  Delay alignment modulation (DAM) is a promising technology for inter-symbol
interference (ISI)-free communication without relying on sophisticated channel
equalization or multi-carrier transmissions. The key ideas of DAM are delay
precompensation and path-based beamforming, so that the multi-path signal
components will arrive at the receiver simultaneously and constructively,
rather than causing the detrimental ISI. However, the practical implementation
of DAM requires channel state information (CSI) at the transmitter side.
Therefore, in this letter, we study an efficient channel estimation method for
DAM based on block orthogonal matching pursuit (BOMP) algorithm, by exploiting
the block sparsity of the channel vector. Based on the imperfectly estimated
CSI, the delay pre-compensations and tap-based beamforming are designed for
DAM, and the resulting performance is studied. Simulation results demonstrate
that with the BOMP-based channel estimation method, the CSI can be effectively
acquired with low training overhead, and the performance of DAM based on
estimated CSI is comparable to the ideal case with perfect CSI.
