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Mitigation of UE Antenna Calibration Errors via Differential STBC in Cell-Free Massive MIMO

Marx M. M. Freitas, Stefano Buzzi

TL;DR

Simulation results demonstrate that the proposed DSTBC-based transmission effectively mitigates the impact of antenna-dependent phase offsets, restoring near-coherent performance in CF-mMIMO networks.

Abstract

This letter investigates the use of differential space-time block coding (DSTBC) to address antenna array calibration impairments at multi-antenna user equipment (UE) in the downlink (DL) of cell-free massive MIMO (CF-mMIMO) systems. We show that, by exploiting DSTBC, reliable DL communication can be achieved without explicit UE-side calibration or channel phase knowledge. Simulation results demonstrate that the proposed DSTBC-based transmission effectively mitigates the impact of antenna-dependent phase offsets, restoring near-coherent performance in CF-mMIMO networks.

Mitigation of UE Antenna Calibration Errors via Differential STBC in Cell-Free Massive MIMO

TL;DR

Simulation results demonstrate that the proposed DSTBC-based transmission effectively mitigates the impact of antenna-dependent phase offsets, restoring near-coherent performance in CF-mMIMO networks.

Abstract

This letter investigates the use of differential space-time block coding (DSTBC) to address antenna array calibration impairments at multi-antenna user equipment (UE) in the downlink (DL) of cell-free massive MIMO (CF-mMIMO) systems. We show that, by exploiting DSTBC, reliable DL communication can be achieved without explicit UE-side calibration or channel phase knowledge. Simulation results demonstrate that the proposed DSTBC-based transmission effectively mitigates the impact of antenna-dependent phase offsets, restoring near-coherent performance in CF-mMIMO networks.
Paper Structure (8 sections, 20 equations, 3 figures, 1 algorithm)

This paper contains 8 sections, 20 equations, 3 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model and Problem Statement
  3. DSTBC-based DL Data Transmission
  4. Differential Encoding and Transmission
  5. Differential Detection at the Receiver
  6. Complexity Analysis and System Overhead
  7. Numerical Results
  8. Conclusions

Figures (3)

  • Figure 1: Channel non-reciprocity effects caused by hardware-induced complex-valued offsets between antenna $m$ at AP $l$ and antenna $m'$ at UE $k$.
  • Figure 2: CDF of the average SE and BER for each setup. Here: $L = 40$, $K = 20$, $N_{\mathrm{AP}} = 8$, $N_{\mathrm{UE}} = 2$, and $N_{\mathrm{s}} = 2$.
  • Figure 3: Average SE as a function of (a) the number of UE $K$ in the network and (b) the number of antennas per UE, $N_{\mathrm{UE}}$. Here, $L \!=\! 40$, $N_{\mathrm{AP}} \!=\! 8$, $L_k \!=\! 2$, and $N_s = N_{\mathrm{UE}}$.