Uplink Power Control for Wireless Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication networks, especially in WCDMA systems, the existing power control methods face instability and performance degradation due to changing signal-to-interference-plus-noise ratios (SINR) and significant self-interference at high data rates, leading to increased block error rates and latency.
Innovation Solution
A method and apparatus for uplink power control that maintains total received power for a set of uplink channels while ensuring target received signal quality for a subset of channels, using two power control loops to adjust data rates and power allocation dynamically, decoupling rate and power settings, and employing an intelligent 'walk' algorithm for rate adaptation based on block errors and signal quality feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SINR-based closed-loop power control is used to maintain signal quality, then received signal quality is improved, but system instability occurs at high data rates due to self-interference
Solution Approach 1:
The patent segments the power control mechanism into two distinct components: outer-loop power control that sets target SINR values based on quality requirements, and inner-loop power control that rapidly adjusts transmit power to track those targets. This segmentation allows the slow outer loop to adapt to changing channel conditions while the fast inner loop maintains stability by quickly correcting deviations, preventing the oscillations that cause instability at high data rates.
Solution Approach 2:
The patent implements a dual-loop feedback system where the outer loop monitors block error rates and adjusts target SINR accordingly, while the inner loop continuously measures received signal quality and provides rapid feedback to adjust transmit power. This layered feedback structure enables the system to maintain reliability by adapting targets to actual performance while preventing instability through rapid correction of power deviations.
2Productivity
If data rate is increased to improve throughput, then productivity is improved, but self-interference increases causing SINR to deviate from target values
Solution Approach 1:
The patent makes the power control system dynamic by implementing adaptive target SINR adjustment in the outer loop. Instead of using fixed SINR targets, the system dynamically adjusts target values based on observed block error rates and channel conditions. This allows the system to maintain reliable communication at varying data rates by adapting the SINR target to the actual interference environment created by high-rate transmissions.
Solution Approach 2:
The patent changes the SINR target parameter dynamically based on operating conditions. The outer loop monitors performance metrics and adjusts the target SINR value to compensate for self-interference effects that increase with data rate. This parameter adaptation allows the system to maintain reliability across a wide range of data rates by tuning the SINR target to match the actual channel conditions.
3Speed
If TTI is shortened to improve responsiveness, then speed is improved, but signal quality becomes approximately constant making closed-loop power control less effective
Solution Approach 1:
The patent segments the power control loops by time scale, with the outer loop operating on a slower timescale to adjust target SINR values based on statistical performance metrics, while the inner loop operates on the faster TTI timescale to rapidly track those targets. This temporal segmentation allows the system to benefit from short TTIs for responsiveness while using the slower outer loop to adapt to the reduced signal quality variation inherent in shorter integration intervals.
Solution Approach 2:
The outer loop performs preliminary action by pre-adjusting target SINR values based on observed block error rates before the inner loop executes rapid power adjustments. This preliminary adaptation to changing channel conditions ensures that the inner loop has appropriate targets to track, maintaining effectiveness even when TTI duration is shortened and signal quality variation is reduced.
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A method and apparatus provide advantageous uplink power control for a set of uplink channels transmitted by a mobile terminal or other item of user equipment (UE). The proposed uplink power control maintains the total received power for the set of uplink channels at or about a target received power, while also maintaining the received signal quality for a subset of those channels---e.g, a particular one of them---at or about a target received signal qualify. In an advantageous but non-limiting example embodiment, the subset comprises a fixed-rate control channel, and the set includes that control channel and a variable-rate traffic channel Correspondingly, a base station generates first power control commands to maintain the received signal quality of the control channel at or about some quality target, and generates second power control commands to maintain the total received power (of the two channels) at or about some power target.