CSI-RS Density Configuration for Overhead Reduction
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing channel state information reference signals (CSI-RS) due to limited resource elements per physical resource block, leading to high overhead and restricted reuse factors, especially with increasing numbers of antenna ports.
Innovation Solution
Implementing a resource element to port mapping scheme for measurement restriction in the frequency domain, allowing for semi-static configuration of user equipment to measure channels on subsets of physical resource blocks, thereby reducing CSI-RS overhead and enabling higher reuse factors by configuring multiple zero-power CSI-RS subframe configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI-RS is transmitted on all physical resource blocks with full density, then channel estimation accuracy is improved, but overhead increases and reuse factor is restricted
Solution Approach 1:
The patent segments the frequency domain into multiple subsets of physical resource blocks (PRBs). Instead of transmitting CSI-RS on all PRBs uniformly, the system divides PRBs into groups and configures different CSI-RS density patterns for different segments. This allows channel estimation to be performed on representative segments while reducing overall overhead across the entire bandwidth.
Solution Approach 2:
The patent applies local quality by configuring different CSI-RS densities for different frequency segments based on local channel conditions and requirements. Certain PRB segments may use higher density for accurate channel estimation, while other segments use lower density to reduce overhead, optimizing the trade-off locally rather than uniformly across all resources.
2Measurement precision
If CSI-RS density is increased to support more antenna ports, then channel state information quality is improved, but resource element availability for data transmission decreases
Solution Approach 1:
The patent implements dynamic CSI-RS density configuration where the density of CSI-RS in different frequency segments can be adjusted based on the number of antenna ports and channel conditions. The system can dynamically select from multiple configured density patterns (e.g., density=1, density=1/2, density=1/4) to match the current antenna port configuration, allowing flexible adaptation without fixed overhead.
Solution Approach 2:
The patent changes the density parameter of CSI-RS transmissions across different frequency segments. By configuring multiple density values (full density, half density, quarter density, etc.) and selecting appropriate densities for different PRB segments, the system optimizes the balance between CSI quality and resource availability for data transmission.
3Quantity of substance
If measurement restriction is applied to subsets of PRBs, then overhead is reduced and reuse factor increases, but channel estimation coverage is limited
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple CSI-RS density patterns and measurement restriction sets before actual channel estimation. The network node configures the UE with multiple PRB subset configurations and density patterns in advance, allowing the UE to select the appropriate configuration based on current channel conditions and antenna port requirements, ensuring adequate coverage without excessive overhead.
Solution Approach 2:
The patent extends the measurement approach by utilizing multiple frequency segments and multiple antenna ports across different dimensions. Instead of relying on a single full-density CSI-RS configuration, the system uses multiple lower-density configurations across different PRB segments and antenna port combinations, achieving comprehensive channel estimation coverage through dimensional expansion.
Data Source
AI summary
According to some embodiments, a method for use in a network node of transmitting channel state information reference signals (CSI-RS) comprises: transmitting, to the wireless device, an indication of the subset of PRBs that the wireless device should use to measure CSI-RS; and transmitting CSI-RS on the indicated subset of PRBs. According to some embodiments, a method for use in a wireless device of receiving CSI-RS comprises: receiving an indication of a subset of PRBs that the wireless device should use to measure CSI-RS associated with an antenna port; and receiving CSI-RS on the indicated subset of PRBs. In some embodiments, the indication of the subset of PRBs that the wireless device should use to measure CSI-RS comprises a density value and a comb offset.