Faculty of Engineering Handbook

DIGITAL COMMUNICATIONS AND TELEPHONY


Subject Code:	ETM3066
Objective:	To develop understanding of basic principles in digital communications. To expose students to fundamental and working principles of telephone system.
Pre-Requisite:	ETM2016 Analog Communications
Credit Hours:	3
Contact Hours:	55 hours (lectures, tutorials and laboratory experiments)
Assessment:	Lab: 10% Test/Quiz: 15% Tutorial/Assignment: 15% Final Examination: 60%
Laboratory:	1. Pulse Code Modulation 2. Bandpass Digital Modulation
References:	H. P. E. Stern and S. A. Mahmound, Communication Systems: Analysis and Design. Upper Saddle River, NJ: Prentice-Hall, 2004. S. Haykin, Communication Systems, 4th ed. New York: Wiley, 2001. L. W. Couch, II, Digital and Analogue Communication Systems, Sixth ed. Upper Saddle River, NJ: Prentice-Hall, 2001. B. P. Lathi, Modern Digital and Analog Communication Systems, 3rd ed. New York: Oxford University Press, 1998. B. Sklar, Digital Communications: Fundamentals and Applications, 2nd ed. Upper Saddle River: Prentice Hall, 2001. J. G. Proakis, Digital Communications, 2nd ed. New York: McGraw-Hill, 1989. J. E. Flood, Telecommunications Switching, Traffic and Networks. New York: Prentice Hall, 1995. H. Taub and D. L. Schilling, Principles of Communication Systems, 2nd ed. New York: McGraw-Hill, 1986.

Course Contents

Signal Analysis and Transmission over a Channel

Fourier transform of pulses, characteristics of distortionless signal transmission, signal distortion over bandlimited channel, non-linear channel, multipath propagation channel, fading channel and additive white Gaussian noise channel.

Pulse Modulations and Digitization of Speech Signals

Pulse amplitude modulation, pulse width modulation, pulse position modulation, time division multiplexing. Sampling theorem, sample-and-hold, time-division multiplexing, pulse code modulation (PCM), quantization noise, companding, differential PCM, delta modulation, overload noise, adaptive delta modulation.

Baseband Data Transmission and Digital Modulation Techniques

Line coding, intersymbol interference, Nyquist waveshaping, eye pattern, adaptive equalization. Transmission over bandpass channel. ASK, FSK, PSK, DPSK, M-ary modulation, continuous phase FSK, MSK.

Performance of Digital Communication Systems

Statistical properties of noise and random signals. Gaussian and Laplacian distribution, Gaussian noise, error function, probability of error calculation, error rates in binary and M-ary transmission, error analysis of PCM repeater systems, narrowband noise, Rayleigh distribution and fading, Rician distribution, matched filter receiver.

Spread Spectrum Communications (5 hours)

Pseudonoise sequences, direct sequence spread spectrum, frequency hopping spread spectrum, CDMA, application examples.

Telephony

Brief history and development of telephony. The telephone set and subscriber loop interface, basic function of the telephone set, cordless telephone, local loop, line characteristics and conditioning. Public switched telephone network, hybrids, echo suppression. Central office switching system. Switching: Strowger switches, crossbar switching, digital switching, switching hierarchy, trunk circuits, transmission media for trunks, multiplex hierarchy.

Learning Outcome of Subject

At the completion of the subject, students should be able to:

Identify the main components of digital communication systems in contrast to analog communication systems

Understand the concept of distortionless signal transmission in both time and frequency domains.

Describe the mechanism that creates multipath propagation and signal fading.

Understand the sampling theorem and the procedure of analog-to-digital conversion and digital-to-analog conversion.

Design basic time-division multiplexing schemes.

Comprehend the effects of quantisation noise and appreciate the rationale of using compander.

Understand the working principles of various pulse code modulation techniques and their limitations.

Design basic timing recovery circuit for binary line codes.

Understand the mechanism that generates intersymbol interference and the mitigation methods such as pulse shaping and adaptive equalization.

Understand the principles of basic modulation techniques including ASK, FSK, PSK, DPSK, M-ary modulation, continuous phase FSK, MSK.

Describe the performance criterion of digital communication systems and the statistical properties of noise and random signals.'

Understand the process of probability of error calculation for binary transmission systems.

Appreciate the function of matched filter and able to design matched filter for arbitrary pulse shapes.

Demonstrate the procedure of generating pseudonoise sequences.

Understand the basics and transceiver design for frequency-hopping and direct-sequence spread spectrum.

Demonstrate in depth understanding the mechanism that creates the near-far problem in cellular environment employing CDMA.

Understand the concept of diversity reception and describe basic operation of Rake receivers, power control, soft and softer handover.

Know the basic elements in switching systems and understand the concept of loads and service grades, switching hierarchy, and multiple-stage switching.

Explain the working principle and design of echo suppressors.

Present technical information and experiment results through report writing.

Carry out preliminary research in digital communications.

Programme Outcomes (% of contribution)

Ability to acquire and apply fundamental principles of science and engineering - 10%

Capability to communicate effectively - 5%

Acquisition of technical competence in specialised areas of engineering discipline - 60%

Ability to identify, formulate and model problems and find engineering solutions based on a systems approach - 5%

Ability to conduct research in chosen fields of engineering - 5%

Understanding of the importance of sustainability and cost-effectiveness in design and development of engineering solutions - 5%

Ability to work independently as well as with others in a team - 10%