Sub-project Reference No.: NextGenerationEU [UNICO-5G I+D/FREE6G-RadEdge (TSI-063000-2021-121)]
FREE6G-RadEdge lays on innovations at the RAN and Fronthaul domains, that will exploit the potential of cell-free networking in future 6G networks. FREE6G-RadEdge will develop novel cell-free networking mechanisms that will allow to leverage the Access Point (AP) deployment in a cost-effective manner, by exploiting the application of the distributed processing cell-free concept. FREE6G-RadEdge proposes to disaggregate the traditional cell-free Central Processing Unit (CPU) in Distributed Units (DU) and a Central Unit (CU) in line with the 3GPP NG-RAN architecture. APs could be interconnected with the cell-free DUs via fronthaul connections, either wirelessly or through a bus interface. As far as the former is concerned, APs will be linked through novel hybrid MIMO mechanisms with beam-steering and beam-sharing support. Many innovative algorithms for optimized AP clustering, local coordination, energy efficiency and topology adaptation will be proposed to optimally exploit the channel and traffic correlation patterns. FREE6G-RadEdge’s cell-free innovations will be implemented and integrated with existing vRAN elements, likewise, opening the door to provide inputs to the O-RAN project. At the transport domain, standard Optical Ethernet technologies will be leveraged for the Midhaul interfaces, while the network will be fully aligned with the Fixed-Mobile Convergence (FMC) paradigm, allowing the Midhaul optical fibres to be flexibly shared with Fixed services.
O-RAN architecture with different types of control loops.
A decentralized CFmMIMO system realized in O-RAN.
Source: Oh, M. S., Das, A. B., Hosseinalipour, S., Kim, T., Love, D. J., & Brinton, C. G. (2023). A Decentralized Pilot Assignment Methodology for Scalable O-RAN Cell-Free Massive MIMO. arXiv preprint arXiv:2301.04774
The specific technical objectives of FREE6G-RadEdge are:
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Objective 1. Design and demonstrate scalable, distributed cell-free massive-MIMO networks supporting massive AP deployments.
i) Optimize cluster formation (AP selection) and radio resource management based on per user-rate and PHY-layer characteristics (e.g., channel fading) by applying ML-based techniques.
ii) Design network topology-aware algorithms for distributed cell-free precoding and receive combining that ensures uniform network performance.
iii) Design of the flexible wireless PtMP mmWave fronthaul solution based on novel hybrid beamforming and beam-sharing schemes.
iv) Design of distributed digital linearization schemes to maximize efficiency and minimize interference in mm-wave hybrid beamforming radios.
vi) Optimize CPU and AP deployment strategies for flexible AP-CPU association.
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Objective Design and implement a cell-free vRAN for 6G, aligned with the O-RAN Alliance architecture.
i) Prototyping of a cell-free vDU, with the integration of cell-free high-PHY functions (i.e., modulation, pre-coding, etc.).
ii) Study modifications required to control plane / user plane (CP-UP) functions and O-RAN specified interfaces (i.e., E2, O1, F1) for cell-free networking.
iii) Design an Xn-like interface to directly interconnect Radio Edge nodes for enhanced inter-DU coordination.
iv) Propose data-driven algorithms for cell-free RRM, in line with the O-RAN specifications for training and deploying ML inference within the Near-RT RIC.
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Objective 3: Architect a disaggregated SDN control plane towards Fixed-Mobile Convergence.
i) Study non-real time slice orchestration of all (fixed and mobile) network segments under a common 6G core.
ii) Develop near-real time dynamic slice reconfiguration and load balancing mechanisms for fixed and mobile network segments, offering increased statistical multiplexing.
iii) Propose data-driven methods (e.g., CNNs) for predictive sub-slice reconfiguration.
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Objective 4: implementation and proof-of-concept of the FREE6G-RadEdge solutions. One Proof-of-Concept (PoC) case will be implemented under the FREE6G-RadEdge framework. The PoC will be based on Cell-Free Networking in ultra-dense hotspot areas and will demonstrate and evaluate FREE6G-RadEdge’s distributed cell-free D-RAN in terms of increased capacity and spectral efficiency gains in overlapping AP coverage in the Experimental Scenario #1. In the Experimental Scenario #2 load balancing across distributed DUs-CUs will be showcased using mobile core loading and midhaul emulation.
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- Objective 5: Dissemination, standardization, and exploitation of FREE6G.
i) Dissemination to relevant industrial and academic communities.
ii) Dissemination of results at EC related initiatives.
iii) Communication outreach to stakeholders including the public.
iv) Contributions to standardization bodies.
v) Cross fertilization and contributions to relevant Spanish and European WGs.
vi) Contributions to top conferences and journals.
vii) Generation of intellectual property.
