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Performance Evaluation of Movable Antenna Arrays in Wideband Multi-User MIMO Systems

Amna Irshad, Emil Björnson, Alva Kosasih, Vitaly Petrov

Abstract

Future wireless networks are expected to support increasingly high data rates and user densities, motivating advanced multi-antenna architectures capable of adapting to dynamic propagation environments. Movable antenna (MA) arrays have recently emerged as an extension of massive MIMO, enabling physical repositioning of antenna elements to better exploit spatial diversity and mitigate inter-user interference. While prior studies report promising gains under idealized assumptions, their performance under realistic wideband multi-user operation remains insufficiently understood. This paper presents a comprehensive evaluation of MA-enabled systems in practical uplink and downlink scenarios. A wideband OFDM system model is developed, and novel closed-form sum-rate expressions are derived for both uplink and downlink under linear and nonlinear processing. Hardware impairments are incorporated via an EVM-based model, from which a distortion-aware UL/DL duality is established and the resulting high-SNR sum rate ceiling is analytically characterized. In addition, the interactions between antenna position optimization, receiver processing, and user loading are examined, and performance is evaluated under both time-division duplexing (TDD) and frequency-division duplexing (FDD). The results show that movable antennas can provide noticeable gains in low-impairment regimes with strong multi-user interference, but these benefits are highly scenario-dependent and diminish under hardware-impairment-limited conditions or in rich-scattering environments. These findings highlight the importance of carefully assessing deployment conditions when considering antenna mobility as an alternative to conventional fixed array configurations.

Performance Evaluation of Movable Antenna Arrays in Wideband Multi-User MIMO Systems

Abstract

Future wireless networks are expected to support increasingly high data rates and user densities, motivating advanced multi-antenna architectures capable of adapting to dynamic propagation environments. Movable antenna (MA) arrays have recently emerged as an extension of massive MIMO, enabling physical repositioning of antenna elements to better exploit spatial diversity and mitigate inter-user interference. While prior studies report promising gains under idealized assumptions, their performance under realistic wideband multi-user operation remains insufficiently understood. This paper presents a comprehensive evaluation of MA-enabled systems in practical uplink and downlink scenarios. A wideband OFDM system model is developed, and novel closed-form sum-rate expressions are derived for both uplink and downlink under linear and nonlinear processing. Hardware impairments are incorporated via an EVM-based model, from which a distortion-aware UL/DL duality is established and the resulting high-SNR sum rate ceiling is analytically characterized. In addition, the interactions between antenna position optimization, receiver processing, and user loading are examined, and performance is evaluated under both time-division duplexing (TDD) and frequency-division duplexing (FDD). The results show that movable antennas can provide noticeable gains in low-impairment regimes with strong multi-user interference, but these benefits are highly scenario-dependent and diminish under hardware-impairment-limited conditions or in rich-scattering environments. These findings highlight the importance of carefully assessing deployment conditions when considering antenna mobility as an alternative to conventional fixed array configurations.
Paper Structure (19 sections, 3 theorems, 36 equations, 11 figures, 1 table, 1 algorithm)

This paper contains 19 sections, 3 theorems, 36 equations, 11 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. Main Contributions
  3. System Model
  4. Uplink Rates with Hardware Distortion
  5. Linear receive combining
  6. Non-linear decoding with interference cancellation
  7. Downlink Rates with Hardware Distortion
  8. Linear transmit precoding
  9. Non-linear precoding with dirty paper coding
  10. Problem Formulation and Solution
  11. Proposed Solution Algorithm
  12. Performance Evaluation
  13. Narrowband vs. wideband
  14. Impact of hardware impairments
  15. Linear vs non-linear processing
  16. ...and 4 more sections

Key Result

Proposition 1

Suppose the power allocation is selected as $\mathbf{D}_\rho[\nu] =\rho\mathbf{A}[\nu]$, where $\mathbf{A}[\nu]=\diag(a_1[\nu],\ldots,a_K[\nu])$ is a fixed matrix and $\rho$ is a parameter. If $\bar{\mathbf{H}}[\nu]$ has rank $K$ and $\hbox{\small $\mathrm{EVM}$}>0$, then

Figures (11)

  • Figure 1: Illustration of the considered multi-suer multipath channel setups.
  • Figure 2: Illustration of all considered benchmark arrays with 16 antennas. The antenna locations for the movable antennas were computed for a single random realization of the user locations.
  • Figure 3: Example of user distribution with 100 Monte Carlo realizations.
  • Figure 4: The average uplink sum rate with SIC for a varying number of subcarriers. The BS has 16 antennas and communicates with 10 users.
  • Figure 5: Variation of the user rates for two specific numbers of subcarriers (1 and 150) for both LoS-dominant and rich scattering environments, for 0.02 EVM and 10 users.
  • ...and 6 more figures

Theorems & Definitions (3)

  • Proposition 1
  • Lemma 1
  • Corollary 1