Uplink Transmission Symbol Nulling for LBT in Adjacent Subframes
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Solution Overview
Problem
In wireless communication systems, user equipment (UE) with a single RF frontend faces challenges in performing listen-before-talk (LBT) procedures for multiple component carriers (CCs) in adjacent subframes, as the RF frontend is already in use for transmission in the first subframe, preventing successful LBT in the adjacent subframe.
Innovation Solution
The UE determines to null one or more symbols of the uplink transmission in the first subframe to allow for an LBT procedure in the second subframe, based on the availability of the RF frontend and the modulation and coding scheme of the first uplink transmission, ensuring successful LBT and uplink transmission in the adjacent subframe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs LBT procedure for the second subframe during the first subframe, then the channel access for the second component carrier is improved, but the uplink transmission in the first subframe cannot be performed due to single RF frontend availability
Solution Approach 1:
The UE segments the subframe structure by identifying and nulling specific symbols (e.g., last 1-3 symbols) within the first subframe. This segmentation allows the LBT procedure to be performed in the remaining portion of the first subframe without completely sacrificing the uplink transmission opportunity, thus resolving the contradiction between performing LBT and maintaining productivity.
Solution Approach 2:
The UE performs the LBT procedure in advance during the first subframe (using nulled symbols) before the second subframe begins. This preliminary action ensures channel access is secured beforehand, allowing the second uplink transmission to proceed without delay, thus improving reliability of LBT while maintaining overall system productivity.
2Reliability
If the UE nulls one or more symbols in the first subframe to perform LBT, then the channel access for the second component carrier is improved, but the data transmission efficiency in the first subframe deteriorates
Solution Approach 1:
The UE applies local quality by selectively nulling only specific symbols (e.g., last 1-3 symbols) rather than the entire subframe. This localized approach minimizes the impact on data transmission efficiency while providing sufficient time for LBT procedure, thus resolving the contradiction between improving channel access reliability and maintaining data transmission productivity.
Solution Approach 2:
The UE changes the parameter of symbol utilization by transitioning from using all symbols for data transmission to using only a subset of symbols (nulling some symbols). This parameter change allows the system to allocate specific symbols for LBT procedure while preserving the majority of symbols for data transmission, thus balancing channel access reliability with data transmission efficiency.
3Productivity
If the UE uses the RF frontend for transmission in the first subframe, then the uplink transmission is maintained, but the LBT procedure for the second subframe cannot be performed
Solution Approach 1:
The UE implements periodic action by alternating between transmission mode (first subframe) and LBT procedure mode (during nulled symbols of first subframe). This periodic switching allows the RF frontend to be used for both purposes sequentially, resolving the contradiction between maintaining uplink transmission productivity and ensuring LBT procedure reliability.
Solution Approach 2:
The UE maintains continuity of useful action by ensuring that the LBT procedure is completed during the first subframe (using nulled symbols) so that the second subframe transmission can proceed without interruption. This continuous approach ensures both transmission productivity and LBT reliability are maintained across adjacent subframes.
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. A user equipment (UE) may receive a first grant to perform a first uplink transmission in a first subframe using a first component carrier. The UE may receive a second grant to perform a second uplink transmission in a second subframe adjacent the first subframe in time. The UE may determine to null one or more symbols of the uplink transmission in the first subframe based at least in part on the second grant. In some cases, the UE may determine to null the one or more symbols of the first uplink transmission is based at least in part on an availability of a single radio frequency (RF) frontend for use by the UE.