Uplink MIMO HARQ Feedback via PHICH Precoding Adaptation
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Solution Overview
Problem
The legacy 3GPP LTE system lacks definitions for HARQ operations and control information methods to support uplink multiple codeword transmission and retransmission using multiple antennas, leading to inefficiencies in MIMO transmission.
Innovation Solution
A method and apparatus for transmitting control information in wireless communication systems that include constructing control information on the Physical Hybrid-automatic repeat request Indicator Channel (PHICH), selecting a precoder, selecting PHICH resources, performing HARQ operations through the PHICH and physical downlink control channel (PDCCH), and constructing downlink control information (DCI) to support uplink MIMO transmission by using a precoding matrix based on the number of NACK transport blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If legacy 3GPP LTE HARQ operations are used for uplink single antenna transmission, then single codeword transmission is supported, but uplink multiple codeword MIMO transmission cannot be supported
Solution Approach 1:
The patent segments the HARQ feedback mechanism by introducing separate PHICH resources for different codewords in uplink MIMO transmission. Each codeword's ACK/NACK feedback is handled through dedicated PHICH resources, allowing independent HARQ operations for multiple codewords while maintaining the existing LTE HARQ framework. This segmentation enables multi-codeword support without requiring complete redesign of the HARQ mechanism.
Solution Approach 2:
The patent extends the existing PHICH structure to serve multiple functions: it maintains backward compatibility with single-antenna single-codeword transmission while simultaneously supporting uplink MIMO with multiple codewords. The PHICH resource allocation mechanism is designed to universally handle both legacy and advanced transmission modes through configurable parameters and resource mapping rules.
2Reliability
If multiple PHICH resources are allocated for uplink MCW transmission, then HARQ feedback for each codeword is provided, but control signal overhead increases
Solution Approach 1:
The patent applies local quality by allocating PHICH resources with different properties for different codewords based on their specific requirements. Each codeword's PHICH resources are configured according to local channel conditions and transmission parameters, allowing optimized feedback reliability for each codeword while avoiding uniform overhead increase across all resources.
Solution Approach 2:
The patent implements partial action by selectively allocating full PHICH resources only when necessary for reliable HARQ feedback, while using reduced or shared resources for other codewords. This approach provides sufficient feedback accuracy for critical transmissions while minimizing overall control signal overhead through graduated resource allocation.
3Productivity
If precoding matrix is selected for retransmission, then transmission performance is improved, but incorrect precoder selection leads to inefficient retransmissions
Solution Approach 1:
The patent implements feedback mechanisms where the receiver provides explicit precoder selection feedback to the transmitter for retransmissions. The receiver evaluates the channel conditions and previous transmission performance, then feeds back the optimal precoder index or selection criteria. This feedback loop ensures accurate precoder selection for retransmissions, improving both reliability and productivity by avoiding incorrect precoder choices that would waste retransmission opportunities.
Data Source
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AI summary
The present invention relates to a wireless communication system, and to a method and apparatus for efficiently transmitting control information to support an uplink multiple antenna transmission technique. According to one embodiment of the present invention, a method for transmitting control information regarding uplink multiple antenna transmission may comprise the steps of: transmitting DCI for scheduling the uplink transmission of a plurality of data blocks through a PDCCH; receiving the plurality of data blocks scheduled by the DCI; transmitting information which indicates positive acknowledgement or negative acknowledgement to each of the plurality of received data blocks through the PHICH; and receiving retransmission for the negative acknowledged data blocks. When the number of the negative-acknowledged data blocks ins not equal to the number data blocks indicated in the PDCCH, a pre-coding matrix, which is for the number of transmission layers equivalent to that of layers corresponding to the negative-acknowledged data blocks, may be used for retransmission.