Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Coupon-eligible converter box wikipedia , lookup
Oscilloscope types wikipedia , lookup
Opto-isolator wikipedia , lookup
Analog-to-digital converter wikipedia , lookup
Analog television wikipedia , lookup
Tektronix analog oscilloscopes wikipedia , lookup
Radio transmitter design wikipedia , lookup
Broadcast television systems wikipedia , lookup
Computer Networks Bhushan Trivedi, Director, MCA Programme, at the GLS Institute of Computer Technology, Ahmadabad © Oxford University Press 2011 Chapter 3 Data Communication Fundamentals © Oxford University Press 2011 The prerequisites to communication • • • • Bandwidth and Data Rate The frequency and the band The media effect on the bandwidth of signal The composite signals and Fourier components • Filters © Oxford University Press 2011 Other factors affecting the data rate • Analog or digital signaling. • Analog – Type of modulation – Amount of constellation points • Digital • number of levels © Oxford University Press 2011 Other factors affecting the data rate • Sensitivity of the receiver • Resistance of the media and thus its temperature • How the wires are structured and shielded © Oxford University Press 2011 Harmonics and composite wave © Oxford University Press 2011 Properties of a channel • More the bandwidth of the media, more the number of harmonics that can pass through the media. • Higher the data rate, less will be the number of harmonics that can pass through the media. • MDR of a channel = 2 × Bandwidth × log2 (signal levels) • MDR of a channel = Bandwidth × log2 (1 + S/N) © Oxford University Press 2011 Signal to noise ratio • S/N =10 log (Ps/Pn) • When Ps/Pn becomes 1 • MDR = Bandwidth × log2 (1+10 × log e 1) = Bandwidth × log 2 (1+0) = Bandwidth × log 2 1 =0 (as log21 = 0) © Oxford University Press 2011 Filtering a specific frequency © Oxford University Press 2011 Differentiating Analog and Digital • Analog and Digital Signaling – Analog Signaling – Digital signaling – Difference between Analog and Digital Signaling • Analog and Digital Transmission – Introduction to Transmission – Analog Transmission – Digital transmission • Digital signaling and errors © Oxford University Press 2011 Digital and analog wave © Oxford University Press 2011 Periodic waves, digital and analog © Oxford University Press 2011 A periodic wave © Oxford University Press 2011 Digital signaling and bit rate If we use 2n different voltage signals, then bit rate = baud rate × n If we use n voltage signals, then bit rate = baud rate × log2 n © Oxford University Press 2011 Characteristics of Digital Signaling • • • • Square waveforms Limited discrete values of voltage levels Need more bandwidth Noise can be completely removed © Oxford University Press 2011 Repeater reshapes, amplifier amplifies © Oxford University Press 2011 Noise addition to waves © Oxford University Press 2011 Signaling is different than transmission • Analog and digital transmission • We can use digital signaling irrespective of whether the transmitted data is analog (voice or video) or digital (zeros and ones) • Similarly, analog signaling can be used for both analog and digital transmission • Coding mechanisms © Oxford University Press 2011 Modulation • • • • • • Amplitude modulation Frequency modulation Phase Modulation Modulation in Practice Modulation in cable TV Modulation in ADSL © Oxford University Press 2011 Amplitude modulation © Oxford University Press 2011 Amplitude modulation © Oxford University Press 2011 A square wave to represent bits © Oxford University Press 2011 A distorted square signal © Oxford University Press 2011 Frequency modulation © Oxford University Press 2011 Phase © Oxford University Press 2011 Phase change to indicate bit © Oxford University Press 2011 Constellation pattern for QPSK © Oxford University Press 2011 QAM-16 constellation pattern © Oxford University Press 2011 Frequency bands used in cable TV transmission © Oxford University Press 2011 Multiplexing • Multiplexing and de-multiplexing – Time Division Multiplexing – Frequency division multiplexing © Oxford University Press 2011 Switching © Oxford University Press 2011 Routing © Oxford University Press 2011 Transmission Errors • Attenuation • Distortion • Noise © Oxford University Press 2011