Differential Channel State Information Reporting for TDD Systems
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Solution Overview
Problem
In TDD systems, network devices face challenges in obtaining a complete downlink channel matrix due to the limited number of transmit antenna ports, leading to inaccurate precoding matrices and impaired data transmission performance, as they cannot accurately measure channel state information for all receive antenna ports using only a sounding reference signal.
Innovation Solution
A method where the terminal device reports differential channel state information between two sets of antenna ports, allowing the network device to account for power differences and reconstruct a more accurate downlink channel matrix, thereby improving data transmission accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the terminal device uses a limited number of transmit antenna ports to send SRS, then the device complexity is reduced, but the network device cannot obtain complete downlink channel matrix information
Solution Approach 1:
The patent divides the channel state information reporting into two parts: SRS-based channel information from transmit antenna ports and CSI-RS-based channel information from receive antenna ports. This segmentation allows the network device to reconstruct the complete downlink channel matrix by combining both parts, resolving the information loss caused by limited transmit antenna ports.
Solution Approach 2:
The patent introduces CSI-RS as an intermediary reference signal that enables the terminal device to measure and feedback channel information for receive antenna ports that cannot be directly obtained through SRS. This intermediary mechanism bridges the gap between limited transmit antenna capabilities and the need for complete downlink channel knowledge.
2Device complexity
If the network device uses SRS measurement to obtain downlink channel information, then the measurement process is simplified, but the channel state information accuracy is reduced due to power gain differences
Solution Approach 1:
The patent implements a feedback mechanism where the terminal device measures CSI-RS and feeds back PMI indicating channel matrix information for receive antenna ports. This feedback loop allows the network device to obtain accurate channel state information that compensates for power gain differences between SRS measurement and actual downlink channel conditions.
Solution Approach 2:
The patent changes the measurement parameter from SRS-based uplink channel measurement to CSI-RS-based downlink channel measurement for receive antenna ports. This parameter change allows direct measurement of downlink channel characteristics including accurate power gain, eliminating the power gain mismatch problem.
Data Source
AI summary
A channel state information reporting method and apparatus are described. The method can include a terminal device obtaining first indication information and sending the first indication information to a network device. The network device receives the first indication information, where the first indication information indicates a differential value between channel state information of a first antenna port set and channel state information of a second antenna port set. The first antenna port set includes x antenna ports of the terminal device, the second antenna port set includes m antenna ports of the terminal device, and the first antenna port set is different from the second antenna port set. The channel state information reporting method and apparatus in embodiments of this application help improve accuracy of channel state information obtained by a network device, and improve data transmission performance.