Consider an OFDM system in which 1000 subcarriers are each to be modulated at 1000 bits per second. Assume that each subcarrier is to be modulated using QPSK. (a) What is the symbol transmission rate?...

Consider an OFDM system in which 1000 subcarriers are each to be modulated at 1000 bits per second. Assume that each subcarrier is to be modulated using QPSK.

(a) What is the symbol transmission rate?

(b) How close can the subcarriers be spaced and still be orthogonal?

(c) Assume that at least one subcarrier always carries QPSK symbols. What is the lowest data rate that can be supported by this scheme?