HSDPA Link Adaptation Using Partial CQI Feedback

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Solution Overview

Problem

In HSDPA radio systems, the delay in receiving CQI feedback information leads to outdated channel condition data, especially during soft handover, resulting in decreased link and system performance due to the reliance on repeated CQI reports, which causes delays in link adaptation and packet scheduling.

Innovation Solution

A method and system for improving link adaptation and packet scheduling by calculating a quality estimate from user equipment feedback information at the base station, allowing for timely and accurate decision-making even before all repetitions are received, thereby reducing delay and enhancing throughput performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If repetition of CQI feedback information is used to improve reliability, then CQI estimate accuracy is improved, but link adaptation delay increases

Engineering Contradiction:

ImproveCQI estimate accuracyVSAvoidlink adaptation delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The base station performs preliminary actions by calculating quality estimates from partial CQI feedback information before all repetitions are received. This allows the system to make link adaptation decisions earlier, reducing delay while still achieving acceptable accuracy through the quality estimate calculation that processes available feedback data proactively

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies partial action by utilizing only the received CQI feedback information up to the current time point rather than waiting for all repetitions. The quality estimate calculation processes partial feedback data to make timely link adaptation decisions, accepting that not all repetitions have been processed but still achieving sufficient accuracy for effective scheduling

Inventive Principle:

Principle #16Partial or excessive action

2Measurement precision

If waiting for all CQI repetitions to be received before making link adaptation decisions, then CQI estimate accuracy is improved, but system throughput decreases

Engineering Contradiction:

ImproveCQI estimate accuracyVSAvoidsystem throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The base station performs preliminary link adaptation decisions by calculating quality estimates from available CQI feedback before all repetitions are received. This preliminary action enables the system to maintain high throughput by continuously making scheduling decisions while still improving accuracy through ongoing feedback processing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system maintains continuity of useful action by continuously processing CQI feedback information and updating quality estimates in real-time. Rather than stopping decision-making until all repetitions are received, the system continuously adapts link parameters based on accumulated feedback, ensuring uninterrupted throughput while improving accuracy over time

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If using power control measurements from downlink DPCH to estimate channel conditions, then link adaptation performance is improved, but this measure cannot be used during soft handover when multiple Node Bs are involved

Engineering Contradiction:

Improvelink adaptation performanceVSAvoidapplicability during soft handover

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system uses CQI feedback information as an intermediary to estimate channel conditions during soft handover, replacing the unreliable power control measurements. The quality estimate calculation processes this intermediary feedback data to derive accurate channel quality information that works reliably across multiple Node Bs involved in soft handover scenarios

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the parameter used for channel quality estimation from power control measurements to CQI feedback information. This parameter change enables the system to maintain link adaptation performance during soft handover by using the appropriate feedback mechanism that remains valid across multiple active Node Bs

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7539207B2Method and base station for controlling link adaptation and packet scheduling in high speed downlink packet access (HSDPA) radio system

Publication Date: 2009.05.26 RPX CORP

AI summary

A method of controlling link adaptation and packet scheduling in an HSDPA (High Speed Downlink Packet Access) radio system and an HSDPA base station communicating over a control channel with one or more user equipment units is provided. According to one embodiment the base station includes a device for receiving feedback information from the user equipment. The base station further includes a device for calculating a quality estimate related to the feedback information and executing link adaptation and packet scheduling based on the calculated quality estimate.