PDCP Status Reporting for Multi-RAT Offloading Buffer Management
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Solution Overview
Problem
Current 3GPP LTE network architectures face issues with transmitter buffer overload and HFN desynchronization due to inadequate PDCP status reporting, leading to unnecessary packet forwarding and retransmissions during handovers and connection re-establishments, especially in multi-RAT scenarios like LTE-WLAN aggregation.
Innovation Solution
Implementing UE-based PDCP status reporting mechanisms that allow for in-band reporting of ACK/NACK status and dynamic flow control, enabling efficient packet management and minimizing network-side impact on WLAN APs, thereby preventing buffer overflows and HFN desynchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PDCP packets are offloaded via secondary link without status reporting, then traffic offloading is enabled, but transmitter buffer overload occurs
Solution Approach 1:
The patent implements a feedback mechanism where the receiver sends PDCP status reports back to the transmitter through the secondary link. These status reports contain acknowledgment information about successfully received PDCP packets, enabling the transmitter to clear its buffer efficiently and prevent buffer overload while maintaining traffic offloading capability
Solution Approach 2:
The patent segments the status reporting mechanism into specific PDCP status report messages that are transmitted through the secondary link. This segmentation allows the status information to be carried separately from the data traffic, enabling efficient buffer management without interfering with the offloaded traffic flow
2Speed
If PDCP packets are transmitted without status reporting, then transmission speed is maintained, but HFN desynchronization occurs
Solution Approach 1:
The PDCP status report provides feedback to the transmitter about which packets have been successfully received and acknowledged. This feedback enables the transmitter to update its HFN counter accurately, preventing HFN desynchronization between transmitter and receiver while maintaining high transmission speed through the offloaded path
Solution Approach 2:
The patent implements preliminary actions by having the receiver prepare and send status reports that include acknowledgment information before the transmitter needs to clear its buffer or update its HFN counter. This preliminary status reporting ensures synchronization is maintained proactively rather than reactively
3Device complexity
If PDCP discard timer is used for buffer clearing, then implementation simplicity is maintained, but unnecessary packet forwarding occurs
Solution Approach 1:
Instead of relying solely on the PDCP discard timer, the patent introduces feedback through PDCP status reports that explicitly inform the transmitter which packets have been successfully delivered. This allows the transmitter to clear packets from the buffer immediately upon receiving acknowledgment, rather than waiting for the discard timer to expire, thereby eliminating unnecessary packet forwarding during handovers and connection re-establishment
Solution Approach 2:
The patent makes the buffer clearing mechanism dynamic by combining the discard timer with event-driven clearing based on PDCP status reports. The transmitter can now clear packets dynamically when status reports indicate successful delivery, rather than relying on a static timer-based approach, thereby improving packet forwarding efficiency while maintaining implementation simplicity
Data Source
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AI summary
Briefly, in accordance with one or more embodiments, an apparatus of user equipment (UE) comprises circuitry to receive data transmissions as packet data convergence protocol (PDCP) packets from a radio bearer via two or more Radio Access Technologies (RATs). One or more PDCP packets are offloaded from a first RAT to a second RAT. The apparatus comprises circuitry to aggregate the received data PDCP packets, and report a status of the PDCP packets to the radio bearer.