Reverse Link Power Control for OFDMA Systems
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Solution Overview
Problem
In wireless communication systems, the lack of complete orthogonality among transmissions from multiple terminals leads to interference, degrading the performance of each terminal due to channel conditions and receiver imperfections, necessitating effective power control techniques to minimize interference and ensure good performance for all terminals.
Innovation Solution
The described techniques involve closed-loop power control mechanisms for control and data channels, using reference channels like the CQI channel to adjust transmit power based on signal quality and erasure detection, with inner, outer, and third loops managing SNR, erasure rate, and conditional error rate to achieve target performance levels, and power offset adjustments for ACK channels to optimize data capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple terminals transmit simultaneously on the reverse link, then system capacity and throughput are improved, but interference between terminals increases due to loss of orthogonality
Solution Approach 1:
The patent implements dynamic power control by continuously adjusting the transmit power parameter of each terminal based on real-time channel conditions and interference levels. The base station sends power control commands to terminals to increase or decrease transmit power, thereby maintaining orthogonality and reducing interference while preserving system capacity.
Solution Approach 2:
The patent establishes a feedback mechanism where the base station monitors the received signal quality and interference levels from multiple terminals, then sends power control commands back to the terminals. This closed-loop feedback system enables continuous optimization of transmit power to maintain orthogonal transmissions and minimize interference.
2Reliability
If transmit power of terminals is increased to improve signal quality, then received signal quality (SNR) is improved, but interference to other terminals increases
Solution Approach 1:
The patent applies local quality control by individually adjusting the transmit power of each terminal based on its specific channel conditions and interference environment. Instead of uniform power adjustment, each terminal receives customized power control commands tailored to its local situation, optimizing signal quality while minimizing interference to specific neighboring terminals.
Solution Approach 2:
The patent dynamically changes the transmit power parameter for each terminal based on real-time measurements of received signal quality and interference levels. The base station monitors SNR and interference metrics, then adjusts power parameters individually for each terminal to maintain reliable communication while suppressing interference.
3Reliability
If power control loops continuously adjust transmit power, then system performance and stability are improved, but control complexity increases
Solution Approach 1:
The patent segments the power control system into distinct functional loops: an inner loop for rapid SNR adjustment, an outer loop for target SNR optimization, and a third loop for erasure rate control. Each loop operates with specific algorithms and time constants, dividing the complex control task into manageable segments that can be implemented and tuned independently.
Solution Approach 2:
The patent implements dynamic power control with multiple operating loops that adapt to changing channel conditions. The inner loop provides rapid dynamic response to maintain SNR, while outer loops provide slower adjustments for optimization. This multi-timescale dynamic approach maintains stability while managing complexity through hierarchical control structures.
Data Source
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AI summary
Techniques for performing power control of multiple channels sent using multiple radio technologies are described. In one aspect, a reference transmit power level is determined, errors in signalling sent on a control channel is detected for, and transmit power of the control channel is then adjusted based on the reference transmit power level and the detected errors on the control channel.