Uplink Control Channel Codebook Design for NR Unlicensed Spectrum
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Solution Overview
Problem
In wireless communication systems, especially in New Radio (NR) unlicensed spectrum, conventional uplink control channel codebook designs are inadequate due to the uncertainty of channel availability caused by listen-before-talk procedures, leading to inconsistent feedback reports and disruption of Hybrid Automatic Repeat Request (HARQ) processes.
Innovation Solution
The proposed solution involves a UE monitoring channels during a monitoring window to detect active channels, selecting formats for first and second sub-codebooks based on detected signals, and transmitting uplink control messages using these sub-codebooks to indicate feedback states and channel activity, with the base station providing indications of active channels to align feedback reports with channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional uplink control channel codebook designs are used in NR unlicensed spectrum, then the system can operate with standard feedback reporting mechanisms, but the feedback reports become inconsistent and HARQ processes are disrupted due to channel availability uncertainty from listen-before-talk procedures
Solution Approach 1:
The codebook format is made dynamic by allowing the UE to select between first and second codebook formats based on whether a signal is detected during the monitoring window. This dynamic adaptation enables the feedback reporting mechanism to adjust to channel availability conditions, resolving the contradiction between maintaining reliable feedback and adapting to uncertain channel access in unlicensed spectrum
Solution Approach 2:
The invention changes the parameter of codebook format selection based on signal detection outcomes. When a signal is detected, one format is selected; when not detected, another format is selected. This parameter change approach allows the system to maintain feedback consistency while adapting to the variable channel availability caused by listen-before-talk procedures
2Measurement precision
If the UE monitors channels during a monitoring window to detect active channels, then the feedback reports accurately reflect channel conditions, but the complexity of codebook format selection and signal detection increases
Solution Approach 1:
The UE performs preliminary signal detection during a monitoring window before constructing the feedback report. This preliminary action of detecting signals and determining codebook formats in advance simplifies the subsequent feedback reporting process while ensuring accurate reflection of channel conditions, resolving the contradiction between measurement precision and device complexity
3Reliability
If the UE transmits uplink control messages indicating feedback states and channel activity, then the HARQ processes are improved, but the overhead of additional control signaling increases
Solution Approach 1:
The invention merges channel activity indication with feedback state reporting in the uplink control message. By combining these two pieces of information into a single signaling mechanism, the system improves HARQ reliability without incurring the overhead of separate control signals, thus resolving the contradiction between reliability improvement and overhead increase
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify, based at least in part on monitoring a set of channels for signals during a monitoring window, a subset of channels in which signals were detected during the monitoring window. The UE may select, based at least in part on the subset of channels, a format for a first sub-codebook and a second sub-codebook, the second sub-codebook indicating a feedback state for corresponding data transmissions received on the channels within the subset of channels. The UE may transmit the first uplink control message using a first sub-codebook, the first uplink control message identifying the format for the second sub-codebook and identifying the channels within the subset of channels. The UE may transmit a second uplink control message using the second sub-codebook according to the selected format.