MIMO HARQ Mapping Reduces Signaling Overhead
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Solution Overview
Problem
In wireless communication systems, four-branch MIMO transmission schemes face challenges with high uplink and downlink signaling due to the need for feedback on multiple channel-encoded transport data blocks, which can result in increased signaling complexity and inefficiency.
Innovation Solution
Implementing a method where two HARQ processes are used to support four downlink transmission layers, with HARQ process identifications and ACK/NACK messages mapped to multiple MIMO transmission/reception layers to reduce signaling overhead, and determining initial and subsequent redundancy versions for data blocks based on acknowledgment and negative acknowledgment messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four HARQ codewords are used to support four downlink transmission layers, then the system can provide comprehensive feedback for each transport data block, but the uplink and downlink signaling complexity increases significantly
Solution Approach 1:
The patent merges multiple HARQ process identifications into a single uplink message. Specifically, multiple HARQ-ACK information elements, each containing a HARQ process ID and acknowledgment status, are combined into one uplink transmission from the wireless terminal to the base station. This reduces the number of separate signaling messages while maintaining complete feedback coverage for all four downlink transmission layers.
Solution Approach 2:
The uplink HARQ-ACK message is designed to serve multiple functions simultaneously: it provides acknowledgment status for multiple different HARQ processes, carries redundancy version information, and enables the base station to determine which downlink transport blocks require retransmission. This multi-functional design reduces overall signaling overhead while maintaining comprehensive feedback capability.
2Device complexity
If multiple HARQ processes are mapped to multiple MIMO transmission layers, then the feedback mechanism is simplified, but the system must efficiently manage mapping and retransmission tracking
Solution Approach 1:
The patent segments the feedback mechanism by creating distinct HARQ-ACK information elements for different HARQ processes. Each information element contains a HARQ process ID field and an acknowledgment indicator, allowing the system to track and manage multiple HARQ processes independently while using a unified uplink message structure. This segmentation enables flexible mapping between HARQ processes and MIMO layers.
Solution Approach 2:
The system implements a feedback mechanism where the base station transmits downlink data with associated HARQ process IDs, the wireless terminal sends back acknowledgment status for each process, and the base station uses this feedback to determine retransmission needs. This closed-loop feedback enables efficient mapping management between HARQ processes and MIMO transmission layers while maintaining system adaptability.
Data Source
AI summary
A method of operating a node of a MIMO network may include transmitting first and second HARQ IDs over a downlink signaling channel to a wireless terminal for a first MIMO TTI. The first HARQ ID is mapped to a first MIMO layer, and the second HARQ ID is mapped to second and third MIMO layers. First, second, and third data blocks are transmitted over the first, second, and third MIMO layers to the wireless terminal for the first MIMO TTI. Responsive to receiving an ACK message associated with the first HARQ ID, a fourth data block is transmitted over the first MIMO layer to the wireless terminal for a second MIMO TTI. Responsive to receiving a NACK message associated with the second HARQ process identification, the second and third data blocks are retransmitted over the second and third MIMO layers to the wireless terminal for the second MIMO TTI.