Mobile Station Packet Reordering During LTE Handover

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Solution Overview

Problem

In LTE communication systems, handover processes result in increased communication delays and degraded throughput due to packet forwarding delays and reordering complexities, leading to interrupted transmissions and packet loss during handovers.

Innovation Solution

A reordering method where the target base station sends jump transmission of packets received from the host station to the mobile station, with discrimination information to differentiate packets forwarded from the source base station, allowing the mobile station to recognize and reorder only necessary packets, reducing communication delays and improving throughput.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If packet forwarding is performed from source base station to target base station during handover, then packet loss is prevented, but communication delay increases due to forwarding time

Engineering Contradiction:
Improvepacket loss preventionVSAvoidcommunication delay
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The source base station performs preliminary actions by storing packets in a buffer before handover occurs, and prepares forwarding information in advance. This allows the target base station to quickly receive and transmit packets without waiting for forwarding during the handover process, thus preventing packet loss while minimizing delay.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary mechanism where the source base station forwards packets to the target base station through a buffered intermediate storage system. This intermediary buffer allows packets to be temporarily held and then quickly transmitted to the mobile station after handover, preventing packet loss while reducing the overall forwarding delay.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If all packets are reordered at the mobile station, then packet sequence is maintained, but device complexity increases

Engineering Contradiction:
Improvepacket sequence orderVSAvoidreordering complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent segments the reordering function by dividing packets into two categories: packets received before handover and packets received after handover. The mobile station only needs to reorder packets within each category separately, rather than reordering all packets globally. This segmentation significantly reduces the complexity of the reordering operation while maintaining proper packet sequence.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extracts the handover-related packets from the overall packet flow and handles them separately. By identifying and separating packets that arrive during handover, the mobile station can apply simplified reordering logic only to these extracted packets, reducing the overall reordering complexity while maintaining sequence integrity.

Inventive Principle:
Principle #2Taking out (Extraction)

3Productivity

If jump transmission is performed for packets received from host station, then throughput is improved, but packet ordering may be disrupted

Engineering Contradiction:
Improvesystem throughputVSAvoidpacket order
Core Design Contradiction:
ProductivityVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by performing jump transmission only for specific packets received from the host station during handover, rather than for all packets. By selectively applying jump transmission to only those packets that would otherwise cause delays, the system improves throughput while maintaining proper ordering for other packets through conventional reordering mechanisms.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP2528385B1Mobile station with packet reordering function
Publication Date: 2022.03.30 FUJITSU LTD
  • EP2528385B1 patent drawingFigure 1
  • EP2528385B1 patent drawingFigure 2(A)~2(D)
  • EP2528385B1 patent drawingFigure 3(A)~4

AI summary

Disclosed is a reordering method of sending packets, to which numbers indicating the packet order are added, to a mobile station from a base station, and rearranging the order of the packets at the mobile station. This reordering method comprises: a step of forwarding from a source base station to a target base station, packets, which have not been sent to the mobile station before a handover sequence, or packets, for which a confirmation response of right reception has not been received from the mobile station; a step of transmitting preferentially those packets from the target base station to the mobile base station and then transmitting packets received from a host station to the mobile station; a step of giving packets information indicating that the packets are jump packets when transmitting the packets to the mobile station that were received from the host station with the order jumped; and a step of deciding jump packets are not objects of reordering, and performing the reordering process for packets that are objects of reordering.