  Decision-directed channel estimation (DDCE) is one kind of blind channel
estimation method that tracks the channel blindly by an iterative algorithm
without relying on the pilots, which can increase the utilization of wireless
resource. However, one major problem of DDCE is the performance degradation
caused by error accumulation during the tracking process. In this paper, we
propose an reliable DDCE (RDDCE) scheme for an OFDM-based communication system
in the time-varying deep fading environment. By combining the conventional DDCE
and discrete Fourier transform (DFT) channel estimation method, the proposed
RDDCE scheme selects the reliable estimated channels on the subcarriers which
are less affected by deep fading, and then estimates the channel based on the
selected subcarriers by an extended DFT channel estimation where the indices of
selected subcarriers are not distributed evenly. Simulation results show that
RRDCE can alleviate the performance degradation effectively, track the channel
with high accuracy on a long time scale, and has good performance under
time-varying and noisy channel conditions.
