Soft Handover Power Control for Uplink Channel Reliability

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Solution Overview

Problem

In wireless cellular networks, especially in WCDMA systems, the inner loop and closed loop power control methods face challenges during soft handover scenarios with uplink and downlink imbalances, leading to unreliable decoding of uplink control channels, particularly the HS-DPCCH, which affects the Quality of Service (QoS) of HSDPA due to interference and power control conflicts between macro and low power NodeBs.

Innovation Solution

A method where a cell belonging to a different Radio Link Set (RLS) from the serving cell sends a fixed power control instruction to increase transmission power for UE in soft handover status, independent of measured Signal-to-Interference Ratio (SIR), and combines SIR measurements from multiple cells to adjust power control instructions when necessary, ensuring reliable uplink channel decoding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE follows power control indications from all cells in soft handover, then the interference to other users is reduced and system capacity is improved, but the uplink control channel decoding becomes unreliable when uplink and downlink are unbalanced

Engineering Contradiction:

Improveuplink control channel decoding reliabilityVSAvoidsystem capacity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the power control management by introducing a serving cell concept. The serving cell (macro NodeB) maintains full power control functionality while non-serving cells (low power NodeBs) transmit fixed power control indications. This segmentation resolves the contradiction by allowing non-serving cells to contribute to system capacity without compromising uplink control channel decoding reliability at the serving cell.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a fixed power control indication mechanism as an intermediary for non-serving cells. Instead of implementing full power control loops that could conflict, non-serving cells act as intermediaries that provide supplemental power control signals without measuring SIR or making decoding decisions, thus avoiding the reliability issue while still contributing to power management.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the UE increases transmission power according to macro NodeB instructions, then the signal quality at macro NodeB is improved, but the interference to low power NodeB increases and may cause downlink quality degradation

Engineering Contradiction:

Improvesignal quality at macro NodeBVSAvoidinterference to low power NodeB

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the power control behavior for different cells. The serving cell (macro NodeB) uses full power control based on its own SIR measurements, while non-serving cells (low power NodeBs) use fixed power control indications. This allows each cell to have optimized power control characteristics suitable for its local conditions, resolving the interference issue.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If the UE decreases transmission power according to low power NodeB instructions, then the interference to other users is reduced, but the signal quality at macro NodeB deteriorates and affects HSDPA QoS

Engineering Contradiction:

Improveinterference reductionVSAvoidsignal quality at macro NodeB

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the UE monitors the quality of uplink control channel decoding at the serving cell. When decoding failures are detected, the UE can request adjustments to the fixed power control indications from non-serving cells. This feedback loop ensures that interference reduction goals are met without compromising the reliability of uplink control channel decoding.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2986064B1Method, base station, computer storage medium for implementing inner loop and closed loop power control

Publication Date: 2020.04.01 ZTE CORP

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AI summary

Provided are a method, a base station and a computer storage medium for implementing inner loop and closed loop power control. The method includes that when User Equipment (UE) is in a soft handover status, a cell which belongs to a Radio Link Set (RLS) different from that of a serving cell of the UE sends a fixed power control instruction to instruct the UE to increase transmission power.