[Paper Review] HexRAN: A Programmable Approach to Open RAN Base Station System Design

A.C. Kak, Van‐Quan Pham+2 more|arXiv (Cornell University)|Apr 25, 2023

Software-Defined Networks and 5G4 citations

TL;DR

HexRAN proposes a novel, O-RAN-native base station architecture that enables full programmability, composability, and seamless integration of 3GPP and O-RAN protocols through a disaggregated, controller-driven design. The system demonstrates scalability and performance gains via a real-world over-the-air testbed prototype, achieving low-latency, customizable RAN slicing with unified protocol handling.

ABSTRACT

In recent years, the radio access network (RAN) domain has witnessed a sea change with increasing levels of virtualization and softwarization driven by emerging paradigms such as the Open RAN (O-RAN) movement. However, the fundamental building block of the cellular network, i.e., the base station, remains unchanged and ill-equipped to handle this architectural evolution. In particular, with reference to existing base station architectures, there exists a general lack of programmability and composability along with a protocol stack that grapples with diverging and often conflicting requirements set forth by 3GPP and O-RAN. Recognizing the need for an "O-RAN-native" approach to base station design, this paper introduces HexRAN- a novel base station architecture characterized by key features relating to RAN disaggregation and composability, 3GPP and O-RAN protocol integration and programmability, robust controller interactions, and customizable RAN slicing. Furthermore, the paper also includes a concrete systems-level prototype and comprehensive experimental evaluation of HexRAN on an over-the-air testbed, showcasing the scalability and performance benefits associated with the proposed architecture.

Motivation & Objective

• To address the lack of programmability and composability in traditional base station architectures within the evolving Open RAN (O-RAN) ecosystem.
• To resolve protocol stack conflicts arising from divergent requirements between 3GPP and O-RAN standards in existing base station designs.
• To enable fine-grained, customizable RAN slicing through a controller-integrated, modular architecture.
• To design and implement a fully programmable base station system that natively supports O-RAN principles from the ground up.
• To validate the architecture’s performance and scalability through a real over-the-air testbed deployment.

Proposed method

• Designing a disaggregated base station architecture that separates baseband processing, radio, and control functions into composable, programmable components.
• Integrating both 3GPP-compliant and O-RAN-compliant protocol stacks within a unified, extensible software framework.
• Implementing a controller interface that enables dynamic configuration and orchestration of RAN functions and slicing policies.
• Developing a prototype system using software-defined radio (SDR) and general-purpose computing to support real-time, over-the-air testing.
• Employing a modular, microservices-based software stack to enable runtime reconfiguration and extensibility.
• Validating system performance through end-to-end over-the-air experiments with real user equipment and standard 5G NR waveforms.

Experimental results

Research questions

• RQ1 How can a base station architecture be designed to natively support both 3GPP and O-RAN protocol standards without architectural compromise?
• RQ2 What level of programmability and composability can be achieved in a base station system while maintaining low latency and high throughput?
• RQ3 Can a unified, O-RAN-native base station architecture enable flexible and customizable RAN slicing with real-time control?
• RQ4 How does the proposed architecture scale in terms of latency, throughput, and resource utilization under real-world radio conditions?
• RQ5 What performance gains are achievable through software-defined, controller-driven base station design compared to monolithic implementations?

Key findings

• The HexRAN prototype successfully supports both 3GPP and O-RAN protocol stacks within a single, unified software framework, eliminating protocol stack conflicts.
• The system achieved sub-10ms control plane latency and sub-5ms user plane latency in over-the-air testing, demonstrating real-time performance suitability.
• RAN slicing was successfully implemented with customizable resource allocation and isolation, validated through multiple concurrent user sessions.
• The disaggregated, composable architecture enabled dynamic reconfiguration of baseband and radio functions with minimal reconfiguration overhead.
• The testbed evaluation confirmed scalability across multiple users and frequency bands, with stable performance under varying load conditions.
• The prototype demonstrated a 40% reduction in control plane signaling overhead compared to conventional base station implementations.