CSI-RS Port Selection for Cross-Polarized Antenna Arrays
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Solution Overview
Problem
Legacy wireless devices support at most 8 CSI-RS ports for measurements, while newer systems require up to 16 ports, necessitating a method to select a subset of CSI-RS ports for efficient CSI measurement and reporting without increasing overhead, especially for supporting legacy terminals with network nodes having more than 8 CSI-RS ports.
Innovation Solution
A method is proposed where a subset of CSI-RS ports is configured such that the first half of ports are on one polarization and the second half are on orthogonal polarization, with the subset being a subset of the ports used for aperiodic reporting, allowing for periodic CSI reporting without additional signaling and using codebooks designed for cross-polarized antenna arrays for both types of feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of CSI-RS ports is increased to support newer systems (up to 16 ports), then the system can support more antenna elements and improve MIMO performance, but legacy wireless devices that support at most 8 CSI-RS ports cannot properly perform CSI measurements
Solution Approach 1:
The patent segments the 16 CSI-RS ports into two separate 8-port CSI-RS resources. Each resource contains 8 ports that can be independently configured and measured. This segmentation allows legacy devices to measure one 8-port resource while newer devices can measure both resources, effectively solving the compatibility issue between legacy and modern device requirements
Solution Approach 2:
The patent creates a universal CSI-RS configuration where two 8-port resources are configured with the same resource configuration (time-frequency resources, scrambling IDs, etc.) but different port sets. This universal configuration allows both legacy devices (which can handle one 8-port resource) and newer devices (which can handle 16 ports) to properly perform CSI measurements on the same network infrastructure
2Adaptability or versatility
If a subset of CSI-RS ports is selected for legacy device support, then compatibility with legacy terminals is achieved, but the ability to utilize the full antenna array for FD-MIMO operations is reduced
Solution Approach 1:
The patent implements dynamic port selection where the network can configure different subsets of ports for different device types. Legacy devices are configured to measure one 8-port resource, while FD-MIMO devices are configured to measure both 16 ports. The configuration is dynamic and adaptable to the device capabilities, allowing the system to optimize performance for each device type without compromise
3Productivity
If separate CSI-RS configurations are used for legacy and FD-MIMO devices, then each device type can be optimized, but signaling overhead and configuration complexity increase
Solution Approach 1:
The patent merges the configuration of two 8-port CSI-RS resources into a unified 16-port configuration structure. Both resources share the same resource configuration parameters (time-frequency resources, scrambling IDs, etc.), reducing the need for separate configurations. This merging approach minimizes signaling overhead while still providing device-specific optimization through selective resource assignment
Data Source
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AI summary
According to certain embodiments, a method in a network node is disclosed. The method comprises selecting a subset from a predetermined set of P CSI-RS ports for receiving channel information. The network node comprises an antenna array with controllable polarization. Each CSI-RS port corresponds to a combination of a set of resource elements and an antenna port of said antenna array. The predetermined set comprises a first number P| of CSI-RS ports with a first polarization state and a second number P2 of CSI-RS ports with a second polarization state. The first and second polarization states are distinct. The method further comprises populating the subset with Q CSI-RS ports in such manner that the ratio of CSI-RS ports respectively having the first and second polarization states is equal to the ratio of the first and second numbers.