Adaptive Uplink Power Control in TDD Mobile Systems
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Solution Overview
Problem
Conventional mobile communication systems in TDD mode either underutilize the advantages of closed-loop and open-loop power control schemes or switch between them inadequately, leading to inefficiencies in uplink power control, particularly due to fixed power control strategies that do not adapt to changing mobile velocities, resulting in suboptimal system capacity and increased interference.
Innovation Solution
An apparatus and method that adaptively selects between closed-loop and open-loop power control schemes based on the mobility index of subscriber stations, switching between them according to a threshold to optimize uplink power control, ensuring efficient resource allocation and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed power control scheme is used in TDD mobile communication systems, then the system implementation is simple, but the uplink power control efficiency deteriorates when mobile velocity changes
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed power control scheme to a dynamic adaptive scheme that changes based on mobile station velocity. The base station estimates velocity using pilot signals and selectively switches between open-loop and closed-loop power control schemes according to the estimated velocity, allowing the system to adapt to changing mobile conditions and maintain optimal power control efficiency.
2Measurement precision
If closed-loop power control is used, then power control accuracy is improved, but system complexity increases due to continuous feedback requirements
Solution Approach 1:
The patent applies segmentation by dividing the power control approach into two distinct schemes: open-loop power control for low-velocity mobiles and closed-loop power control for high-velocity mobiles. This segmentation allows each scheme to be optimized for its specific velocity range, reducing unnecessary complexity while maintaining accuracy where needed.
Solution Approach 2:
The system dynamically selects between open-loop and closed-loop power control schemes based on estimated mobile velocity. This dynamic selection ensures that closed-loop feedback mechanisms are only activated when necessary (for high-velocity mobiles), thereby reducing overall system complexity while maintaining power control accuracy when required.
3Device complexity
If open-loop power control is used, then system complexity is reduced, but interference increases due to less precise power control
Solution Approach 1:
The patent segments the mobile population based on velocity characteristics, applying open-loop power control to low-velocity mobiles and closed-loop power control to high-velocity mobiles. This segmentation ensures that precise power control is applied where interference is most problematic (high-velocity scenarios), while reducing complexity for low-velocity scenarios where interference is less of an issue.
Solution Approach 2:
The system changes the power control parameter (selecting between open-loop and closed-loop schemes) based on mobile velocity. This parameter change allows the system to optimize the balance between complexity and interference control by using closed-loop control for high-velocity mobiles that generate more interference and open-loop for low-velocity mobiles.
4Productivity
If adaptive power control switching is implemented, then uplink power control efficiency is improved, but mobility estimation complexity increases
Solution Approach 1:
The patent uses pilot signals as an intermediary to estimate mobile velocity. The base station utilizes existing pilot signals transmitted by mobile stations to derive velocity information without requiring additional dedicated measurement signals. This intermediary approach enables mobility estimation while minimizing additional system complexity.
Data Source
AI summary
An apparatus and method for changing an uplink power control scheme according to mobile status in a TDD mobile communication system are provided. A subscriber station transmits to a base station a power control change request message including information about a requested power control scheme. Upon receipt of the power control change request message, the base station selects a power control scheme for the uplink of the subscriber station and transmits to the subscriber station a power control change command message including information about the selected power control scheme. The subscriber station extracts, upon receipt of the power control change command message from the base station, the power control scheme information from the power control change command message and selects a power control scheme according to the extracted information.