Partial Uplink Subframes for Unlicensed Carrier LBT Adaptation
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently utilizing unlicensed carriers for uplink transmissions due to unpredictable medium occupancy, leading to suboptimal resource utilization and increased overhead in adapting to listen before talk (LBT) outcomes.
Innovation Solution
The implementation of partial uplink subframes with dynamic symbol durations and flexible DMRS positioning allows for adaptive transmission strategies, enabling efficient use of unlicensed carriers and reducing the need for reservation signals, while allowing for UL to DL switching and LBT gap creation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full subframe transmissions are used on unlicensed carriers, then transmission reliability is maintained, but medium utilization efficiency deteriorates due to unpredictable LBT outcomes and fixed symbol durations
Solution Approach 1:
The patent implements dynamic subframe structures where the number of symbols in a subframe can vary (e.g., 2, 3, 4, or more symbols) based on LBT outcomes. This allows the system to adapt transmission length dynamically rather than using fixed full subframes, thereby improving medium utilization efficiency while maintaining reliability through flexible adaptation to channel access results.
Solution Approach 2:
The invention changes the parameter of subframe duration by allowing variable symbol counts within subframes. Instead of fixed-duration subframes, the system can adjust subframe length (e.g., partial subframes with 2-4 symbols) based on actual channel conditions and LBT outcomes, resolving the contradiction between efficiency and adaptability.
2Productivity
If fixed symbol durations are used in uplink subframes, then transmission simplicity is maintained, but resource utilization efficiency deteriorates due to inability to adapt to variable LBT completion times
Solution Approach 1:
The patent segments the traditional fixed subframe into variable-length partial subframes with different symbol counts (2, 3, 4, or more symbols). This segmentation allows the system to use only the necessary portion of the subframe based on LBT outcomes, improving resource utilization without requiring complete fixed-duration subframes.
Solution Approach 2:
The invention applies partial subframe transmissions where only the necessary number of symbols (2-4 symbols) are transmitted based on actual channel access timing. This partial action approach avoids wasting resources on complete fixed subframes when channel access occurs mid-subframe, thereby improving efficiency while managing complexity through standardized partial subframe formats.
3Productivity
If traditional DMRS positioning is used, then demodulation reliability is maintained, but overhead increases in partial subframes with shifted symbol positions
Solution Approach 1:
The patent places DMRS symbols at predetermined positions within partial subframes (e.g., at specific symbol indices within 2-4 symbol subframes). This preliminary positioning of reference signals allows the receiver to perform demodulation reliably without requiring additional overhead, as the DMRS positions are pre-planned and known in advance for each partial subframe configuration.
Solution Approach 2:
The invention applies different DMRS positioning strategies tailored to specific partial subframe configurations. Instead of using a single fixed DMRS position for all subframe types, the system optimizes DMRS placement locally for each partial subframe format (2-symbol, 3-symbol, 4-symbol), ensuring demodulation reliability while minimizing overhead for each specific case.
Data Source
AI summary
Technology for a user equipment (UE), operable for an uplink partial subframe transmission on an unlicensed carrier is disclosed. The UE can select one or more uplink (UL) partial subframe configurations based on one or more prospective lengths of a listen before talk (LBT) period, wherein each prospective length of the LBT period provides a prospective starting time. The UE can encode data for each of the one or more UL partial subframe configurations to form one or more UL partial subframe configuration encodings. The UE can identify an actual LBT period. The UE can select one of the one or more UL partial subframe configuration encodings for UL transmission of the data on the unlicensed carrier based on the actual LBT period and a corresponding prospective starting time.