Codeword-to-Layer Mapping for Flexible HARQ Retransmission Rank
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Solution Overview
Problem
Conventional codeword to layer mappings in multi-antenna systems are not optimal for HARQ operations, particularly during retransmissions, as they limit the ability to reduce the number of simultaneously transmitted codewords without changing the number of layers, leading to inefficiencies and performance losses.
Innovation Solution
Additional codeword to layer mappings are introduced that allow for reducing the number of simultaneously transmitted codewords during retransmissions by mapping a single codeword to two or more layers, enabling flexible transmission rank adjustments based on changing channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional codeword to layer mappings are used in multi-antenna systems, then the number of simultaneously transmitted codewords is maintained, but the ability to reduce transmission rank during retransmissions is limited, leading to HARQ inefficiency
Solution Approach 1:
The patent implements dynamic codeword-to-layer mapping that adapts based on transmission type (initial vs. retransmission). During retransmissions, the system dynamically reduces the number of simultaneously transmitted codewords by mapping them to fewer layers, allowing flexible adjustment of transmission rank according to channel conditions and HARQ requirements, thereby resolving the contradiction between maintaining codeword transmission capacity and enabling rank reduction for efficient retransmissions
2Productivity
If the number of simultaneously transmitted codewords is reduced during retransmissions, then HARQ efficiency improves, but additional mapping configurations are required, increasing system complexity
Solution Approach 1:
The patent changes the mapping parameters (number of layers per codeword) based on transmission state. For initial transmissions, conventional mappings are used, while for retransmissions, the system switches to reduced-rank mappings where fewer layers are allocated to each codeword. This parameter change approach enables improved HARQ efficiency without requiring entirely new mapping structures, thereby managing complexity while achieving better reception accuracy
3Device complexity
If fixed layer mapping is used for all transmissions, then system complexity is reduced, but performance losses occur during retransmissions under varying channel conditions
Solution Approach 1:
The patent segments the transmission process into distinct phases (initial transmission and retransmission) with different mapping strategies. During initial transmissions, a first mapping configuration is applied, while during retransmissions, a second mapping configuration with reduced rank is applied. This segmentation allows the system to maintain simplicity for initial transmissions while optimizing performance for retransmissions under varying channel conditions
Data Source
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AI summary
In a transmitter or transceiver, codewords from HARQ processes can be mapped or assigned to various layers for transmission and/or retransmission of information on a radio channel. Exemplary embodiments provide for various mappings which facilitate, for example, HARQ processes. For example, a codeword (700 or 720) can be mapped onto a plurality of layers (702, 704 or 722, 724, 726) which are equal in number to a channel rank of a radio channel to be used for the transmission.