Channel Parameter Estimation Using a Wideband LFM Preamble: Comparison of the Fractional Fourier Transform and Matched Filtering

In this paper, we present an improvement of an existing method to estimate the channel parameters of an underwater acoustic channel in a wideband scenario. For underwater acoustic communications, the channel is characterized by paths having both time delay and Doppler scale. In this paper we focus on using a linear frequency modulated (LFM) preamble to estimate the channel parameters. We propose an improvement to the state-of-the-art method, which utilizes the fractional Fourier transform (FrFT), and show that matched filtering and the FrFT method can both be viewed as integral transforms having the same kernel. We argue that, contrary to the prevailing belief in the literature, matched filtering is superior compared to the FrFT method for channel parameter estimation. We support our findings using numerical experiments.