Feedback Codebook Rules for BWP and Cell Switching
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Solution Overview
Problem
In wireless communications systems, there is ambiguity regarding what feedback information to include and when to transmit feedback signaling after a bandwidth part (BWP) switch, especially when cell switching is involved, leading to unclear feedback codebook construction for control channel carrier switching.
Innovation Solution
User equipment (UE) generates feedback messages based on a feedback scheme that determines whether to include or exclude feedback information for physical downlink shared channels (PDSCHs) occurring prior to a BWP switch, considering factors like cell switching mode, cell of transmission, and BWP switch conditions, and supports retransmission rules to handle dropped feedback signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback information for PDSCHs prior to BWP switch is included in the feedback message, then feedback completeness is improved, but feedback message complexity and transmission timing ambiguity increase
Solution Approach 1:
The feedback message is segmented into two distinct parts: feedback information for PDSCHs received before the BWP switch and feedback information for PDSCHs received after the BWP switch. This segmentation allows the UE to clearly distinguish and handle feedback for different time periods, resolving the ambiguity about what feedback information to include while maintaining completeness.
Solution Approach 2:
The patent establishes preliminary rules and criteria for determining which PDSCHs should be included in the feedback message before the BWP switch occurs. The UE determines the timing of the BWP switch in advance and uses this information to pre-identify which PDSCHs require feedback inclusion, eliminating post-switch confusion and ensuring complete feedback coverage.
2Reliability
If feedback information for all PDSCHs is included regardless of BWP switch timing, then feedback completeness is improved, but transmission timing accuracy deteriorates
Solution Approach 1:
The UE determines the BWP switch timing in advance and uses this information to pre-identify which PDSCHs require feedback inclusion. By establishing the feedback inclusion criteria before the BWP switch occurs, the system maintains both feedback completeness and transmission timing accuracy without conflict.
Solution Approach 2:
Different feedback inclusion rules are applied to different time periods: before the BWP switch and after the BWP switch. This local differentiation allows the system to optimize feedback completeness for pre-switch PDSCHs while maintaining timing accuracy for post-switch PDSCHs, resolving the contradiction between completeness and timing precision.
3Reliability
If retransmission of feedback signaling is supported, then feedback reliability is improved, but system complexity and resource overhead increase
Solution Approach 1:
The patent implements a feedback mechanism where the network can detect missing or dropped feedback signaling and trigger retransmission requests. This feedback-based approach improves feedback reliability by providing a corrective mechanism for transmission errors while keeping the system relatively simple by only activating retransmission when actually needed, rather than continuously monitoring and managing all feedback transmissions.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may generate feedback messages according to a feedback codebook according to a feedback scheme indicating whether the UE is to include, or exclude, feedback information for physical downlink shared channels (PDSCHs) occurring prior to a bandwidth part (BWP) switch. For example, the UE may determine whether to include feedback information for any PDSCHs that occur prior to an uplink BWP switch for a UE that supports cell switching based on the cell in which the uplink BWP switch occurs, the cell in which the feedback message is scheduled for transmission (e.g., the same cell in which the PDSCHs occur, or a different cell), and a mode of PUCCH cell switching (e.g., dynamic or semi-static). The UE may also determine whether to send retransmissions of feedback information after a BWP switch.