RRC-Inactive Small Data Feedback Mapping to Reduce Collisions
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Solution Overview
Problem
Future wireless communications networks face challenges in efficiently handling diverse devices with varying data traffic profiles and requirements, particularly in configuring uplink feedback resources for small data transmissions in the RRC_INACTIVE state, leading to potential collisions and inefficiencies.
Innovation Solution
The proposed solution involves configuring dedicated uplink feedback resources, such as PRACH + PUCCH, PRACH + PUSCH, or PRACH alone, for UEs in the RRC_INACTIVE state to transmit HARQ-ACK feedback for downlink small data transmissions, using pre-specified mappings between PRACH preambles and PUCCH/PUSCH resources within a bandwidth part (BWP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated uplink feedback resources are configured for UEs in RRC_INACTIVE state, then feedback reliability is improved, but device complexity and network configuration complexity increase
Solution Approach 1:
The network pre-configures multiple uplink feedback resource sets and PRACH preamble groups before the UE enters RRC_INACTIVE state. This preliminary configuration enables the UE to autonomously select appropriate feedback resources without real-time network intervention, improving feedback reliability while avoiding continuous configuration overhead.
Solution Approach 2:
The uplink feedback resources are segmented into multiple resource sets, each associated with specific PRACH preamble groups. This segmentation allows fine-grained resource allocation where different resource sets can be optimized for different feedback scenarios, improving reliability without requiring a single complex configuration for all cases.
2Productivity
If multiple UEs share common uplink feedback resources, then resource utilization efficiency is improved, but collision probability increases
Solution Approach 1:
Uplink feedback resources are divided into multiple resource sets, each associated with specific PRACH preamble groups. By segmenting resources this way, the patent reduces collision probability among multiple UEs while maintaining efficient resource utilization through shared access within each segmented group.
Solution Approach 2:
The patent introduces an additional dimension for resource differentiation by associating feedback resource sets with specific PRACH preamble groups. This dimensional separation allows multiple UEs to share resources in one dimension (time/frequency) while being distinguished in another dimension (preamble group association), thereby reducing collisions.
3Loss of time
If UEs in RRC_INACTIVE state transmit feedback without full synchronization, then access delay is reduced, but synchronization accuracy deteriorates
Solution Approach 1:
The network performs preliminary synchronization configuration and provides reference signals before the UE needs to transmit feedback. This allows the UE to maintain sufficient synchronization accuracy while in RRC_INACTIVE state without requiring full re-synchronization, thereby reducing access delay while preserving measurement precision.
Solution Approach 2:
The system provides beforehand cushioning through pre-configured uplink feedback resources that are designed to be robust against synchronization errors. These resources include reference signals and timing information that compensate for potential synchronization drift, allowing UEs to transmit feedback with reduced access delay while maintaining adequate synchronization accuracy.
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AI summary
A method of operating a communications device configured to transmit signals to and/or to receive signals from a wireless communications network via a wireless radio interface provided by the wireless communications network is provided. The method comprises, while the communications device is operating in an inactive state, receiving, from the wireless communications network, a small data transmission, SDT, within a set of downlink resources of the wireless radio interface, determining, based on a configuration indicated by signalling information received from the wireless communications network previously to the SDT, a set of uplink resources of the wireless radio interface, and transmitting, to the wireless communications network in the determined set of uplink resources, a feedback signal in response to the received SDT.