Please give complete explanation, so that it would be easy to understand. Thank you

For the bandpass digital transmissions

(i) Both linear and non-linear modulations are used to support the bandpass digital transmissions. Describe the difference between the two types of modulation

. (ii) Binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) are commonly used. Compare the bit error performance achieved by the two schemes.