ACK/NACK Mapping in LTE-A Carrier Aggregation
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Solution Overview
Problem
In LTE-A systems using Carrier Aggregation (CA) technology, the base station incorrectly interprets ACK/NACK response messages due to unclear mapping relationships between ACK/NACK states and bits, leading to errors in feedback processing.
Innovation Solution
The method involves determining the number of bits for ACK/NACK response messages based on the number of downlink component carriers and their transmission modes, and mapping these messages according to specific orders of code word streams and component carriers, using channel selection mapping tables to ensure accurate feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ACK/NACK response messages are mapped without a standardized order in LTE-A Carrier Aggregation systems, then the system supports multiple downlink component carriers with different transmission modes, but the base station incorrectly interprets the feedback messages leading to errors
Solution Approach 1:
The patent segments the ACK/NACK feedback bits into distinct groups corresponding to different downlink component carriers and code word streams. Each component carrier's ACK/NACK messages are mapped to specific bit positions in a standardized sequence, allowing the base station to correctly identify and interpret feedback from each carrier independently, thereby resolving the interpretation errors caused by ambiguous mapping
Solution Approach 2:
The patent changes the mapping parameter from an undefined order to a standardized sequence based on component carrier indices and code word stream numbers. This parameter change ensures that the k-th ACK/NACK message always maps to a predictable bit position, enabling reliable feedback interpretation while maintaining support for multiple carriers with different transmission modes
2Adaptability or versatility
If the mapping relationship between ACK/NACK states and bits is not clearly defined, then the system can accommodate various transmission modes, but the base station cannot correctly process the feedback messages
Solution Approach 1:
The patent establishes the mapping relationship between ACK/NACK states and bits in advance through standardized rules before feedback transmission occurs. The mapping sequence is predetermined based on component carrier indices and code word stream numbers, allowing both user equipment and base station to prepare the correct mapping tables beforehand, ensuring precise and consistent interpretation of feedback messages
Solution Approach 2:
The patent defines specific mapping parameters including the sequence order (first by component carrier index, then by code word stream number) and bit position assignment rules. These parameter definitions transform the ambiguous mapping relationship into a precise, deterministic mapping that maintains adaptability to different transmission modes while ensuring accurate feedback processing
Data Source
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AI summary
The present invention provides a method and a user UE for mapping ACK/NACK response messages. The method comprises the UE determining a number L of bits of ACK/NACK response messages according to predetermined conditions, wherein, the predetermined conditions include at least one of: a number of downlink component carriers or cells that are allocated to the UE by a base station, and a transmission mode of each of the downlink component carriers; and the UE mapping the ACK/NACK response messages to the L bits so as to handle them correctly.