ACK/NACK Feedback in 1 Symbol Wireless Terminal
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Solution Overview
Problem
Conventional methods require 2 symbols to feedback ACK/NACK in future radio communication systems, limiting latency reduction and not considering how to feedback ACK/NACK in a shortened Transmission Time Interval (TTI) of 1 symbol.
Innovation Solution
A user terminal with an error detector and mapper that associates ACK with one frequency resource and NACK with a different frequency resource within the same symbol, allowing notification of ACK/NACK in 1 symbol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the sTTI length is shortened to 1 symbol to reduce latency, then the transmission time is reduced, but conventional methods require 2 symbols for ACK/NACK feedback which cannot be accommodated in 1 symbol
Solution Approach 1:
The patent transitions from time-domain resource allocation (2 symbols in time) to frequency-domain resource allocation (different frequency resources within 1 symbol). By mapping ACK and NACK to different frequency resources (e.g., different subcarriers or resource elements) within the same 1-symbol time window, the system accommodates feedback capability while maintaining shortened TTI latency requirements.
2Reliability
If conventional 2-symbol ACK/NACK feedback method is used, then reliable error notification is achieved, but the TTI length cannot be shortened to 1 symbol
Solution Approach 1:
The patent segments the frequency resources within the 1-symbol TTI into distinct regions for ACK and NACK feedback. By allocating specific frequency resources (e.g., different subcarriers, resource elements, or orthogonal sequences) to represent ACK and NACK states, the system maintains reliable error notification capability while compressing the feedback into a single symbol duration.
Data Source
AI summary
A user terminal (20) is provided with: an error detection unit (205) that detects the presence/absence of an error concerning a downlink data signal and generates ACK or NACK which are error detection results; and a mapping unit (207) that maps a transmission signal on a first frequency resource in one symbol and corresponding to ACK when the error detection result is ACK, and maps a transmission signal on a second frequency resource different from the first frequency resource in the same symbol corresponding to NACK when the error detection result is NACK.