Semi-Persistent Scheduling Resource Grid for Wireless Uplink
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Solution Overview
Problem
In wireless communication systems, especially in low latency communications, the limited size of downlink control information (DCI) restricts the quality of service and efficiency, and dynamic radio channel conditions require frequent reassignment of resources, leading to inefficiencies, particularly in resource-constrained systems.
Innovation Solution
Implementing semi-persistent scheduling (SPS) with flexible modulation and coding schemes (MCS) and resource assignments, allowing user equipment (UE) to perform blind decoding on downlink semi-persistent resources and using a resource grid for uplink transmissions, enabling dynamic reassignment of resources without additional DCI, and employing conditional and non-conditional SPS resources for adaptive retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DCI information size is increased to provide more scheduling information, then quality of service and communication reliability improve, but control channel overhead and system complexity increase
Solution Approach 1:
The scheduling information is divided into two parts: semi-persistent scheduling configuration (SPS-C) transmitted via higher layer signaling that remains valid for multiple transmissions, and dynamic scheduling information transmitted via DCI for real-time adjustments. This segmentation allows comprehensive QoS information to be provided without constantly expanding DCI size.
Solution Approach 2:
Semi-persistent scheduling configuration is established in advance through RRC signaling, pre-defining resource allocations, modulation and coding schemes, and other parameters. This preliminary action eliminates the need to transmit all this information repeatedly in DCI, reducing control overhead while maintaining comprehensive scheduling capabilities.
2Reliability
If resources are frequently reassigned to adapt to changing radio channel conditions, then communication reliability improves, but system overhead and complexity increase
Solution Approach 1:
Semi-persistent scheduling establishes periodic resource allocations that automatically recur without requiring repeated DCI transmissions. This periodic action adapts to channel conditions by updating parameters at scheduled intervals rather than continuously, reducing system overhead while maintaining reliability.
Solution Approach 2:
The system combines semi-persistent configurations with dynamic adjustment capabilities through DCI, allowing resource allocations to adapt to changing channel conditions. This dynamic approach enables the system to balance between frequent reassignment for reliability and reduced overhead through semi-persistent patterns.
3Productivity
If semi-persistent scheduling is implemented with flexible MCS selection, then resource allocation efficiency improves, but decoding complexity at UE increases
Solution Approach 1:
The UE performs blind decoding on semi-persistent resources to autonomously determine the actual MCS used by the gNB. This self-service approach allows flexible MCS selection for resource allocation efficiency while managing decoding complexity through targeted blind decoding rather than exhaustive searching.
Solution Approach 2:
The system uses feedback mechanisms where the UE monitors for DCI indications that confirm or modify the semi-persistent configuration. This feedback loop allows the gNB to select optimal MCS values while the UE efficiently decodes by comparing received signals against expected patterns from the semi-persistent configuration.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. A User equipment (UE) may identify a set of semi-persistent scheduled resources configured for uplink transmissions by the UE. The UE may receive, from a base station, a resource grid that indicates scheduled uplink communications for one or more other UEs. The UE may determine a set of uplink resources for the UE based on the set of semi-persistent scheduled resources and the resource grid. The UE may then transmit an uplink message to the base station via the set of uplink resources. In some cases, the UE may identify resources for the scheduled uplink communications based on the resource grid and determine a set of conditional resources available for the UE based on the resources for the scheduled uplink communications, where the set of uplink resources includes at least a portion of the set of conditional resources.