Cross-Carrier Scheduling Timing Gap for PDCCH Decoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In cellular communications, cross-carrier scheduling with different numerologies can lead to increased buffering due to slow PDCCH decoding, as PDCCH decoding on smaller subcarrier spacing cells takes longer than on higher spacing cells, causing conflicts and inefficiencies in scheduling between dynamic grant and semi-persistent PDSCH transmissions.
Innovation Solution
A method is introduced to determine a timing gap based on the smallest subcarrier spacing of involved carriers, ensuring that the dynamic grant DCI is transmitted sufficiently in advance of the semi-persistent PDSCH to allow for cancellation, thereby avoiding conflicts and optimizing scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cross-carrier scheduling is implemented with different numerologies, then scheduling flexibility and resource utilization are improved, but PDCCH decoding time increases causing scheduling conflicts and buffering issues
Solution Approach 1:
The patent introduces a timing gap parameter that is determined in advance based on the subcarrier spacing of the scheduled carrier. This timing gap is calculated before scheduling decisions are made, allowing the system to pre-determine the minimum time required for PDCCH decoding. By establishing this timing gap beforehand, the system can proactively avoid scheduling conflicts rather than reacting to them after they occur.
Solution Approach 2:
The patent dynamically adjusts the timing gap parameter based on the subcarrier spacing configuration. When the scheduled carrier has a smaller subcarrier spacing (which requires longer decoding time), the timing gap is increased accordingly. This parameter adaptation allows the system to maintain scheduling flexibility while accommodating the varying decoding requirements of different numerologies.
2Productivity
If dynamic grant PDSCH is scheduled to overlap with SPS PDSCH to improve resource utilization, then spectral efficiency increases, but scheduling conflicts occur requiring complex collision handling
Solution Approach 1:
The system determines the timing gap in advance based on subcarrier spacing, which establishes a clear rule for handling potential collisions between dynamic grant PDSCH and SPS PDSCH. Instead of dealing with complex collision detection and resolution algorithms in real-time, the timing gap provides a pre-established criterion that simplifies the scheduling decision process.
Solution Approach 2:
By introducing the timing gap parameter that varies with subcarrier spacing, the patent provides a dynamic yet simple mechanism for collision handling. The network device can straightforwardly compare the timing gap against the scheduling parameters to determine whether a collision exists, avoiding the need for complex collision resolution protocols while maintaining spectral efficiency.
3Measurement precision
If PDCCH decoding time is increased to accommodate smaller subcarrier spacing, then decoding accuracy improves, but scheduling responsiveness decreases causing buffering
Solution Approach 1:
The patent directly addresses this contradiction by making the timing gap parameter dependent on subcarrier spacing. When smaller subcarrier spacing is used (which requires more time for accurate decoding), the timing gap is automatically increased to provide sufficient decoding time. Conversely, when larger subcarrier spacing is used, the timing gap is reduced, maintaining fast scheduling responsiveness. This parameter adaptation resolves the trade-off between decoding accuracy and scheduling speed.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method for cross carrier scheduling can include: determining that a candidate DCI for a UE schedules a DG PDSCH that at least partially overlaps an SPS PDSCH for the UE, wherein the DCI is configured to be transmitted on a first CC having a first SCS, and the DG PDSCH is configured for transmission on a second CC having a second SCS different from the first SCS; determining a timing gap based on the smallest of the first SCS and the second SCS; determining that an available time between the scheduled SPS PDSCH and the DCI is equal to or greater than the timing gap; cancelling the SPS PDSCH responsive to determining that the available time between the scheduled SPS PDSCH and the DCI is equal to or greater than the timing gap; and transmitting the DCI to the UE.