Distributed Iterative ML and Message Passing for Grant-Free Cell-Free Massive MIMO Systems

Zhao Z, Forsch C, Cottatellucci L, Slock D (2026)

Publication Type: Conference contribution

Publication year: 2026

Publisher: IEEE

Pages Range: 65-70

Conference Proceedings Title: 2025 IEEE Middle East Conference on Communications and Networking (MECOM)

Event location: Cairo EG

DOI: 10.1109/MECOM67453.2025.11439572

Abstract

Cell-Free (CF) Massive Multiple-Input Multiple-Output (MaMIMO) is considered one of the leading candidates for enabling next-generation wireless communication. With the growing interest in the Internet of Things (IoT), the Grant-Free (GF) access scheme has emerged as a promising solution to support massive device connectivity. The integration of GF and CF-MaMIMO introduces significant challenges, particularly in designing distributed algorithms for activity detection and pilot contamination mitigation. In this paper, we propose a distributed algorithm that addresses these challenges. Our method first employs a component-wise iterative distributed Maximum Likelihood (ML) approach for activity detection, which considers both the pilot and data portions of the received signal. This is followed by a Pseudo-Prior Hybrid Variational Bayes and Expectation Propagation (PP-VB-EP) algorithm for joint data detection and channel estimation. Compared to conventional VBEP, the proposed PP-VB-EP demonstrates improved convergence behavior and reduced sensitivity to initialization, especially when data symbols are drawn from a finite alphabet. The pseudo prior used in PP-VB-EP acts as an approximated posterior and serves as a regularization term that prevents the Message Passing (MP) algorithm from diverging. To compute the pseudo prior in a distributed fashion, we further develop a distributed version of the Variable-Level Expectation Propagation (VL-EP) algorithm.

Authors with CRIS profile

Christian Forsch Lehrstuhl für Digitale Übertragung (IDC) Laura Cottatellucci Professur für Digitale Übertragung

Involved external institutions

Institut Eurécom (EURECOM) FR France (FR)

How to cite

APA:

Zhao, Z., Forsch, C., Cottatellucci, L., & Slock, D. (2025). Distributed Iterative ML and Message Passing for Grant-Free Cell-Free Massive MIMO Systems. In 2025 IEEE Middle East Conference on Communications and Networking (MECOM) (pp. 65-70). Cairo, EG: IEEE.

MLA:

Zhao, Zilu, et al. "Distributed Iterative ML and Message Passing for Grant-Free Cell-Free Massive MIMO Systems." Proceedings of the 2025 IEEE Middle East Conference on Communications and Networking (MECOM), Cairo IEEE, 2025. 65-70.

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