UNIT-1 Elements of Digital Communication

it describes about the basic structure of Digital Communication and comparison with Analog systems .

1. DIGITAL COMMUNICATION Course Code : PC601EC Presented Mr.A.Abhishek Reddy, Assistant Professor, Dept. ECE,MECS Email:[email protected] 8121444996

2. PREREQUSISITE PC403EC –PTSP PC502EC-ANALOG COMMUNIATION

3. COURSE OBJECTIVES Familiarize the students with elements of digital communication system and waveform coding techniques like PCM, DPCM, DM and ADM. Introduce the concepts of information theory and source coding. Familiarize the students with channel coding techniques such as LBC, BCC and convolution codes. Introduce the concepts of baseband digital data transmission and analyze the error performance of different digital carrier modulation schemes like ASK, FSK, PSK etc. Familiarize the students with the concepts of spread spectrum communication with emphasis on DSSS and FHSS

4. COURSE OBJECTIVES <after completion of course students should be able to> Classify the different types of digital modulation techniques PCM, DPCM, DM and ADM and compare their performance by SNR. Illustrate the classification of channels and Source coding methods. Distinguish different types of Error control codes along with their encoding/decoding algorithms. Examine the Performance of different Digital Carrier Modulation schemes of Coherent and Non-coherent type based on Probability of error. Generation of PN sequence using Spread Spectrum and characterize the Acquisition Schemes for Receivers to track the signals.

5. UNIT – I Elements of Digital Communication System Comparison of Digital and Analog Communication Systems Waveform Coding: Analog to Digital Conversion, Quantization and Encoding techniques, PCM. Companding in PCM systems - u law and A law, Applications PCM Introduction to Linear Prediction Theory. Modulation and demodulation of DPCM, DM and ADM. Comparison of PCM, DPCM, DM and ADM. SNRQ of PCM and DM

6. UNIT – II Information Theory and Source Coding Uncertainty, Information and entropy Source coding: Shannon – Fano and Huffman coding . Discrete memory less channel – Probability relations in a channel, priori & posteriori entropies, mutual information Channel capacity - Binary Symmetric Channel, Binary Erasure Channel, cascaded channels, information rate. Shannon-Hartley Theorem – Shannon Bound .

7. UNIT – III Channel Coding Types of transmission errors, need for error control coding. Linear Block Codes (LBC): description of LBC, generation, Syndrome and error detection, Minimum distance of Linear block code, error correction and error detection capabilities, Standard array and syndrome decoding Hamming codes. Binary cyclic codes (BCC): Description of cyclic codes, encoding, decoding and error correction using shift registers. Convolution codes: description, encoding – code tree, state diagram.

8. UNIT – IV Introduction to Base band Digital data transmission B lock diagram, ISI, eye pattern. Digital Carrier Modulation Schemes –– Description and generation of ASK, FSK, PSK. O ptimum receiver – matched filter, correlation receiver. Gaussian error probability -Coherent detection of Binary ASK, FSK, PSK. DPSK. Comparison of digital carrier modulation schemes. M-arysignalingschemes:Introduction,QPSK, Synchronization methods.

9. UNIT – V Spread Spectrum Communication Advantages of Spread Spectrum. Generation and characteristics of PN sequences. Direct sequence spread spectrum and their applications. Frequency hopping spread spectrum systems and their applications. Acquisition and Tracking of DSSS and FHSS signals.

10. Suggested Reading-prescribed by OU Simon Haykin , ―Communication systems‖ 4/e, Wiley India 2011. Sam Shanmugam K, ―Digital and Analog Communication systems‖, Wiley 1979. B.P.Lathi , ―Modern digital and analog communication systems‖ 3/e, Oxford University Press. 1998

11. UNIT – I Elements of Digital Communication System The word digital comes from the Latin word digit and digitus (the Latin word for finger ), as fingers . What is Digital Communication? Digital communication is a mode of communication where the information or the thought is encoded digitally as discrete signals and electronically transferred to the recipients .

12. First Communication –Digital in nature by Samuel Morse in 1837.

13. Manager wanted to meet all his team members at the Conference room to discuss their key responsibility areas and areas of expertise. He didn’t have the time to go to their workstations and invite them individually . Instead he opted an easier and cheaper mode to communicate his idea. He sent an email marking a cc to all the participants , inviting them for the meeting. This is an example of Digital communication where the information was sent electronically . Example of Digital Communication

14. In digital communication Information flows in a digital form and the source is generally the keyboard of the computer. A single individual is capable of digital communication. It also saves wastage of manpower and is one of the cheapest modes of communication. Digital communication is also a really quick way to communicate. The information can reach the recipient within a fraction of a second. An individual no longer has to wait to personally meet the other individual and share his information.

15. Some examples of digital communication are • E-mailing- Computers • Texting- Cell Phones • Fax • Teleconferencing • Video conferencing

16. Communications Techniques Digital communication covers a broad area of communications techniques including: • Digital transmission is the transmission of digital pulses between two or more points in a communication system. • Digital radio is the transmitted of digital modulated analog carriers between two or more points in a communication system.

17. Basic Digital Communication Nomenclature Textual Message : information comprised of a sequence of characters. Binary Digit ( Bit ): the fundamental information unit for all digital systems. Symbol ( mi where i =1,2,… M ): for transmission of the bit stream; groups of k bits are combined to form new symbol from a finite set of M such symbols; M =2 k . Digital Waveform : voltage or current waveform representing a digital symbol. Data Rate : Symbol transmission is associated with a symbol duration T . Data rate R = k / T [bps ]. Baud Rate : number of symbols transmitted per second [baud]

18. Building blocks of Digital Communication System

19. Digital communication system Low Pass Filter Sampler Quantizer Channel Encoder Line Encoder Pulse Shaping Filters Source Encoder Modulator Multiplexer Input Signal Analog/ Digital To Channel Detector Receiver Filter De- Modulator From Channel Channel Decoder Digital-to-Analog Converter De- Multiplexer Signal at the user end Carrier Analog Digital Carrier Recovery Symbol timing Recovery Digital Analog Twisted Pair Co-axial Cable Optical Fiber Wireless Space

20. Typical Digital Communication