The book Principles of Communication Systems from its very first edition has been considered as one of the most respected and authentic texts in the field of communication system engineering. Its profound mathematical treatment, clarity of concepts, rich set of assignment problems and of course, novelty in approach defined in many a ways how analog or digital communication are taught in engineering institutions. The latest edition builds on the strength of earlier editions of the book and gives as much stress to principles as practice.

The primary objective has been to make this book more student-friendly with more illustrations, solved examples, etc., so that it can be taken up for self-study. Each chapter in this edition has been completely reorganized and begins with an introduction that gently introduces the topics and links them with previous chapter(s). This is followed by a few facts and figures, relevant to that chapter from the history of communication engineering, aiming to motivate young minds. Objective-type self-test questions are intended to be a self-check of key ideas or concepts in the preceding sections, while a large number of new solved numerical examples elucidate the mathematical treatment. Each chapter ends with a summary of the major topics discussed in that chapter. More than fifty MATLAB based simulation examples, besides giving readers important insights of the theory, enables them to play with different parameters, note their effects and compare with the given theory. MATLAB based SIMULINK models are also introduced and all these can serve as building blocks of various student projects.

The Online Learning Centre available with this edition is designed to provide supplementary study material. New texts are added wherever required to make the book self-contained with an emphasis on circuit level description and additional coverage on digital communication concepts. Two new chapters on Phase Locked Loop and Miscellaneous Topics on Communication System increase the depth and breadth of the book. The wider coverage makes the book suitable for a one-semester course on communication system as well as two separate one-semester courses on analog and digital communication. A summary of how each chapter is strengthened in this edition by the introduction of new material is as follows.

In Chapter 1, an overview of electronic communication system has been included. Signals dealt in the communication context are classified in a systematic manner. Discussions on Fourier series and Fourier transforms are strengthened by inclusion of their properties and a large number of illustrative examples. Hilbert transform is introduced through an example.

In Chapter 2, the use of set theory in describing probability space is described. Probability distributions like Poisson distribution and Rician distribution are introduced. A classification of random processes is presented. Transmission of random processes through linear system has been highlighted along with a discussion on Weiner—Hopf filter.

In Chapter 3, circuit-level description of Amplitude Modulation (AM) systems and its mathematical analysis are presented. Topics like Single Side Band (SSB) and Vestigial Side Band (VSB) modulation have been improved upon and Quadrature Amplitude Modulation (QAM) has been introduced. Instead of introducing a separate chapter on ‘Radio Transmitter-Receiver’ the relevant concepts are included here through a discussion on AM broadcasting.

In Chapter 4, pulse averaging discriminator has been included as a part of frequency demodulation scheme and a discussion on phase modulator-demodulator has been presented.

In Chapter 5, Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) have been included. Certain important issues in digital transmission are introduced, e.g., line coding, scrambling, etc. The usefulness of linear prediction, adaptive linear prediction has been discussed here and the Least Mean Square (LMS) algorithm has been introduced. The discussion on voice coders has been improved upon by introducing newer voice-coding techniques.

In Chapter 6, use of Regenerative Repeater, Equalizer, Eye Pattern, etc., in the transmission of digital signals corrupted by channel noise has been discussed. The discussion on pulse shaping and its effect on inter-channel and inter-symbol interference has been improved upon.

Chapters 7, 8 and 9 have minor modifications in them. Phase Locked Loop (PLL) based frequency demodulation has been moved to Chapter 10.

Chapter 10 is a new chapter on ‘Phase Locked Loops’ which is finding increasing use in communication engineering. It discusses analog, digital, all digital and software PLL and its various components and characteristics. Applications of PLL in phase or frequency modulation and demodulation, carrier recovery, clock recovery, frequency synthesis have been illustrated here.

Chapter 11 has been reorganized to highlight optimal receiver design for digital signals. Maximum Likelihood Detector and Bayes’ Receiver have been introduced to find optimum threshold. The discussion on Matched Filter based reception has been strengthened. Chapter 12 has minor modifications.

In Chapter 13, Huffman Coding and Lempel-Ziv coding have been introduced and have been compared with Shannon–Fano coding. Mutual Information and its role in defining Channel Capacity have also been discussed. Rate distortion theory and its usefulness in lossy source coding has been presented. Chapters 14 and 15, again have only minor modifications done to them.

Chapter 16 is a new chapter dealing with ‘Miscellaneous Topics in Communications Systems’. This briefly covers Telephone Switching, Computer Communication, Optical Communication, Cellular Communication, Satellite Communication and RADAR system. Each of these topics justifies a separate book written on them. However, the goal here is to make the students aware of the basic concepts behind each and make it serve as a bridge between courses developed on this book and a higher level course. In today’s context, it also helps readers understand often-used terms such as ISDN, ATM, SONET, SDH, DSL, TCP, UDP, GSM, CDMA, GPS, etc.

The Online Learning Centre (OLC) is designed to supplement the textbook by providing in the student’s section (i) additional reading material on important developments on this subject, (ii) all of ready to use MATLAB codes in the form of .m and .mdl files described in the text, and (iii) additional number of chapter-wise objective questions. In a password-protected instructor’s section, instructors who adopt the textbook will find (i) solutions to selected chapter-end problems, and (ii) Power-Point slides that can be used as lecture material. Care has been taken to avoid any mistake in the print edition as well as in the OLC. However, a note on oversight, if any will be gratefully received as also all suggestions for further improvement.

Here, I would like to acknowledge the inspiration and support I always received from Prof. R. V. Rajakumar, Prof. P. P. Chakraborti, Prof. D. Datta, Prof. S. Chakraborti, Prof. S. S. Pathak and all my faculty colleagues at the Indian Institute of Technology, Kharagpur, India, more particularly from the Department of Electronics and Electrical Communication Engineering and G S Sanyal School of Telecommunication. My sincere thanks to my host Prof. Spiros H. Courellis at the University of Southern California (USC), Los Angeles, USA, where most of the manuscript for this edition was written. Prof. S. K. Mitra of USC too, had been a great inspiration. I take this opportunity to thank Prof. B. N. Chatterji (Retd.) and Prof. R. N. Pal (Retd.) and all my teachers. Thanks are also due to all my research students—Sandipan, Suman, Samit, Anindya, Arindam, Prashanta and others. I am grateful to all the reviewers for their encouraging comments and valuable suggestions.

I also thank the entire publishing team of McGraw-Hill India, more specifically Ms. Vibha Mahajan for her able guidance, Mr. Baldev Raj, Media Developer for OLC development, Ms. Shalini Jha who initiated this work, Ms. Shukti Mukherjee and Ms. Sohini Mukherjee who continued the interaction. The input from the marketing team has also been very useful.

At this point, I humbly remember my father, the late G. N. Saha. Last but not the least, I must mention the help and support I received from my family members—my mother, my parents-in-law, my sisters, my wife, Sanghita, and my daughter, Upasana.

GOUTAM SAHA