CSI-RS Mapping in Extended Cyclic Prefix Subframes
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Solution Overview
Problem
In wireless communication systems, particularly in next-generation multimedia systems, the challenge lies in improving channel estimation performance due to the abnormal characteristics of wireless channels, such as path loss, noise, and fading, which affect the reliability and efficiency of high-speed data transmission, especially in subframes with an extended cyclic prefix structure where the density of reference signals is low.
Innovation Solution
The method involves generating channel state information (CSI)-reference signals for each layer, mapping them to a resource element set with constant subcarrier spacing in two neighboring OFDM symbols within a subframe having an extended cyclic prefix structure, and using code division multiplexing to increase the number of resources elements available for CSI-RS mapping, thereby enhancing channel estimation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are assigned to all subcarriers, then channel estimation performance is improved, but the amount of transmitted data is reduced
Solution Approach 1:
The patent segments the reference signal assignment by introducing different resource element sets (first set for CRS, second set for CSI-RS) that are disjoint in the frequency-time grid. This allows CSI-RS to be assigned to specific resource elements without overlapping with CRS, enabling channel estimation for multiple purposes simultaneously while preserving data transmission capacity on non-reference signal subcarriers.
Solution Approach 2:
The patent resolves the contradiction by adding a dimensional separation in the resource element allocation space. By defining distinct resource element sets in the time-frequency grid (different OFDM symbols and subcarrier positions), the system can provide dense reference signal coverage for channel estimation while maintaining data transmission on other resource elements, effectively trading spatial arrangement for performance improvement.
2Productivity
If reference signals are assigned between data subcarriers, then the amount of transmitted data is increased, but channel estimation performance is deteriorated
Solution Approach 1:
The patent segments the resource elements into distinct sets: the first resource element set for cell-specific reference signals and the second resource element set for channel state information reference signals. This segmentation allows each reference signal type to have dedicated resource elements, ensuring sufficient reference signal density for accurate channel estimation while maximizing data transmission on remaining resource elements.
Solution Approach 2:
The patent applies local quality by assigning different reference signal patterns to different resource element sets based on local requirements. The first resource element set provides reference signals for basic channel estimation, while the second resource element set provides additional reference signals specifically for channel state information feedback, allowing optimized channel estimation performance in specific resource locations without uniformly increasing reference signal overhead across the entire bandwidth.
3Measurement precision
If the density of reference signals is increased, then channel estimation accuracy is improved, but the number of available resource elements for data transmission is reduced
Solution Approach 1:
The patent segments resource elements into disjoint sets, allowing dense reference signal placement in the second resource element set for CSI-RS without reducing the number of resource elements available for data transmission in the first resource element set. This segmentation enables independent optimization of reference signal density and data capacity.
Solution Approach 2:
The patent resolves the resource element quantity contradiction by utilizing different positions in the time-frequency dimension. By assigning CSI-RS to specific OFDM symbols and subcarrier combinations in the second resource element set, the system achieves high reference signal density for accurate channel estimation and CSI feedback while preserving data transmission capacity on resource elements not allocated to reference signals.
Data Source
AI summary
A method for a user equipment (UE) in a wireless communication system, includes receiving channel state information reference signal (CSI-RS) for at one antenna port from a network in a subframe, wherein the CSI-RS is mapped to at least one pair of resource elements (REs) per physical resource block (PRB) pair in consecutive orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and wherein the subframe includes two slots, and each slot includes six OFDM symbols based on an extended cyclic prefix (CP).