Inter-DU Carrier Aggregation via Direct MAC Data Exchange

The patent introduces a transparent data transfer mechanism where the primary DU acts as an intermediary between the secondary DU and the UE. The primary DU receives data from the secondary DU via direct DU-DU interface and forwards it to the UE, eliminating the need for complex L3 messaging and multiple links towards the UE. This intermediary approach maintains high data throughput while reducing device complexity and preserving UE transparency.

The patent extracts the complex PDCP combining and parallel RLC entity operations from the UE side and relocates them to the network side (primary DU). The secondary DU sends data directly to the primary DU, which handles all the complex processing and forwards it to the UE through a single logical link. This extraction eliminates dependence on UE capability while maintaining enhanced data transfer capability and preserving operation transparency.

The patent segments the data transfer path into two distinct parts: (1) a direct, low-latency DU-DU interface for data exchange between primary and secondary DUs, and (2) the existing Uu interface for UE communication. This segmentation allows the network-side data transfer to occur independently and simultaneously with UE processing, eliminating sequential delays and reducing overall data transfer time while maintaining device complexity at acceptable levels.

The patent moves the data transfer operation from the radio dimension (multiple links towards UE) to the network dimension (direct DU-DU interface). By establishing the data path in the network dimension between DUs and then using a single robust link from primary DU to UE, the system achieves throughput enhancement without compromising cell edge coverage reliability. The secondary DU's contribution is delivered through the network backbone rather than through additional radio links that would be vulnerable at cell edges.