1.  Assign 2 pts for a reasonable attempt.  Deduct 1 point for
incorrect data packet transmissions, 1pt for incorrect use of DIFS, 1
pt for incorrect use of SIFS, 1 pt for incorrect ACK transmissions,
and 1 pt for incorrect backoff implementation.

Some people may have assumed that the backoff counter is used for the
very first transmission.  If so, this is fine.  In this case, their
answer would be different from the sample solution.  Give full credit
for them if they got the answer right under this assumption.

2. 4 points for each part.  

For part (a), 1 pt for a reasonable attempt.  Deduct 0.5 point for
wrong source or destination IP address in outer or inner header.
Similarly, deduct 0.5 point for wrong MAC destination address.

For part (b), same policy as part (a).

3. 4 points for each part.

(a) 1 point for attempt.  1 pt for each value of N.  If reasonable
attempt but wrong answer for any N, deduct 0.5 points.

(b) Note that their answers may differ here since they need not assign
just one control channel per cell.  As long as they have a total of
640 voice channels and at least one control channel per cell, they are
fine.  Use the same guidelines as (a).

4. 1.5 points for the first 4 parts and 2 points for part (e).

For first 4 parts, 1 for incorrect reasonable attempt and full otherwise.  

For part (e), 1 pt for attempt. Give another 0.5 pt if they made a minor
mistake.  Full points for correct answer.

5. 8 + 8 + 4 

(a) 2 pts formulae, 2 pts correct application of formulae, 2 pts
BER->FER, and 2 pts final plot.  Give at least 1 pt for each part if
only partially correct -- (1.5 if minor mistake).

(b) 2.5 pts formulae, 2.5 pts correct application of formulae, and 3
pts final plot.  Give at least 1.5 pt for each part if only partially
correct -- (2 if minor mistake).

(c) 2 pts for pointing out intersection, and 2 points for final plot.
Give at least 1 pt for each part if only partially correct -- (1.5 if
minor mistake).