Abstract
In most blind channel estimations, the channel gains are correctly estimated but the channel phases are not necessarily estimated correctly: the channel estimates are often accompanied with phase ambiguity. To resolve this phase ambiguity problem, we propose a semi-blind channel estimation for QAM (Quadrature Amplitude Modulation) -OFDM (Orthogonal Frequency Division Multiplex) systems using the statistical properties of transmitted symbols in addition to the measurement of received symbols in each subcarrier under LoS (Line of Sight) transmission environments; i) the absolute value of the channel phase is less than π/2 at all subcarrier and is less than π/4 for at least one subcarrier. The proposed method can estimate the channel phase up to ±π/2 without phase wrapping. From several simulations for 50 subcarriers with 16 QAM using 256 OFDM blocks, it has been confirmed that the proposed estimation can estimate the channel at high precision using 256 OFDM blocks at SNR ＝ 20[dB].
