Why do different modulation schemes(BPSK, QPSK, QAM16, QAM64 and StarQAM16) yield different numbers of receive bits at high SNRs? For some SNRs, lower order modulation schemes yield higher bit rates. Why is this the case?
i am not expert , but i think the high modulation schemes compact more bits inside one symbol and symbols are more close to each other, so on low sinr the error of high modulation schemes increase because the symbols are close to each other ,and when error occur it will affect more bits than low modulation schemes.
so yes in low sinr low modulation scheme is better