Hybrid Power Control for Inter-Cell Interference
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Solution Overview
Problem
Current inter-cell interference management in orthogonal OFDM systems is inefficient due to lack of awareness of interference caused by serving cells' terminals to other cells, leading to reduced system coverage and increased interference, especially in urban canyon areas where dynamic load conditions complicate power control.
Innovation Solution
Implementing a hybrid closed and open-loop power control method that utilizes path loss readings from both serving and neighboring non-serving cells to adjust transmit power spectral density (PSD), switching from open-loop to closed-loop control once an initial target value is established, allowing for accurate interference mitigation and flexible bandwidth allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If open loop power control is used to set initial transmit power, then the end node can establish communications quickly, but the transmit power level will be in error causing unnecessary interference to other mobile stations
Solution Approach 1:
The patent implements a closed-loop power control mechanism where the base station measures the actual received power from each end node and sends power control commands back to adjust the transmit power. This feedback loop corrects the initial power estimation errors caused by open-loop control, thereby reducing unnecessary interference to other mobile stations while maintaining fast communication establishment.
Solution Approach 2:
The patent uses open-loop power control to establish an initial transmit power level before actual communication begins. This preliminary action allows the end node to quickly establish communications, and then the closed-loop control refines this initial setting to eliminate interference issues.
2Measurement precision
If closed loop power control is used to improve accuracy, then the transmit power can be precisely controlled, but the system requires a proper starting point which delays the process
Solution Approach 1:
The patent applies open-loop power control as a preliminary action to establish an initial transmit power level quickly, before switching to closed-loop control for precise adjustment. This eliminates the time delay that would occur if closed-loop control had to establish power from scratch.
Solution Approach 2:
The patent merges open-loop and closed-loop power control mechanisms into a hybrid system. The open-loop provides quick initial establishment while the closed-loop ensures precise accuracy, combining the advantages of both approaches to achieve both speed and precision.
3Reliability
If end nodes transmit at high power to ensure coverage, then communications can be established, but inter-cell interference increases reducing system capacity
Solution Approach 1:
The patent implements inter-cell interference coordination through feedback mechanisms where base stations exchange interference information and coordinate power control decisions. This allows end nodes to transmit at appropriate power levels that ensure coverage while preventing excessive interference to neighboring cells, thereby maintaining system capacity.
Solution Approach 2:
The patent applies different power control strategies to different end nodes based on their local conditions such as distance from base station, cell loading, and interference environment. This localized approach ensures each end node transmits at the minimum necessary power for reliable communication, preventing unnecessary interference while maintaining coverage.
4Reliability
If multiple probes are sent to ensure connection, then coverage is improved, but call setup time increases and reverse link interference increases
Solution Approach 1:
The patent uses feedback-based power control to ensure the first access probe is transmitted at the correct power level, eliminating the need for multiple retry probes. The base station provides power control commands that ensure the end node transmits at the precise power needed for successful connection establishment.
Solution Approach 2:
The patent replaces the mechanical retry mechanism (sending multiple probes) with a precision control mechanism (accurate power control based on path loss estimation and feedback). This substitution achieves reliable connection establishment on the first attempt without the time delay and interference caused by multiple probes.
Data Source
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AI summary
A system and method for inter-cell power control for interference management in an OFDM system is provided. The system provides for a combination use of open loop and closed loop PSD control algorithms. The open loop control is a function of path loss from the serving cell as well as the neighboring cells. The closed loop control updates the end node transmit PSD by listening to the load indicators from the serving cell and at least one other neighboring non-serving cell which generates the highest level of interference. The system thus provides a fast and tight control with multi-cell information that allows improved inter-cell interference control.