1. DATA COMMUNICATION Lecture

2. Overview of Lecture 27  Frequency Ranges  Microwave Communication  Satellite Communication  Cellular Telephony

3. Frequency Ranges  The type of propagation used in radio transmission depends upon the frequency of the signal

4. Very Low Frequency (VLF)

5. Contd… VLF waves are propagated as surface waves through air Do not suffer much attenuation in TX but are susceptible to high levels of atmospheric noise I.e. electricity and heat Used for Long-range radio navigation and Submarine Communication

6. Low Frequency (LF)

7.  Also propagated as surface waves  Used for Long-range radio and for navigational locators  Attenuation is greater

8. Middle Frequency (MF)

9. – The distance they cover is limited by the angle needed to get the signal reflect – Used for AM Radio

10. High Frequency (HF)

11. – Used for International Broadcasting, Military Communication, Telephone, Telegraph and Fax

12. Very High Frequency (VHF)

13. – Most VHF waves use line-of- sight propagation – Used for VHF Television, FM Radio, Aircraft AM Radio

14. Ultra High Frequency (UHF)

15. – Always use line-of-sight propagation – Used for UHF Television, Mobile Telephone, Cellular Radio, Paging, Microwave Links – Note that microwave communication begins at 1GHz in UHF and continues into SHF and EHF band

16. Super High Frequency (SHF)

17. – SHF waves are TX using mostly line-of-sight and some Space propagation – Used for Terrestrial and Satellite Microwave and Radar Communication

18. Extremely High Frequency (EHF)

19. – Used for Radar, Satellite and Experimental Communication

20. Terrestrial Microwave  Microwaves do not follow the curvature of earth  Line-of-sight transmission  Height allows the signal to travel farther

21. Terrestrial Microwave

22. Satellite Communication  Line-of-sight microwave communication using satellite   Satellite acts as a very tall antenna and a repeater

23. Satellite Communication

24. Geosynchronous Satellites

25. Satellite Frequency Bands  Each satellite sends and receives over two bands – Uplink: From the earth to the satellite – Downlink: From the satellite to the earth

26. Satellite Frequency Bands BandDownlink Uplink C 3.7-4.2 GHz 5.925-6.425 GHz Ku 11.7-12.2 GH 14-14.5 GHz Ka 17.7-21 GHz 27.5-31 GHz

27. Cellular Telephony  Each service area is divided into small ranges called cells  Each cell office is controlled by a switching office called MTSO

28. Cellular Telephony

29. Operations of Cellular Telephony  Transmitting – Mobile phone sends the number to the closest cell office – Cell office  MTSO  Telephone office – MTSO assigns an unused voice channel

30. Operations of Cellular Telephony  Receiving – Telephone office sends the signal to MTSO – MTSO sends queries to each cell (paging) – If mobile phone is found and available, assigns a channel

31. Operations of Cellular Telephony  Handoff – MTSO monitors the signal level every few seconds – If the strength diminishes, MTSO seeks a new cell and changes the channel carrying the call