Non-Transparent Small-Delay CDD for Accurate DMRS Channel Estimation
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Solution Overview
Problem
Existing wireless communication systems face challenges with channel estimation performance due to inconsistent delay spread estimation in transparent small delay cyclic delay diversity (CDD), which can reduce performance.
Innovation Solution
Implement non-transparent small delay CDD by determining and indicating a set of small delay values to a user equipment (UE), using a multi-port reference signal or its associated signal, to derive a second delay profile for demodulation reference signals (DMRS), enabling accurate channel estimation and data decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transparent small delay CDD is used, then device complexity is reduced, but channel estimation accuracy deteriorates due to inconsistent delay spread estimation
Solution Approach 1:
The patent introduces delay information as an intermediary parameter that mediates between the transmitter's CDD application and the receiver's channel estimation. The transmitter determines delay information based on the delay spread of the channel and applies it to generate delayed versions of the signal for different antenna ports. The receiver uses this delay information to accurately estimate the delay spread and perform channel estimation, thus resolving the contradiction between simplicity and accuracy.
Solution Approach 2:
The transmitter performs preliminary determination of delay information based on the channel delay spread before transmitting the signal. This preliminary action allows the receiver to use the pre-determined delay information for accurate channel estimation without having to perform complex measurements, thus maintaining simplicity while improving accuracy.
2Measurement precision
If delay information is determined based on channel delay spread, then channel estimation accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent changes the parameter representation by determining delay information as a function of the channel delay spread rather than transmitting raw delay spread values. This parameter transformation allows the delay information to be derived from existing channel measurements without requiring additional signaling, thus improving channel estimation accuracy without increasing overhead.
3Reliability
If multiple antenna ports are used for CDD, then transmission diversity is improved, but delay profile consistency deteriorates
Solution Approach 1:
The patent applies different delay values to different antenna ports based on their specific roles in the CDD scheme. The delay information is determined locally for each antenna port based on the channel delay spread, allowing each port to have optimized delay characteristics while maintaining overall consistency. This local optimization improves transmission diversity while preserving delay profile consistency across ports.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive a first control signal that indicates a set of delay values corresponding to a set of antenna ports. The UE may receive a first reference signal that has a first delay profile. The first reference signal may be a multi-port reference signal or associated with the multi-port reference signal. The UE may determine a second delay profile for a demodulation reference signal (DMRS) based on the first delay profile of the first reference signal, the set of delay values, and an antenna port mapping between the multi-port reference signal and a set of DMRS. The UE may perform a channel estimation on the DMRS based on the set of delay values and the second delay profile.