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Multi-Band Wireless Access-and-Backhaul (WAB) for 5G: Implementation and Experiments

Chiara Rubaltelli, Marcello Morini, Eugenio Moro, Ilario Filippini

TL;DR

The paper addresses the challenge of extending FR2 mmWave coverage and reliability by proposing Wireless Access Backhaul (WAB), a two-system architecture that decouples access (FR1) and backhaul (FR2) and tunnels N2/N3 between 5G core networks. It delivers the first physical, multi-band WAB testbed built from commercial off-the-shelf hardware and open-source software (OpenAirInterface/Open5GS), validating end-to-end operation in urban vehicular and indoor scenarios. Results show that FR2 backhaul quality largely governs end-to-end throughput, while FR1 access enhances coverage and uplink reliability, effectively mitigating typical FR2 impairments in challenging environments. The work demonstrates the practicality of WAB for scalable 5G+ deployments and sets the stage for broader topologies and richer backhaul options, with notable implications for cost-effective network densification.

Abstract

The growing demand for wireless capacity and coverage has driven research into new radio architectures and higher frequency bands. The recently standardized Wireless Access Backhaul (WAB) architecture represents a key evolution, enabling cost-effective network densification through wireless relaying. This paper presents the first experimental realization of a multi-band WAB testbed, combining an FR2 backhaul and an FR1 access link using open-source software and commercial off-the-shelf components. The proposed framework validates the feasibility of end-to-end WAB operation and demonstrates its ability to extend FR2 coverage while maintaining compatibility with legacy FR1 user equipment. Experimental campaigns conducted in vehicular and outdoor-to-indoor scenarios confirm that WAB effectively mitigates the limitations of FR2 links, particularly in uplink and Non-Line-of-Sight conditions. These results highlight WAB as a practical and scalable approach for next-generation wireless networks.

Multi-Band Wireless Access-and-Backhaul (WAB) for 5G: Implementation and Experiments

TL;DR

The paper addresses the challenge of extending FR2 mmWave coverage and reliability by proposing Wireless Access Backhaul (WAB), a two-system architecture that decouples access (FR1) and backhaul (FR2) and tunnels N2/N3 between 5G core networks. It delivers the first physical, multi-band WAB testbed built from commercial off-the-shelf hardware and open-source software (OpenAirInterface/Open5GS), validating end-to-end operation in urban vehicular and indoor scenarios. Results show that FR2 backhaul quality largely governs end-to-end throughput, while FR1 access enhances coverage and uplink reliability, effectively mitigating typical FR2 impairments in challenging environments. The work demonstrates the practicality of WAB for scalable 5G+ deployments and sets the stage for broader topologies and richer backhaul options, with notable implications for cost-effective network densification.

Abstract

The growing demand for wireless capacity and coverage has driven research into new radio architectures and higher frequency bands. The recently standardized Wireless Access Backhaul (WAB) architecture represents a key evolution, enabling cost-effective network densification through wireless relaying. This paper presents the first experimental realization of a multi-band WAB testbed, combining an FR2 backhaul and an FR1 access link using open-source software and commercial off-the-shelf components. The proposed framework validates the feasibility of end-to-end WAB operation and demonstrates its ability to extend FR2 coverage while maintaining compatibility with legacy FR1 user equipment. Experimental campaigns conducted in vehicular and outdoor-to-indoor scenarios confirm that WAB effectively mitigates the limitations of FR2 links, particularly in uplink and Non-Line-of-Sight conditions. These results highlight WAB as a practical and scalable approach for next-generation wireless networks.

Paper Structure

This paper contains 12 sections, 6 figures.

Table of Contents

  1. Introduction
  2. Wireless Access Backhaul
  3. Architecture
  4. Basic Procedures
  5. WAB Experimental Framework
  6. FR2 components
  7. FR1 components
  8. Connectivity
  9. Validation and Results
  10. Mobile experiments
  11. experiments
  12. Conclusion

Figures (6)

  • Figure 1: WAB's fundamental architecture, including the corresponding elements in the testbed.
  • Figure 2: Aerial view of the urban neighborhood covered by the FR2 together with experiment locations. Mobile experiment trajectory shows and regions higlighted, respectively, in red and green.
  • Figure 3: Mobile measurements of mmWave RSRP (on the left) and end-to-end throughput (on the right).
  • Figure 4: End-to-end throughput, FR2 and FR1 and beam changes in mobile experiments.
  • Figure 5: experiment positions.
  • ...and 1 more figures