Two-Step Approach to Time-Domain Channel Estimation for Wideband Millimeter Wave Systems With Hybrid Architecture

Abstract

We consider the problem of time domain (TD) channel estimation for wideband millimeter wave systems with a hybrid architecture. TD channel estimators can exploit both angular and delay domain sparsity, and can perform better than frequency domain (FD) estimators exploiting only angular domain sparsity; however, the former usually require a heavier computational load than the latter. To overcome this difficulty, we propose an efficient, two-step TD channel estimator: in the first step, an effective channel incorporated with beamforming, array responses, and pulse shaping is estimated by the least squares (LS) method; in the second, the desired channel is estimated via an orthogonal matching pursuit (OMP) algorithm. It is analytically shown that the proposed two-step method can yield the same outputs as the original single-step TD estimator when an identity pulse shaping matrix and a unitary pilot matrix are employed. The proposed algorithm is simpler to implement than the other estimators based on OMP, because its sensing matrix is block-diagonal. The simulation results demonstrate that complexity reduction of the proposed method is achieved without (or with minor) performance degradation.