Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Caching Yields up to 5x Spectral Efficiency in Multi-Beam Satellite Communications

Hui Zhao, Dirk Slock, Petros Elia

TL;DR

This work tackles the spectral-efficiency bottleneck in multi-beam SATCOM by introducing vector coded caching (VCC), which uses receiver caches to enable interference-aware, parallel transmission of multiple precoded vectors under Rician-shadowed fading. By combining two-phase cache placement with MF precoding and accounting for CSI acquisition overhead and imperfect CSIT, it derives closed-form approximations for average sum-rate and the effective spectral-efficiency gain, showing substantial gains of $3\times$ to $5.5\times$ over cacheless MU-MISO. The results are validated by simulations across static and dynamic channel scenarios, demonstrating that the gains persist under practical conditions and CSI imperfections. Overall, VCC represents a pure physical-layer enhancement that can significantly narrow the spectral efficiency gap between SATCOM and wired networks, while enabling potentially leaner, higher-throughput satellite architectures.

Abstract

This paper examines the integration of vector coded caching (VCC) into multi-beam satellite communications (SATCOM) systems and demonstrates that even limited receiver-side caching can substantially enhance spectral efficiency. By leveraging cached content to suppress interference, VCC enables the concurrent transmission of multiple precoded signal vectors that would otherwise require separate transmission resources. This leads to a multiplicative improvement in resource utilization in SATCOM. To characterize this performance, we model the satellite-to-ground channel using Rician-shadowed fading and after incorporating practical considerations such as matched-filter precoding, channel state information (CSI) acquisition overhead as well as CSI imperfections at the transmitter, we here derive closed-form expressions for the average sum rate and spectral efficiency gain of VCC in SATCOM. Our analysis, tightly validated through numerical simulations, reveals that VCC can yield spectral efficiency gains of 300% to 550% over traditional multi-user MISO SATCOM with the same resources. These gains -- which have nothing to do with multicasting, prefetching gains nor file popularity -- highlight VCC as a pure physical-layer solution for future high-throughput SATCOM systems, significantly narrowing the performance gap between satellite and wired networks.

Caching Yields up to 5x Spectral Efficiency in Multi-Beam Satellite Communications

TL;DR

This work tackles the spectral-efficiency bottleneck in multi-beam SATCOM by introducing vector coded caching (VCC), which uses receiver caches to enable interference-aware, parallel transmission of multiple precoded vectors under Rician-shadowed fading. By combining two-phase cache placement with MF precoding and accounting for CSI acquisition overhead and imperfect CSIT, it derives closed-form approximations for average sum-rate and the effective spectral-efficiency gain, showing substantial gains of to over cacheless MU-MISO. The results are validated by simulations across static and dynamic channel scenarios, demonstrating that the gains persist under practical conditions and CSI imperfections. Overall, VCC represents a pure physical-layer enhancement that can significantly narrow the spectral efficiency gap between SATCOM and wired networks, while enabling potentially leaner, higher-throughput satellite architectures.

Abstract

This paper examines the integration of vector coded caching (VCC) into multi-beam satellite communications (SATCOM) systems and demonstrates that even limited receiver-side caching can substantially enhance spectral efficiency. By leveraging cached content to suppress interference, VCC enables the concurrent transmission of multiple precoded signal vectors that would otherwise require separate transmission resources. This leads to a multiplicative improvement in resource utilization in SATCOM. To characterize this performance, we model the satellite-to-ground channel using Rician-shadowed fading and after incorporating practical considerations such as matched-filter precoding, channel state information (CSI) acquisition overhead as well as CSI imperfections at the transmitter, we here derive closed-form expressions for the average sum rate and spectral efficiency gain of VCC in SATCOM. Our analysis, tightly validated through numerical simulations, reveals that VCC can yield spectral efficiency gains of 300% to 550% over traditional multi-user MISO SATCOM with the same resources. These gains -- which have nothing to do with multicasting, prefetching gains nor file popularity -- highlight VCC as a pure physical-layer solution for future high-throughput SATCOM systems, significantly narrowing the performance gap between satellite and wired networks.
Paper Structure (14 sections, 4 theorems, 32 equations, 6 figures, 2 tables, 1 algorithm)

This paper contains 14 sections, 4 theorems, 32 equations, 6 figures, 2 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. Vector Coded Caching
  4. Cache Placement Phase
  5. Content Delivery Phase
  6. Matched-Filter (MF) Precoding
  7. Main Results
  8. Numerical Performance Evaluation and Validation
  9. Numerical Results Under Static Channel
  10. Extension to Dynamic Channel
  11. Conclusion and Discussions
  12. Proof of Proposition \ref{['alpha_prop']}
  13. Proof of Proposition \ref{['Xi_prop']}
  14. Proof of Theorem \ref{['VCC_thm']}

Key Result

Proposition 1

In the ML estimation of the channel vector $\mathbf{h}_{\psi,b}$ over Rician-shadowed fading channels, each element of $\hat{\mathbf{h}}_{\psi,b}$ shares the same statistical parameters $m$ and $\Omega$ as the corresponding element of $\mathbf{h}_{\psi,b}$, differing only in the average scattering c

Figures (6)

  • Figure 1: Average sum rate and effective gain versus $P_t$ for $L=8$ and $Q_{\max} = Q_{\max}' = 8$ in FHS, where $\text{SNR}_{\text{ave}} = P_t - 9.0$ [dB].
  • Figure 2: Effective gain versus $P_t$ for $L=8$ and $Q_{\max}=Q_{\max}'=8$, where the values of $\text{SNR}_{\text{ave}}$ in FHS, AS and ILS are respectively $P_t - 9.0$ [dB], $P_t + 0.4$ [dB], and $P_t + 2.1$ [dB].
  • Figure 3: Effective gain versus $P_t$ in AS, where $Q_{\max}=Q_{\max}' = 8$ and $\text{SNR}_{\text{ave}} = P_t + 0.4$ [dB]. For $P_t \approx 18.1$ dB in AS, the $\text{SNR}_{\rm ave} \approx 18.5$ dB, corresponding to gain $\ge 5$.
  • Figure 4: Effective gain versus $P_t$ in AS, where $L=16$, $Q_{\max}=Q_{\max}' = 8$, and $\text{SNR}_{\text{ave}} = P_t + 0.4$ [dB]. For $P_t \approx 18.1$ dB in AS, the $\text{SNR}_{\rm ave} \approx 18.5$ dB, corresponding to gain $\ge 5$.
  • Figure 5: Effective gain versus $P_t$ in AS, where $L=16$ and $\text{SNR}_{\text{ave}} = P_t + 0.4$ [dB]. For $P_t \approx 18.1$ dB in AS, the $\text{SNR}_{\rm ave} \approx 18.5$ dB, corresponding to gains between $3.5$ and $5.5$.
  • ...and 1 more figures

Theorems & Definitions (11)

  • Remark 1
  • Remark 2
  • Remark 3
  • Remark 4
  • Proposition 1
  • Proposition 2
  • Proposition 3
  • Theorem 1
  • Remark 5
  • Remark 6
  • ...and 1 more