OLLA Adjustment via Sequential Hypothesis Testing
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Solution Overview
Problem
In 4G and 5G mobile communication networks, inaccuracies in Channel Quality Information (CQI) reports lead to inefficient link adaptation, causing network performance issues and inefficient use of radio resources, particularly due to delays in reporting and slow responses to changes in channel conditions.
Innovation Solution
Implementing a network node that uses Sequential Hypothesis Testing (SHT) to determine Outer Loop Link Adaptation (OLLA) adjustments based on channel quality information, allowing for quick responses to changes in SINR inaccuracies without significant variance in Block Error Rate (BLER) targets, and reducing unnecessary perturbations in SINR estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large step sizes are used for outer loop adjustment, then the response speed to SINR inaccuracies improves, but the variance around BLER target increases
Solution Approach 1:
The patent applies dynamics by making the step size adaptive rather than fixed. The outer loop adjustment step size is dynamically modified based on the current BLER estimate and the target BLER. When the BLER estimate is far from the target, larger step sizes are used to quickly compensate for SINR inaccuracies. When the BLER estimate is close to the target, smaller step sizes are used to reduce variance. This dynamic adjustment resolves the contradiction between fast response speed and low variance around the BLER target.
2Reliability
If small step sizes are used for outer loop adjustment, then the variance around BLER target decreases, but the response speed to SINR inaccuracies slows down
Solution Approach 1:
The patent makes the step size dynamic based on the BLER estimation error. When the error is large, the system uses larger steps to quickly reduce the error. When the error is small, the system uses smaller steps to maintain precision and avoid overshooting. This dynamic behavior allows the system to achieve both fast initial response and low steady-state variance, resolving the contradiction between these two opposing requirements.
3Adaptability or versatility
If OLLA frequently adjusts SINR estimate, then the adaptation to channel changes improves, but unnecessary perturbations of SINR estimate increase
Solution Approach 1:
The patent implements feedback by continuously monitoring the BLER estimate and using it to control the outer loop adjustment. The system only applies adjustments when the BLER estimate deviates from the target by more than a threshold, and the adjustment magnitude is proportional to the deviation. This feedback mechanism ensures that adjustments are made only when necessary, improving adaptability while avoiding unnecessary perturbations that would destabilize the SINR estimate.
4Reliability
If classic step-up/step-down strategy is used, then the BLER target is achieved, but the trade-off between response speed and variance cannot be optimized
Solution Approach 1:
The patent changes the parameter of step size from a fixed value to a variable that depends on the BLER estimation error. The classic strategy uses constant step sizes, while this patent modifies the step size parameter dynamically based on the current BLER estimate and target BLER. This parameter change allows the system to optimize the trade-off between response speed and variance, achieving better performance while maintaining the same basic feedback control structure.
Data Source
AI summary
Embodiments herein relate to a network node operable in a radio communication network and a method performed by the network for communication between the network node and a wireless device. The method comprises obtaining (110) information associated with a channel quality of a channel between the network node and the wireless device; and estimating (120) respective one or more variables associated with the channel quality based on the obtained channel quality information. The method (100) further comprises determining (130) an Outer Loop Link Adaptation, OLLA, adjustment based on the obtained channel quality information, and based on the estimated respective one or more variables associated with the channel quality, and when the obtained channel quality information indicates that the channel performance is acceptable: also based on a Sequential Hypothesis Testing, SHT, of the obtained channel quality information.