Estimating Downlink CoMP Channel Quality for Legacy UEs

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Solution Overview

Problem

Legacy user equipment (UE) in LTE networks can only measure channel state information for a single link, making it difficult to enable downlink coordinated multipoint (CoMP) modes, which require accurate quality measurement and reporting from multiple access points.

Innovation Solution

A method to estimate the aggregate or cooperative link Channel State Information (CSI) for legacy UEs by using serving access point CSI reports and uplink measurements from cooperative access points, allowing for the calculation of coordinated downlink multipoint channel quality and precoding matrices to enhance CoMP deployment without modifying the UE.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If downlink CoMP modes are deployed to improve signal reception and throughput at cell edges, then network performance is improved, but legacy UEs cannot benefit because they only measure CSI for a single link and lack multi-link measurement capability

Engineering Contradiction:

Improvenetwork throughputVSAvoidUE compatibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent introduces an intermediary estimation mechanism where the network node uses uplink measurements from multiple access points and the serving access point CSI report to derive downlink CoMP channel quality indicators. This intermediary approach allows legacy UEs to indirectly benefit from CoMP without requiring direct multi-link measurement capabilities at the UE side.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Instead of requiring the UE to measure downlink channels from multiple access points (the conventional approach), the patent inverts the measurement direction by having access points measure uplink channels and then estimating the downlink CoMP channel quality from these uplink measurements. This inversion enables legacy UE compatibility while maintaining CoMP functionality.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If accurate downlink channel quality measurement from multiple access points is required for CoMP, then transmission quality is improved, but device complexity increases due to the need for multiple measurements and reports at the UE

Engineering Contradiction:

Improvechannel quality accuracyVSAvoidmeasurement and reporting complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The access points perform self-service by measuring the uplink channels from their own receivers and providing these measurements to the network node. This eliminates the need for the UE to perform complex downlink measurements from multiple access points, as the access points themselves generate the necessary measurement data through their normal uplink reception operations.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If legacy UEs are to benefit from CoMP without modifications, then backward compatibility is maintained, but the channel quality estimation must be derived indirectly using uplink measurements and path gain ratios

Engineering Contradiction:

Improvelegacy UE supportVSAvoidchannel quality estimation accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameters from direct downlink channel quality measurements (which would require UE modifications) to uplink path gain measurements combined with serving access point CSI reports. By transforming the measurement approach while maintaining the essential channel quality information, the patent enables legacy UE support without sacrificing estimation accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the mechanical measurement system at the UE (direct downlink measurements) with a network-based estimation system using uplink measurements and path gain ratios. This substitution replaces the need for complex UE measurement hardware and processing with network-side calculations that leverage existing uplink measurement capabilities.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP2989821B1A method and device for enabling downlink coordinated multipoint communication

Publication Date: 2018.07.25 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

The present disclosure relates to a method and device (10) for enabling downlink (DL) coordinated multipoint (CoMP) communication. In particular it relates to a method of enabling CoMP in legacy user equipments, i.e. devices that only measures and reports the channel quality of the link to its primary serving point. The method comprises the steps receiving the at least one DL channel quality measurement (SI), receiving at least one uplink (UL) measurement of the respective UL channels from the wireless device to one of the multiple access points (S2), and estimating a coordinated DL multipoint channel quality of a coordinated multipoint channel corresponding to one or more different coordinated transmission states of the access points, based on the at least one DL channel quality measurement and the received UL measurements, by assuming that the DL path gains from the multiple access points to the wireless device are proportional to the UL path gains to the multiple access points for respective access point, thereby predicting link quality of inter-access-points-coordinated DL multipoint transmissions from the access points.