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Secure Transmission in Cell-Free Massive MIMO under Active Eavesdropping

Yasseen Sadoon Atiya, Zahra Mobini, Hien Quoc Ngo, Michail Matthaiou

TL;DR

PPZF can substantially outperform the conventional maximum-ratio transmission (MRT) scheme by providing around 2-fold improvement in the SSE compared to the MRT scheme, and a large-scale-based greedy AP selection scheme to improve the secrecy spectral efficiency (SSE).

Abstract

We study secure communications in cell-free massive multiple-input multiple-output (CF-mMIMO) systems with multi-antenna access points (APs) and protective partial zero-forcing (PPZF) precoding. In particular, we consider an active eavesdropping attack, where an eavesdropper contaminates the uplink channel estimation phase by sending an identical pilot sequence with a legitimate user of interest. We formulate an optimization problem for maximizing the received signal-to-noise ratio (SINR) at the legitimate user, subject to a maximum allowable SINR at the eavesdropper and maximum transmit power at each AP, while guaranteeing specific SINR requirements on other legitimate users. The optimization problem is solved using a path-following algorithm. We also propose a large-scale-based greedy AP selection scheme to improve the secrecy spectral efficiency (SSE). Finally, we propose a simple method for identifying the presence of an eavesdropper within the system. Our findings show that PPZF can substantially outperform the conventional maximum-ratio transmission (MRT) scheme by providing around 2-fold improvement in the SSE compared to the MRT scheme. More importantly, for PPZF precoding scheme, our proposed AP selection can achieve a remarkable SSE gain of up to 220%, while our power optimization approach can provide an additional gain of up to 55% compared with a CF-mMIMO system with equal power allocation.

Secure Transmission in Cell-Free Massive MIMO under Active Eavesdropping

TL;DR

PPZF can substantially outperform the conventional maximum-ratio transmission (MRT) scheme by providing around 2-fold improvement in the SSE compared to the MRT scheme, and a large-scale-based greedy AP selection scheme to improve the secrecy spectral efficiency (SSE).

Abstract

We study secure communications in cell-free massive multiple-input multiple-output (CF-mMIMO) systems with multi-antenna access points (APs) and protective partial zero-forcing (PPZF) precoding. In particular, we consider an active eavesdropping attack, where an eavesdropper contaminates the uplink channel estimation phase by sending an identical pilot sequence with a legitimate user of interest. We formulate an optimization problem for maximizing the received signal-to-noise ratio (SINR) at the legitimate user, subject to a maximum allowable SINR at the eavesdropper and maximum transmit power at each AP, while guaranteeing specific SINR requirements on other legitimate users. The optimization problem is solved using a path-following algorithm. We also propose a large-scale-based greedy AP selection scheme to improve the secrecy spectral efficiency (SSE). Finally, we propose a simple method for identifying the presence of an eavesdropper within the system. Our findings show that PPZF can substantially outperform the conventional maximum-ratio transmission (MRT) scheme by providing around 2-fold improvement in the SSE compared to the MRT scheme. More importantly, for PPZF precoding scheme, our proposed AP selection can achieve a remarkable SSE gain of up to 220%, while our power optimization approach can provide an additional gain of up to 55% compared with a CF-mMIMO system with equal power allocation.
Paper Structure (19 sections, 2 theorems, 77 equations, 10 figures, 1 table, 2 algorithms)

This paper contains 19 sections, 2 theorems, 77 equations, 10 figures, 1 table, 2 algorithms.

Table of Contents

  1. System Model
  2. Uplink Training
  3. Downlink Data Transmission
  4. Precoding Design
  5. Secrecy Performance Analysis
  6. Spectral Efficiency of the Legitimate Links
  7. Spectral Efficiency of the Eavesdropper
  8. Secrecy Spectral Efficiency
  9. Access Point Selection and Power Optimization
  10. Access Point Selection
  11. Power Optimization
  12. Detection of Eavesdropping Attack
  13. Simulation Results
  14. Performance Evaluation
  15. Multiple-Antenna Eavesdropper
  16. ...and 4 more sections

Key Result

Proposition 1

The closed-form expression for the SE of user $k$ with PPZF precoding under an active eavesdropping attack can be expressed as eq:SE_k1, where where $\delta_{l, k} \triangleq 1$ if $k\in \mathcal{S}_{l}$ and $\delta_{l, k} \triangleq 0$ if $k\in \mathcal{W}_{l}$.

Figures (10)

  • Figure 1: Uplink training phase
  • Figure 2: Downlink data transmission phase
  • Figure 4: Probability of active eavesdropping attack detection as a function of $\epsilon_{\text{threshold}}$.
  • Figure 5: SSE versus $L$ for PZZF and MRT precoding schemes with AP selection and without it. Here, $M=4$, $K=10$, and $r = 100$ m.
  • Figure 6: SSE with AP selection and the proposed power allocation versus $L$ for PPZF, ZF, and MRT precoding schemes. Here, $M=4$ and $K=10$, and $r = 100$ m with AP selection scheme, EPA, and OPA.
  • ...and 5 more figures

Theorems & Definitions (8)

  • Proposition 1
  • proof
  • Proposition 2
  • proof
  • Remark 1
  • Remark 2
  • Remark 3
  • Remark 4