ICE111 Introduction to Information and Communication Engineering PDF

ICE111 Introduction to Information and Communication Engineering Dr. O. I. Oshin  Objective Learning Outcomes Teach the basic Draw a block diagram concepts of signal that represents a typical transmissio...

ICE111 Introduction to Information and Communication Engineering Dr. O. I. Oshin  Objective Learning Outcomes Teach the basic Draw a block diagram concepts of signal that represents a typical transmission, communication system. reception, and State the functions of different kinds of each component of the Module 2 channels in communication system communication block diagram. engineering systems. Compare and contrast the different categories and types of communication channels. 2 Communication System The purpose of a communication system is to transmit an information-bearing signal, from a source, located at one point, to a sink (user or destination), located at another point some distance away. The major elements of a communication system are the Transmitter of information, the Channel or medium of communication and the Receiver of information. 3 4 Components of a Communication System Information Source The message or information is the entity that is to be transmitted. The function of the information source is to produce the required message to be transmitted over the channel. Examples of information sources and the types of information generated: sine wave generator (generates sine waves), square wave generator (generates square waves, oscillator (generates pulses or clock signal), microphone (generates audio), computer (generates text, audio, image, video, e.t.c), radio (generates audio), TV (generates audio, video, image), e.t.c 5 Components of a Communication System Input Transducer Typically, a transducer is an electronic device that converts one form of energy to another. The purpose of an input (electrical) transducer is to convert the information generated into a time-varying electrical signal (facilitating easier transmission). For example, a microphone converts audio signals into electrical signals. The photodetector converts light signals into electrical signals. 6 7  Categorization of Communication Systems According to signal specification/technology: Analogue – communicates data as electronic signals of varying frequency or amplitude. Digital – the data are generated and processed in two states: High (represented as 1) and low (represented as 0). Digital technology stores and transmits data in the form of 1s and 0s. Assignment – Describe the analogue signal to digital conversion process of a speech signal (sampling, quantization, encoding) 8 Components of a Communication System Amplifier The electronic circuit or device that increases the amplitude or the strength of the transmitted signal is called an amplifier. When the signal strength becomes less than the required value, amplification can be done. An amplifier is an electronic device that increases the voltage, current, or power of a signal. 9 A microphone amplifier circuit 10 Components of a Communication System Modulation The information signal cannot be transmitted over a large distance because of its low frequency and amplitude. These signals are superimposed with high frequency and amplitude waves called carrier waves. This phenomenon of superimposing of message signals with a carrier wave is called modulation, and the resultant wave is a modulated wave which can then be transmitted. 11 Analogue Modulation 12  Components of a Communication System Modulation (Analog/ Analogue) Amplitude Modulation – the amplitude of the carrier signal is changed in proportion to the message signal while the phase and frequency are kept constant. Frequency Modulation – the frequency of the carrier signal is changed in proportion to the message signal while the amplitude and phase are kept constant. Phase Modulation – the amplitude of the carrier signal remains unchanged while phase change occurs. With the change in phase, the frequency of the signal also shows variation. While phase modulating any signal, the phase, as well as the frequency of the carrier signal, shows variation. Assignment – What were the problems with AM that FM solved? Differentiate between AM and FM 13  Components of a Communication System Modulation (Digital) Digital modulation uses discrete signals for modulating a carrier wave. Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) Quadrature Amplitude Modulation (QAM) Assignment – Describe the digital modulation techniques 14 Components of a Communication System Antenna An antenna is a specialized transducer that converts electric current into electromagnetic (EM) waves or vice versa. An antenna is a metallic structure that receives and/or transmits radio electromagnetic waves. To operate efficiently, antennas need to be in the order of the magnitude of the wavelength of the transmitted signal. 𝐿 = 𝜆 = 𝑐$𝑓 15 Components of a Communication System Antenna The human ear can hear sounds within the frequency range 20 𝐻𝑧 − 20 𝑘𝐻𝑧. Assume a speech signal of 20 𝑘𝐻𝑧 is transmitted, calculate the length of the antenna suitable to transmit this signal. 