Handover Mechanism Using Uplink Channel Quality

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Solution Overview

Problem

Conventional handover mechanisms in wireless communication systems rely solely on downlink channel quality metrics, neglecting uplink channel quality, which can lead to link imbalance and inadequate handover decisions due to disparate propagation environments for uplink and downlink signals.

Innovation Solution

The proposed solution involves generating and utilizing both uplink (UL) and downlink (DL) channel quality indicators by conveying a sounding reference signal from the mobile station to both serving and target base stations, allowing for handover decisions based on comprehensive UL and DL performance metrics, such as RSRP, RSSI, and RSOT, through backhaul communication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If handover decisions rely only on downlink channel quality indications, then the handover mechanism is simple and based on readily available DL metrics, but the handover reliability deteriorates due to link imbalance between UL and DL channel conditions

Engineering Contradiction:

Improvehandover reliabilityVSAvoidhandover mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system performs preliminary uplink channel quality measurements at target base stations before handover decisions are finalized. Target base stations measure uplink channel quality indicators (such as SRS received power) in advance, and these measurements are communicated to the serving base station through backhaul interfaces, enabling more reliable handover decisions that account for both uplink and downlink conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces backhaul communication interfaces as intermediaries to transfer uplink channel quality measurements from target base stations to the serving base station. This intermediary mechanism enables the serving base station to access target cell uplink channel quality information without requiring direct mobile station reporting, thus resolving the information asymmetry between UL and DL measurements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If uplink channel quality measurements are incorporated into handover decisions, then the handover reliability improves by addressing link imbalance, but the device complexity increases due to additional measurement and communication requirements

Engineering Contradiction:

Improvehandover reliabilityVSAvoidmeasurement and communication complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Target base stations autonomously perform uplink channel quality measurements using sounding reference signals transmitted by the mobile station. The target base stations self-generate and self-measure the uplink channel quality indicators, eliminating the need for the mobile station to actively report to each potential target base station, thereby reducing overall system complexity.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If both UL and DL channel quality metrics are used for handover decisions, then the handover accuracy improves by considering comprehensive channel conditions, but the information processing requirements increase

Engineering Contradiction:

Improvehandover decision accuracyVSAvoidchannel quality data volume

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential uplink channel quality indicators (such as SRS received power, signal-to-interference ratios) from the target base station measurements and transmits these specific metrics through the backhaul interface. This selective extraction approach provides the serving base station with sufficient uplink quality information without overwhelming it with excessive data, thus balancing measurement precision with information processing requirements.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentEP3255926B1Handover mechanism that exploits uplink channel quality of a target cell

Publication Date: 2020.02.26 QUALCOMM INC

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AI summary

System(s) and method(s) are provided for handover of a mobile terminal in a wireless communication system. Handoff resolution relies on both a downlink channel quality indication between a serving base station and the mobile terminal, and uplink channel quality indications amongst the terminal and a measurement set of target base stations. To generate UL channel quality indicators, the mobile station conveys a narrowband or broadband sounding reference signal, and serving and target base stations measure UL and DL performance metrics (e.g., RSRP, RSSI, or RSOT). In backward handover, UL channel state information from target cells is received at the serving base station through backhaul communication, and handoff is resolved based on both UL and DL quality reports. In forward handover, the set of UL quality reports are conveyed to the mobile station to determine a target cell for handoff.