Assume that we have a BPSK modem operating on a wireless voiceband channel with a symbol transmission rate of 2400 symbols/s and a bandwidth efficiency of 1. We want to increase the data rate to 19.2 kb/s.
(a) If we increase the number of points in the constellation until the data rate becomes 19.2 kb/s while the baud rate remains at 2400 symbols/s, what is the number of points in the constellation? What is the bandwidth efficiency of the modulation technique? What is the additional power requirement for the transmitter to keep the quality the same as before? The approximations used in Section 7.2 can be applied.
(b) Repeat part (a) if we use a trellis-coded modulation that doubles the number of points in the constellation and has an overall coding gain of 3 dB.
(c) If we increase the symbol transmission rate to 19,200 and use the same BPSK modulation, what is the additional power requirement for the transmitter to maintain the same quality as a 2400-bit/s modem?