𝐿 = 𝜆 = 𝑐$𝑓 ! 𝐿=𝜆= 3×10 $20,000 = 15,000 𝑚‼‼‼‼‼ Applying frequency modulation (a carrier wave of 2000 𝑘𝐻𝑧): ! 𝐿=𝜆= 3×10 $2,000 𝑘 = 150 𝑚 16 Components of a Communication System Channel A channel refers to a physical medium such as wire, cables, or space through which the information signal is passed from the transmitter to the receiver. Noise is the major channel impairment in communications. There are external and internal sources that cause noise. External sources include interference, i.e. interference from nearby transmitted signals, interference generated by a natural source such as lightning, solar or cosmic radiation, automobile-generated radiation, buildings (building materials). Internal sources include noise due to random motion and collision of electrons in the conductors and thermal noise due to diffusion and recombination of charge carriers in electronic devices. 17 Categorization of Communication Systems According to communication channel: Wired (Guided media) – the signal is contained within the physical limits of the transmission medium and is directed along with it. Twisted pair cable Coaxial cable Optical fiber Wireless (Unguided media) – free space propagation. Bluetooth Wi-Fi Cellular communications Microwave communications Satellite communications 18 Categorization of Communication Systems Twisted Pair Cable It was invented by Alexander Graham Bell. Twisted pair cables have two conductors twisted together that are generally made up of copper and each conductor has insulation. One of the conductors is used to carry the signal and the other is used as a ground reference only. The receiver uses the difference of signals between these two conductors. It is the least expensive of the three guided media There are two types: Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP). 19  Categorization of Communication Systems Uses of twisted pair cables: Twisted Pair cables are used in telephone lines to provide data and voice channels. The DSL lines make use of these cables. Local Area Networks (LAN) also make use of twisted pair cables. RJ-45 is a very common application of twisted pair cables. 20 Types of twisted pair cables 21  Categorization of Communication Systems Coaxial Cable The core copper conductor is used for the transmission of signals. The insulator provides insulation to the copper conductor. The insulator is surrounded by a braided metal conductor which helps to prevent the interference of electrical signals and prevent cross talk. This entire setup is again covered with a protective plastic layer to provide extra safety to the cable. 22  Categorization of Communication Systems Uses of Coaxial Cable Television, Internet: RG-6 cables are used for this. CCTV: RG-59 and RG-6 cables can be used. Video: RG-6 and RG-59 (cheaper) are used. HDTV: The HDTV uses RG-11 as it provides more bandwidth for signal transfer. Advantages of Coaxial Cables (compared with twisted pair) Coaxial cables support high bandwidth. It is easy to install coaxial cables. Coaxial cables have better cut-through resistance, so they are more reliable and durable. Less affected by noise or cross-talk or electromagnetic inference. 23 Categorization of Communication Systems Optical Fiber An optical fiber cable is a thin, cylindrical structure with strands of fiber made of glass or plastic that guides light through total internal reflection, allowing light to travel from one point to another. Optical fibers are about the diameter of a strand of human hair and when bundled into a fiber-optic cable, they’re capable of transmitting more data over longer distances and faster than other mediums. 24 Categorization of Communication Systems Optical Fiber The section of the fiber that transmits light is called the core. The material used for cladding often has a lower refractive index than the core. The total internal reflection takes advantage of this index difference and prevents light from escaping through the sidewalls. 25 Categorization of Communication Systems Advantages of Optical Fiber Their greatest advantage is bandwidth. Because of the wavelength of light, it is possible to transmit a signal that contains considerably more information than is possible with a metallic conductor. They are widely used in the backbone of networks. Current optical fibers provides transmission rate up to 1000X more than copper-based media. Electrical Isolation — Fiber optics do not need a grounding connection. Both the transmitter and the receiver are isolated from each other and are therefore free of ground loop problems. Also, there is no danger of sparks or electrical shock. Freedom from EMI — Fiber optics are immune to electromagnetic interference (EMI), and they emit no radiation themselves to cause other interference. Low Power Loss — This permits longer cable runs and fewer repeater amplifiers. Lighter and Smaller — Fiber weighs less and needs less space than metallic conductors with equivalent signal-carrying capacity. Copper wire is about 13 times heavier. Fiber also is easier to install and requires less duct space. 26 Twisted Pair vs Coaxial vs Optic Fiber 27 28