CU-DU Mobility Control via F1 Interface Standardization
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Solution Overview
Problem
Next-generation radio access technologies, such as 5G, require efficient mobility control mechanisms due to the smaller coverage area of mmWave frequency base stations and the need for multiple small-cell base stations, necessitating a protocol for controlling user equipment (UE) mobility between distributed units within a base station.
Innovation Solution
A method and apparatus for controlling UE mobility by receiving measurement reports from distributed units (DUs), initiating UE context setup and bearer creation through a central unit (CU), and performing RRC connection reconfiguration, including random access procedures to ensure seamless data transmission as the UE moves between DUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a 5G base station uses mmWave frequency, then high-speed transmission rate is achieved, but coverage area becomes smaller
Solution Approach 1:
The base station is divided into multiple distributed units (DUs) that can independently serve different user equipment. When a UE moves out of one DU's coverage, the CU can quickly switch the UE to another DU, enabling seamless handover and maintaining continuous service despite the limited coverage of each individual DU.
Solution Approach 2:
The patent introduces a new dimension of control by separating the base station into CU and DU components with standardized interfaces. This architectural dimension allows flexible deployment of multiple DUs to expand effective coverage while maintaining high-speed mmWave transmission capabilities.
2Adaptability or versatility
If mobility control operations are performed frequently, then UE mobility is maintained, but network complexity increases
Solution Approach 1:
The F1 interface provides a universal standardized protocol that handles all mobility control operations between DUs and the CU. This single standardized interface replaces multiple complex proprietary interfaces, simplifying the network architecture while enabling frequent and flexible mobility control.
Solution Approach 2:
The patent changes the control parameter from traditional base station-level handover to DU-level handover. By operating at the DU level with standardized F1 interfaces, the system achieves more flexible and frequent mobility control without proportionally increasing overall network complexity.
3Adaptability or versatility
If distributed unit structure is implemented, then deployment flexibility is improved, but protocol complexity for mobility control increases
Solution Approach 1:
The F1 interface is designed as a universal standardized protocol that handles all communication between DUs and the CU. This single standardized interface performs multiple functions including mobility control, resource allocation, and data transmission, thereby reducing protocol complexity despite the distributed architecture.
Solution Approach 2:
The CU acts as an intermediary between multiple DUs and the core network. By centralizing control functions at the CU level while maintaining standardized F1 interfaces with DUs, the system achieves deployment flexibility without requiring complex peer-to-peer protocols between distributed units.
4Speed
If multiple small-cell base stations are established, then high-band frequency utilization is achieved, but construction cost increases
Solution Approach 1:
The base station is segmented into multiple DUs that can be deployed as independent units. This segmentation enables the use of multiple small-cell base stations for high-band frequency utilization while the standardized F1 interface architecture reduces construction costs through modular deployment and simplified network management.
Solution Approach 2:
The patent changes the operational parameter from traditional monolithic base stations to distributed units with standardized interfaces. This parameter change enables cost-effective deployment of multiple small cells while maintaining high-speed transmission capabilities through efficient resource allocation and mobility management.
Data Source
AI summary
Provided are a method and a base station for controlling mobility of UE. The method may include receiving, by a CU, a measurement report from a UE through a DU; sending, by the CU, a UE context setup request message to a target DU to create a UE context and set a bearer up; sending, by the target DU, a UE context setup response message to the CU to inform the CU of completion of creating the UE context and setting up a bearer; sending, by the CU, a UE context modification request message including a RRC connection reconfiguration message to the source DU; performing, by the target DU, a random access procedure with the UE; and forwarding, by the target DU, an RRC connection reconfiguration complete message received from the UE to the CU.