Pre-Equalization Aided Grant-Free Massive Access in Massive MIMO System

Yueqing Wang, Yikun Mei, Zhen Gao*, Ziwei Wan, Boyu Ning, De Mi, Sami Muhaidat

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The spatial diversity and multiplexing advantages of massive multi-input-multi-output (mMIMO) can significantly improve the capacity of massive non-orthogonal multiple access (NOMA) in machine type communications. However, state-of-the-art grant-free massive NOMA schemes for mMIMO systems require accurate estimation of random access channels to perform activity detection and the following coherent data demodulation, which suffers from excessive pilot overhead and access latency. To address this, we propose a pre-equalization aided grant-free massive access scheme for mMIMO systems, where an iterative detection scheme is conceived. Specifically, the base station (BS) firstly activates one of its antennas (i.e., beacon antenna) to broadcast a beacon signal, which facilitates the user equipment (UEs) to perform downlink channel estimation and pre-equalize the uplink random access signal with respect to the channels associated with the beacon antenna. During the uplink transmission stage, the BS detects UEs' activity and data by using the proposed iterative detection algorithm, which consists of three modules: coarse data detection (DD), data-aided channel estimation (CE), and fine DD. In the proposed algorithm, the joint activity and DD is firstly performed based on the signals received by the beacon antenna. Subsequently, the DD is further refined by iteratively performing data-aided CE module and fine DD module using signals received by all BS antennas. Our simulation results demonstrate that the proposed scheme outperforms state-of-the-art mMIMO-based grant-free massive NOMA schemes with the same access latency.

Original languageEnglish
JournalIEEE Transactions on Vehicular Technology
DOIs
Publication statusAccepted/In press - 2025

Keywords

  • approximate message passing
  • compressive sensing
  • Massive access
  • massive MIMO
  • massive non-orthogonal multiple access (NOMA)
  • pre-equalization

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