Relative Delay Indication for Channel Measurement in Massive MIMO
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Solution Overview
Problem
In Massive MIMO systems, timing errors between uplink and downlink channels cause significant errors in reconstructing the downlink channel, leading to poor channel estimation performance due to delay deviations.
Innovation Solution
A method where a network device indicates relative delays to a terminal device, allowing it to perform channel measurement based on precoded reference signals, thereby reducing the impact of timing errors and signaling overheads, by using the feature that relative delays are unrelated to absolute timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delay information is estimated by using uplink channel measurement, then channel estimation can be performed based on partial reciprocity, but timing errors cause significant delay deviations between uplink and downlink channels
Solution Approach 1:
The patent changes the parameter from absolute delay to relative delay. Instead of using absolute delay values that are sensitive to timing errors between uplink and downlink channels, the system uses relative delay information that represents the difference between delays. This parameter transformation eliminates the impact of timing errors while preserving the essential channel characteristics needed for estimation.
Solution Approach 2:
The patent introduces relative delay as an intermediary parameter between the uplink channel measurement and downlink channel reconstruction. This intermediary transforms the raw delay measurement into a form that is independent of absolute timing, serving as a bridge that connects uplink measurements to downlink characteristics without propagating timing errors.
2Measurement precision
If absolute delay information is indicated to the terminal device, then channel measurement can be performed, but signaling overhead increases due to timing error compensation requirements
Solution Approach 1:
The patent extracts only the essential relative delay information from the complete delay description. By taking out only the relative delay component and discarding the absolute timing information, the system reduces signaling overhead while maintaining the necessary accuracy for channel measurement. This extraction eliminates redundant information that would be needed for timing error compensation.
3Measurement precision
If uplink and downlink timing errors are corrected, then delay accuracy improves, but system complexity increases due to additional synchronization mechanisms
Solution Approach 1:
The patent converts the harmful effect of timing errors into a beneficial feature by using relative delay. Instead of attempting to correct and eliminate timing errors through complex synchronization mechanisms, the system embraces the timing differences and uses them to create a timing-error-invariant representation of channel delays. This transforms the problem into an advantage.
Data Source
AI summary
Example channel measurement methods and a communication apparatus are described. One example method include receiving a precoded reference signal and indication information by a terminal device, where the indication information is used to indicate a relative delay between a first delay and a second delay, and the first delay and the second delay are determined through uplink channel measurement. The terminal device performs channel measurement based on the precoded reference signal and the indication information.