Integrated Sensing and Communications with Joint Beam Squint and Beam Split for Massive MIMO

TL;DR

This paper proposes a novel ISAC method leveraging joint beam squint and beam split effects in massive MIMO-OFDM systems to enhance sensing range and reduce time overhead, demonstrating superior performance through simulations.

Contribution

It introduces a new sensing approach that exploits beam squint and beam split effects, using TTD lines and frequency feedback to improve efficiency and range in massive MIMO systems.

Findings

Effective utilization of beam squint for direction sensing.

Expanded sensing range via beam split effect.

Significant reduction in sensing time overhead.

Abstract

Integrated sensing and communications (ISAC) has attracted tremendous attention for the future 6G wireless communication systems. To improve the transmission rates and sensing accuracy, massive multi-input multi-output (MIMO) technique is leveraged with large transmission bandwidth. However, the growing size of transmission bandwidth and antenna array results in the beam squint effect, which hampers the communications. Moreover, the time overhead of the traditional sensing algorithm is prohibitive for practical systems. In this paper, instead of alleviating the wideband beam squint effect, we take advantage of joint beam squint and beam split effect and propose a novel user directions sensing method integrated with massive MIMO orthogonal frequency division multiplexing (OFDM) systems. Specifically, with the beam squint effect, the BS utilizes the true-time-delay (TTD) lines to steer the beams of different OFDM subcarriers towards different directions simultaneously. The users feedback the subcarrier frequency with the maximum array gain to the BS. Then, the BS calculates the direction based on the subcarrier frequency feedback. Futhermore, the beam split effect introduced by enlarging the inter-antenna spacing is exploited to expand the sensing range. The proposed sensing method operates over frequency-domain, and the intended sensing range is covered by all the subcarriers simultaneously, which reduces the time overhead of the conventional sensing significantly. Simulation results have demonstrated the effectiveness as well as the superior performance of the proposed ISAC scheme.