Hard Handover RLC State Migration in Wireless Networks

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Solution Overview

Problem

Conventional inter-RNS hard handover procedures in wireless communication networks result in data loss due to implicit or explicit RLC resets, leading to incomplete packet discards and the need for higher-layer retransmissions, especially when transitioning between base station routers, causing severe disruptions and service interruptions.

Innovation Solution

A method for hard handovers that involves providing configuration information and state information associated with a mobile unit to a target base station router, allowing seamless channel reconfiguration and minimizing data loss by migrating RLC state information before uplink synchronization is re-established, ensuring continuous communication with minimal interruption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional inter-RNS hard handover procedure is used, then handover between base stations is achieved, but data loss occurs due to RLC resets and incomplete packet discards

Engineering Contradiction:

Improvedata lossVSAvoidhandover procedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing RLC state information migration from source BSR to target BSR before the actual handover occurs. The source BSR forwards RLC state information (including sequence numbers, acknowledgment states, and buffer status) to the target BSR in advance, ensuring that when handover occurs, the target BSR already has the necessary state information to continue data transmission without resets or data loss.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies copying by creating a duplicate of the RLC state information from the source BSR and transferring it to the target BSR. The RLC state information is copied including transmit sequence numbers, receive sequence numbers, acknowledgment states, and buffer status, allowing the target BSR to resume transmission exactly where the source BSR left off without losing any data.

Inventive Principle:

Principle #26Copying

2Reliability

If soft handover is implemented in wireless networks with base station routers, then wireless connectivity is provided, but large jitter buffers are required leading to long round-trip delays

Engineering Contradiction:

Improvewireless connectivityVSAvoidround-trip delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies taking out by extracting the synchronization requirement from the handover procedure. Instead of requiring synchronized backhaul links between BSRs (which would need large jitter buffers), the invention allows independent BSRs to perform handover by copying state information through the core network, removing the need for time-critical synchronized operation and thus eliminating large jitter buffers and associated delays.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies intermediary by using the core network as a mediator to transfer RLC state information from source BSR to target BSR. Rather than requiring direct synchronized communication between BSRs, the state information is routed through the core network infrastructure, which acts as an intermediary buffer, allowing asynchronous operation between BSRs without incurring large delay penalties.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If RLC reset is performed during hard handover, then handover is completed, but incomplete packets are discarded requiring higher-layer retransmissions

Engineering Contradiction:

Improvehandover completion speedVSAvoidincomplete packet loss

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent applies preliminary action by completing the RLC state information migration before the handover is executed. The source BSR prepares and forwards all necessary RLC state information (sequence numbers, buffer status, acknowledgment states) to the target BSR in advance, so that when handover occurs, the target BSR can immediately continue transmission without resetting the RLC layer, thus avoiding incomplete packet loss while maintaining fast handover completion.

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If inter-BSR hard handover is implemented, then mobility between base station routers is supported, but service interruptions occur due to data loss

Engineering Contradiction:

Improvemobility supportVSAvoidservice continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies copying by duplicating the complete RLC state information from the source BSR to the target BSR before handover. This includes copying transmit sequence numbers, receive sequence numbers, acknowledgment states, and buffer status information, ensuring that the target BSR can seamlessly continue service without interruption or data loss, thus maintaining service continuity while supporting mobility between BSRs.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS7920866B2Method of hard handover in a wireless communication system

Publication Date: 2011.04.05 NOKIA OF AMERICA CORP

AI summary

The present invention provides a method of wireless communication with a mobile unit and a base station router. The method may include providing, over a first channel, configuration information indicative of a second channel associated with the base station router and the mobile unit. The method may also include providing state information associated with the mobile unit to the base station router.