Question: Suppose you are asked to design a 400 bit per second modem for a noisy bandlimited and power-limited passband channel. You determine that with reasonable excess bandwidth, a symbol rate of 100 symbol per second is possible.
(a) For an uncoded system, what is the required alphabet size? Choose a constellation.
(b) For a two-dimensional trellis coded system, what is the required alphabet size? Choose a constellation.
(c) Suppose that to get an acceptable probability of error the uncoded system requires 4 dB more power than the channel can tolerate. How would you overcome this problem?