NACK Feedback Symbol Allocation for HARQ Latency and Reliability
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Solution Overview
Problem
Current wireless communication systems, particularly in V2V and V2X technologies, face challenges in efficiently managing HARQ feedback mechanisms, leading to increased latency and reduced reliability in data packet transmission and reception.
Innovation Solution
The implementation of a method and apparatus that allow receiving UEs to transmit NACK feedback in dedicated symbols after the end of transmission slots, enabling efficient error detection and retransmission without compromising data rate, using a reserved feedback symbol within the slot structure to switch between receiving and transmitting modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If receiving UEs transmit NACK feedback immediately after receiving data packets, then latency is reduced, but reliability deteriorates due to mode switching conflicts and feedback collisions
Solution Approach 1:
The patent pre-allocates dedicated NACK feedback symbols within the slot structure before data transmission begins. Receiving UEs are configured to transmit NACK feedback in these predetermined symbols, eliminating the need for dynamic mode switching and feedback collision resolution during actual transmission.
Solution Approach 2:
The patent segments the slot structure into distinct regions: data transmission symbols and dedicated NACK feedback symbols. This segmentation allows receiving UEs to transmit NACK feedback without interfering with ongoing data transmissions, as each UE transmits only in its assigned feedback symbol.
2Reliability
If dedicated NACK feedback symbols are allocated within the slot structure, then feedback transmission reliability is improved, but data rate deteriorates due to reduced available data transmission symbols
Solution Approach 1:
The patent allocates only the minimum necessary feedback symbols required for reliable NACK transmission, rather than dedicating entire slots or excessive symbols. This partial allocation provides sufficient feedback capability while preserving the majority of symbols for data transmission, thus maintaining high data rates.
3Adaptability or versatility
If receiving UEs switch between receiving and transmitting modes dynamically, then feedback flexibility is improved, but device complexity increases due to mode switching management
Solution Approach 1:
The patent pre-configures receiving UEs with specific slot formats and feedback symbol positions before transmission begins. UEs know in advance which symbols to monitor for data and which symbols to use for NACK feedback, eliminating the need for dynamic mode switching decisions and reducing processing complexity.
Data Source
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AI summary
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The apparatus may receive from a second device a first data packet in one or more receiving slots of a time division duplex frame that includes a plurality of slots. The apparatus may determine whether the first data packet is received incorrectly. The apparatus may wait until the end of the one or more receiving slots and may transmit to the second device a first NACK in a NACK feedback symbol in a configured slot after the end of the one or more receiving slots in response to determining that the first data packet was not received correctly.