1.ec6801 introduction final
- 1. EC6801 WIRELESS COMMUNICATION Mrs.R.Ramalakshmi Assistant Professor Department of ECE Ramco Institute of Technology Rajapalayam
- 2. Introduction • Communication is defined as the process of transferring or exchanging the information from one place to other place. • Communication channel is a connection between transmitter and receiver through which Data can be transmitted. • Communication channel also called as communication media or transmission media
- 4. Types of Communication Channel
- 5. • Communication channel is essential for communication systems. • The transmission characteristics are important in selecting channel because they directly affect the communication quality. • Different types of communication channels have different transmission characteristics and costs, they are used in different applications.
- 6. Twisted-pair cable One of the wires carries signal, the other is used only as a ground reference. Number of twists per unit length determines the quality of the cable.
- 7. Coaxial cable • Used for both analog and digital signals • Effectively used at higher data rate and higher bandwidth • For analog signals need amplifiers every few km • For digital signals requires repeater every 1km
- 9. Terrestrial Microwave Requires fewer repeaters Use a parabolic dish to focus a narrow beam. 1-40GHz frequencies
- 10. Satellite Communication Receives on one frequency, and transmits on another frequency eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz • Height 35,784km
- 11. Broadcast Radio • Radio frequency range is 3kHz to 300GHz • Use broadcast radio of 30MHz - 1GHz, for: – FM radio – UHF and VHF television • Is unidirectional • Suffers from multipath interference • Reflections from land, water, other objects • Are used for multicasts communications, such as radio and television, and paging system.
- 12. Wireless Communication • Transmitting voice and data using electromagnetic waves in open space.
- 13. Need for Wireless Communication Freedom from wires • No cost of installing the wires, No bunches of wires. • Running around e.g. Bluetooth , Wi-Fi
- 14. Global coverage where wired communication is not feasible or costly. e.g. rural areas, battle field and outer space. Stay Connected Any where any time Flexibility Connect to multiple devices simultaneously
- 16. CELLULAR SYSTEMS-BASIC CONCEPTS • Cellular system solves the problem of spectral congestion. • Offers high capacity in limited spectrum. • High capacity is achieved by limiting the coverage area of each BS to a small geographical area called cell. • Replaces high powered transmitter with several low power transmitters. • Additional radio capacity is achieved.
- 17. FREQUENCY REUSE • Used by service providers to improve the efficiency of a cellular network and to serve millions of subscribers using a limited radio spectrum • After covering a certain distance a radio wave gets attenuated and the signal falls below a point where it can no longer be used or cause any interference • A transmitter transmitting in a specific frequency range will have only a limited coverage area
- 18. • Beyond this coverage area, that frequency can be reused by another transmitter. • The entire network coverage area is divided into cells based on the principle of frequency reuse • A cell is the basic geographical unit of a cellular network; is the area around an antenna where a specific frequency range is used.
- 19. • When a subscriber moves to another cell, the antenna of the new cell takes over the signal transmission • A cluster is a group of adjacent cells, usually 7 cells; no frequency reuse is done within a cluster • The frequency spectrum is divided into sub-bands and each sub-band is used within one cell of the cluster • In heavy traffic zones cells are smaller, while in isolated zones cells are larger • The design process of selecting and allocating channel groups for all of the cellular base stations within a system is called frequency reuse or frequency planning.
- 20. • Cell labelled with same letter use the same set of frequencies. • Cell Shapes: Circle, Square, Triangle and Hexagon.