CoMP Point Association via Segmented CSI-RS Configurations
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Solution Overview
Problem
In CoMP scenario 4 of LTE-Advanced systems, accurate channel state information (CSI) is needed for UE-specific MIMO precoding to enable frequency reuse, but there are challenges in point association, measurement configuration, and feedback procedures, particularly for low-power remote radio heads (RRHs) within macrocell coverage, leading to degraded system throughput.
Innovation Solution
The solution involves configuring multiple CSI-RS configurations with non-zero transmission power for UE measurements and feedback, allowing for serving point selection and CSI reporting, and using CSI-RS configuration indices for uplink power control, thereby reducing UE measurement burden and feedback overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UE-specific MIMO precoding is used to enable frequency reuse, then system throughput is improved, but accurate channel state information (CSI) for each connection is required which increases measurement and feedback complexity
Solution Approach 1:
The patent segments the measurement and feedback process by introducing two distinct higher-layer configurations: one for RSRP measurement (containing first number of CSI-RS configurations) and one for CSI reporting (containing second number of CSI-RS configurations). This segmentation allows the system to obtain accurate CSI for UE-specific MIMO precoding while managing measurement complexity through structured configuration management.
Solution Approach 2:
The patent applies preliminary action by having the serving eNB pre-configure multiple CSI-RS configurations with non-zero transmission power before UE measurements and feedback. The UE performs RSRP measurements based on these pre-configured CSI-RS resources, and the serving eNB pre-configures the second higher-layer configuration for CSI reporting based on reported RSRP measurement results, reducing real-time processing complexity.
2Measurement precision
If multiple CSI-RS configurations are configured for serving point selection and CSI reporting, then accurate CSI feedback is achieved, but UE measurement burden and feedback overhead increase
Solution Approach 1:
The patent applies local quality by configuring different numbers of CSI-RS configurations for different purposes: the first higher-layer configuration contains a first number of CSI-RS configurations for RSRP measurement, while the second higher-layer configuration contains a second number (which can be a subset) of CSI-RS configurations for CSI reporting. This allows optimized measurement precision for each function while managing feedback overhead.
3Measurement precision
If CSI-RS configurations with non-zero transmission power are used for measurements, then serving point selection accuracy is improved, but interference management becomes more challenging in heterogeneous networks
Solution Approach 1:
The patent uses CSI-RS configurations as an intermediary mechanism to manage interference in heterogeneous networks. By configuring specific CSI-RS resources with non-zero transmission power for serving point selection and CSI reporting, the system enables accurate measurements while the network can coordinate transmission power and resource allocation across macro-eNB and RRHs to manage interference.
Data Source
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AI summary
Procedures for point association as well as measurement and feedback required to enable point association for CoMP deployment scenario 4 are proposed. In a first novel aspect, a serving eNB configures a first higher-layer configuration for RSRP measurement to be used by a UE for serving point selection. The higher-layer configuration contains multiple CSI-RS configurations, and each CSI-RS configuration indicates a set of resource elements (REs) or subcarriers in both frequency domain and time domain as one CSI-RS resource with non-zero transmission power. The UE then performs RSRP measurements based on the multiple CSI-RS configurations and reports RSRP measurement results to the serving eNB. In a second novel aspect, the serving eNB configures a second higher-layer configuration for CSI reporting based on the reported RSRP measurement results. In a third novel aspect, the serving eNB sends CSI- RS information to the UE for uplink power control.