Communication Systems Lecture 1 Intro pdf.
- 1. EEE 3105 : Communication Systems Course Instructor: Dr. Mosabber Uddin Ahmed
- 2. Syllabus • Overview of Communication Systems: Basic Principles, Fundamental Elements, System Limitations, Message Source, Bandwidth Requirements, Transmission Media Types, Bandwidth and Transmission Capacity. • Noise: Sources of Noise, Characteristics of Various Types of Noise and Signal to Noise Ratio. • Analog Communication Systems: Continuous Wave Modulation: Transmission Types, Base-Band Transmission, Carrier Transmission, Amplitude Modulation- Introduction, Double Side Band, Single Side Band, Vestigial Side Band, Quadrature, Spectral Analysis of Each Type, Envelope and Synchronous Detection, Angle Modulation-Instantaneous Frequency, Frequency Modulation (FM) and Phase Modulation (PM), Spectral Analysis, Demodulation of FM and PM, AM Broadcast Technical Standards, AM Transmitter and Receiver, Superheterodyne Receiver, FM Transmitters and Receivers, Comparison of AM and FM Receivers, Noise in Receiver, Noise Limiting Circuits, AGC Circuits, Receiver Sensitivity, Cross Modulation, Spurious Response Converters, Detector and Modulation Circuits, Sampling- Sampling Theorem, Nyquist Criterion, Aliasing, Instantaneous and Natural Sampling, Flat-Topped Sampling, Pulse Amplitude Modulation- Principle, Bandwidth Requirements, Pulse Code Modulation (PCM)- Quantization Principle, Quantization Noise, Nonuniform Quantization, Signal to Quantization Noise Ratio, Differential PCM, Demodulation of PCM, Delta Modulation (DM)- Principle, Adaptive DM, Delta-Sigma Modulation, Adaptive DPCM (ADPCM), Line Coding- Formats and Bandwidths. • Digital Modulation and Demodulation: Amplitude-Shift Keying-Principle, ON-OFF Keying, Bandwidth Requirements, Detection, Noise Performance, Phase-Shift Keying (PSK)- Principle, Bandwidth Requirements, Detection, Differential PSK, Quadrature PSK, Noise Performance, Frequency-Shift Keying (FSK)- Principle, Continuous and Discontinuous Phase FSK, Minimum-Shift Keying (MSK), GMSK, Bandwidth Requirements, Detection of FSK, Multilevel Signalling, M-Ary Modulation Techniques, Spread Spectrum Modulation Techniques, DSSS, FHSS. • Multiplexing: Time-Division Multiplexing (TDM), Principle, Receiver Synchronization, Frame Synchronization, TDM of Multiple Bit Rate Systems, Frequency-Division Multiplexing (FDM) Principle, Demultiplexing; Wavelength-Division Multiplexing, Multiple-Access Network- Time-Division Multiple-Access (TDMA), Frequency-Division Multiple Access (FDMA), Code-Division Multiple-Access (CDMA) Spread Spectrum Multiplexing, Coding Techniques and Constraints of CDMA. • Communication System Design: Design Parameters, Channel Selection Criteria and Performance Simulation.
- 3. Text: Modern Digital and Analog Communication Systems, 5th Edition, B.P. Lathi and Zhi Ding, Oxford University Press.
- 4. References: 1. Digital Communications Fundamentals and Applications, Third Edition, Bernard Sklar and fred harris, Pearson Education. 2. Communication Systems, 5th Edition, Simon Haykin and Michael Moher, Wiley. 3. Principles of Electronic Communication Systems, Fourth Edition, Louis E. Frenzel Jr., McGraw-Hill Education 4. Principles of Communication Systems, 4th Edition, Herbert Taub, Donald Schilling and Goutam Saha, McGraw-Hill Education. 5. Communication Systems Engineering, 2nd Edition, John G. Proakis and Masoud Salehi, Pearson. 6. Digital Communications, I. A. Glover & P.M. Grant, Prentice Hall. 7. Principles of Communications: Systems, Modulation, and Noise, 4th Edition, Rodger E. Ziemer and W. H. Tranter, Wiley. 8. Introduction to Digital Communications, R.E. Ziemer & R.L. Peterson, MacMillan.
- 5. Overview • Communication System • Analog Communication System • Digital Communication System • Advantages & Disadvantages of Analog and Digital Communication • Noise in Communication System • SNR • Communication Channels • Channel BW (channel capacity) & Rate of Communication
- 6. Communication System • Communication ~ To convey or transfer information from one point to another. ~ A two-way process of imparting or exchanging information from one entity to other . Communication takes place through a system that involves a sender, message and a recipient. Noise
- 7. Cont.. • The main components of communication system are: i. Transmitter ii. Channel/Medium/Link iii. Receiver • The process starts with sender/communicator who has some data/information (e.g. voice, text, audio/video) to communicate with others. • The input data/information sends over physical medium needs to be converted into electromagnetic signal by an input transducer.
