Repeater-Assisted MIMO Can Also Boost Frequency Diversity: A Semi-Analytic Study

TL;DR

This study demonstrates that repeater-assisted massive MIMO can enhance frequency diversity, improving BER performance at high SNRs through a semi-analytic analysis of DFT-s-OFDM systems.

Contribution

It provides a semi-analytic BER expression for repeater-assisted MIMO systems and shows how repeater delay can be used to optimize frequency diversity.

Findings

Repeater delay reshapes frequency correlation.

The derived BER expression matches simulation results.

Delay tuning improves high-SNR BER decay.

Abstract

Massive multiple-input multiple-output (MIMO) has enabled substantial spatial multiplexing and array gains in real-world systems, while distributed MIMO (D-MIMO) improves macro-diversity over wide areas at the cost of deployment complexity. Repeater-assisted massive MIMO (RA-MIMO) is a lower-cost alternative that can recover key distributed-MIMO advantages. This paper asks whether repeater assistance can also enhance frequency diversity. We study an uncoded discrete Fourier transform-spread orthogonal frequency-division multiplexing (DFT-s-OFDM) uplink with one-tap single-carrier frequency-domain equalization (SC-FDE) based on minimum mean-square error (MMSE) and derive a receiver-matched semi-analytic bit-error rate (BER) expression by averaging over channel and interference realizations, without Gaussian approximation of residual despreading interference. The analysis clarifies how repeater delay reshapes frequency correlation, and waveform simulations confirm tight agreement with the derived expression together with improved high-signal-to-noise ratio (SNR) BER decay, highlighting delay as a practical tuning knob.