Computer Laboratory – Course material 2007–08: Digital Communication I

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Digital Communication I

Lecturer: Dr A.W. Moore

No. of lectures: 12

This course is a prerequisite for Digital Communication II (Part II), Distributed Systems (Part II and Diploma) and Security (Part II).

Aims

The aims of this course are to develop an understanding of communications networks from a wide perspective, within a framework of principles rather than technologies or architectures. Technologies and architectures will, however, be used as examples and motivation.

Lectures

Scope. Two example systems: Ethernet and the telephone system: basic operation; common issues; differing constraints; differing approaches.
Partitioning the problem. Abstraction, service versus implementation; layering as a restricted form of abstraction; motivation for layering; the channel as an abstraction; layered channels.
Fundamental transmission. Emphasis on the service provided by physical channel; limitations: noise, attenuation. Channel capacity (bandwidth). Modulation techniques for digital systems.
Coding. Coding as a general concept: modulation as a form of coding, A/D,D/A, error correcting and detecting codes, other forms of coding, relation to layering.
Multiplexing. Basic definitions, FDM, synchronous and asynchronous TDM. Circuit switching, packet switching, ATM. Shared media networks with particular emphasis on media access control. Packet scheduling. Non orthogonal multiplexing. Multiplexing and channel characteristics.
Switching and routing. Introduction from LAN perspective (repeaters, bridges, routers). Fundamental view of switching extended to telephone network, connectionless versus connection oriented.
Protocols and state. Imperfect view of state at far end of channel. ARQ as an example of an error control protocol; sliding window ARQ as an example of a flow control protocol; flow control in general: X.25 as an example.
Naming, addressing and routing. Service access points, binding. Hierarchical versus flat address spaces. Routing classifications and algorithms.
The Internet. Internet architecture, context of development, addressing and routing, transmission control protocol (TCP), higher layer protocols, evolution.
Standards. Role of standards, dynamics of standards process, standards bodies.

Objectives

At the end of the course students should

be able to analyse a communication system by separating out the different functions provided by the network
understand that there are fundamental limits to physical transmission systems
understand the general principles behind multiplexing, addressing, routing and stateful protocols as well as specific examples of each
understand what FEC is and how CRCs work
be able to compare communications systems in how they solve similar problems
have an informed view of the internal workings of the Internet

Recommended reading

* Peterson, L.L. & Davie, B.S. (2007). Computer networks: a systems approach. Morgan Kaufmann (4th ed.).
Comer, D. & Stevens, D. (1995). Internetworking with TCP-IP, vol. 1 and 2. Prentice Hall (3rd ed.).
Schwartz, M. (1987). Telecommunication networks: protocols, modeling and analysis. Addison-Wesley.

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