PDCP Entity Sequential Delivery Timer for Dual Connectivity
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Solution Overview
Problem
In wireless communication systems with dual connectivity, the PDCP SDUs received by user equipment (UE) through multiple flows are not delivered in sequence to the upper layer, leading to inefficiencies in downlink transmission.
Innovation Solution
A method and apparatus are provided to ensure in-sequence delivery of PDCP SDUs to the upper layer by configuring a sequential delivery timer in the UE, using a predefined PDCP sequence number (SN) and RRC messages to manage the delivery of PDCP PDUs across multiple radio link control entities in the macro and small base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-flow structure is used in dual connectivity system, then transmission capacity and coverage are improved, but in-sequence delivery of PDCP SDUs cannot be guaranteed
Solution Approach 1:
The patent introduces an in-sequence delivery timer as an intermediary mechanism between the multi-flow reception and upper layer delivery. This timer mediates the delivery process by holding PDCP SDUs until their predecessors are received, ensuring in-sequence delivery while maintaining multi-flow transmission capacity. The timer acts as a buffer that reconciles the parallel nature of multi-flow reception with the sequential requirements of upper layer processing.
Solution Approach 2:
The patent implements preliminary ordering of PDCP SDUs based on sequence numbers before delivery to the upper layer. By pre-organizing the sequence of data units from multiple flows and using timers to ensure proper ordering, the system prepares data in the correct sequence in advance, allowing multi-flow transmission to proceed in parallel while guaranteeing sequential delivery when required.
2Productivity
If PDCP PDUs are received through multiple RLC entities simultaneously, then transmission efficiency is improved, but delivery sequence cannot be maintained
Solution Approach 1:
The patent implements a feedback mechanism where the reception status of PDCP SDUs from multiple RLC entities is monitored and fed back to the delivery mechanism. The in-sequence delivery timer receives feedback about which sequence numbers have been received and uses this information to control delivery timing, ensuring that data is delivered in sequence while maintaining efficient parallel reception across multiple flows.
Solution Approach 2:
The patent introduces dynamic timing control through the in-sequence delivery timer, which adapts its behavior based on the reception status of data from multiple RLC entities. The timer dynamically adjusts the delivery timing of PDCP SDUs, allowing flexible coordination between parallel reception channels and sequential delivery requirements, thereby maintaining transmission efficiency while ensuring proper ordering.
3Reliability
If sequential delivery timer is configured in UE, then in-sequence delivery is achieved, but system complexity increases
Solution Approach 1:
The patent manages complexity by controlling the timer parameter - it is only activated when out-of-sequence reception is detected. The timer uses simple parameters such as sequence numbers and timeout values rather than complex algorithms. This parameter-based approach ensures in-sequence delivery while keeping the implementation relatively simple and avoiding excessive system complexity.
Data Source
AI summary
The present invention provides a method for user equipment receiving multi-flow data with respect to one evolved packet system (EPS) bearer through a macro base station (macro eNB) and a small base station (small eNB) in a wireless communication system supporting dual connectivity. The method comprises the steps of: a packet data convergence protocol (PDCP) entity of the user equipment receiving PDCP packet data units (PDU) through the macro base station and the small base station from a PDCP entity of the macro base station; obtaining PDCP service data units (SDU) corresponding to PDCP PDUs; and receiving from the macro base station information related to a sequence timer for the PDCP SDUs through a radio resource control (RRC) message, wherein the PDCP SDUs are indicated by a predefined PDCP sequence number (SN).