University of Manchester

School of Computer Science

CS3282: Digital Communications

 

Lecturer: Dr. Barry Cheetham (www.cs.man.ac.uk/~barry )

Aims: To gain an understanding of fundamental principles of digital transmission systems as used for applications in fixed and mobile telephony, wired and wireless computer networks, data storage and digital broadcasting. This course is mainly concerned with the physical layer and the different ways in which bit-streams may be transmitted and received over communication links such as cable or radio channels. Source and channel coding are briefly considered and also the demands for multiple access to radio channels.

Syllabus: www.cs.man.ac.uk/~barry/mydocs/CS3282/Syllabus

Lecture notes: www.cs.man.ac.uk/~barry/mydocs/CS3282/Notes

Lecture slides: www.cs.man.ac.uk/~barry/mydocs/CS3282/Slides

MATLAB material: www.cs.man.ac.uk/~barry/mydocs/CS3282/DC_MATLAB

Past exam papers with solutions: www.cs.man.ac.uk/~barry/mydocs/CS3282/Exams

Solutions to selected problems: www.cs.man.ac.uk/~barry/mydocs/CS3282/Solutions

Web references: www.cs.man.ac.uk/~barry/mydocs/CS3282/Webrefs

Survey of the course and its objectives:

A ‘discrete time’ or ‘digital’ transmission channel is a communication link capable of sending and receiving digitised data. Such a link is generally achieved by placing a "digital transmitter" and a "digital receiver" at the ends of a "real channel" which is invariably analogue in nature.

In traditional telephony, the "real channel" may be wire or cable, optical fibre, a radio channel, an infra-red or ultrasound link or perhaps a combination of several of these types. Such channels are also used for transmitting broadcast material for TV and radio and the data generated by computer networks and the Internet. Another form of transmission channel is obtained by magnetic and optical recording devices and their corresponding read-back devices (magnetic disks, tapes, CDROMs, DVDs. Zip-drives, etc.). The similarities between the technical problems of storage and transmission are as striking as the differences between them: e.g. efficient bandwidth utilisation and error concealment raise similar issues in both cases whereas overall delay and cost requirements are considerably different.

This course addresses mainly the "digital transmitter" and "digital receiver" and "real channel" issues arising in digital communications, though we will look at other aspects higher up the chain of "layers" of "protocols" governing telephone and data network communications.

In many ways the digital transmitter is a digital-to-analogue converter converting the stream of binary digits (obtained possibly by digitising analogue speech) into an analogue signal suitable for the channel in question. Similarly, the receiver is a type of analogue-to-digital converter.

To understand digital transmission and the demands of the analogue-digital conversion process, we must have a grounding in the relationship between the shape of an analogue waveform in the time-domain and its frequency-spectrum. Each binary digit will be represented by a segment of such an analogue waveform. So we have a brief section on Fourier transforms and spectral analysis.

It will become apparent that the performance of a digital transmission link is governed by two main factors: channel bandwidth and system noise. We will discuss the design of digital transmitters and receivers with reference to the bandwidth and noise characteristics of the channel and fundamental limitations in what can be achieved in a given situation will be established.

Background knowledge needed:

Basic mathematics: (As surveyed in first year Mathematics courses covering: complex numbers, Argand diagram, modulus & argument, differentiation, simple integration, sum of an arithmetic series, factorisation of quadratic equation, De Moivre's Theorem, exponential function and natural logarithms. Sine waves and the Fourier series.)

Computing: Experience with any high-level computer programming language.

 

Summary of Objectives & Learning Outcomes:

Specific objectives are that after successful completion of the course, students will be able to:

 

Text-books referred to:

"Digital Communications", Glover & Grant, Prentice-Hall, (new ed. due).

"Digital Communications" 2nd ed., B. Sklar, Prentice -Hall, 2001.

"Computer Networks, 4th edition" A.S Tanenbaum, Prentice-Hall, 2003.

Assessment: Two hour written examination.