Variable Transmit Power Control for HSDPA Throughput
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Solution Overview
Problem
In wireless multi-cell communications, especially in HSDPA systems, there is a mismatch between the reported channel quality and actual conditions due to sudden changes in total transmit power, leading to inaccurate link adaptation and reduced throughput, particularly during TCP slow start phases with frequent retransmissions and exponential backoff.
Innovation Solution
Implementing a variable transmit power increase factor that adjusts based on the current total downlink transmitted power, using a more conservative factor at the beginning of high-speed downlink transmission and becoming more liberal as transmission continues, to minimize interference and maximize throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If constant power increase method is used, then implementation is simple, but throughput is reduced and bit rate is low due to interference mismatch
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant power increase factor to a dynamic variable power increase factor that adapts based on current downlink transmit power levels. The power increase factor is adjusted dynamically according to the ratio of available high speed shared channel power to total downlink power, enabling the system to optimize throughput while maintaining implementation feasibility through formula-based adaptation.
Solution Approach 2:
The patent implements parameter changes by modifying the power increase factor parameter based on system conditions. Specifically, the power increase factor is changed as a function of the ratio between available HS-DSCH power and total downlink power, allowing the system to adapt power allocation parameters dynamically to maximize throughput while avoiding the interference mismatch problems of constant power increase methods.
2Productivity
If transmit power is increased suddenly, then throughput can be maximized, but channel quality estimation becomes inaccurate leading to retransmissions
Solution Approach 1:
The patent applies preliminary action by adjusting the power increase factor before significant interference mismatch occurs. The system proactively limits the rate of power increase based on the current power ratio, preventing the channel quality estimation from becoming inaccurate due to sudden power changes. This preliminary control action avoids the need for corrective retransmissions while still enabling throughput optimization.
Solution Approach 2:
The patent implements feedback by using the ratio of available HS-DSCH power to total downlink power as a feedback signal to adjust the power increase factor. This feedback mechanism ensures that power increases are proportional to available resources and current system conditions, maintaining accurate channel quality estimation while maximizing throughput through adaptive power control.
3Reliability
If conservative power increase factor is used, then interference is minimized and channel quality estimation is accurate, but achievable bit rate is reduced
Solution Approach 1:
The patent resolves this contradiction through dynamics by making the power increase factor variable rather than fixed. The factor dynamically adjusts based on the ratio of available HS-DSCH power to total downlink power, allowing the system to be conservative when necessary (maintaining estimation accuracy) while being more aggressive when resources permit (maximizing bit rate). This dynamic adaptation eliminates the need to choose between reliability and productivity.
Solution Approach 2:
The patent applies parameter changes by modifying the power increase factor according to system conditions. When the ratio of available HS-DSCH power to total downlink power is high, the factor can be larger to increase bit rate. When the ratio is low, the factor becomes more conservative to maintain estimation accuracy. This parameter adaptation allows the system to optimize both reliability and productivity across different operating conditions.
Data Source
AI summary
To increase throughput efficiency and attain a higher achieved bit rate for data transmissions over a high speed shared channel, a variable transmit power increase factor is used to control the maximum rate at which the power at which data is transmitted over the high speed shared channel can increase. In one non-limiting implementation, the power increase factor F is varied with the current total downlink transmitted power available for high speed downlink transmission. For example, when the available high speed shared channel power is large, the variable transmit power increase factor assumes a more conservative value, e.g., a smaller F value, at the beginning of the high speed downlink transmission, and then a more liberal value, e.g., a larger F value, later during the high speed downlink transmission.