Is Repeater-Assisted Massive MIMO Compatible with Dynamic TDD?

TL;DR

This paper develops an optimization framework for repeater gain in dynamic TDD massive MIMO networks, balancing amplification of desired signals against interference to improve spectral efficiency.

Contribution

It introduces a joint amplification and phase shift optimization method for repeater gain in dynamic TDD massive MIMO, addressing interference challenges.

Findings

The proposed algorithm effectively calibrates repeater gain to enhance desired signals.

Spectral efficiencies are derived for both uplink and downlink in the presence of repeaters.

Numerical results demonstrate improved performance through optimized gain calibration.

Abstract

We present a framework for joint amplification and phase shift optimization of the repeater gain in dynamic time-division duplex (TDD) repeater-assisted massive MIMO networks. Repeaters, being active scatterers with amplification and phase shift, enhance the received signal strengths for users. However, they inevitably also amplify undesired noise and interference signals, which become particularly prominent in dynamic TDD systems due to the concurrent downlink (DL) and uplink (UL) transmissions, introducing cross-link interference among access points and users operating in opposite transmit directions. This causes a non-trivial trade-off between amplification of desired and undesired signals. To underpin the conditions under which such a trade-off can improve performance, we first derive DL and UL spectral efficiencies (SEs), and then develop a repeater gain optimization algorithm for SE maximization. Numerically, we show that our proposed algorithm successfully calibrates the repeater gain to amplify the desired signal while limiting the interference.