ELEC 456 - Mobile Communications
Assignment #2 - Due March 5, 1999

1. For a delay spread of 2 ms:
   a) Is a 200 kHz channel bandwidth considered to be wideband or narrowband?
   b) Compute the number of effective diversity branches for a 200 kHz channel and for a 1.25 MHz channel.
   c) Using the theoretical model, find the correlation for the magnitudes and phases for two signals separated by 200 kHz
2. What causes delay spread and why is it important in digital mobile communication systems?
3. In the context of cellular telephone services, comment on the practicality of each of the six methods for counteracting short-term fading that are mentioned in the course notes. Two sentences for each method is appropriate.
4. The industrial designer for a cellular telephone wishes to reduce the size of the case. This telephone has two monopole antennas and, after investigating the reduction in size, you find that the spacing between the antennas would be reduced from 0.5l to 0.3l. Determine if this would have a significant impact on performance.
   a) Use the theoretical value.
   b) Use the measured data for a suburban area.
5. For the case of several diversity branches, briefly explain which combining technique(s) would be most appropriate.