UE Feedback for Unknown Coding Rates in Downlink Retransmissions
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Solution Overview
Problem
In wireless communications systems, if a user equipment (UE) fails to successfully receive initial downlink control information (DCI) indicating the coding rate for a downlink transmission, the UE is unable to decode subsequent retransmissions due to an unknown coding rate, leading to inefficiencies in network scheduling and user experience.
Innovation Solution
The UE transmits feedback messages that include additional bits to indicate whether the coding rate for downlink transmissions is known or unknown, allowing the network to adjust scheduling strategies and utilize soft-combining techniques based on UE capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE does not transmit feedback indicating unknown coding rate, then the feedback message format remains simple, but the network cannot adjust scheduling strategies and decode fails
Solution Approach 1:
The patent implements a feedback mechanism where the UE transmits an indication in the feedback message (e.g., HARQ-ACK) to inform the network whether the coding rate is known or unknown. This feedback allows the network to adjust scheduling strategies and retransmit with explicit coding rate information when needed, thereby resolving the contradiction between maintaining simple feedback formats and ensuring reliable decoding.
Solution Approach 2:
The patent enables the network to take preliminary action by detecting the unknown coding rate indication in advance of retransmission. This allows the network to prepare and include explicit coding rate information in subsequent retransmissions, preventing decode failures before they occur rather than reacting after the fact.
2Reliability
If the network always transmits explicit coding rate information, then the UE can always decode successfully, but network scheduling efficiency decreases
Solution Approach 1:
The patent applies partial action by transmitting explicit coding rate information only when necessary (when the UE indicates unknown coding rate or when the network determines it's needed), rather than always transmitting it. This selective approach maintains decoding reliability while avoiding unnecessary overhead that would reduce scheduling efficiency.
Solution Approach 2:
The patent dynamically changes the parameter of coding rate information transmission based on UE capability and channel conditions. When the UE can determine the coding rate from previous transmissions, the network omits explicit coding rate information; when the UE cannot determine it, the network includes the information. This adaptive parameter change optimizes both reliability and efficiency.
3Measurement precision
If the UE requests retransmission with explicit coding rate, then decoding accuracy improves, but transmission latency increases
Solution Approach 1:
The patent enables preliminary action by having the network detect and respond to unknown coding rate indications before the UE attempts failed decoding. The network can proactively retransmit with explicit coding rate information in the next opportunity, avoiding the need for the UE to request retransmission and reducing overall latency.
Solution Approach 2:
The patent allows the system to skip unnecessary retransmission requests by implementing proactive detection and response. When the network detects an unknown coding rate indication, it can immediately prepare and send the next retransmission with explicit coding rate information, rushing through the process faster than a traditional request-response cycle would allow.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described for an indication by a user equipment (UE) that a coding rate for a downlink transmission to the UE is unknown. A UE may receive a second control information message that indicates a set of wireless resources for a downlink transmission to the UE, and that indicates that a coding rate for the downlink transmission is provided in a prior first control information message, where the first control information message has not been successfully received and decoded at the UE. The UE may transmit a feedback message associated with the second control information message that includes an indication that the coding rate associated with the downlink transmission is unknown at the UE.