EE3723 : Digital Communications EE 4723: Digital Communications II Instructor: Dr. Noor Muhammad Khan Week 1: Introduction Course Information A Review of Fourier Transforms (Lecture On Board) Basic Diagram of A Communication System Text book Bernard Sklar, Digital Communications: Fundamentals and Applications, Prentice Hall, 2nded, 2001. References/Additional readings: B. P. Lathi, Modern Digital and Analog Communication Systems, 3rd edition, Oxford University Press, 1998. J. G. Proakis, Digital Communications, 2001 Lecture slides, Handouts uploaded on the class folder. 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 1 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 2 Grading Policy Midterm: 20% 4 Major Quiz: 30% Surprised Quizzes/Class Conduct 5% Assignments: 5% Final: 40% Course objectives At the end of this course, the students should be able to Explain in simple words the working principles of basic building blocks of a digital communication system. Demonstrate knowledge related to the concepts, tools and techniques for the design of a digital communication system. Demonstrate knowledge related to the line coding schemes and implement them in digital communication links. Identify methods of digital modulation and compare their performance using signal-space analysis. Explain receiver techniques for detection of a signal in AWGN channel. 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 3 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 4
Course objectives (Contd.) Demonstrate knowledge related to carrier and phase synchronization techniques. Characterize error-control coding techniques and explain the working of Viterbi algorithm. Explain the basic concepts of notable multiplexing techniques used in digital communications. Apply the acquired knowledge to simulate digital communication applications using Matlab. To prepare students for ever expanding telecommunications market, so that they can become valuable engineers in this field. Motivations Recent Development Satellite Communications, Optical Fibre Telecommunications: Internet boom in last two decades Wireless Communications: present boom Job Market Probably one of the most easy and high paid job recently Intel and Micron changed to wireless Research Potential One to one communications has less room to go, but multiuser communication is still an open issue. 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 5 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 6 Communication System Main purpose of communication is to transfer information from a source to a recipient via a channel or medium. Basic block diagram of a communication system: Source Transmitter Channel Receiver Recipient EE3723 : Digital Communications Week 2: Basic blocks of Analog and Digital Communication Systems 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 7 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 8
Analog and digital communication systems Communication system converts information into electrical electromagnetic/optical signals appropriate for the transmission medium. Analog systems convert analog message into signals that can propagate through the channel. Digital systems convert bits (digits, symbols) into signals Computers naturally generate information as characters/bits Most information can be converted into bits Analog signals converted to bits by sampling and quantizing (A/D conversion) 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 9 Why digital communication? Digital techniques need to distinguish between discrete symbols allowing regeneration versus amplification Good processing techniques are available for digital signals, such as medium. Data compression (or source coding) Error Correction (or channel coding) Equalization Security Easy to mix signals and data using digital techniques 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 10 Digital vs Analog Analog communication system example Advantages of digital communications: Regenerator receiver Original pulse Regenerated pulse Propagation distance Different kinds of digital signal are treated identically. Data Voice Media A bit is a bit! Message signals Modulated signals 2006-01-24 Lecture 1 11 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 12
Digital Communication: Transmitter Digital Communication: Receiver 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 13 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 14 Digital communications: Main Points Transmitters modulate analog messages or bits in case of a DCS for transmission over a channel. Receivers recreate signals or bits from received signal (mitigate channel effects) Performance metric for analog systems is fidelity, for digital it is the bit rate and error probability. Performance Metrics Analog Communication Systems Metric is fidelity: want mˆ ( t) m( t) SNR typically used as performance metric Digital Communication Systems Metrics are data rate (R bps) and probability of bit error P b = p( bˆ b) Symbols already known at the receiver Without noise/distortion/sync. problem, we will never make bit errors 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 15 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 16
Digital communication blocks Processes Involved 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 17 26-Feb-15 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 18