OLLA Offset Optimization for Cellular Link Adaptation
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Solution Overview
Problem
Existing link adaptation mechanisms in cellular networks are sensitive to parameter selection, often using conservative values that sacrifice performance due to inefficiencies in adapting radio connections.
Innovation Solution
A method that monitors and optimizes the initial offset value for the Outer Loop Link Adaptation (OLLA) process by generating histograms of offset values, particularly focusing on high activity radio connections to determine an optimized initial value for improved convergence and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conservative parameter values are used in OLLA mechanism, then reliability of link adaptation is improved, but productivity (data throughput) deteriorates
Solution Approach 1:
The patent changes the parameter selection strategy by using activity-based classification to determine appropriate step sizes and initial offset values. High activity connections use larger step sizes (e.g., 1.5 dB) and higher initial offsets, while low activity connections use smaller step sizes (e.g., 0.5 dB) and lower initial offsets. This dynamic parameter adjustment resolves the contradiction by allowing aggressive parameter changes for active connections (maximizing throughput) while using conservative parameters for inactive connections (maintaining reliability).
Solution Approach 2:
The patent introduces dynamics into the previously static OLLA parameters by making step sizes and initial offset values dependent on connection activity level. The system continuously monitors activity and adjusts parameters accordingly, allowing the link adaptation mechanism to be aggressive when needed (high throughput) and conservative when appropriate (high reliability), thus resolving the contradiction between reliability and productivity.
2Speed
If large step sizes are used for offset adaptation, then convergence speed is improved, but reliability deteriorates due to instability
Solution Approach 1:
The patent makes the step size dynamic by linking it to connection activity level. High activity connections use larger step sizes (faster convergence) while low activity connections use smaller step sizes (more stable). This resolves the contradiction by allowing fast convergence only when the connection is actively transmitting data, where speed is more critical, while maintaining stability during low activity periods.
Solution Approach 2:
The patent applies different step size qualities to different subsets of connections based on their activity characteristics. Instead of using a uniform step size for all connections, the system tailors the step size to the local conditions of each connection group (high vs. low activity), allowing optimal convergence speed and stability for each subset simultaneously.
3Adaptability or versatility
If activity-based classification is implemented, then adaptability of link adaptation is improved, but device complexity increases
Solution Approach 1:
The patent segments the population of radio connections into distinct groups (high activity and low activity) based on simple transmission counters. This segmentation enables differentiated parameter settings for each group, improving adaptability. The complexity is kept manageable by using straightforward segmentation criteria (transmission counters) rather than complex classification algorithms.
Solution Approach 2:
The system uses existing transmission counters that are already maintained for other purposes (HARQ operations, scheduling) to classify connections into activity groups. This self-service approach leverages existing data structures and logic, minimizing additional complexity while achieving activity-based adaptability.
Data Source
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AI summary
An offset is monitored which is applied by at least one access node (100) of a cellular network to adapt a signal quality value determined for a radio connection to a communication device (10). The adapted signal quality value is applied in a first control loop to select, a modulation and coding scheme for the radio connection. The offset is adapted in a second control loop, starting from an initial value and depending on feedback information concerning transmissions on the radio connection. Depending on the monitored offset, the initial value of the offset to be applied by the at least one access node (100) with respect to further radio connections to communication devices is determined.