Base Station Function Splitting for Fronthaul Bandwidth Reduction
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Solution Overview
Problem
In current LTE wireless communication systems, the band required for the Front Haul (FH) between the DU and RU in C-RAN is significantly high due to the implementation of Layer 1 and Layer 2 functions on the DU side, which may increase further with the expected peak rates and reduced latency in 5G networks, necessitating a method to shift some functions from the DU to the RU to reduce FH bandwidth requirements.
Innovation Solution
A base station configuration that enables a portion of the DU's functions to be realized on the RU, with specific processing and transmission units handling downlink physical data channels, and a method to share functions between the DU and RU, optimizing the interface and data transmission to reduce the FH bandwidth by omitting unnecessary information and using predictive parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If Layer 1 and Layer 2 functions are implemented on the DU side, then the control and management capability is improved, but the FH bandwidth requirement increases significantly
Solution Approach 1:
The patent segments the base station functions by introducing a new interface (S1 interface) that separates Layer 1 (physical layer) functions from Layer 2 (MAC, RLC, PDCP) functions. The RU implements Layer 1 functions locally, while the DU retains Layer 2 functions for centralized control. This segmentation reduces the amount of data that needs to be transmitted over the FH, as only processed data from Layer 2 needs to be forwarded to the RU for physical layer transmission.
2Speed
If peak rate is increased to 10 Gbps or higher for 5G, then the data transmission capability is improved, but the FH bandwidth requirement increases remarkably
Solution Approach 1:
The patent extracts the physical layer processing functions from the DU and places them in the RU. By taking out Layer 1 functions (modulation, coding, antenna processing) from the centralized DU, the system allows the RU to handle high-speed physical layer operations locally. This extraction reduces the bandwidth burden on the FH, as only higher-layer control and processed data need to be transmitted between DU and RU, even when peak rates reach 10 Gbps or higher.
3Loss of time
If latency is reduced for 5G networks, then the response speed is improved, but the data transmission requirement over FH increases
Solution Approach 1:
The patent implements preliminary action by having the RU perform physical layer processing locally without waiting for complete data packets from the DU. The RU can prepare and transmit physical layer signals in advance based on pre-configured parameters from the DU, reducing the time needed for data transmission over the FH. This preliminary processing at the RU enables lower latency operation while minimizing the amount of data that needs to be transmitted through the FH.
4Adaptability or versatility
If a new interface between DU and RU is defined for function sharing, then the system flexibility is improved, but the interface complexity increases
Solution Approach 1:
The patent applies universality by designing the S1 interface to handle multiple types of information transmission for different function sharing scenarios. The interface can carry various parameters including modulation scheme, coding rate, resource allocation, and control data, making it a multi-functional interface that adapts to different Layer 1/2 function distribution configurations. This universal interface design provides system flexibility without requiring separate specialized interfaces for each function sharing scenario.
Data Source
AI summary
A base station used as a first base station in a wireless communication system including the first base station, a second base station that communicates with the first base station, and a user equipment that communicates with the first base station includes: a reception unit that receives a parameter used for generating a downlink physical data channel and data to be transmitted toward the user equipment from the second base station; a generating unit that generates the downlink physical data channel by performing processing of Layer 1 on the data using the parameter; and a transmission unit that transmits the generated downlink physical data channel.