Subframe-Based Link Adaptation for LTE Throughput
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Solution Overview
Problem
Conventional adaptive Modulation and Coding (AMC) techniques in LTE cellular communications networks result in varying Block Error Rates (BLER) for downlink transmissions, leading to inconsistent throughput due to subframe-specific noise and interference variations, with some subframes experiencing high BLER (up to 50%) while others have low BLER (as low as 0%).
Innovation Solution
Implementing subframe-based link adaptation by updating the Modulation and Coding Scheme (MCS) parameters, specifically the Signal to Interference plus Noise (SINR) offset, based on Hybrid Automatic Repeat Request (HARQ) acknowledgments for each subframe or subframe bundle/group, allowing for adaptive MCS selection to match varying channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional adaptive MCS selection techniques are used, then the system can operate with simple link adaptation mechanisms, but the BLER varies significantly between subframes (0% to 50%) resulting in poor downlink throughput
Solution Approach 1:
The patent segments the link adaptation process by introducing separate outer loop link adaptation mechanisms for different subframe types (e.g., subframes with and without Almost Blank Subframes). This allows independent BLER control and MCS optimization for each subframe category, ensuring consistent throughput across varying channel conditions rather than using a single unified adaptation mechanism that results in high BLER variability.
Solution Approach 2:
The patent implements dynamic link adaptation by adjusting the outer loop MCS based on subframe-specific conditions. The base station dynamically selects different MCS values for different subframe types according to their respective channel qualities and interference levels, enabling the system to adapt to time-varying channel conditions and maintain consistent BLER across all subframes.
2Reliability
If a single outer loop link adaptation is used for all subframes, then the system complexity is low, but it cannot compensate for subframe-specific noise and interference variations
Solution Approach 1:
The patent divides the link adaptation functionality into multiple outer loops, each dedicated to specific subframe types. This segmentation enables precise BLER control for each subframe category by independently tracking and adjusting MCS based on HARQ feedback from corresponding subframes, rather than using a single averaged adaptation mechanism that cannot address subframe-specific conditions.
Solution Approach 2:
The patent applies local quality by assigning different adaptation characteristics to different subframe groups. Each outer loop is optimized for its specific subframe type, allowing the system to apply appropriate MCS adjustments localized to each subframe category's channel conditions, interference patterns, and BLER requirements, rather than applying a uniform adaptation approach to all subframes.
Data Source
AI summary
Systems and methods for subframe-based link adaptation for a radio signal in a cellular communications network are disclosed. In one embodiment, a base station obtains a hybrid automatic repeat request acknowledgement for data transmitted between the base station and a mobile terminal in a radio signal of the base station. The base station then updates a parameter (e.g., SINR offset) used to control a Modulation and Coding Scheme (MCS) for transmission of data between the base station and the mobile terminal in the radio signal for one or more subframes in a frame structure of the radio signal based on the hybrid automatic repeat request acknowledgement. The one or more subframes are a subset of all of the subframes in the frame structure of the radio signal.