ACK/NACK Feedback Mapping for Carrier Aggregation
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Solution Overview
Problem
Current 3GPP LTE-A systems face challenges in designing an efficient uplink transmission scheme for ACK/NACK feedback, especially in Frequency Division Duplex (FDD) mode with low-order modulation and low transmit power, where the number of radio resources available for feedback transmission is limited, leading to unreliable feedback and increased retransmissions.
Innovation Solution
The proposed solution involves mapping multiple ACK/NACK feedback sequences to a single feedback resource combination, using a feedback mapping rule that considers the probability of positive acknowledgments and minimizes unnecessary retransmissions by optimizing the modulation scheme and resource allocation, ensuring reliable feedback even with limited radio resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple ACK/NACK feedback sequences are transmitted using separate radio resources, then feedback reliability is improved, but radio resource overhead increases
Solution Approach 1:
The patent combines multiple ACK/NACK feedback sequences into a single feedback message by mapping them to one selected radio resource. Instead of allocating separate radio resources for each ACK/NACK sequence, the invention merges them by selecting one radio resource from available options based on the feedback content, thereby reducing radio resource overhead while maintaining feedback reliability through the mapping mechanism
Solution Approach 2:
The patent makes a single radio resource universal by enabling it to carry multiple different feedback sequences through the mapping rule. The selected radio resource can represent different ACK/NACK combinations based on the mapping relationship, allowing one resource to serve multiple feedback purposes and reducing the total number of resources needed
2Loss of information
If feedback mapping is optimized to reduce ambiguous feedback, then feedback clarity is improved, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining mapping rules that associate specific feedback sequences with selected radio resources before transmission occurs. The mapping relationship is established in advance through configuration, allowing the system to reduce feedback ambiguity without requiring complex real-time processing during actual feedback transmission
Solution Approach 2:
The patent changes parameters by adjusting the mapping configuration between feedback sequences and radio resources. By modifying the mapping rule parameters (such as which radio resource corresponds to which feedback pattern), the system optimizes feedback clarity while managing complexity through configurable parameters rather than fixed complex logic
Data Source
AI summary
The invention relates to methods and apparatuses for providing HARQ feedback in a mobile communication system using carrier aggregation. To suggest a scheme for transmitting feedback on the successful/unsuccessful decoding of transmissions that is operable in FDD mode, the invention proposes to utilize only a single one of plural radio resources available for feedback transmission for signaling feedback for multiple transmissions. A feedback sequence of ACK/NACKs for the transmissions is mapped to one feedback resource combination that is one of the radio resources available for feedback transmission and a modulation symbol of the given modulation scheme that is transmitted on said one radio resource. This scheme can also be used in cases where the number of possible feedback sequences of ACK/NACKs for the transmissions is larger than the number of feedback resource combinations available for feedback transmission.