transmission-reception system is a three-block system, consisting of a) a transmitter, b) a transmission medium and c) a receiver. If we think of a combination of the transmission device and reception device in the form of a ‘transceiver’ and if (as is usually the case) the transmission medium allows signal both ways, we are in a position to think of a both-way (bi-directional) communication system. For ease of description, we will discuss about a one-way transmission-reception system with the implicit assumption that, once understood, the ideas can be utilized for developing / analyzing two-way communication systems. So, our representative communication system, in a simple form, again consists of three different entities, viz. a transmitter, a communication channel and a receiver.
A digital communication system has several distinguishing features when compared with an analog communication system. Both analog (such as voice signal) and digital signals (such as data generated by computers) can be communicated over a digital transmission system. When the signal is analog in nature, an equivalent discrete-time-discrete-amplitude representation is possible after the initial processing of sampling and quantization. So, both a digital signal and a quantized analog signal are of similar type, i.e. discrete-time-discrete-amplitude signals.