Uplink Acknowledgement Channel Waveform Design for Low Latency
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Solution Overview
Problem
Conventional wireless communication systems face challenges in achieving low latency and robustness for acknowledgement (ACK) and negative-acknowledgement (NACK) messages, particularly for high-priority transmissions, due to delayed ACK/NACK message transmissions and susceptibility to corruption, which increases round trip time and retransmission requirements.
Innovation Solution
The system configures an uplink ACK channel based on the transmission time interval (TTI) format, employing interleaved frequency division multiple access (iFDMA) waveforms and scheduling ACK message resources prior to decoding subsequent symbols, to reduce latency and improve robustness by spreading acknowledgement information across multiple tones, thereby reducing peak-to-average power ratio (PAPR) and enhancing frequency diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ACK/NACK transmission methods are used, then the system maintains simple channel configuration, but latency increases and reliability decreases for high-priority transmissions
Solution Approach 1:
The patent applies dynamics by making the UL ACK channel configuration adaptable to different TTI formats. The system dynamically selects between single-symbol and multi-symbol TTI configurations based on service requirements, enabling low-latency transmission for high-priority traffic while maintaining robustness through multi-symbol transmission when needed. This dynamic adaptation resolves the contradiction between speed and reliability.
Solution Approach 2:
The patent changes key parameters including TTI duration (single vs. multi-symbol), resource allocation timing (earlier scheduling), and waveform characteristics (iFDMA with specific tone configurations). These parameter changes enable the system to achieve both low latency (through shorter TTIs and earlier scheduling) and high reliability (through frequency diversity and robust waveform design) simultaneously.
2Loss of time
If ACK messages are sent earlier in the TTI, then latency is reduced, but the transmission may be corrupted due to incomplete decoding
Solution Approach 1:
The patent applies preliminary action by scheduling ACK message resources before the receiving device completes decoding of subsequent symbols in a multi-symbol TTI. The receiver prepares and transmits the ACK message based on partial decoding information from the first symbol, achieving low latency. The system accepts potential corruption risk in exchange for speed, which is appropriate for time-sensitive high-priority transmissions where quick feedback is more valuable than perfect accuracy.
3Reliability
If iFDMA waveforms are used to spread ACK information across multiple tones, then frequency diversity and robustness improve, but peak-to-average power ratio increases
Solution Approach 1:
The patent manages the PAPR parameter by carefully configuring the iFDMA waveform characteristics, including the selection and spacing of non-zero tones. By optimizing these parameters, the system achieves sufficient frequency diversity for robust ACK transmission while controlling the PAPR to acceptable levels for power amplifier operation.
Data Source
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AI summary
Method, systems, and devices are described for low latency, robust acknowledgement reporting in a wireless communication system. A receiving device may receive a transmission in the transmission time interval (TTI), the transmission may include one or a plurality of symbols. The receiving device may identify an uplink acknowledgement channel configuration based on the format of the TTI. The receiving device may send an acknowledgement message to the sending device on the uplink acknowledgement channel according to the uplink acknowledgement channel configuration.