al discovery of Heinrich Hertz that led to the invention of wireless telegraphy? 2. In which applications would directional antennas be used? 3. Why are omnidirectional antennas more useful in mobile communications? 4. What is a simplex communication system? How does it differ from a half-duplex system? 5. What is the difference between the characteristics of a satellite channel and a terrestrial mobile channel? Terrestrial Broadband Wireless Telecommunications 6. Calculate the path loss for a device transmitting over a 2 km path at 2 GHz frequency band in a Free Space system and a Hata system. 7. Name and describe two methods for compensating fading effects. 8. What is bit error rate (BER) and why is it of interest? 9. How can improvement in system performance due to diversity be quantified? 10. What is the main difference between FDD and TDD systems? 11. Give examples of TDD and FDD systems. 12. In what circumstances does TDD help improve frequency utilisation efficiency? 13. Give examples of TDD and FDD systems. 14. In what circumstances does TDD help improve frequency utilisation efficiency? 15. What is frequency reuse? Why is it necessary? 16. Calculate the number of voice channels for a 2G system. Assume an operator has been allocated 10 MHz bandwidth for downlink and 10 MHz bandwidth for uplink. The stan- dard specifies 25 kHz carriers, each supporting 3 (or 6) voice channels. Assume frequency reuse factors of 7 and 4. How many voice channels exist in each cell? How much traffic (in erlangs) can be supported in each cell? [You need to calculate 4 sets of figures.] 17. What is spreading gain and why is it important? 18. How are users distinguished from each other in a CDMA system? 19. A CDMA base station connects to 8 mobiles simultaneously as shown in the figure. a. How is signal to interference ratio calculated at each mobile (uplink)? Assume interference from neighbour- ing cells is insignificant, and that the re- ceived signal power from each mobile at the base station is equal as power control Mobile 1