IT438 Communication Technology Lecture Notes PDF

Fall Semester 2024-2025 IT438 Communication Technology Kamal Hamza, PhD Acknowledgement: This presentation contains some figures and text from Data Communications...

Fall Semester 2024-2025 IT438 Communication Technology Kamal Hamza, PhD Acknowledgement: This presentation contains some figures and text from Data Communications and Networks book by W. Stallings Introduction Communication – Basic process of exchanging information from one location (source) to destination (receiving end). Refers to the process of sending, receiving and processing of information/signal/input from one point to another point. IT438 Communication Technology 1 Communication Systems Components Any communication system consists of three basic blocks: Transmitter Receiver Communication Channel Source Transmitter Channel Receiver Recipient A transmitter prepares the data (information) to be transmitted in the appropriate format in order to be transmitted over the communication channel. IT438 Communication Technology 2 Communication System Components (cont.) Transmitter Receiver IT438 Communication Technology 3 Communication System Components (cont.) Information Source Generates the message(s). Examples are voice, pictures, computer key board, etc.. If the message is not electrical, a transducer is used to convert it into an electrical signal. Source can be analog or digital. IT438 Communication Technology 4 Communication System Components (cont.) Source encoder/decoder The source encoder maps the signal produced by the source into a digital form. The mapping is done so as to remove redundancy in the output signal and also to represent the original signal as efficiency as possible (using as few bits as possible). The mapping must be such that an inverse operation (source decoding) can be easily done. If the message is a voice signal, the source encoder would convert the analog voice signal into a digital form (binary data) and compress it (e.g., MP3 compression for audio). Focus: Efficient representation of the message, removing unnecessary bits. IT438 Communication Technology 5 Communication System Components (cont.) Channel encoder/decoder Maps the input digital signal into another digital signal in such a way that the noise will be minimized. When transmitting binary data, the channel encoder could add extra bits (redundancy) that help detect and correct errors. Focus on Error detection and correction to ensure reliable transmission over noisy channels. Modulator Modulation provides for efficient transmission of the signal over channel. Most modulation schemes impress the information on either the amplitude, phase or frequency of a sinusoid. IT438 Communication Technology 6 Examples of Guided Comm. Channels IT438 Communication Technology 7 8 Examples of Unguided Comm. Channels IT438 Communication Technology 8 9 Why Different Types of Comm. Systems? There are several factors that give rise to the need for different types of communication systems: The nature of the communication channel (undersea communication requires optical fiber cables) The nature of the application (mobile applications needs wireless systems) Required level of quality (performance and quality of the received signal) Cost IT438 Communication Technology 9 Problems that Face Comm. Systems Any communication system can be subject to three main sources of problems: Noise: undesired effect from the communication environment. Usually, it is not under our control (your system has to deal with it). Interference: due to superposition of two or more signals. May result from bad design of communication systems (interference of voice channels in telephone systems, for example) Jamming: intentional interference that aims at destroying the quality of the transmitted signal to prevent transmission. IT438 Communication Technology 10 Problems that Face Comm. Systems (cont.) IT438 Communication Technology 11 Problems that Face Comm. Systems (cont.) IT438 Communication Technology 12 Data versus Signal Differentiate between two terms: data (information) and signal. Data (information): are generated by the application and need to be transmitted to some receiver. Signal: is the representation of the data in the communication system. Data are generated from the source (application) and signals are generated from the transmitter of the communication system we build. Speaking in a microphone: data (information) is what I say, whereas signal is what moves inside the wire of the microphone (electricity). IT438 Communication Technology 13 Types of Data and Signal Depending on the application nature, we have four possible combinations of data and signals: Analog Data, Analog Signal: Traditional telephone system. Analog Data, Digital Signal: Voice over IP (VoIP), digital music streaming. Digital Data, Analog Signal: Modems (used in early internet connections), Optical networks. Digital Data, Digital Signal: Ethernet, Wi-Fi, modern computer networks. Since any communication system deals with signals, we first need to understand the nature and types of signals. IT438 Communication Technology 14 Signal Representation in the Time Domain Viewed as a function of time, an electromagnetic signal can be either continuous or discrete. A continuous signal is one in which the signal intensity varies in a smooth fashion over time. IT438 Communication Technology 15 Signal Representation in the Time Domain (cont.) A discrete signal is one in which the signal intensity maintains a constant level for some period of time and then changes to another constant level. Discrete Signal IT438 Communication Technology 16 Signal Representation in the Time Domain (cont.) Smoothly rises and falls, following a Sine Wave continuous curve. used to represent analog signals in communication systems. Quickly switches between high and low Square Wave values, creating sharp, rectangular steps. used in digital systems to represent binary data (0s and 1s). IT438 Communication Technology 17 Signal Representation in the Time Domain A sine wave is a fundamental mathematical function that describes a smooth, periodic oscillation. Key Features of a Sine Wave: Amplitude (A): This is the peak value (height) of the wave, representing the maximum displacement of the wave from its central position. Higher amplitude means a stronger or louder. Frequency (f): Frequency refers to how many cycles (complete waves) occur per second, measured in Hertz (Hz). A higher frequency means the wave oscillates faster. IT438 Communication Technology 18 Signal Representation in the Time Domain Period (T): The period is the time it takes to complete one full cycle of the wave. It is the inverse of frequency (T = 1/f). A shorter period means a higher frequency. Phase (φ): Phase refers to the horizontal shift of the wave. If two sine waves have different phases, one wave may start at a different point in its cycle compared to the other. Phase differences are crucial in signal modulation and communication. IT438 Communication Technology 19 Signal Representation in the Time Domain (cont.) Sine Wave Amplitude, Frequency, Phase IT438 Communication Technology 20 Signal Representation in the Time Domain (cont.) Sine Wave (cont.) IT438 Communication Technology 21