Dynamic Power Headroom Threshold for CDMA Reverse Link
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Solution Overview
Problem
In wireless communication systems, the fixed power headroom threshold in mobile stations implementing ARQ or HARQ can lead to inefficient data transmission rates due to unpredictable channel conditions, as it either limits retransmissions or reduces average data transmission rates, depending on the reserved power.
Innovation Solution
The power headroom threshold in mobile stations is dynamically adjusted based on reverse link load indications from the base station, allowing for increased power headroom during high loads and reduced power headroom during low loads, using a combination of load tracking values and counter-based mechanisms for open loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed power headroom threshold is used to ensure sufficient power for retransmissions, then retransmission reliability is improved, but the average data transmission rate deteriorates
Solution Approach 1:
The power headroom threshold is transformed from a fixed value to a dynamic value that adapts to current channel conditions. The mobile station continuously monitors reverse link quality metrics (such as signal-to-interference ratio or bit error rate) and adjusts the power headroom threshold accordingly, allowing the system to maintain high retransmission reliability when channel conditions are poor while maximizing data transmission rate when conditions are good
Solution Approach 2:
The invention changes the parameter of power headroom threshold from a static configuration to a dynamically adjustable parameter based on channel quality indicators. By monitoring reverse link load and quality metrics, the system modifies the power headroom threshold parameter in real-time, enabling optimal balance between retransmission reliability and data transmission efficiency under varying channel conditions
2Reliability
If too much power is reserved for retransmissions, then retransmission capability is improved, but the average data transmission rate deteriorates
Solution Approach 1:
The system dynamically adjusts the amount of power reserved for retransmissions based on real-time channel conditions. When reverse link quality is good, the mobile station reduces the power headroom reservation, allowing higher transmission rates. When quality deteriorates, the reservation increases automatically to ensure retransmission capability, thus optimizing the trade-off between retransmission capability and data transmission rate
3Productivity
If too little power is reserved for retransmissions, then the average data transmission rate is improved, but retransmission capability deteriorates
Solution Approach 1:
The mobile station performs preliminary assessment of channel conditions and proactively adjusts the power headroom threshold before retransmission is needed. By monitoring reverse link quality in advance, the system prepares appropriate power reservations, ensuring that when retransmission becomes necessary, sufficient power is already allocated, thus maintaining both high data rates and reliable retransmission capability
Data Source
AI summary
Closed loop and open loop control mechanisms are disclosed for adjusting the power headroom in a mobile station. The closed loop control comprises receiving a load indication from a base station indicative of the reverse link load, and adjusting the power headroom of the mobile station based on the load indication. The open loop control mechanism comprises counting the number of times that the mobile station is power limited, and adjusting the power headroom threshold based on the count.