Uplink Scheduling Modes for Limited Downlink Subframes
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Solution Overview
Problem
In wireless communication systems, particularly in LTE and LTE-A, the uncertainty in channel availability due to Listen-Before-Talk (LBT) regulations and the time delay between uplink (UL) data transmission and UL grant transmission lead to challenges in scheduling and transmitting UL data, especially when the number of UL subframes exceeds the number of downlink (DL) subframes, resulting in insufficient DL subframes for UL grants.
Innovation Solution
The solution involves determining at least two UL scheduling modes based on the number of DL and UL subframes, allowing for different scheduling time delays, and using these modes to perform UL transmission. This includes using a predetermined scheduling mode or an indicated mode to schedule UL subframes, enabling flexible scheduling even when DL subframes are limited, by allowing one DL subframe to send UL grants for multiple UL subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If legacy UL transmission schemes are used with fixed scheduling time delay, then the scheduling process is simple, but there are not enough DL subframes to send UL grants when UL subframes exceed DL subframes
Solution Approach 1:
The patent introduces dynamic scheduling time delays (k values) that can be adjusted based on the ratio of UL to DL subframes. Instead of a fixed scheduling delay, the system selects from multiple possible k values (e.g., k=4, k=7, k=10) depending on the actual subframe configuration, allowing the scheduling mechanism to adapt to varying traffic demands and subframe availability.
Solution Approach 2:
The patent changes the scheduling parameter (time delay k) based on the subframe configuration. When UL subframes exceed DL subframes, the system increases the scheduling time delay to allow sufficient DL subframes to accumulate for sending UL grants, thereby maintaining grant availability while supporting higher UL capacity.
2Productivity
If multiple UL subframes are scheduled by single DL subframe, then UL scheduling efficiency improves, but the uncertainty of channel availability due to LBT makes grant validity uncertain
Solution Approach 1:
The patent sends UL grants in advance in DL subframes before the actual UL transmission occurs. By preparing and transmitting the grants beforehand, the system ensures that grants are available when needed, while the flexible timing allows accounting for LBT channel access delays. The grant includes timing information that specifies when it becomes valid for use.
Solution Approach 2:
The patent introduces a timing indicator field in the grant that acts as an intermediary parameter, specifying the exact time when the grant becomes valid. This mediator allows the system to decouple the grant transmission time from the actual transmission time, handling the uncertainty introduced by LBT channel access through explicit timing information.
3Reliability
If flexible scheduling time delays are introduced to handle subframe mismatches, then UL grant availability improves, but the scheduling mechanism becomes more complex
Solution Approach 1:
The patent segments the scheduling time delay into discrete, predefined options (e.g., k=4, k=7, k=10) rather than allowing continuous adjustment. This segmentation simplifies the selection process by providing a finite set of valid delay values, reducing the complexity of the scheduling mechanism while still providing flexibility to handle different subframe configurations.
Solution Approach 2:
The patent implements dynamic selection from a predefined set of scheduling time delays based on the actual UL-to-DL subframe ratio. The system monitors the subframe configuration and dynamically selects the appropriate k value from the predefined options, providing adaptability without requiring complex real-time calculation or continuous parameter adjustment.
Data Source
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AI summary
Embodiments of the present disclosure relate to a method and apparatus for performing UL scheduling and a method and apparatus for perform UL transmission. In an embodiment of the present disclosure, the method of performing UL scheduling comprises determining at least two modes for the UL scheduling based on the number of downlink (DL) subframes and the number of UL subframes, wherein the at least two modes indicate different scheduling time delays.