Channel Estimation with Selective Superimposed Pilot Sequences under Fast Fading Environments

Abstract

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 there is no drop in information rate. 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 the longer frame leads to the lower correlation, but also to the lower channel tracking capability. In this paper, we propose a selective superimposed pilot channel estimation scheme with selecting a pilot sequence that has a low correlation with a data symbol sequence from the set of the pilot sequences assigned to the transmitter. Note that the superimposed channel estimation scheme with one pilot sequence assigned to the transmitter is the conventional superimposed channel estimation scheme. We show that the proposed channel estimation scheme is superior to the conventional superimposed channel estimation scheme (pilot sequence = 1). We also show that the proposed channel estimation scheme can achieve the good channel estimate even under fast fading environments. Moreover, we show that the proposed channel estimation scheme is superior to the pilot assisted channel estimation scheme, although pilot symbol power is a deterioration factor in the proposed channel estimation scheme.