LTE Base Station MCS and TBS Selection for Special Subframes
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Solution Overview
Problem
Inefficient link adaptation in Citizens Broadband Radio Service (CBRS) systems using Long-Term Evolution (LTE) results in poor throughput and resource inefficiency due to mismatched modulation and coding schemes (MCS) and transmit block sizes (TBS) with channel conditions, especially in special subframes with fewer symbols.
Innovation Solution
A base station processor selects a customized MCS and TBS by tracking nominal parameters, accounting for the number of resource blocks, control format indicators, and subframe types, using lookup tables to map nominal values to customized pairs that match channel conditions more accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional link adaptation selects MCS and TBS based on standard LTE procedures, then the system maintains compatibility with standard LTE operations, but rate efficiency varies significantly in special subframes due to mismatched MCS and TBS with channel conditions
Solution Approach 1:
The patent modifies the TBS selection by introducing a scaling factor applied to the number of resource blocks allocated in special subframes. This parameter change adjusts the TBS calculation to account for the reduced number of available symbols in special subframes compared to normal subframes, thereby improving rate efficiency while maintaining compatibility with standard LTE MCS selection procedures
Solution Approach 2:
The patent introduces dynamic adjustment of TBS based on subframe type detection. The system dynamically selects between different TBS calculation methods depending on whether the current subframe is identified as a special subframe or a normal subframe, allowing optimal adaptation to varying channel conditions and subframe structures without disrupting standard LTE operations
2Adaptability or versatility
If the number of resource blocks and control data vary in special subframes, then flexibility in resource allocation is improved, but the variation in rate efficiency for a given MCS increases
Solution Approach 1:
The patent applies a scaling factor to the number of resource blocks when calculating TBS in special subframes. This parameter modification compensates for the variable control data and resource block allocation in special subframes, reducing rate efficiency variation while preserving the flexibility of dynamic resource allocation
Solution Approach 2:
The patent implements a feedback mechanism where the system monitors the actual rate efficiency achieved in special subframes and adjusts the TBS scaling factor accordingly. This closed-loop approach ensures that rate efficiency remains consistent across varying resource allocation scenarios while maintaining the adaptability needed for flexible resource management
Data Source
AI summary
A base station for selecting a modulation and coding scheme (MCS) and a total block size (TBS) for a UE is provided. The base station includes a processor and memory storing instructions. The instructions are executable to map a nominal MCS to a TBS index and determine a nominal TBS per resource block value based on the TBS index. The instructions are also executable to determine a target TBS based on the nominal TBS per resource block value and a number of resource blocks allocated to the UE. The instructions are also executable to determine a customized TBS, from a plurality of predefined TBSs, that is closest to the target TBS. The instructions are also executable to map the customized TBS to a customized MCS. The instructions are also executable to use the customized TBS and the customized MCS to transmit to the UE during a downlink transmission time interval.