UL MIMO Retransmission Precoding Matrix Determination
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Solution Overview
Problem
In wireless communication systems, particularly in LTE systems supporting UL MIMO, the existing retransmission methods consume excessive control information resources due to the need to transmit additional control channels during retransmissions, which increases the load and inefficiency.
Innovation Solution
A method and apparatus for efficiently controlling retransmissions in UL MIMO by determining a precoding matrix based on negatively acknowledged transport blocks, allowing retransmissions to occur without receiving a Physical Downlink Control Channel (PDCCH) from the Node B, thereby reducing the transmission of control information and optimizing resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional control channels are transmitted during retransmissions in UL MIMO, then retransmission reliability is improved, but control information resource consumption increases
Solution Approach 1:
The patent extracts and removes the PDCCH transmission step from the retransmission process. By determining precoding matrices directly from NACK indications without requiring additional PDCCH transmissions, the solution eliminates unnecessary control channel overhead while maintaining retransmission reliability through implicit precoding determination.
Solution Approach 2:
The system enables self-service retransmission where the UE autonomously determines the precoding matrix for retransmission based on the NACK indication received on PHICH, without requiring the Node B to explicitly signal precoding information via PDCCH. This self-determination mechanism reduces control information exchange while ensuring reliable retransmission.
2Ease of operation
If PDCCH is transmitted for each retransmission in UL MIMO, then transmission property control is improved, but system load and complexity increase
Solution Approach 1:
The PHICH channel is given a dual function: it not only indicates ACK/NACK status but also implicitly conveys precoding matrix information for retransmission. This multi-functionality eliminates the need for separate PDCCH transmissions for precoding control, reducing system load and complexity while maintaining effective transmission property control.
Solution Approach 2:
The patent merges the precoding control function into the existing PHICH transmission mechanism. By combining the acknowledgment function and precoding indication function into a single control channel, the solution reduces the number of separate control channels needed, thereby lowering system complexity and load.
3Measurement precision
If explicit PDCCH indication is used for precoding during retransmission, then precoding accuracy is improved, but resource efficiency deteriorates
Solution Approach 1:
The NACK indication on PHICH serves as an intermediary that carries dual information: both the acknowledgment status and the implicit precoding matrix indication. This intermediary mechanism allows the system to convey precise precoding information without requiring separate explicit signaling channels, thereby maintaining precoding accuracy while improving resource efficiency.
Data Source
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AI summary
A method is provided for controlling retransmission by a User Equipment (UE) in a wireless communication system supporting Multiple Input Multiple Output (MIMO) technology. A plurality of transport blocks is initially transmitted to a Node B. A retransmission request for at least one transport block among the plurality of transport blocks is received from the Node B. A precoding matrix is determined based on a number of at least one layer corresponding to the at least one transport block negatively acknowledged (NACKed) from the Node B, if the UE does not receive a Physical Downlink Control CHannel (PDCCH) intended for the UE from the Node B.