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 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 4 Components of a Communication System Wireless Channels A wireless channel is defined as a communication channel where information is transmitted through electromagnetic waves in free space. When free space is the medium, the signal is generally said to be transmitted as radio waves. Radio wave is the broad general term applied to any form of wireless communication from one point to another. Radio waves are typically used to refer to frequencies from 3 kHz to 300 GHz. 5 The Electromagnetic Spectrum What are your observations? 6 The Radio Wave Spectrum What are your observations? 7 The Radio Wave Spectrum What are your observations? 8 Components of a Communication System – Channel Radio wave propagation This can either be by ground waves, sky waves, or space waves. Radio waves can travel for long distances. Radio waves can penetrate through materials. They travel at the speed of light in vacuum. When they travel through materials the speed differs, depending on the object’s permeability and permittivity. Radio waves cannot be felt, and they are invisible. Radio waves are emitted naturally by lightning and astronomical objects that have a changing magnetic field. They are also created by varying electric currents. Radio waves experience reflection, refraction, scattering, absorption, diffraction e.t.c. Radio waves have both electric and magnetic components. 9 The Radio Wave Propagation 10 Radio Wave Propagation Impairments Reflection Whenever an electromagnetic wave is incident on a smooth surface (or certain sharp edges), a portion of the wave will be reflected. Angle of incidence = Angle of reflection. 11 Radio Wave Propagation Impairments Scattering Scattering occurs when an electromagnetic wave is incident on a rough or irregular surface. When a wave is scattered, the resulting reflections occur in many different directions 12 Radio Wave Propagation Impairments Diffraction Diffraction occurs when the path of an electromagnetic wave is blocked by an obstacle with a relatively sharp edge (as compared to the wavelength of the wave). The effect of diffraction is to fill in the shadow that is generated by the blockage. 13 Radio Wave Propagation Impairments Refraction Is the alteration of the direction of travel of the wave as the transmitted portion enters the second material (i.e., penetrates the surface). It is governed by Snell’s Law. Snell’s law states that: As a wave passes from low n to high n, it bends towards the normal. As a wave passes from high n to low n, it bends away from the normal. If n is the same for both media, the wave does not bend 14 Radio Wave Propagation Impairments Absorption Anytime an electromagnetic wave is present in a material other than free space, there will be some loss of strength with distance. 15 Channel – Cellular Communication The cellular concept: multiple lower- power base stations that service mobile users within their coverage area and handoff users to neighboring base stations as users move. Together base stations tessellate the system coverage area. 16  Channel – Cellular Communications Features Offer very high capacity in a limited spectrum. Reuse of radio channel in different cells. Enable a fixed number of channels to serve an arbitrarily large number of users by reusing the channel throughout the coverage region. Communication is always between mobile and base station (not directly between mobiles). Each cellular base station is allocated a group of radio channels within a small geographic area called a cell. Neighboring cells are assigned different channel groups. By limiting the coverage area to within the boundary of the cell, the channel groups may be reused to cover different cells. Keep interference levels within tolerable limits. Frequency reuse or frequency planning. Organization of Wireless Cellular Network. 17 Channel – Microwave Communications Microwaves are widely used for point- to-point communications. Transmitting and receiving antennas are highly directional to enable point to point communication. They involve wired (coaxial, two-wire line, parallel plate, waveguides) and wireless mediums. 18 Microwave Links 19  Channel – Microwave Communications Properties of microwaves Microwave links consist of a Transmitting station, a Relay station or Repeaters, and a Receiving station. Microwaves travel in straight lines, so stations should be aligned to each other. Microwave links require clear LOS (line of sight ), so antennas are installed high up to avoid the interference of obstacles in their path. They do not pass through buildings, thus reducing the efficiency. Receivers are added to boost the power of the signal so that it can travel a longer distance. Microwaves cannot penetrate through obstacles such as hills, buildings, and trees due to their high frequency. Atmospheric and environmental disturbances such as rain and snow can scatter microwave signals. Some Applications of Microwaves Bluetooth Wi-Fi GPS Satellite TV 20 Channel – Satellite Communications Satellite communication is transporting information from one place (Earth Station) to another using a communication satellite in orbit around the Earth. 21 Channel – Satellite Communications Three major stages are involved, which explain the working of satellite communication channels. Uplink Transponders Downlink 22 23  Channel – Satellite Communications Advantages Area of coverage is more than that of terrestrial systems. Every corner of the earth can be covered. More bandwidth and broadcasting possibilities. Disadvantages Launching of satellites into orbits is a costly process. Propagation delay of satellite systems is more than that of conventional terrestrial systems. Difficult to provide repairing activities if any problem occurs in a satellite system. Free space loss is more. 24 Advantages of Wireless over Wired Flexibility Accessibility Constant connectivity Coverage Convenience Cost? 25 Advantages of Wired over Wireless Control Security Speed 26