ACK/NACK Bundling Across Code Words in Carrier Aggregation
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Solution Overview
Problem
In LTE-A systems using carrier aggregation, the combination of carrier aggregation and ACK/NACK bundling leads to uneven retransmission probabilities across different code words, resulting in reduced system transmission efficiency due to varying numbers of ACK/NACKs used for bundling, which affects retransmission efficiency and overall communication quality.
Innovation Solution
A terminal apparatus and method that employs a bundling rule to associate code word blocks across different downlink unit bands into bundling groups, ensuring that at least one code word block from each code word is included in both groups, thereby balancing the number of ACK/NACKs used for bundling and enhancing transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ACK/NACK bundling is used in carrier aggregation, then the number of bits for transmitting ACK/NACK is reduced, but retransmission efficiency deteriorates due to uneven distribution of code word blocks across bundling groups
Solution Approach 1:
The invention segments code word blocks into different bundling groups based on their mapping to downlink unit bands. By dividing the code word blocks into first and second bundling groups with balanced sizes, the system achieves both bit reduction and maintained retransmission efficiency. Each bundling group is assigned a separate ACK/NACK bit, reducing total bits while ensuring balanced retransmission probability across groups.
Solution Approach 2:
The invention applies different bundling strategies to different code word blocks based on their local characteristics (mapping to specific downlink unit bands). Code word blocks are selectively grouped based on their band assignments, creating locally optimized bundling groups that balance the number of blocks while maintaining the bit reduction benefit of bundling.
2Device complexity
If code word blocks are bundled without considering their distribution across downlink unit bands, then transmission complexity is reduced, but retransmission probability becomes uneven across different code words
Solution Approach 1:
The invention considers the local mapping relationship between code word blocks and downlink unit bands when forming bundling groups. By analyzing which bands each code word block maps to, the system creates bundling groups that balance the distribution of blocks, ensuring uniform retransmission probability while maintaining relatively simple control mechanisms.
Solution Approach 2:
The invention changes the bundling parameters (group composition) based on the mapping characteristics of code word blocks to downlink unit bands. By adjusting which blocks are grouped together based on their band assignments, the system achieves balanced retransmission probability without requiring complex control mechanisms.
Data Source
AI summary
A terminal apparatus and a response signal transmitting method wherein the system transmission efficiency can be improved by devising a bundling rule. In a terminal (200), a PDSCH receiving unit (208) receives first and second code words, which comprise code word block (CWB) groups to be mapped to the respective ones of a plurality of downstream unit bands, and detects errors of the CWBs; and an A/N bundling unit (216) transmits, based on a bundling rule in which each CWB is associated with any one of first and second bundling groups, a single bundle of response signals into which the error detection results are bundled for each bundling group. According to the bundling rule, at least one of the first and second bundling groups includes both the CWB belonging to the first code words and the CWB belonging to the second code words.