PDF Drive is your search engine for PDF files. As of today we have 78,, eBooks for Modern Digital And Analog Communication Systems 4ed by Lathi. of digital communication systems that are unique to those systems. That is systems required the architectural principles of information theory. ples in the analysis and design of digital communication systems. Since digital to digital communications, the text hardly considers actual physical realiza-.
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PDF | Digital communication has proliferated in a big way in the previous years. Digital communication is the physical transfer of data over. Types of Digital Communication Systems. Signal Type. Transmission. Example. Analog. Analog. Classical telephony. Analog. Digital. PCM TDM. Digital. Analog. Demodulation and Detection, A Vectorial View of Signals and Noise, The Basic SNR Parameter for Digital Communication Systems, .
However not only does time axis need to be discretized, the analog amplitude values of the samples also must be quantized. Since this step is a many-to-one mapping, it inherently produces a distortion or a loss. Various quantizers to minimize this distortion, with a performance measure of signal-to-quantization noise power ratio, have been analyzed and discussed. The final step, encoding, is to map quantized sample values to a set of discrete symbols, typically a sequence of binary digits called variously a binary string, binary word, or simply codeword. The codeword however is an abstract quantity, i. To transmit the information that a codeword represents one needs to map each bit to an electrical signal or waveform. As has been mentioned several times this mapping is called modulation and it, along with demodulation, is the subject of succeeding chapters.
The quantization and encoding discussed in this chapter go under the general topic of source coding. But some sources, as pointed out the keyboard, are already discrete in nature.
Traditional source coding was concerned primarily with this step. Some aspects of this are presented in the problems at the end of the chapter but the interested reader is referred to the literature for a more comprehensive treatment.
Estimate the maximum recording duration for each of the following sources, using a straightforward PCM representation. Above are deterministic signals and most of you are quite familiar with their crest factors. Hint: For parts d , e and f , the peak value appears to be infinity. Optimal quantizer Consider a message source that with confidence you feel is well modelled by a first order Laplacian density function, i.
You wish to design an L-level optimum quantizer for the message. Derive equation for Tl for the given message source. Hint: Since fm m is symmetric about zero, one needs to worry only about the positive m axis, i.
However, it should be pointed out that bits are just abstractions and there is nothing physical about the bits. Start on.
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Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. Digital communication system 1. Digital communication is one of the most commonly used modes of communication now a days. Instead he opted an easier and cheaper mode to communicate his idea. He sent an email marking a cc to all the participants, inviting them for the meeting.
This is an example of Digital communication where the information was sent electronically. The information can reach the recipient within a fraction of a second. An individual no longer has to wait to personally meet the other individual and share his information. Communications Techniques Digital communication covers a broad area of communications techniques including: Building blocks of Digital Communication System 7. For this we need source encoder.
We should like to use as few binary digits as possible to represent the signal. In such a way this efficient representation of the source output results in little or no redundancy. This sequence of binary digits is called information sequence. The information sequence is passed through the channel encoder.
The purpose of the channel encoder is to introduced, in controlled manner, some redundancy in the binary information sequence that can be used at the receiver to overcome the effects of noise and interference encountered in the transmission on the signal through the channel. Building blocks of Digital Communication System 9. The binary sequence is passed to digital modulator which in turns convert the sequence into electric signals so that we can transmit them on channel.
The digital modulator maps the binary sequences into signal wave forms , for example if we represent 1 by sin x and 0 by cos x then we will transmit sin x for 1 and cos x for 0. The communication channel is the physical medium that is used for transmitting signals from transmitter to receiver. The digital demodulator processes the channel corrupted transmitted waveform and reduces the waveform to the sequence of numbers that represents estimates of the transmitted data symbols.