Two Choice Hard Thresholding Pursuit (TCHTP) for Delay-Doppler Channel Estimation in OTFS

In this letter, we develop a low complexity fast greedy sparse recovery algorithm known as Two Choice Hard Thresholding Pursuit (TCHTP) to estimate delay-Doppler locations and the associated channel state information (DDLCSI) for orthogonal-time-frequency-space (OTFS) systems, without the explicit knowledge of the number of delay-Doppler (DD) paths. Unlike the existing greedy algorithms, the proposed scheme simultaneously estimates the DDLCSI as well as the number of DD paths. Furthermore, we perform computational complexity calculations for the proposed TCHTP and the state-of-the-art technique, and observe that the proposed method enjoys reduced computational complexity along with fast convergence speed compared to the state-of-the-art technique. Numerical simulations validate the superiority of the proposed TCHTP algorithm in terms of mean squared error of the DDLCSI estimate, estimate of the number of DD paths, bit-error-rate, computational complexity and execution time.