Target Base Station Handover Data Transmission

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Solution Overview

Problem

Handover procedures in mobile communications networks experience increased latency due to collisions on Random Access Channels, leading to delays in user data transmission during handovers, especially when multiple user terminals attempt to access the same base station simultaneously.

Innovation Solution

The method involves the target base station transmitting user data before the user terminal registers, utilizing uplink feedback as an indication of the terminal's presence, allowing for reduced latency by scheduling data transmission before the completion of the handover procedure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the target base station waits for the user terminal to register before transmitting user data, then the registration procedure is completed properly, but the handover latency increases

Engineering Contradiction:

Improveregistration completionVSAvoidhandover latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The target base station transmits user data to the user terminal in advance during the handover execution phase, before the terminal completes the registration procedure by sending the first message. This preliminary data transmission reduces handover latency while maintaining reliable delivery through subsequent acknowledgment mechanisms.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If multiple user terminals access the same target base station simultaneously via Random Access Channel, then the Random Access Channel resources are utilized, but collisions occur preventing successful access

Engineering Contradiction:

ImproveRandom Access Channel utilizationVSAvoidaccess success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Radio resources in the uplink direction are assigned to the user terminal during the preparation phase before the handover is executed. This preliminary resource allocation prevents collisions on the Random Access Channel during the execution phase, ensuring reliable access while maintaining efficient channel utilization.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the minimum value of timers is increased with every unsuccessful trial, then collision probability is reduced, but handover latency increases

Engineering Contradiction:

Improvecollision avoidanceVSAvoidhandover latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of increasing timer values to avoid collisions, the system assigns uplink radio resources in advance during the preparation phase. This eliminates the need for retry mechanisms with increased delays, achieving both collision avoidance and low latency simultaneously.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8300595B2Method for handover procedure of user terminal on radio interfaces, a base station and a network therefor

Publication Date: 2012.10.30 ALCATEL-LUCENT USA LNC

AI summary

The invention concerns a method for a handover procedure of a user terminal (UE) on radio interfaces from a source base station (SBS) to a target base station (TBS) whereby the target base station (TBS) sends out user data to the user terminal (UE) before reception of a message indicating the termination of the handover procedure (HO Complete), the user terminal (UE) uses an uplink feedback for sending at least one message (Feedback) associated to the downlink transmission of said user data to the target base station (TBS), and the target base station (TBS) uses said at least one message (Feedback) associated to the downlink transmission of said user data as an indication of the presence of the user terminal (UE) within the range of the target base station (TBS), a base station (BS1-BS8) and a network (CN) therefor.