Variable Power Control Step Sizes for HSUPA Link Adaptation
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Solution Overview
Problem
The current wireless communication systems face inefficiencies in power control due to limited step size granularity, leading to slower link adaptation and suboptimal resource allocation in HSUPA systems, where a 1 dB step size is insufficient for rapid power adjustments, resulting in wasted radio resources and inefficient power management.
Innovation Solution
Implementing a set of non-uniform power control increment step sizes, allowing for configurable and dynamic adjustments based on current power levels, enabling the Node B to send messages indicating power changes relative to a known value, thereby allowing more precise power adjustments without the need for multiple commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a uniform 1 dB power control step size is used, then the system maintains simple and consistent power adjustment, but the link adaptation speed is slow and requires multiple commands for larger power changes
Solution Approach 1:
The power control step sizes are segmented into multiple discrete values (e.g., 0.5 dB, 1 dB, 2 dB, 4 dB, 8 dB) that can be selectively applied based on channel conditions and power adjustment needs. This segmentation allows the system to choose appropriate step sizes for different scenarios, achieving faster link adaptation when needed while maintaining simplicity when conditions are stable.
Solution Approach 2:
The power control step size is made dynamic rather than fixed, allowing the system to adjust the step size based on current channel conditions, power levels, and traffic requirements. The Node B can select from multiple configured step sizes to optimize the balance between convergence speed and power control precision in different operational contexts.
2Measurement precision
If multiple power control commands are sent to achieve larger power changes, then the power adjustment becomes more accurate, but the signaling overhead increases and resource efficiency decreases
Solution Approach 1:
The system applies partial power control actions by selecting step sizes that are appropriate for the current situation rather than always using the maximum or minimum step size. This allows the Node B to achieve the necessary power adjustment with fewer commands by using larger step sizes when appropriate, reducing signaling overhead while maintaining sufficient precision.
Solution Approach 2:
The system changes the parameter of power control step size from a fixed value to a selectable set of values. By configuring multiple step size options and dynamically selecting from them, the system can achieve larger power changes in fewer commands when needed, thereby reducing the number of control messages and associated signaling overhead.
3Reliability
If the packet scheduler is located in the RNC with conservative power allocation, then the system maintains stability and accounts for inactive users, but spectral efficiency is reduced for high data rates
Solution Approach 1:
The system performs preliminary configuration of multiple power control step sizes at the RNC before actual power control operations begin. This preliminary action allows the RNC to maintain oversight and stability while enabling the Node B to execute faster, more efficient power adjustments locally, thus improving spectral efficiency without sacrificing overall system stability.
Solution Approach 2:
The configured set of power control step sizes acts as an intermediary mechanism between the RNC's conservative power allocation policy and the Node B's need for rapid power adjustment. The RNC configures the available step sizes, maintaining policy control, while the Node B selects appropriate step sizes from this configured set to achieve faster link adaptation and better spectral efficiency.
Data Source
Figure 1
Figure 2~2A
Figure 2B
AI summary
A set of power control step size increments are determined such that at least two step size increments differ from one another. The set is sent to a Mobile Station MS. A first power command to the MS informs of a first power for a uplink data transmission on a radio resource (E-DPDCH). To change power on the same radio resource, an offset is computed, the set of step size increments is accessed to determine which one, or combination of them, yield the offset, and the MS is informed of the second power by a second message that identifies those elements of the set that alone or in combination yield the offset. The MS determines the second power as a function of the first power and the step size increment(s) from the second message.