Spatial- and Frequency-Wideband Effects in Millimeter-Wave Massive MIMO Systems

TL;DR

This paper investigates the dual-wideband effects in millimeter-wave massive MIMO systems, addressing spatial and frequency wideband effects with novel channel estimation strategies that reduce training overhead and eliminate pilot contamination.

Contribution

It introduces a new array signal processing approach to model and mitigate dual-wideband effects in massive MIMO, applicable to both TDD and FDD systems.

Findings

Efficient channel estimation reduces training overhead.

Proposed methods effectively handle dual-wideband effects.

Numerical results confirm improved system performance.

Abstract

When there are a large number of antennas in massive MIMO systems, the transmitted wideband signal will be sensitive to the physical propagation delay of electromagnetic waves across the large array aperture, which is called the spatial-wideband effect. In this scenario, transceiver design is different from most of the existing works, which presume that the bandwidth of the transmitted signals is not that wide, ignore the spatial-wideband effect, and only address the frequency selectivity. In this paper, we investigate spatial- and frequency-wideband effects, called dual-wideband effects, in massive MIMO systems from array signal processing point of view. Taking mmWave-band communications as an example, we describe the transmission process to address the dual-wideband effects. By exploiting the channel sparsity in the angle domain and the delay domain, we develop the efficient uplink and downlink channel estimation strategies that require much less amount of training overhead and cause no pilot contamination. Thanks to the array signal processing techniques, the proposed channel estimation is suitable for both TDD and FDD massive MIMO systems. Numerical examples demonstrate that the proposed transmission design for massive MIMO systems can effectively deal with the dual-wideband effects.