Title: Interference in dynamic TDD: effect of MIMO rank on DoF and transceiver design

Authors: Amel Tibhirt; Dirk Slock; Yi Yuan-Wu

Addresses: Orange Labs, Châtillon, 92320, France ' Communication Systems Department, EURECOM, Biot, 06410, France ' Orange Labs, Châtillon, 92320, France

Abstract: Dynamic time division duplexing (DynTDD) provides greater flexibility than static time division duplexing (TDD) by dynamically adjusting time slot allocation based on communication needs. However, flexibility may be limited by crosslink interference (CLI) from neighboring cells using different transmission directions on partially-overlapping time-frequency resources. To mitigate this interference, coordinated beamforming is critical. This study focuses on zero-forcing (ZF) transmit beamforming at initialisation, with and without water-filling, and the iterative weighted minimum mean-square error (WMMSE) algorithm to maximise the sum rate in a MIMO user equipment to user equipment (UE-to-UE) interference channel (IC). Additionally, the study explores the potential benefits of non-uniform degrees-of-freedom (DoF) at uplink (UL) and/or downlink (DL) UEs, increasing the sum of DoF, resulting in a higher sum rate at high SNR.

Keywords: DynTDD; dynamic time division duplexing; MIMO; multiple input multiple output; CLI; cross link interference; interference alignment; rank deficient; DoF; degree of freedom; beamforming; WMMSE; weighted minimum mean-square error; zero-forcing; water-filling.

DOI: 10.1504/IJMNDI.2023.133246

International Journal of Mobile Network Design and Innovation, 2023 Vol.10 No.4, pp.222 - 232

Received: 26 May 2023
Accepted: 08 Jun 2023
Published online: 03 Sep 2023 *