- 8. Cont..
- 9. Cont.. ❖ Transducer~convertsnon-electricalquantity intoelectricalquantity. ~ convertsoneformofenergyintoanotherformofenergy. The transducer after converting input into input signal is then feed to transmitter. i. Transmitter ~modifies the signal to make it compatible with the channel characteristics. It includes; ▪ Modulator ▪ ADC (Analog to digital converter) ▪ Encoder ii. Channel ~is a medium (e.g. wire, coaxial cable, waveguide, optical fiber or radio link) that carries information from transmitter to receiver. Channel can impart distortion in electromagnetic waves along with noise. Channel can be: i. Guided Medium i.e. wired ii. Unguided Medium i.e. wireless
- 10. Cont.. i. Guided Channel ~When the signal is confined within the walls of medium or channel, the signal can be guided by the channel direction. E.g. telephone exchange have wires. Wires used as a channel can be copper wires, twisted pair, coaxial cable, optical fiber etc. ii. Unguided/wireless channel ~When the signal leaves the premises of transmitter , then there is no control over the signal. The signal can travel in any direction. In wireless medium, the signal is in the form of electromagnetic waves. The carrier of such signal is “antenna”. ❖ Antenna~actsastransducerforwirelesssignalthat transmits andreceivesEMwaves. Current → EMwaves(At Transmissionside) EMwaves→ current (At Receivingside) o Mobilephoneshavepatchantennaormicrostrip patchantenna,whichischeap/lowcost& canbeeasily fabricated&arelowprofileantennai.e.it cannotbeseen.
- 11. Cont.. ❖Signals are received in multipath propagation i.e. multiple copies of same signal are received. • Two main phenomenon occurs during multipath propagation; i. Constructive interference (Signals are added up i.e. in phase) ii. Destructive interference (Signals cancels each other i.e. out of phase)
- 12. Cont.. • Some signals work on line of sight e.g. TV remote • Line of sight ~ A direct path from transmitter to receiver ❖Transmission Impairment: Signals travel through transmission medium causes signal impairment. This means the signal at the beginning of the medium is not the same as the signal at the end of the medium. Three causes of impairment are attenuation, distortion and noise.
- 13. Cont.. ❖Attenuation~reduction in amplitude of signal or loss of energy in the signal. It depends on distance i.e. the amount of attenuation is directly proportional to the distance the signal has to travel. ▪ When a signal, simple or composite, travels through a medium, losses some of its energy in overcoming the resistance of the medium. That is why wire carrying electrical signal gets warm. ▪ To compensate for this loss, amplifiers are used to amplify the signal.
- 14. Cont.. ❖Distortion ~means that the signal changes its shape or form. ▪ It can occur in composite signal made of different frequencies. ▪ Each signal component has its own propagation speed through a medium and therefore its own delay in arriving at the final destination. Difference in delay may create a difference in phase. ▪ The shape of composite signal is therefore not the same.
- 15. Cont.. ❖Noise ~is another cause of impairment. Several types of noise such as thermal noise, induced noise, cross-talk, and impulse noise may corrupt the signal. o Crosstalk ~ whentwochannelsarebeingusedbytwopersonsandtheyareclosedenoughthat they interferewitheachother.Toseparatethem,guardbandisused.Thisinterferenceisclassifiedasnoise. o Looseconnectionalsoaccountsto noise. o Sunlightisalsoanoise(differenttypesofwavesareinvolved).
- 16. Cont.. iii. Receiver ~ reprocess the received signal i.e. reverses the process done by the transmitter on the signal. It is also called destination. It removes the distortion & noise. It consists of: • Demodulator • DAC (digital to analog converter) • Decoder The output transducer converts the electrical signal into its original form. The destination is the unit to which the message is communicated. Channel capacity/Max data rate ~ The max rate (bits/sec) at which data can be transmitted over a given communication channel. Two criterion are used for measuring channel capacity; i. Nyquist criterion that’s is used for noiseless channel/medium. 𝑪 = 𝟐𝑩𝒍𝒐𝒈2𝑴; B is channel bandwidth, M =2m;m= no. of bits/symbol, M= no. of signaling values or symbols. ii. Shannon's Criterion that isused for noisy channel/medium. 𝑪 = 𝑩𝒍𝒐𝒈𝟐(𝟏 + 𝑺𝑵𝑹)
- 17. Analog Communication System An analog communication system is a communication system where the information signal sent from point A to point B can only be described as an analog signal. An analog signal is any continuous time signal that change with time period. The sine wave is the representation of time-varying feature of analog signal.
