Flexible Duplexing for Multi-User Distributed MIMO Networks

Abstract

Distributed MIMO networks can improve coverage and reliability through spatial diversity, but their performance is often limited by external interference and fixed duplex operation. This paper develops an interference-aware distributed MIMO framework that integrates flexible duplexing (FlexD) with maximum ratio transmission and combining (MRT/MRC), enabling communication directions to adapt dynamically to channel and interference conditions. Closed-form and asymptotic outage probability expressions are derived under both full and partial channel state information (CSI), explicitly characterizing the joint benefits of spatial diversity and opportunistic duplex scheduling. For shared-spectrum operation, a max-min fairness problem is formulated to jointly optimize communication directions and transmit powers in the presence of inter-pair interference. Numerical results validate the analysis and show that the proposed distributed MIMO FlexD framework substantially outperforms conventional half-duplex (HD) and full-duplex (FD) schemes in outage probability, energy efficiency, and data availability, with performance gains increasing with spatial diversity.