HARQ Codeword-to-Layer Mapping for Flexible MIMO Retransmission
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Solution Overview
Problem
Conventional codeword to layer mappings in multi-antenna systems, such as LTE, are not optimal for HARQ operations, particularly during retransmissions, as they restrict 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 or alternative codeword to layer mappings are introduced that allow for reducing the number of simultaneously transmitted codewords without altering the number of layers, specifically by providing mappings for a single codeword to multiple layers for different channel ranks, enhancing flexibility and efficiency, especially during retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional codeword to layer mappings are used in multi-antenna systems, then the number of layers remains fixed, but the ability to reduce the number of simultaneously transmitted codewords during retransmissions is restricted, leading to HARQ operation inefficiency
Solution Approach 1:
The patent introduces dynamic codeword to layer mappings that allow the system to adapt the number of simultaneously transmitted codewords based on channel conditions and retransmission requirements. Unlike conventional fixed mappings, the new mappings enable dynamic adjustment where a single codeword can be mapped to multiple layers when needed for retransmissions, providing the flexibility to optimize HARQ operations without changing the total number of layers
Solution Approach 2:
The patent changes the mapping parameters between codewords and layers by introducing alternative mapping schemes. Specifically, it provides mappings where a single codeword can be distributed across multiple layers (e.g., codeword 0 to layers 0-3, codeword 1 to layers 0-1) rather than the conventional one-to-one mapping. This parameter change enables efficient retransmissions by allowing the receiver to combine multiple layer receptions for the same codeword
2Reliability
If the number of simultaneously transmitted codewords is reduced during retransmissions, then HARQ performance improves, but conventional mappings require changing the number of layers which increases system complexity
Solution Approach 1:
The patent creates universal codeword to layer mappings that serve multiple functions: they support both initial transmissions and retransmissions without requiring separate mapping configurations. The same mapping structure (e.g., codeword 0 to layers 0-3) can be used regardless of whether it's a first transmission or a retransmission, eliminating the need for complex dynamic reconfiguration and reducing system complexity while maintaining reliability
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 can be mapped onto a plurality of layers which are equal in number to a channel rank of a radio channel to be used for the transmission.