1. TVS, By Ya Bao 1 Telecommunications and Video Systems Weeks1--67--12 Lecture/Tuto rial/Lab Ya BaoVincent Siyau Contents Introduction to telecommunications and video systems Modulation and radio broadcast; Telephone set and subscriber loop interface; Telephone network; Voice over Internet protocol, ADSL and cable telephony. Basic TV systems and standards Multimedia communicati ons & basic video/image processing

2. TVS, By Ya Bao 2 ASSESMENT OF THE UNIT There will be one 2-hour written examination (70%), and laboratory assessed work (30%). Deadline of submission 4 May. 2007. CORE MATERIALS Schweber, W., Electronic Communication Systems: A Complete Course, 4/e Prentice Hall, 2002, ISBN: 0-13-091621-8 http://eent3.sbu.ac.uk/staff/baoyb/TVS

3. TVS, By Ya Bao 3 1. Introduction to communication systems 1.1 What is telecommunications  Communication  Telecommunications 1.2 Development of telecommunications 1837telegraphS.Morse 1876telephoneA. Bell 1894radio communications G. Marconi 1915transcontinental telephone line 1948first transistor 1962first communication satellite 1963first laser 60’soptical fibres, IC, PCM 70’scomputer net, microprocessor 80’scellular telephone, Internet 90’sGPS, ATM, ISDN, GSM 21 Century3G, Broad access, DAB radio, digital and HD TV, WLAN, 4G,...

4. TVS, By Ya Bao 4 1.3 The block diagram of a communication system

5. TVS, By Ya Bao 5 2. The Electromagnetic Spectrum 2.1 Electromagnetic Waves and Energy wavelength: distance between peaks velocity: speed at which the energy travels through frequency: the number of oscillations or cycles per second (hertz, abbreviated Hz) of the waveform Wavelength: the distance between peaks of the oscillations of the energy wave

6. TVS, By Ya Bao 6 Wavelength can also be measured as the distance between the negative peaks, zero points,

7. TVS, By Ya Bao 7 speed of light: The propagation velocity is less in any medium other than vacuum In wire, it is anywhere from 60% to 85% of c a common type of cable used for cable TV has a propagation factor of 75% of c. Example 1 What is the wavelength in vacuum for a frequency of 1 million hertz? Example 2 What is the frequency when the measured wavelength is 6 m?

8. TVS, By Ya Bao 8 2.2 The Electromagnetic Spectrum

9. TVS, By Ya Bao 9 TABLE 1 ‑ 1 CCIR Band Designations Frequency RangeDesignations --------------------------------------------------- 30 Hz ‑ ----300 HzELF 0.3 kHz ‑ --3 kHzVF 3 kHz----- ‑ 30 kHzVLF 30 kHz ‑ ---300 kHzLF 0.3 MHz ‑ -3 MHzMF 3 MHz ‑ ----30 MHzHF 30 MHz---300 MHzVHF 0.3 GHz ‑ --3 GHzUHF 3 GHz ‑ ----30 GHzSHF 30 GHz ‑ ---300 GHzEHF 0.3 THz ‑ ---3 THzInfrared light 3 THz ‑ ------30 THzInfrared light 30 THz ‑ ----300 THzInfrared light 0.3 PHz ‑ ---3 PHzVisible light 3 PHz ‑ -----30 PHzUltraviolet light 30 PHz ‑ ----300 PHzX ‑ rays 0.3 EHz ‑ ---3 EHzGamma rays 3 EHz ‑ ------30 EHzCosmic rays 1 kilohertz (kHz)= 10 3 Hz, 1 megahertz (MHz)= 1*10 6 Hz 1 gigahertz (GHz)= 1*10 9 Hz, 10 12 : terahertz (THz); 10 15 : petahertz (PHz); 10 18 : exahertz (EHz);

10. TVS, By Ya Bao 10 2.3 BANDWIDTH AND INFORMATION CAPACITY Bandwidth: Bandwidth is the span of frequencies within the spectrum occupied by a signal and used by the signal for conveying information. To send more information in a short time requires more bandwidth. Example Suppose that a communications link is using a transmitter of 10 W power, and there is 1 W of noise power in the same link. The available bandwidth is 1 kHz. What is the channel capacity?

11. TVS, By Ya Bao 11 2.4 SIMPLEX, DUPLEX, AND HALF ‑ DUPLEX SYSTEMS SIMPLEX: one direction only DUPLEX: both directions at a time HALF ‑ DUPLEX: either direction, but only one direction at a time

12. TVS, By Ya Bao 12 2.5 TIME AND FREQUENCY DOMAINS Description of a signal versus time --- time ‑ domain representation Description of a signal versus frequency -- frequency ‑ domain representation