CDMA Uplink Congestion Detection via SIR Error Reports
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Solution Overview
Problem
In WCDMA cellular communication systems, accurately estimating uplink load to detect and avoid congestion without limiting capacity is challenging, especially since all User Equipments send data simultaneously, leading to varying Signal-to-Interference Ratio (SIR) and interference levels.
Innovation Solution
Measuring the number of Signal-to-Interference Ratio Error (SIRe) reports and setting thresholds to detect potential and serious congestion, allowing for flexible operational adjustments to prevent or improve congestion by differentiating between types of congestion and taking direct actions before the cell becomes unstable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit power control is implemented to reduce mutual interference, then system capacity is improved, but different User Equipments experience different Signal-to-Interference Ratio SIR values
Solution Approach 1:
The patent implements a feedback mechanism where the Network measures the actual SIR for each User Equipment and compares it against the target SIR. Based on this feedback, power control commands are adjusted to bring all users closer to the target SIR, thereby improving SIR distribution uniformity while maintaining system capacity.
Solution Approach 2:
The patent dynamically adjusts the power control step size based on the current SIR distribution characteristics. When SIR values are close to the target, smaller adjustment steps are used to achieve fine-tuned uniformity. When deviations are large, larger steps are applied for faster convergence, optimizing both capacity and SIR uniformity.
2Manufacturing precision
If power control commands are transmitted frequently (1500 times per second), then transmit power accuracy is improved, but system complexity increases
Solution Approach 1:
The patent applies partial power control adjustments rather than continuous full-step adjustments. By using smaller power control steps (e.g., 0.5 dB instead of 1 dB) and selectively applying control only when necessary, the system achieves sufficient power accuracy without the full complexity of continuous high-frequency control.
Solution Approach 2:
The patent makes the power control loop dynamic by adjusting the control frequency and step size based on current system conditions. The Network adapts the control parameters in real-time based on measured SIR values and traffic conditions, optimizing the balance between control accuracy and system complexity.
3Measurement precision
If a threshold for SIRe reports is set to detect congestion, then congestion detection accuracy is improved, but false detection risk increases
Solution Approach 1:
The patent performs preliminary actions by monitoring SIRe report trends over time rather than making single-point threshold comparisons. The Network tracks whether SIRe reports consistently exceed the threshold across multiple measurement intervals, which helps distinguish true congestion from temporary anomalies or false detections.
Solution Approach 2:
The patent incorporates a cushioning mechanism by setting the congestion detection threshold with a margin that accounts for normal variations in SIRe values. The threshold is designed to trigger only when SIRe reports consistently exceed the threshold by a significant margin, providing a buffer against false detections while maintaining sensitivity to real congestion conditions.
Data Source
AI summary
The present invention relates in general to the radio communications field and, in particular, to a method and apparatus for detecting congestion in a spread spectrum Code Division Multiple Access (CDMA) cellular communication system. By measuring the number of Signal-to-Interference Ratio Error reports being received at the Radio Network Controller a potential congestion can be detected in the cell when the number of reports being received is above a threshold. Further can a differentiation be made between a potential or a serious congestion and different actions be performed dependant on if a potential or a serious congestion is detected.