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Rician Channel Modelling for Super Wideband MIMO Communications

Sachitha C. Bandara, Peter J. Smith, Erfan Khordad, Robin Evans, Rajitha Senanayake

TL;DR

This work develops a physically‑consistent Rician MIMO channel model for super‑wideband systems by integrating circuit theory with multiport networks to capture mutual coupling (MC) across an extremely large bandwidth. It reexpresses the circuit‑theoretic model as a standard MIMO channel, enabling conventional analysis of MC, antenna layout, and bandwidth effects, and derives a frequency‑dependent K‑factor $K(f)$ to describe the LoS dominance. The authors formulate a whitened, MC‑aware channel $ ilde{ extbf{H}}(f)$ that combines a distorted LoS term with a frequency‑dependent, Kronecker‑structured scattered term through effective correlation matrices $ extbf{C}_R(f)$ and $ extbf{C}_T(f)$, and they model spatial and frequency correlations using a local scattering model and Jake’s correlation, respectively. Numerical results across $100 ext{ MHz}$ to $30 ext{ GHz}$ show bandwidth widening due to MC, LoS steering‑vector distortion impacting beamforming, and a frequency‑dependent reduction of spatial correlations at low frequencies, highlighting the interplay between MC, bandwidth, and correlation. The framework enables physically‑grounded design insights for SW‑MIMO arrays and motivates extension to multi‑user scenarios under the same correlated Rician channel model.

Abstract

Recent developments in Multiple-Input-Multiple-Output (MIMO) technology include packing a large number of antenna elements in a compact array to access the bandwidth benefits provided by higher mutual coupling (MC). The resulting super-wideband (SW) systems require a circuit-theoretic framework to handle the MC and channel models which span extremely large bands. Hence, in this paper, we make two key contributions. First, we develop a physically-consistent Rician channel model for use with SW systems. Secondly, we express the circuit-theoretic models in terms of a standard MIMO model, so that insights into the effects of antenna layouts, MC, and bandwidth can be made using standard communication theory. For example, we show the bandwidth widening resulting from the new channel model. In addition, we show that MC distorts line-of-sight paths which has beamforming implications. We also highlight the interaction between spatial correlation and MC and show that tight coupling reduces spatial correlations at low frequencies.

Rician Channel Modelling for Super Wideband MIMO Communications

TL;DR

This work develops a physically‑consistent Rician MIMO channel model for super‑wideband systems by integrating circuit theory with multiport networks to capture mutual coupling (MC) across an extremely large bandwidth. It reexpresses the circuit‑theoretic model as a standard MIMO channel, enabling conventional analysis of MC, antenna layout, and bandwidth effects, and derives a frequency‑dependent K‑factor to describe the LoS dominance. The authors formulate a whitened, MC‑aware channel that combines a distorted LoS term with a frequency‑dependent, Kronecker‑structured scattered term through effective correlation matrices and , and they model spatial and frequency correlations using a local scattering model and Jake’s correlation, respectively. Numerical results across to show bandwidth widening due to MC, LoS steering‑vector distortion impacting beamforming, and a frequency‑dependent reduction of spatial correlations at low frequencies, highlighting the interplay between MC, bandwidth, and correlation. The framework enables physically‑grounded design insights for SW‑MIMO arrays and motivates extension to multi‑user scenarios under the same correlated Rician channel model.

Abstract

Recent developments in Multiple-Input-Multiple-Output (MIMO) technology include packing a large number of antenna elements in a compact array to access the bandwidth benefits provided by higher mutual coupling (MC). The resulting super-wideband (SW) systems require a circuit-theoretic framework to handle the MC and channel models which span extremely large bands. Hence, in this paper, we make two key contributions. First, we develop a physically-consistent Rician channel model for use with SW systems. Secondly, we express the circuit-theoretic models in terms of a standard MIMO model, so that insights into the effects of antenna layouts, MC, and bandwidth can be made using standard communication theory. For example, we show the bandwidth widening resulting from the new channel model. In addition, we show that MC distorts line-of-sight paths which has beamforming implications. We also highlight the interaction between spatial correlation and MC and show that tight coupling reduces spatial correlations at low frequencies.

Paper Structure

This paper contains 13 sections, 27 equations, 6 figures.

Table of Contents

  1. Introduction
  2. System Model with Circuit Theory framework
  3. Super Wideband Channel Model
  4. Spatial correlations
  5. Frequency selective channels
  6. Modelling the Rician K-factor
  7. Numerical Results
  8. Simulation setup
  9. Results for received signal to noise ratio
  10. Coupling effects on received scattered power
  11. Coupling effects on the LoS channel
  12. Coupling effects on spatial correlations
  13. Conclusion

Figures (6)

  • Figure 1: SIMO Instantaneous SNR under equal power allocation for $N_r = {4, 32}$. The transmitter antenna size, $a_T$ is set to $100\delta$ to avoid bandwidth constraints.
  • Figure 2: SIMO received signal power CDFs of scattered components at $5$ GHz, and $50$ GHz under tight and weak coupling.
  • Figure 4: Effective spatial correlations at the receiver with $N_r = 32$, under tight and weak coupling, for $5$ GHz and $50$ GHz.
  • Figure : (a) Receiver Array Steering Vector
  • Figure : (a) Receiver Array Steering Vector
  • ...and 1 more figures