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Robust mmWave/sub-THz multi-connectivity using minimal coordination and coarse synchronization

Lorenzo Miretti, Giuseppe Caire, Sławomir Stańczak

TL;DR

This study investigates simpler alternatives to coherent joint transmission for supporting robust connectivity against signal blockage in mmWave/sub-THz access networks and demonstrates analytically that with a careful design, full macrodiversity gains and significant SNR gains can be achieved through canonical receivers and minimal coordination and synchronization requirements at the infrastructure side.

Abstract

This study investigates simpler alternatives to coherent joint transmission for supporting robust connectivity against signal blockage in mmWave/sub-THz access networks. By taking an information-theoretic viewpoint, we demonstrate analytically that with a careful design, full macrodiversity gains and significant SNR gains can be achieved through canonical receivers and minimal coordination and synchronization requirements at the infrastructure side. Our proposed scheme extends non-coherent joint transmission by employing a special form of diversity to counteract artificially induced deep fades that would otherwise make this technique often compare unfavorably against standard transmitter selection schemes. Additionally, the inclusion of an Alamouti-like space-time coding layer is shown to recover a significant fraction of the optimal performance. Our conclusions are based on a statistical single-user multi-point intermittent block fading channel model that, although simplified, enables rigorous ergodic and outage rate analysis, while also considering timing offsets due to imperfect delay compensation. In addition, we validate our theoretical approach by means of deterministic ray-tracing simulations that capture the essential features of next generation mmWave/sub-THz communications.

Robust mmWave/sub-THz multi-connectivity using minimal coordination and coarse synchronization

TL;DR

This study investigates simpler alternatives to coherent joint transmission for supporting robust connectivity against signal blockage in mmWave/sub-THz access networks and demonstrates analytically that with a careful design, full macrodiversity gains and significant SNR gains can be achieved through canonical receivers and minimal coordination and synchronization requirements at the infrastructure side.

Abstract

This study investigates simpler alternatives to coherent joint transmission for supporting robust connectivity against signal blockage in mmWave/sub-THz access networks. By taking an information-theoretic viewpoint, we demonstrate analytically that with a careful design, full macrodiversity gains and significant SNR gains can be achieved through canonical receivers and minimal coordination and synchronization requirements at the infrastructure side. Our proposed scheme extends non-coherent joint transmission by employing a special form of diversity to counteract artificially induced deep fades that would otherwise make this technique often compare unfavorably against standard transmitter selection schemes. Additionally, the inclusion of an Alamouti-like space-time coding layer is shown to recover a significant fraction of the optimal performance. Our conclusions are based on a statistical single-user multi-point intermittent block fading channel model that, although simplified, enables rigorous ergodic and outage rate analysis, while also considering timing offsets due to imperfect delay compensation. In addition, we validate our theoretical approach by means of deterministic ray-tracing simulations that capture the essential features of next generation mmWave/sub-THz communications.
Paper Structure (31 sections, 16 theorems, 78 equations, 9 figures)

This paper contains 31 sections, 16 theorems, 78 equations, 9 figures.

Table of Contents

  1. Introduction
  2. Summary of prior studies
  3. Limitations of prior studies
  4. Contributions of this study
  5. Outline and notation
  6. Intermittent block fading channels
  7. System architecture
  8. Channel model
  9. Capacity and optimal transmission
  10. Practical transmission schemes
  11. Transmitter selection
  12. Non-coherent joint transmission
  13. Phase diversity
  14. Space-time coding
  15. Two transmitters selection
  16. ...and 16 more sections

Key Result

Proposition 1

The ergodic capacity of the considered channel assuming partial CSIT $\bm{\beta}$ and an instantaneous power constraint $P\in \mathbbmss{R}_+$ per transmitter is given by where $\alpha = \sum_{l=1}^L\beta_l \sim \text{Binomial}(L,1-p_B)$.

Figures (9)

  • Figure 1: Network of multiple transmitters simultaneously connected to multiple receivers via high-rate and directional mmWave/sub-THz links.
  • Figure 2: Pictorial representation of the CCDF of the instantaneous capacity.
  • Figure 3: CCDF of the instantaneous capacity, and of the instantaneous rate of non-coherent joint transmission (NCJT) with and without phase diversity, for a given choice of the parameters $(p_B,P,L)$ of the simplified channel model in Section \ref{['sec:model']}.
  • Figure 4: Outage rate achieved by non-coherent joint transmission (NCJT) without phase diversity, NCJT with phase diversity, non-coherent joint Alamouti space-time coding (NCJA) with phase diversity, and capacity achieving schemes, by varying in each plot one of the three parameters $(p_B,P,L)$ of the simplified channel model in Section \ref{['sec:model']}.
  • Figure 5: Ergodic rate achieved by transmitter selection, non-coherent joint transmission (NCJT), two transmitters selection, non-coherent joint Alamouti space-time coding (NCJA), and capacity achieving schemes, by varying in each plot one of the three parameters $(p_B,P,L)$ of the simplified channel model in Section \ref{['sec:model']}. NCJT and NCJA can be with or without phase diversity.
  • ...and 4 more figures

Theorems & Definitions (31)

  • Proposition 1
  • proof
  • Corollary 1
  • Proposition 2
  • proof
  • Proposition 3
  • proof
  • Proposition 4
  • proof
  • Proposition 5
  • ...and 21 more