CSI-RS Resource Design for Accurate Non-Cellular Channel Measurement
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Solution Overview
Problem
In modern network designs where the identity and location of network transmission reception points (TRPs) are unknown to user equipment (UEs), accurate channel measurements are challenging due to non-reciprocal uplink and downlink channels, especially in UE-centric no-cell systems.
Innovation Solution
A method for configuring CSI-RS transmission using an NxK CSI-RS resource with non-adjacent OFDM symbols and PRBs, including gaps and repetitions, and utilizing sequence seeds dependent on cell and UE-specific parameters for orthogonal or low cross-correlation sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If CSI-RS is transmitted using traditional resource allocation, then the measurement coverage is limited, but the resource flexibility and adaptability are reduced
Solution Approach 1:
The patent divides the CSI-RS resource into an NxK grid structure where N non-adjacent OFDM symbols and K non-adjacent PRBs are selected. This segmentation allows the resource to be split into multiple configurable dimensions (time and frequency), enabling both extended coverage through multiple symbols/PRBs and flexible adaptation by adjusting the spacing and selection of individual elements.
Solution Approach 2:
The patent introduces a two-dimensional NxK resource grid structure combining time (OFDM symbols) and frequency (PRBs) dimensions. This dimensional expansion allows the system to achieve broader measurement coverage by distributing CSI-RS across multiple time-frequency points while maintaining flexibility through configurable spacing and repetition patterns in each dimension.
2Device complexity
If uplink and downlink channels are assumed reciprocal, then measurement complexity is reduced, but measurement accuracy deteriorates due to frequency differences and interference
Solution Approach 1:
The patent transmits CSI-RS sequences as preliminary downlink reference signals before actual data transmission. By providing known reference sequences at multiple configured time-frequency positions, the system enables UEs to perform accurate downlink channel measurements in advance, accounting for actual downlink conditions including interference and frequency-specific effects, rather than relying on potentially inaccurate uplink reciprocity assumptions.
3Area of stationary object
If multiple TRPs transmit the same CSI-RS, then coverage is extended, but interference and cross-correlation between sequences increase
Solution Approach 1:
The patent configures each TRP with specific local qualities including unique CSI-RS sequence seeds, distinct time-frequency resource positions within the NxK grid, and potentially different comb patterns or cyclic shifts. This local differentiation ensures that while multiple TRPs provide extended coverage, their transmitted sequences have low cross-correlation, minimizing interference and enabling UEs to distinguish between different TRP signals.
Data Source
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AI summary
Systems and methods of assigning channel state information-reference symbol (CSI-RS) ports to user equipment are provided. In addition resource configurations for transmission of CSI-RS are provided, and methods of mapping CSI-RS sequences to such resources are provided.