PDCP Entity Immediate SDU Delivery During RLC Re-establishment

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Solution Overview

Problem

In the Evolved Universal Mobile Telecommunications System (E-UMTS) and Long Term Evolution (LTE) systems, the delivery of Packet Data Convergence Protocol (PDCP) Service Data Units (SDUs) to the upper layer is delayed due to re-establishment processes, leading to unnecessary time delays and resource wastage, especially during handovers, where repeated re-transmissions occur and stored SDUs are not immediately delivered.

Innovation Solution

Implement a method where PDCP SDUs received through RLC re-establishment are immediately delivered to the upper layer if their sequence number is equal to or greater than the last delivered SDU, ensuring consecutive SDUs with ascending sequence numbers are also delivered, thereby minimizing delays and resource wastage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PDCP SDUs are stored in buffer during RLC re-establishment, then reordering can be performed, but delivery time is delayed

Engineering Contradiction:

Improvereordering capabilityVSAvoiddelivery time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the delivery process into two paths: immediate delivery for consecutive SDUs (sequence number equals last delivered SDU sequence number + 1) and buffered storage for non-consecutive SDUs. This segmentation allows the system to maintain reordering capability for out-of-order packets while enabling immediate delivery for sequential packets, thus resolving the contradiction between reliability and time loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a dynamic delivery mechanism where the PDCP entity adjusts its behavior based on the sequence number of received SDUs. When a consecutive SDU is received, the entity immediately delivers it to the upper layer without buffering. When a non-consecutive SDU is received, the entity stores it in the buffer for later delivery after reordering. This dynamic approach optimizes both reliability and time efficiency.

Inventive Principle:

Principle #15Dynamics

2Reliability

If repeated re-transmissions occur during handovers, then data can be delivered, but resource wastage increases

Engineering Contradiction:

Improvedata deliveryVSAvoidresource wastage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements preliminary action by having the PDCP entity immediately deliver consecutive SDUs to the upper layer as they are received, without waiting for re-transmissions or buffering. This preliminary delivery of in-order packets eliminates the need for repeated re-transmissions during handovers, thereby reducing resource wastage while maintaining reliable data delivery.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies the skipping principle by rushing through the delivery of consecutive SDUs immediately without undergoing the full re-transmission cycle. When a packet arrives with the correct sequence number (last delivered SDU sequence number + 1), the system skips the buffering and reordering process, delivering the packet directly to the upper layer. This reduces the time and resources required during handovers.

Inventive Principle:

Principle #21Skipping (Rushing through)

3Reliability

If stored SDUs are not immediately delivered, then reordering can be performed, but deadlock situations may occur

Engineering Contradiction:

Improvereordering capabilityVSAvoiddeadlock prevention

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent segments the SDU delivery process into immediate delivery for consecutive packets and buffered storage for non-consecutive packets. This segmentation ensures that consecutive SDUs are delivered without delay, preventing deadlock situations, while non-consecutive SDUs are stored for later reordering, maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a dynamic delivery strategy where the PDCP entity continuously monitors the sequence number of received SDUs. When a consecutive SDU is detected, the entity dynamically switches to immediate delivery mode, delivering the SDU to the upper layer without buffering. This dynamic behavior prevents deadlock situations by ensuring progress on consecutive packets while maintaining reordering capability for out-of-order packets.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUSRE48291E1Method of delivering a PDCP data unit to an upper layer

Publication Date: 2020.10.27 LG ELECTRONICS INC

AI summary

Disclosed is a radio (wireless) communication system providing a radio communication service and a terminal, and more particularly, to a method of delivering a continuously and/or consecutively received Packet Data Convergence Protocol (PDCP) Service Data units (SDUs) to an upper layer immediately if a PDCP entity receives the PDCP SDUs during a process of a RLC re-establishment within an Evolved Universal Mobile Telecommunications System (E-UMTS) that has evolved from a Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.