PDCP Sequence Number Synchronization for Wireless Packet Reordering

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Solution Overview

Problem

In wireless communication systems, particularly in 5G and LTE networks, there is a challenge in managing packet data convergence protocol (PDCP) sequence numbers during events like state variable resets, leading to out-of-order packets and potential data loss due to incorrect reordering criteria, which affects synchronization and performance.

Innovation Solution

A method is implemented where user equipment (UE) receives packets at the PDCP layer, determines if they satisfy reordering criteria based on sequence numbers and state variable resets, and discards packets before a reordering timer expires to prevent data loss and maintain synchronization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If packets are discarded based on traditional reordering criteria after state variable reset, then data loss is prevented, but unnecessary packet discarding occurs and data integrity deteriorates

Engineering Contradiction:

Improvedata integrityVSAvoidpacket loss

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent changes the reordering criterion from comparing absolute sequence numbers to comparing relative sequence number differences. Specifically, it introduces a threshold-based comparison where packets are only discarded if the sequence number difference exceeds the threshold, rather than using fixed reordering window criteria. This parameter change allows legitimate out-of-order packets to be retained while still discarding truly lost packets.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary evaluation of sequence number differences before final packet discarding decisions. By calculating and comparing sequence number differences against thresholds in advance, the system can identify packets that should be retained versus those that should be discarded, preventing unnecessary loss of valid data while maintaining protection against actual packet loss.

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If reordering timer is used to wait for out-of-order packets, then synchronization is maintained, but processing time increases and productivity decreases

Engineering Contradiction:

Improvenetwork synchronizationVSAvoidpacket processing speed

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent introduces dynamic threshold adjustment based on network conditions and packet characteristics. Instead of using a fixed reordering timer duration, the system dynamically determines thresholds for sequence number differences, allowing faster processing when conditions permit while maintaining synchronization when needed. This dynamic approach balances synchronization requirements with processing efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes from fixed timer-based reordering to flexible threshold-based decision making. By modifying the parameter from a static timer duration to dynamic sequence number difference thresholds, the system can make faster decisions about packet ordering without compromising synchronization, thereby improving overall processing productivity.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If strict reordering criteria are applied, then sequence number synchronization is maintained, but device complexity increases due to additional evaluation logic

Engineering Contradiction:

Improvesequence number synchronizationVSAvoidreordering logic complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the essential synchronization requirement from complex reordering logic by focusing solely on sequence number difference comparison. Instead of implementing full reordering state machines and multiple evaluation criteria, the system isolates the critical function of comparing sequence number differences against thresholds, significantly reducing device complexity while maintaining synchronization precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent inverts the traditional approach by not trying to reorder all out-of-order packets, but instead identifying and retaining only those that should be kept based on sequence number differences. This inversion simplifies the logic from complex reordering algorithms to a simpler filter-based approach that maintains synchronization with less complexity.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS20230319630A1Techniques for packet data convergence protocol and radio link control sequence number synchronization

Publication Date: 2023.10.05 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, at a packet data convergence protocol (PDCP) layer, a packet having a PDCP sequence number. The UE may determine whether the received packet, having the PDCP sequence number, satisfies one or more reordering criteria. The UE may discard, before an expiration of a reordering timer, the received packet based at least in part on the determination of whether the received packet satisfies the one or more reordering criteria. Numerous other aspects are provided.