Channel estimation with selective superimposed pilot sequences under fast fading environments

Recently, superimposed pilot channel estimation has been proposed for wireless communications, where the pilot symbol sequence is superimposed on a data symbol sequence and transmitted together, and thus it has a high spectral efficiency. In this scheme, the receiver correlates the received signal sequence with the pilot symbol sequence, and obtains the channel estimate. However, the correlation between the pilot symbol sequence and the data symbol sequence deteriorates the channel estimation accuracy. The use of a longer frame leads to lower correlation, but also to a lower channel tracking capability. In this paper, we propose a selective superimposed pilot channel estimation scheme by selecting a pilot sequence that has a low correlation with the data symbol sequence from the set of the pilot sequences assigned to the transmitter. We show that the proposed channel estimation is superior to the conventional superimposed channel estimation (pilot=1), and the proposed scheme can achieve good channel estimation even under fast fading environments.