1. What makes the wireless channel more unpredictable than the wireline channel?

2. Rayleigh fading occurs when there is:

3. Spread spectrum systems employ a form of diversity called _________, where the signal is spread over a much larger bandwidth than is needed.

4. The use of equalizers adds to the complexity and costs of the ______ systems, because equalization requires significant amounts of signal-processing power.

5. With ______, fast and accurate power-control loops must be used so that the signal from one user does not drown out the signals from other users, and each cell must be tightly synchronized. Errors in power control and time synchronization will result

6. Both OFDM and CDMA systems have code sequences that are truly orthogonal in the presence of multipath delay spread.

7. Whereas TDMA segments are according to time and CDMA segments are according to spreading codes, OFDM segments are according to frequency.

8. OFDM therefore provides the best of the benefits of TDMA (in that users are orthogonal to one another) and CDMA, thus enabling frequency diversity and out-of-cell interference.

9. Time dispersion leads to intersymbol interference, or ISI, where the energy from one symbol spills over into another symbol, decreasing the BER as a result.

10. OFDM allows the spectrum of each tone to overlap, and because they are orthogonal, they do not interfere with each other. By allowing the tones to overlap, the overall amount of spectrum required is reduced.