Continuous phase modulation is commonly used in wireless modems. In contrast with other coherent digital phase modulation techniques where the carrier phase abruptly resets to zero at the start of every symbol (e.g., M-PSK), with CPM the carrier phase is modulated in a continuous manner. For instance, with QPSK the carrier instantaneously jumps from a sine to cosine (i.e., a 90 degree phase shift) whenever one of the two message bits of the current symbol differs from the two message bits of the previous symbol. this discontinuity requires a relatively large percentage of the power to occur outside of the intended band (e.g., high fractional out of band power), leading to poor spectral efficiency. Therefore, CPM is attractive because phase continuity yield high spectral efficiency, and the constant envelope yields excellent power efficiency. Here drawback can be the high implementation complexity required for an optimal receiver.