Channel Estimation Under Non-Uniform Reference Signal Patterns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in LTE, reference signals do not uniformly span over time and/or frequency on a resource unit, leading to suboptimal channel estimation and potential collisions with synchronization signals, which limits the effectiveness of channel estimation and data demodulation.
Innovation Solution
A method and apparatus that allow a user equipment (UE) to utilize a subset of UE-specific reference signals (UE-RSs) for channel estimation, either in subframes with or without primary and secondary synchronization signals (PSS/SSS), by deriving improved channel estimates using data tones from successfully decoded code blocks or segments, enabling more accurate demodulation of data in non-uniform signal patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are transmitted uniformly over time and frequency, then channel estimation accuracy is improved, but resource utilization efficiency deteriorates due to collisions with synchronization signals and non-uniform data distribution
Solution Approach 1:
The patent applies local quality by allowing different reference signal configurations in different time-frequency regions. Specifically, UE-specific reference signals are transmitted only in resource blocks allocated to that UE, rather than uniformly across all resource blocks. This local adaptation improves channel estimation accuracy where needed while avoiding collisions with synchronization signals in other regions, thus resolving the contradiction between measurement precision and productivity.
Solution Approach 2:
The patent implements dynamic reference signal transmission where the presence and configuration of UE-specific reference signals adapt based on scheduling decisions and synchronization signal locations. The system dynamically adjusts which resource blocks contain reference signals versus synchronization signals, allowing optimal resource utilization while maintaining channel estimation accuracy when reference signals are present.
2Measurement precision
If UE-specific reference signals are transmitted in all resource blocks, then channel estimation coverage is improved, but signal collisions with PSS/SSS increase
Solution Approach 1:
The patent extracts UE-specific reference signals from the uniform grid structure and places them only in specifically allocated resource blocks. This extraction approach removes the harmful collisions with PSS/SSS that occur when reference signals are transmitted in all resource blocks, while still providing adequate channel estimation coverage in the resource blocks where data is actually transmitted to the UE.
Solution Approach 2:
The system performs preliminary scheduling decisions to allocate resource blocks for data transmission before transmitting UE-specific reference signals. By determining in advance which resource blocks will contain data and synchronization signals, the system can pre-position reference signals in appropriate locations, avoiding collisions with PSS/SSS while ensuring coverage where needed.
3Quantity of substance
If a subset of reference signals is used for channel estimation, then resource overhead is reduced, but channel estimation accuracy deteriorates
Solution Approach 1:
The patent changes the spatial distribution parameters of reference signals by concentrating them in specifically allocated resource blocks rather than distributing them uniformly. This parameter change reduces the total quantity of reference signals needed (lowering overhead) while maintaining or improving estimation accuracy in the relevant data regions, as reference signals are placed precisely where channel estimation is required.
Data Source
AI summary
Reference signals may not uniformly span over time and/or frequency on a resource unit. For example, reference signals may non-uniformly occupy symbols of a subframe. Alternatively, reference signals normally transmitted over certain tones of a subframe may have to be punctured to avoid collisions with a PSS and/or SSS transmitted over the same tones. Consequently, a UE may only be able to use a subset of reference signal tones for performing channel estimation. Accordingly, a method, an apparatus, and a computer program product for wireless communication are provided for improving channel estimation under a non-uniform signal pattern. The apparatus indicates to a UE to utilize a subset of reference signals to derive a channel estimate for demodulating data in a specific subframe, and transmits a plurality of subframes, the plurality of subframes including the reference signals and the specific subframe, the specific subframe including a PSS and/or SSS.