Adaptive linear predictive frequency tracking and CPM demodulation

Abstract

CPM signals find widespread use in wireless communication systems due to their constant modulus property and spectral efficiency. Frequency discrimination based CPM demodulation approaches require efficient instantaneous frequency tracking. Prior attempts at frequency tracking via adaptive linear prediction have invoked the use of the fixed step-size LMS algorithm. In this paper, we present an efficient algorithm that combines aspects of adaptive linear prediction, frequency tracking and frequency transformations based on multirate operations for CPM demodulation using both the adaptive step-size LMS and adaptive forgetting factor RLS algorithms. Simulation results indicate that these algorithms offer a significant reduction in the associated demodulation errors over the conventional LMS/RLS algorithms.