Generalized Partial Full-Pilot Zero-Forcing Combining for Distributed Massive MIMO

Abstract

Efficient uplink processing in distributed massive multiple-input multiple-output (D-mMIMO) systems requires effective local combining to significantly mitigate inter-user interference. Recent zero-forcing (ZF) based combining schemes, such as partial full-pilot ZF (PFZF) and protected weak PFZF (PWPFZF), rely on heuristic threshold-based user grouping that may lead to inefficient utilization of spatial degrees of freedom across access points. To address this limitation, we propose an adaptive pilot-aware local combining scheme, generalized PFZF (G-PFZF), that dynamically allocates spatial degrees of freedom based on local channel conditions and replaces heuristic grouping with a decentralized pilot-level optimization framework. Numerical results demonstrate that the proposed G-PFZF scheme achieves significantly higher sum spectral efficiency compared to PFZF and PWPFZF.