Carrier Phase Recovery with Linear Modulations

In this chapter we investigate algorithms for carrier phase estimation with linear modulations. As with frequency recovery, ML estimation methods will play a central role in our study. We shall see that various approximations to the ML formulation are possible, leading to different estimation methods. Thus, a rather disparate set of synchronization schemes is anticipated. This is also a consequence of the many scenarios that can be thought of, depending on the specific modulation format and the availability of data/clock information. In this regard the following categories may be envisaged: (i) Modulation format: Modulation may be either offset or non-offset. (ii) Additional knowledge: Clock information may be available or not. Information symbols may be known or not. When they are, they may come either from a known preamble (data-aided schemes) or from the detector output (decision-directed schemes) (iii) Estimator topology: Estimators may be either open loop or closed loop.