- 18. Cont.. • An analog signalisone type of continuous time-varyingsignals,and are classified into composite and simple signals. ❖ A simple type of analog signal isnothing but a sinewave, and that can’t be decomposed,whereas ❖ A composite type analog signal can be decomposed intonumeroussinewaves. • An analog signalcan be defined by usingamplitude,timeperiod, frequency,& phase. Amplitudeisthemaximumvalueorpeakvalueofthesignal. Frequencyistherateatwhichananalogsignalisvarying. Phaseisthesignalpositionwithrespecttotime. • An analog signal isnot resistanttoward the noise, therefore; it faces distortion as well asreduces the transmissionquality.The analog signalvalue range cannot be fixed. ❖ Thebest examplesof the analog signalare video, human voice inthe air,radio transmissionwavesorTV transmissionwaves.
- 19. Digital Communication System Digital communication is a mode of communication where the information is encoded into digital signals and electronically transferred to the recipients. Digital signals are discrete or not continuous. A digital signal carries the data in the form of binary because it signifies in the bits.
- 20. Cont.. • Digital signals can be decomposed into sine waves which are termed as harmonics. • Every digital signal has amplitude, frequency, & phase like the analog signal. • This signal can be defined by bit interval as well as bit rate. Here, bit interval is the required time for transmitting a single bit, whereas the bit rate is bit interval frequency. • Digital signals are more resistant towards noise; therefore, it barely faces some distortion. • These waves are simple in transmitting as well as more dependable while contrasted to analog waves. • Digital signals include a limited variety of values which lies among 0- to-1.
- 21. Advantages& Disadvantagesof Analog & DigitalCommunication The analog and Digital signal characteristics mainly include adaptability, continuity, representation, data type, signal type, medium of transmission, type of values, security, bandwidth, hardware, data storage, portability, data transmission, impedance, power consumption, recording data, use, rate of data transmission, examples and applications. ❖ Adaptability: Analog signals are less adjustable for a range of use, whereas digital signals are more adjustable for a range of use. ❖ Continuity: Analog signals use a continuous variety of amplitude values whereas digital signal takes a limited set of distinct values at consistently spaced spots in the time. ❖ Type of Data: Analog signals are continuous in nature, whereas digital signals are discrete. ❖ Type of Waves: Analog signal wave type is sinusoidal, whereas a digital signal is a square wave.
- 22. Cont.. ❖ Medium of Transmission: Analog signal medium of transmission is wire or wireless, whereas a digital signal is a wire. ❖ Type of Values: Analog signal value type is positive as well as negative, whereas a digital signal is positive. ❖ Security: The security of an analog signal cannot be provided as it is not encrypted, whereas a digital signal is encrypted. ❖ Bandwidth: The analog signal bandwidth is low, whereas the digital signal is high. ❖ Hardware: Analog signal hardware is not elastic, whereas digital is elastic in execution. ❖ Data Storage: The data storage of an analog signal is in the wave signal form, whereas digital signal stores the data in the binary bit form. ❖ Portability: Analog signals are portable similar to the thermometer and low cost, whereas digital signals are portable similar to computers and expensive.
- 23. Cont.. ❖ Data transmission: In analog, the signal can suffer from deterioration due to noise throughout transmission, whereas digital signal can be noise resistant throughout transmission devoid of any deterioration. ❖ Impedance: The impedance of the analog signal is low, whereas the digital signal is high. ❖ Power Consumption: Analog devices use more power, whereas digital devices use less power . ❖ Data Transmission Rate: The data transmission rate in the analog signal is slow, whereas in the digital signal it is faster . ❖ Applications: Analog signals can be utilized in analog devices exclusively, like thermometer, whereas digital signals are appropriate for digital electronic devices like computers, PDA, cell phones etc.
- 24. Cont.. • Analog Communication Advantages: • Less tolerance for noise. • Flexibility with bandwidth. • Rectification of faulty components easy. • Easy to manipulate using mathematical formations and calculation. • Great lifespan. • Ambient weather dependencies are low. • Easy to handle, not expensive over sensitive routings. • Less sensitive in terms of electrical tolerance. • Disadvantages: • Not easy to implement. • Needed perfect receiver and transmitter for specific communication scenario. If you move into a new system and you want to change the analog signal, you need to tune or change both receiver and transmitter. • No security for transmission data. • Can't be saved and transmit under urgency.
- 25. Cont.. • Digital Communication • Advantages: • The digital communication systems are simpler and cheaper compared to analog communication systems because of the advances made in the IC technologies. • In digital communication, the speech, video and other data may be merged and transmitted over a common channel using multiplexing. • Using data encryption, only permitted receivers may be allowed to detect the transmitted data. This property is most important in military applications. • Since the transmission is digital and the channel encoding is used, therefore the noise does not accumulate from repeater to repeater in long distance communications. • Since the transmitted signal is digital in nature, therefore, a large amount of noise interference may be tolerated. • Since in digital communication, channel coding is used, therefore, the errors may be detected and corrected in the receivers. • Digital communication is adaptive to other advanced branches of data processing such as digital signal processing, image processing and data compression, etc. • Disadvantages: • Due to analog to digital conversion, the data rate becomes high. Therefore more transmission bandwidth is required for digital communication. • Digital communication needs synchronization in case of synchronous modulation.
- 26. Analog Signal vs Digital Signal