Continuous phase modulation has been described to me very similar to wikipedia's definition, which basically indicated that the CPM is different from QPSK, for example, because QPSK abruptly shifts phase on symbol transitions. But this isn't true. Every real system is bandlimited, and as such there is no such thing as an abrupt or instantaneous change. In QPSK systems, the bandwidth is limited by a nyquist filter such as a root raised cosine, to be 2*(1+ the excess bandwidth)* the symbol rate.
Per wikipedia; in CPM, "Each symbol is modulated by gradually changing the phase of the carrier from the starting value to the final value, over the symbol duration." This is exactly how PSK works.
My question is, every real system is bandlimited, which means that symbol transitions occur over a finite time period (1/2T ?), which means the instantanous phase of the waveform is continous. That said, what does Continous Phase Modulation mean to imply is done differently than in any other phase modulated waveform