DLLA OLLA Path Segmentation for MCS Accuracy
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Solution Overview
Problem
The existing downlink link adaptation (DLLA) process in eNBs does not effectively consider the transmission mode (MIMO method) used for downlink transmission, leading to inaccuracies in modulation and coding scheme (MCS) calculations and resulting in loss of spectral efficiency and reliability.
Innovation Solution
The DLLA process is enhanced by dividing the outer loop link adaptation (OLLA) into separate paths for transmit diversity (TD) and spatial multiplexing (SM) transmission modes, modifying offset coefficients based on HARQ ACK/NACK feedback and the number of code words, and providing these offsets to the inner loop link adaptation (ILLA) to calculate accurate MCS for each mode, thereby improving spectral efficiency and transmission mode recommendations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single OLLA path is used for all transmission modes, then the system complexity is reduced, but the MCS calculation accuracy deteriorates for specific transmission modes
Solution Approach 1:
The patent divides the single OLLA path into separate paths for different transmission modes (TD and SM). Specifically, it implements first and second paths within the OLLA routine, where each path processes offset calculations independently for its designated transmission mode. This segmentation allows mode-specific offset adjustments without requiring complete redesign of the entire link adaptation system.
2Productivity
If transmission mode is not considered in OLLA, then the processing simplicity is maintained, but the spectral efficiency deteriorates
Solution Approach 1:
The patent applies different offset coefficients (first offset coefficient for TD, second offset coefficient for SM) based on the specific transmission mode being processed. The OLLA routine selectively applies the appropriate offset coefficient according to the transmission mode indicated by the RI report, thereby optimizing spectral efficiency for each mode without requiring complete system redesign.
3Reliability
If a single offset coefficient is used for all modes, then the system complexity is minimized, but the reliability of data transfer deteriorates
Solution Approach 1:
The patent implements dynamic offset coefficient selection based on the transmission mode indicated by the UE's RI report. The system transitions from a static single offset coefficient to a dynamic selection mechanism that chooses between first and second offset coefficients depending on whether TD or SM mode is active. This dynamic adaptation improves reliability while adding minimal complexity through mode-based selection logic.
Data Source
AI summary
A method is disclosed for enhancing downlink link adaptation (DLLA) for spectral efficiency maximization, comprising: providing an outer loop link adaptation (OLLA) routine with a first path for a first transmission mode and a second path for a second transmission mode; modifying, upon receiving a retransmit message for a first transmission with the first transmission mode, a first offset coefficient; modifying, upon receiving a second retransmit message for a second transmission with the second transmission mode, a second offset coefficient; and calculating a modulation and coding scheme (MCS) offset for the first transmission based on the first offset coefficient.