Grant-Free Uplink NACK Differentiation for Retransmission Control
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Solution Overview
Problem
In grant-free transmission, base stations face challenges in efficiently performing retransmission control for uplink data that lacks clear uplink radio resource allocation, complicating the management of ACK/NACK signals and retransmissions.
Innovation Solution
The implementation of a communication system where terminal apparatuses transmit uplink data with an identification signal, allowing base stations to use Symbol Level Interference Cancellation and other methods to detect and manage uplink data, and differentiate between various NACKs to guide retransmissions based on error causes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If grant-free transmission is implemented to allow multiple terminal apparatuses to transmit uplink data using the same frequency, time, coding, and spatial resources, then spectral efficiency and system capacity are improved, but the complexity of retransmission control and ACK/NACK management increases due to lack of clear uplink radio resource allocation
Solution Approach 1:
The patent segments the retransmission control process into distinct types based on error causes. It differentiates between Type 1 NACK (error in detecting presence of uplink data) and Type 2 NACK (error in decoding uplink data), allowing the base station to apply different retransmission control strategies for each type, thereby managing complexity through structured classification
Solution Approach 2:
The patent changes the parameter of NACK signal interpretation by introducing type differentiation. Instead of treating all NACKs uniformly, the system modifies how NACK signals are processed by identifying their type based on detection outcomes, enabling adaptive retransmission control that reduces overall system complexity
2Quantity of substance
If grant-free transmission is used to enable non-orthogonal multiple access, then the number of terminals that can be accommodated increases, but the reliability of uplink data transmission decreases due to interference and lack of resource allocation control
Solution Approach 1:
The patent implements a feedback mechanism where the base station transmits differentiated NACK signals to terminals based on the specific error cause. Terminals receive feedback indicating whether the error was in detection (Type 1) or decoding (Type 2), allowing them to adjust their retransmission strategies accordingly, thereby improving transmission reliability
Solution Approach 2:
The patent introduces dynamic retransmission control where the retransmission behavior is adjusted based on the NACK type received. Terminals dynamically change their transmission parameters and strategies depending on whether they received a Type 1 or Type 2 NACK, enabling adaptive reliability improvement while maintaining high terminal capacity
3Productivity
If the base station transmits differentiated NACK signals to guide retransmissions based on error causes, then retransmission efficiency is improved, but the complexity of ACK/NACK signal management increases
Solution Approach 1:
The patent segments the NACK signal management into two distinct types: Type 1 NACK for detection errors and Type 2 NACK for decoding errors. This segmentation allows the base station to manage each type separately with dedicated processing logic, improving retransmission efficiency while containing complexity through structured organization
Solution Approach 2:
The patent applies preliminary action by pre-defining the two NACK types and their corresponding handling procedures before actual transmission occurs. The base station and terminals are pre-configured with the understanding of Type 1 and Type 2 NACK meanings, enabling efficient real-time processing without ad-hoc decision complexity
Data Source
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AI summary
Abase station apparatus receives an uplink shared channel and a reference signal, the uplink shared channel including uplink data, an identifier of a terminal apparatus that has transmitted the uplink data, a first CRC generated from the identifier bits, and a second CRC generated from the uplink data bits. In a case that an error is detected based on the first CRC, the base station apparatus transmits a first NACK by using a control signal associated with the reference signal sequence. In a case that an error is detected based on the second CRC, the base station apparatus transmits a second NACK by using a control signal associated with the identifier indicating the terminal apparatus.