Outer Loop Link Adaptation Bundled Feedback
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Solution Overview
Problem
The existing outer loop link adaptation (OLA) in cellular communications networks is not effective with bundled HARQ feedback, leading to suboptimal target Block Error Rate (BLER) due to the imbalance between downlink and uplink capabilities and the bundling of HARQ feedback in Time Division Duplexing (TDD) and carrier aggregation modes.
Innovation Solution
The proposed solution involves updating the outer loop LA parameter based on the number of HARQ processes and a metric indicative of channel correlation, adjusting the target BLER to optimize link adaptation, and using these adjustments to increment or decrement the outer loop LA parameter accordingly based on successful or unsuccessful bundled feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If HARQ feedback is bundled in TDD and carrier aggregation modes, then uplink feedback overhead is reduced, but target BLER becomes suboptimal due to imbalance between downlink and uplink capabilities
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the outer loop LA parameter based on the number of bundled HARQ processes and channel correlation metrics. This allows the system to adapt the target BLER to the actual bundled feedback scenario, transforming the fixed parameter approach into a dynamic one that accounts for the imbalance between downlink and uplink capabilities.
Solution Approach 2:
The patent implements a feedback mechanism where the outer loop LA parameter is updated based on received bundled HARQ feedback. The system uses the feedback information, combined with the number of bundled processes and channel correlation, to adjust subsequent transmissions, creating a closed-loop control system that optimizes performance despite feedback bundling.
2Reliability
If outer loop LA parameter is updated based on traditional HARQ feedback, then link adaptation is optimized for individual transmissions, but convergence to throughput-optimal BLER is slow in bundled feedback scenarios
Solution Approach 1:
The patent applies preliminary action by pre-calculating the adjustment to the outer loop LA parameter based on the number of bundled HARQ processes and channel correlation metrics before actual transmissions occur. This allows the system to proactively compensate for the effects of bundling, accelerating convergence to the throughput-optimal BLER.
Solution Approach 2:
The patent changes the approach from updating LA parameters based solely on individual transmission outcomes to updating based on bundled feedback outcomes, incorporating the number of bundled processes and channel correlation. This parameter change in the update mechanism enables faster convergence in bundled feedback scenarios.
3Adaptability or versatility
If the number of HARQ processes in bundled feedback varies, then system flexibility is improved, but determining appropriate target BLER becomes more complex
Solution Approach 1:
The patent uses parameter changes by establishing a relationship between the number of bundled HARQ processes and the target BLER adjustment. As the number of bundled processes varies, the system dynamically adjusts the target BLER parameter based on pre-determined relationships, maintaining flexibility while managing complexity through systematic parameter adjustment.
Solution Approach 2:
The patent introduces channel correlation as an intermediary parameter that mediates between the varying number of HARQ processes and the target BLER determination. This intermediary helps simplify the relationship by providing a metric that captures the essential characteristics of channel conditions across bundled processes.
Data Source
AI summary
Systems and methods for outer loop Link Adaptation (LA) with bundled feedback are disclosed. In some embodiments, a method of operation of a radio access node in a cellular communications network to provide outer loop LA includes receiving, from a wireless device, a bundled feedback acknowledging reception of data by multiple Hybrid Automatic Repeat Request HARQ) processes at the wireless device. The method also includes, in response to receiving the bundled feedback, updating an outer loop LA parameter based on the number of HARQ processes in the HARQ processes and/or a metric indicative of channel correlation for a channel from the radio access node to the wireless device.