Carrier frequency drift estimation for high mobility hierarchical-modulated MIMO-OFDM systems

In this paper the implementation of hierarchical- modulated pilot signals for carrier frequency drift estimation in high mobility multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system is introduced. Specifically for a hierarchical-modulated 64QAM-OFDM system in which three Layers with two bits in each Layer are defined from the constellation point and the carrier frequency drift estimation is facilitated from every Layer instead of using all six constellation bits to possibly simplify the design and reduce the time in the estimation process. The carrier frequency drift estimation by using only one Layer and the system performance at the receiver terminal by utilizing this Layer's estimated carrier frequency drift are simulated and compared for various high mobile speeds in Rayleigh fading channels.