HARQ Feedback Encoding for HSDPA MIMO Stream Detection
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Solution Overview
Problem
In wireless communication systems, the existing HARQ feedback mechanisms fail to accurately distinguish between single stream and dual stream transmissions, leading to incorrect detection by the UE, which can result in unnecessary re-transmissions when the Node-B interprets detection misses as ACKs.
Innovation Solution
The proposed solution encodes HARQ feedback information to unambiguously indicate the number of streams received, using specific code words and repetition codes to differentiate between single and dual stream ACK/NACK signaling, allowing the Node-B to correctly interpret the feedback and avoid unnecessary re-transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If independent HARQ operation is applied for each stream in dual code word MIMO, then transmission reliability is improved, but feedback signaling complexity increases
Solution Approach 1:
The feedback signaling is segmented into distinct fields: a first field indicating the number of detected streams and a second field containing ACK/NACK information for each stream. This segmentation allows the Node-B to clearly distinguish between single-stream and dual-stream feedback scenarios, resolving the ambiguity that causes unnecessary retransmissions while maintaining independent HARQ operation for each stream.
2Reliability
If the UE detects the number of streams incorrectly, then feedback accuracy deteriorates, but unnecessary re-transmissions occur
Solution Approach 1:
The UE performs preliminary detection of the number of streams transmitted by the Node-B before generating HARQ feedback. This preliminary action allows the UE to correctly configure its feedback message structure, ensuring that the number of ACK/NACK indications matches the actual number of streams received, thereby preventing detection errors from propagating into feedback accuracy issues.
Solution Approach 2:
The feedback mechanism includes an explicit indication field that communicates the number of detected streams back to the Node-B. This feedback loop enables the Node-B to verify whether the UE correctly detected the transmission parameters, allowing for error detection and correction in the stream counting process and preventing unnecessary retransmissions.
Data Source
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AI summary
A method includes generating automatic repeat request feedback information at a first device in response to a downlink transmission from a second device; encoding the feedback information to comprise an indication of a number of streams received in the downlink transmission and transmitting encoded feedback information to the second device. Another method includes transmitting a multi-stream downlink transmission from a first device to a second device; receiving encoded hybrid automatic repeat request feedback information from the second device; decoding the received hybrid automatic repeat request feedback information at the first device; and determining from the encoding of the hybrid automatic repeat request feedback information at least a number of streams that were actually received by the device from the downlink transmission. A wireless link between the devices can be a 2x2 MIMO link. Also disclosed are memory mediums for storing program instructions to implement the methods, and apparatus including user equipment and base stations constructed to carry out the methods.