DU–RU Data Transfer Using Semi-Persistent U-Plane Messaging
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Solution Overview
Problem
The challenge in cloud-based Radio Access Networks (RAN) lies in the inefficient design of the interface between the distributed unit (DU) and radio unit (RU), which affects transport latency and bandwidth requirements, especially with the introduction of massive MIMO solutions, leading to high upgrading costs for mobile network operators.
Innovation Solution
A method is introduced where the distributed unit (DU) transmits control information to the radio unit (RU) using semi-persistent and periodic c-plane and m-plane messages, reducing front haul signaling bandwidth by optimizing the exchange of u-plane data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional RAN architecture with integrated base station is used, then processing is handled locally, but upgrading and evolution is difficult due to application specific hardware
Solution Approach 1:
The base station is segmented into three functional units: Central Unit (CU) for higher layer processing, Distributed Unit (DU) for real-time processing, and Radio Unit (RU) for RF processing. This segmentation enables independent upgrading of each unit, particularly the virtualized CU and DU, without replacing entire hardware infrastructure, thus improving network upgradeability while reducing hardware specificity.
Solution Approach 2:
The patent replaces traditional application-specific hardware processing with virtualized software processing for the CU and DU functions. By implementing these units as virtual instances that can be deployed on general-purpose servers, the system eliminates dependency on specific hardware applications, enabling flexible software-based upgrades and evolutions.
2Productivity
If RAN functions are split into CU and DU for cloud-based processing, then scalability and cost reduction are achieved, but transport latency and bandwidth requirements increase
Solution Approach 1:
The patent applies different processing qualities at different locations: the RU performs real-time RF processing locally at the cell site with minimal latency requirements, while the DU handles real-time but less critical processing, and the CU handles non-real-time processing. This local quality differentiation allows the system to maintain scalability while managing transport latency through functional distribution.
Solution Approach 2:
The system dynamically adjusts the functional split between CU, DU, and RU based on network conditions and requirements. The DU can be configured to handle different portions of the protocol stack depending on bandwidth and latency constraints, allowing flexible adaptation to optimize the trade-off between scalability and transport performance.
3Ease of manufacture
If RAN functions are split into CU and DU, then capital and operating costs are reduced, but interface design complexity increases due to multiple communication requirements
Solution Approach 1:
The patent defines universal interfaces between CU, DU, and RU units that can support multiple communication requirements through standardized protocols. The F1 interface between CU and DU, and the E1 interface between DU and RU, are designed as universal interfaces that can carry various types of traffic (control plane, user plane, management plane) through a common framework, reducing interface design complexity despite the functional split.
4Quantity of substance
If semi-persistent and periodic messaging is used for control information, then front haul signaling bandwidth is reduced, but message transmission complexity increases
Solution Approach 1:
The patent implements periodic and semi-persistent messaging mechanisms where control information is transmitted at predetermined intervals or for predetermined durations rather than continuously. This periodic action reduces the total amount of signaling traffic on the front haul interface, lowering bandwidth requirements. The DU and RU units follow standardized periodic messaging patterns that simplify the complexity of message transmission through predictable timing and structure.
Data Source
AI summary
A base station (BS) and a method of operating the BS. The BS comprises a distributed unit (DU) and a radio unit (RU). The DU is configured to transmit control information to the RU using a control message. The DU is configured to transmit u-plane data to the RU using a u-plane message. The RU is configured to receive the u-plane message according to a semi persistent technique or a periodic technique. The control message comprises a c-plane message or an m-plane message. The control message comprises an indication to use the semi persistent technique or the periodic technique to receive the u-plane message. The indication is valid to be used by the RU to receive the u-plane message carrying the u-plane data and at least one u-plane message subsequently received by the RU, for a predetermined time period as indicated by the control message.