HARQ Feedback Resource Segmentation for Shortened TTI
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in HARQ feedback due to collisions between legacy PUCCH and shortened PUCCH resources, leading to resource waste and increased latency in next-generation networks like 5G, particularly in TDD configurations with varying TTI lengths.
Innovation Solution
The proposed solution involves multiplexing ACK/NACK responses of different TTI lengths in an efficient manner by separating resource sets based on offset values and resource allocation indices, ensuring non-overlapping and optimized use of resources for both legacy and shortened TTI transmissions, thereby reducing collisions and improving resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HARQ feedback resources are shared between legacy and shortened TTI, then resource utilization improves, but resource collisions occur leading to feedback failures
Solution Approach 1:
The PUCCH resource space is segmented into distinct regions: legacy PUCCH resources (nPUCCH,1 to nPUCCH,1+NRG-1) and shortened PUCCH resources (nPUCCH,1+NRG to nPUCCH,1+2NRG-1). This segmentation prevents collisions by allocating separate resource pools for different TTI types while maintaining overall resource utilization efficiency.
2Reliability
If separate resource sets are allocated for legacy and shortened TTI, then resource collisions are avoided, but resource waste increases due to dedicated allocation
Solution Approach 1:
The system dynamically selects between legacy and shortened TTI configurations based on service requirements. The offset value k is adjusted dynamically to map shortened PUCCH resources to appropriate uplink subframes, allowing flexible resource allocation that adapts to different traffic patterns and reduces waste while maintaining reliability.
3Loss of time
If processing time for HARQ feedback is reduced in shortened TTI, then latency decreases, but resource allocation complexity increases
Solution Approach 1:
The network pre-configures offset values and resource mapping parameters through RRC signaling before shortened TTI transmission begins. This preliminary configuration establishes the resource allocation rules in advance, allowing the UE to quickly determine feedback resources without complex real-time calculations, thus reducing latency while managing complexity through pre-computed parameters.
Data Source
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AI summary
Methods and apparatuses for improving HARQ feedback in shortened TTI in a wireless communication system are disclosed herein. In one method, a user equipment is configured with a processing interval between receiving a downlink data and transmitting a corresponding acknowledgement (ACK)/ negative acknowledgement (NACK) response (1105). The UE receives downlink data with 1 millisecond TTI at a downlink subframe (1110). The UE transmits the ACK/NACK response of the downlink data on a resource at an uplink subframe, wherein the resource is based on an offset value if the processing interval is shorter than 4 milliseconds (1115).