Joint Channel Estimation and Sensing for Wideband mmWave Systems With Beam Squint and Split

Abstract

Next-generation wireless communications must be capable of meeting large capacity demands while simultaneously enabling highly accurate sensing. Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) is a pivotal enabler for integrated sensing and communication (ISAC) systems, owing to its large available bandwidth that supports both high-capacity communications and high-resolution sensing. In wideband mmWave massive MIMO systems, beam squint results in frequency-dependent beam directions, while beam split produces mirrored beams when the antenna spacing exceeds half a wavelength. Although these phenomena can impair channel estimation, they also offer opportunities to exploit additional diversity and enable more flexible system design. In this paper, we investigate a chirp-based ISAC mmWave massive MIMO system with beam squint and beam split. Specifically, we first propose a chirp-based mmWave massive MIMO system, derive the input-output relationship under beam squint conditions, and analyze the conditions required for estimating Doppler shifts and delays. Next, we develop a channel estimation framework that exploits the phase-jump characteristics of chirp signals to enable efficient parameter estimation. By jointly leveraging beam split and beam squint, the proposed scheme accelerates the beam scanning process, thereby improving both the accuracy and efficiency of channel estimation. We also propose a sensing algorithm that leverages multipath delay differences to compensate for transmitter-receiver clock asynchronism, enabling precise localization without external synchronization. Finally, simulation results demonstrate the effectiveness of our proposed channel estimation and sensing schemes.