Mutual Information Power Control for WCDMA Convergence

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing power control methods in telecommunication systems, particularly in interference-limited cellular networks like WCDMA and GSM, are not optimal for time-varying channels with varying Signal-to-Interference Ratio (SIR) distributions across neighboring Transmission Time Intervals (TTIs), leading to suboptimal decoding quality and increased interference.

Innovation Solution

The method employs mutual information (MI) to determine a quality target based on Block Error Rate (BLER) rather than SIR, adjusting transmit power for each slot to reach the BLER target, and incorporates a bias-removing step for accurate SIR estimation, enabling quicker and more accurate power adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If traditional SIR-based power control is used, then power control functionality is maintained, but convergence rate is slow in time-varying channels

Engineering Contradiction:

Improveconvergence rateVSAvoiddecoding quality

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent changes the fundamental parameter used for power control from SIR (Signal-to-Interference Ratio) to Mutual Information (MI). This parameter transformation enables the system to achieve faster convergence rates in time-varying channels because MI directly captures the relationship between transmit power and decoding quality, whereas SIR requires complex statistical assumptions that break down when channel conditions change rapidly.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If SIR target is adjusted based on long-term quality measurements, then system stability is maintained, but response to channel variations is slow

Engineering Contradiction:

Improvesystem stabilityVSAvoidresponse time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The patent implements a feedback mechanism where the receiver calculates Mutual Information from received signals and feeds this information back to the transmitter. This MI feedback provides real-time information about the actual decoding quality, enabling the system to respond quickly to channel variations while maintaining stability through the natural smoothing effect of the MI calculation over multiple symbols.

Inventive Principle:

Principle #23Feedback

3Reliability

If power control is optimized for one TTI, then decoding quality is improved for that TTI, but neighboring TTIs with different SIR distributions are not served optimally

Engineering Contradiction:

Improvedecoding qualityVSAvoidadaptability to different SIR distributions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

By transforming the power control parameter from SIR to Mutual Information, the patent creates a universal metric that directly relates to decoding quality regardless of the underlying SIR distribution. MI naturally adapts to different channel conditions and SIR distributions because it is calculated directly from the received signal statistics, making the power control equally effective across neighboring TTIs with varying conditions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7817972B2Method and arrangement for mutual information based power control

Publication Date: 2010.10.19 UNWIRED PLANET LLC

AI summary

In a method for power control in a telecommunication system, the transmit power is adjusted based on at least the mutual information expression or a representation thereof. According to one aspect the transmit power for a coming slot is controlled based on the previously received slots, wherein an estimated quality is compared to a determined quality target based on the mutual information expression.