Retransmission Control for Carrier Aggregation Without DAI
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Solution Overview
Problem
In LTE-A systems, terminals may fail to receive downlink assignment control signals, leading to unrecognized downlink data and subsequent failure in generating response signals, especially when carrier aggregation is used with multiple component bands, resulting in degraded QoS and increased overhead due to the absence of DAI in downlink assignment control information.
Innovation Solution
A terminal apparatus and retransmission control method that maintains downlink data quality across component bands by employing phase point and resource mapping rules based on error detection patterns, even without DAI, to ensure accurate response signal transmission and retransmission control, thereby reducing overhead in downlink assignment control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DAI is inserted into downlink assignment control information for each component band, then the terminal can recognize downlink data presence even when control signals are missed, but the overhead of downlink assignment control information increases significantly
Solution Approach 1:
The patent extracts the DAI insertion function from all component bands and applies it only to a specific first component band. This selective approach maintains the reliability benefit of DAI while significantly reducing the overhead increase, as DAI is inserted into fewer control information messages.
Solution Approach 2:
The patent applies different DAI insertion policies to different component bands based on their characteristics. The first component band (with better reception quality) receives DAI insertion while the second component band (with poorer reception quality) does not, optimizing the balance between reliability and overhead for each band's specific conditions.
2Productivity
If the terminal uses the PUCCH resource corresponding to the CCE with the smallest index when multiple continuous CCEs are occupied, then downlink communication resources are used efficiently, but the terminal may transmit response signals using incorrect resources when control information is missed
Solution Approach 1:
The patent uses DAI as feedback information to inform the terminal about the actual number of component bands with downlink data assignments. This feedback mechanism allows the terminal to correctly determine PUCCH resources even when some control information is missed, preventing incorrect resource selection while maintaining efficient resource usage.
Solution Approach 2:
The patent performs preliminary DAI insertion into control information before transmission, so the terminal receives advance notice about the assignment pattern across component bands. This preliminary information enables the terminal to correctly identify PUCCH resources without needing to successfully receive all control information messages.
Data Source
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AI summary
Provided are a communcation apparatus and a corresponding retransmission control method, the communication apparatus communicating with a terminal configured with one or more downlink component carrier(s), the communication apparatus comprising: a transmitting section configured to transmit, to the terminal, downlink assignment information indicating one or more resources for downlink data, each of the one or more resources being assigned to one of the one or more downlink component carrier(s), and configured to transmit the downlink data to the terminal; a receiving section configured to receive one or more response signals for the downlink data, which is transmitted from the terminal, wherein: each response signal denotes an outcome of decoding downlink data, or denotes a Discontinuous Transmission, DTX, representing that the outcome is not transmitted; when downlink component carriers including a first downlink component carrier and a second downlink component carrier are configured, response signals for a plurality of downlink data in the downlink component carriers are transmitted using at least one phase point and at least one resource index of at least one uplink control channel depending on an outcome of decoding each of the plurality of downlink data; and a first outcome that a first response signal for downlink data in the first downlink component carrier denotes with a first phase point, with which a second response signal for downlink data in the second downlink component carrier denotes the DTX, is the same as the first outcome, which a third response signal for downlink data in the first downlink component carrier denotes with the same first phase point when only the first downlink component carrier is configured, such that: when the first downlink component carrier and the second component carrier are configured, an acknowledgment, ACK, for downlink data in the first downlink component carrier and a DTX for downlink data in the second downlink component carrier are denoted by the first response signal and the second response signal with the first phase point; and when only the first downlink component carrier is configured, an ACK for downlink data in the first downlink component carrier is denoted by the third response signal with the same first phase point.