PDCP Packet Reordering During UM Handover
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Solution Overview
Problem
In existing multimedia broadcast and multicast services, the PDCP entity associated with RLC entities in unacknowledged mode (UM) directly delivers data packets to high-layer protocols during handovers, leading to inefficiencies and potential packet loss due to the lack of acknowledgment mechanisms.
Innovation Solution
The PDCP entity determines a target working mode and sends data packets to high-layer protocols in a numbering order, utilizing different reordering strategies (modes A, B, and C) to optimize data transmission, including reordering and processing based on configuration changes and reestablishment scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the PDCP entity directly delivers data packets to high-layer protocols during handover in UM mode, then transmission speed is improved, but packet loss increases due to lack of acknowledgment mechanism
Solution Approach 1:
The patent dynamically adjusts the working mode of the PDCP entity between mode A (direct delivery) and mode B (numbering order delivery) based on handover detection. When handover is detected, it switches to mode B to ensure reliable delivery; otherwise, it uses mode A for fast delivery. This dynamic adaptation resolves the contradiction between speed and reliability.
Solution Approach 2:
The patent changes the delivery parameter (working mode) of the PDCP entity based on handover status. By detecting handover events and adjusting the delivery mode parameter accordingly, the system achieves both fast delivery during normal operation and reliable delivery during handover, resolving the speed-reliability contradiction.
2Reliability
If the PDCP entity uses numbering order delivery to ensure packet sequence, then packet loss is reduced, but transmission delay increases
Solution Approach 1:
The patent dynamically switches between delivery modes: mode A (direct delivery without reordering) for normal operation to minimize delay, and mode B (numbering order delivery) during handover to ensure reliability. This dynamic approach resolves the contradiction by applying the appropriate delivery strategy based on operational context.
3Reliability
If the PDCP entity implements reordering mechanism during handover, then packet loss is minimized, but device complexity increases
Solution Approach 1:
The patent segments the delivery process into two distinct modes: mode A for normal fast delivery and mode B for handover reliable delivery. By activating reordering functionality only when needed (during handover), the system maintains simplicity during normal operation while ensuring reliability during critical transitions, thus resolving the complexity-reliability contradiction.
Data Source
AI summary
A method for data transmission is performed by a packet data convergence protocol (PDCP) entity. The PDCP entity is associated with a radio link control (RLC) entity in an unacknowledged mode (UM). The method includes: determining a target working mode of the PDCP entity; and sending a data packet to a high layer protocol entity in a numbering order based on the target working mode.