1) Diversity techniques in mobile wireless systems take advantage of multiple propagation paths to improve reliability by creating independent fading channels and combining the signals. 2) Common diversity techniques include space, time, frequency, angle, and polarization diversity which are created using multiple antennas, frequency bands, time slots, antenna angles or polarizations. 3) A Rake receiver is used to implement path diversity, capturing multipath signal energy with fingers tuned to peaks in the delay profile and maximizing ratio combining.

3. Communication - Mobile Telephone Exchange Subscriber Line Inter-Exchange Junction Mobile Switching Centre ( MSC ) BSC BTS MS

4. HOW DO WE OVERCOME LIMITATIONS IMPOSED BY THE RADIO CHANNEL? • Flat Fading Countermeasures – Fade Margin – Diversity – Coding and Interleaving – Adaptive Techniques • Delay Spread Countermeasures – Equalization – Multicarrier – Spread Spectrum – Antenna Solutions 8C32810.104-Cimini-7/98

5. Cultural Dimensions UNITY IN DIVERSITY PERSONAL CORPORATE ETHNIC GENERATIONAL RELIGIOUS CLASS GENDER REGIONAL NATIONAL PROFESSIONAL / EDUCATIONAL

11. Steel Rake Leaf Rake

12. SNOW RAKE

13. GARDEN RAKE

14. GARDEN RAKE

16. Propagation of Tx Signal

22. RAKE Receiver Block Diagram

25. Another ways to create diversity: ?

34. POLARIZER

37. Terrestrial microwave radio system with two antenna arrays configured for space-diversity

44. CONCEPTS OF DIVERSITY BRANCH AND SIGNAL PATH

45. (a) Branch Construction method using frequency diversity

46. (b) Branch Construction method using Time diversity

47. COMBINING AND SWITCHNING METHODS

48. COMBINING AND SWITCHNING METHODS FOR COHERENT DETECTION FOR NON - COHERENT DETECTION

50. (a) Maximal ratio combining (MRC)

52. (b) Equal Gain Combining (EGC)

55. (c) Selection or Switching Combining

58. SWITCHNING METHODS FIXED THERSHOLD VARIABLE THERSHOLD

59. (a) Switching Methods with Fixed threshold

61. (b) Switching Methods with Variable threshold