The theoretical BER for QPSK modulation, with gray constellation ordering, is given by 1 P. = = erfc () You are asked to derive the theoretical BER for QPSK modulation with binary constellation ordering. Present your theoretical BER formula for QPSK with binary constellation ordering mapping. You must include the key steps of your derivation. Note that you may either derive the exact BER expression or an approximated BER expression. Please mention whether your BER formula is exact or approximated. In either case, in addition to the derivation steps, you may also write a few sentences to explain how the formula is obtained. [3 marks]