CSI-RS Resource Allocation Patterns for LTE-Advanced
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Solution Overview
Problem
In LTE wireless communication systems, maintaining channel state information reference signals (CSI-RS) on multiple antenna ports incurs significant overhead, and existing solutions do not efficiently allocate CSI-RS resources to balance channel quality measurement and coherent demodulation requirements.
Innovation Solution
The implementation of various CSI-RS per-cell patterns, such as Type 1 and Type 2, with specific reuse factors and frequency domain shifting, allows for efficient allocation of CSI-RS resources across multiple antenna ports, optimizing channel quality measurement while minimizing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CRS is broadcast to all UEs based on the largest number of MIMO layers/ports, then channel estimation and channel quality measurement can be performed, but overhead increases significantly when supporting multiple antenna ports
Solution Approach 1:
The patent segments the reference signal function into two separate types: CRS for channel estimation and CSI-RS for channel quality measurement. This segmentation allows each reference signal type to be optimized independently, with CSI-RS being sparsely allocated in time-frequency resources while CRS maintains its comprehensive coverage, thereby reducing overall overhead while supporting multiple antenna ports
Solution Approach 2:
The patent introduces new time-frequency resource allocation patterns for CSI-RS that differ from traditional CRS allocation. By defining specific resource element positions and density parameters for CSI-RS that are distinct from CRS patterns, the system can efficiently support multiple antenna ports through dimensional differentiation in resource allocation
2Measurement precision
If CSI-RS resources are allocated for channel quality measurement, then multi-user scheduling can be improved, but resource allocation complexity increases
Solution Approach 1:
The patent applies local quality by configuring different CSI-RS resource densities and patterns for different cells and different antenna ports based on local requirements. Each cell can independently configure its CSI-RS parameters (density, pattern type, resource elements) according to its specific channel conditions and antenna configuration, achieving accurate channel quality measurement without requiring complex centralized resource allocation
Solution Approach 2:
The patent simplifies resource allocation complexity by establishing standardized parameter sets for CSI-RS configuration, including density parameters, pattern types (e.g., CDM patterns), and resource element position rules. These parameter changes transform the complex resource allocation problem into a manageable configuration process with defined parameter ranges and selection criteria
Data Source
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AI summary
A method of allocating resource elements in an orthogonal frequency division multiplexed (OFDM) system for transmission of a channel state information reference signal (CSI-RS) is disclosed. The method includes converting one or more resource elements to a two-dimensional frequency-time domain; and partitioning the one or more converted resource elements to units of a physical resource block (PRB). One or more resource elements are patterned over at least a portion of the PRB for transmission of the CSI-RS. According to an embodiment, the CSI-RS resource elements with a same subcarrier index for a common cell are code division multiplexed (CDM), with a CDM dimension equal to a number of CSI-RS resource elements with the same subcarrier index for the common cell.