Flexible Time Domain Resource Allocation for URLLC Latency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The current New Radio (NR) time domain-resource allocation (TD-RA) framework is insufficient for ultra-reliable and low-latency communications (URLLC) due to rigid slot boundary references, inability to schedule data across slot boundaries, and inefficient DCI design, which leads to latency and reliability issues for URLLC services.
Innovation Solution
The proposed solutions involve configuring the starting symbol position based on a more flexible reference point, such as a half-slot or a reference time-domain region, and allowing dynamic scheduling across slot boundaries, with the option to remove the TD-RA field from the DCI to reduce payload size and enable compact DCI design, supporting URLLC and eMBB services simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slot boundary reference is used for TD-RA configuration, then the current NR framework is maintained, but latency requirements for URLLC services cannot be met
Solution Approach 1:
The reference point for determining start symbol position is changed from fixed slot boundaries to flexible reference points (such as end of PDCCH, end of SSB, or configurable symbols within slot). This parameter change allows transmissions to start immediately after control signals without waiting for slot boundaries, reducing latency while maintaining reliable transmission through proper timing alignment.
Solution Approach 2:
The TD-RA framework is made dynamic by allowing the reference point to be configurable and adaptable to different service requirements. Instead of a static slot-boundary-based system, the reference point can be dynamically selected based on the timing of control channels and service requirements, enabling instantaneous URLLC transmissions when needed.
2Productivity
If data scheduling is restricted within a single slot, then the current TD-RA framework is maintained, but time domain distribution efficiency and latency are reduced
Solution Approach 1:
The scheduling flexibility is segmented by allowing different service types to have different scheduling behaviors. URLLC services can utilize cross-slot scheduling with flexible reference points, while other services continue to use traditional slot-boundary-based scheduling. This segmentation enables efficient time domain distribution for latency-sensitive traffic without disrupting the overall framework.
3Reliability
If normal DCI fields are included for URLLC transmissions, then comprehensive control information is provided, but DCI payload size increases and reliability decreases
Solution Approach 1:
The DCI payload is streamlined by extracting and removing fields that are not applicable or unnecessary for URLLC transmissions. Since URLLC uses pre-configured parameters and flexible reference points, many traditional DCI fields (such as detailed resource allocation information that is pre-configured) can be omitted, reducing payload size and improving reliability without losing essential control information.
Solution Approach 2:
Instead of including all normal DCI fields, only the essential and URLLC-specific fields are included in the DCI payload. This partial action approach provides sufficient control information for URLLC transmissions while minimizing payload size, achieving the right balance between comprehensiveness and efficiency for latency-critical services.
Data Source
AI summary
Various solutions for enhancing time domain-resource allocation (TD-RA) framework with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive an indication of a reference point. The apparatus may determine a start symbol position according to the reference point rather than a slot boundary. The apparatus may determining a TD-RA according to the start symbol position. The apparatus may perform a transmission according to the TD-RA.