CSI-RS Subframe Patterns for LTE TDD Small Cells
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Solution Overview
Problem
The availability of CSI-RS resources is insufficient in Rel-12 LTE systems, particularly in denser small-cell deployments, due to constraints in CSI-RS subframes and patterns, which hampers the implementation of new carrier type (NCT) features and CoMP operations.
Innovation Solution
The proposed solution involves configuring CSI-RS subframes and patterns to increase resource availability by allowing CSI-RS transmission in additional subframes and OFDM symbols, using a nested structure for antenna ports and optimizing patterns to minimize interference with CRS and DMRS, thereby enhancing CSI-RS reuse and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If CSI-RS transmission is restricted to limited subframes and patterns to avoid interference with CRS and DMRS, then interference is minimized, but the availability of CSI-RS resources becomes insufficient
Solution Approach 1:
The patent segments the resource allocation by introducing separate configuration parameters for CSI-RS subframes (different from regular downlink subframes) and defines specific pattern structures that segment the resource elements within those subframes. This allows dedicated resource allocation for CSI-RS without conflicting with CRS and DMRS resources.
Solution Approach 2:
The patent extends the resource allocation in the time dimension by allowing CSI-RS to be transmitted in special subframes with specific configurations, and in the frequency dimension by defining specific resource element patterns. This multi-dimensional resource allocation increases overall resource availability while maintaining interference avoidance through structured separation.
2Adaptability or versatility
If CSI-RS resources are increased to support denser small-cell deployments and CoMP operations, then network capacity and flexibility are improved, but interference management becomes more complex
Solution Approach 1:
The patent introduces new configuration parameters including CSI-RS subframe configuration values, pattern types, and resource element position indicators. These parameters provide flexible control over CSI-RS resource allocation, enabling adaptation to different deployment scenarios (denser small-cells, CoMP operations) while maintaining systematic interference management through standardized parameter-based configuration.
3Productivity
If CSI-RS is transmitted in additional subframes and OFDM symbols to increase resource availability, then radio resource utilization is improved, but the risk of collision with other reference signals increases
Solution Approach 1:
The patent applies preliminary action by configuring CSI-RS resources in advance through higher-layer signaling with specific subframe and pattern configurations. The resource allocation is predetermined and structured to avoid collisions with CRS and DMRS, allowing the system to proactively manage resource conflicts before they occur while maximizing resource utilization.
Data Source
AI summary
A user equipment (UE) for time division duplex (TDD) communication through a wireless communication channel has a receiver to receive a channel state information reference signal (CSI-RS) subframe configuration value, a CSI-RS configuration value, and a CSI-RS; and circuitry to determine a subframe index corresponding to a temporal position of a special subframe including the CSI-RS; determine a CSI-RS pattern of one or more orthogonal frequency division modulation (OFDM) resource elements carrying the CSI-RS, the pattern being from among a group of CSI-RS patterns that include OFDM resource elements in OFDM symbols corresponding to a physical downlink control channel (PDCCH) region of a legacy LTE wireless communication channel; control the receiver to receive the special subframe carrying the CSI-RS during the temporal position and at the one or more OFDM resource elements of the CSI-RS pattern; and measure the wireless communication channel based on the CSI-RS.