Disaggregated RAN CU-DU Signaling for Unicast-Multicast Switching
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Solution Overview
Problem
In disaggregated RAN architectures, there is a need for dynamic switching between unicast and multicast transmission methods to maintain service continuity, but current solutions face challenges in information exchange and configuration between the CU and DU.
Innovation Solution
Implementing a protocol architecture that allows for dynamic switching between unicast and multicast by configuring unicast DRBs and SC-MRBs, with data replication and forwarding handled in the central unit or distributed unit, and utilizing F1 interfaces for necessary signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic switching between unicast and multicast is implemented in disaggregated RAN architecture, then service continuity is maintained and resource usage is optimized, but information exchange and configuration complexity between CU and DU increases
Solution Approach 1:
The patent segments the layer-2 architecture into separate CU and DU entities with defined interfaces. The switching functionality is divided between CU (which makes switching decisions based on service requirements) and DU (which executes the switching), with configuration information exchanged through standardized F1 interfaces. This segmentation allows dynamic switching capability while managing complexity through clear functional boundaries.
Solution Approach 2:
The patent introduces standardized F1 interface protocols as intermediaries between CU and DU for information exchange. The F1-C interface carries control plane signaling for switching decisions, while F1-U interface handles user plane data forwarding. These intermediary protocols simplify the interaction between CU and DU, enabling dynamic switching without requiring complex direct integration.
2Adaptability or versatility
If layer-2 architecture is integrated into disaggregated RAN architecture to enable switching, then unicast and multicast switching is enabled, but information exchange problems between CU and DU arise
Solution Approach 1:
The patent implements a universal F1 interface architecture that handles multiple functions including switching control, data forwarding, and configuration management between CU and DU. The F1-C interface provides universal control plane functionality for switching decisions, while F1-U provides universal user plane functionality. This multi-functional interface design ensures reliable information exchange for switching operations without requiring separate dedicated channels.
Solution Approach 2:
The patent establishes feedback mechanisms through the F1 interface where the DU reports service requirements and transmission status to the CU, and the CU provides switching decisions and configuration updates to the DU. This closed-loop feedback ensures that switching operations are based on accurate real-time information, preventing information loss and maintaining switching reliability.
Data Source
AI summary
According to an aspect, there is provided a distributed unit for a distributed access node. The distributed unit maintains, in a memory, information on a configuration of a first radio link control leg for a unicast data radio bearer or a single cell multicast radio bearer for point-to-point transmissions and a configuration of a second radio link control leg for the single cell multicast radio bearer for point-to-multipoint transmissions. The distributed unit receives channel state information and/or hybrid automatic repeat request feedback associated with one of the first and second radio link control legs being active from a terminal device and determines, based thereon, that improved efficiency is enabled if the second radio link control leg is set as active. The distributed unit transmits, to the terminal device, an activation command for activating downlink monitoring and decoding using the group radio network temporary identifier.