PUCCH Feedback for Beamformed CSI RS in 3D MIMO
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Solution Overview
Problem
Conventional cellular systems face limitations in beamforming performance due to fixed antenna directions and limited vertical beamforming capabilities, which hinder effective implementation of 3D multiple-input multiple-output (MIMO) and 3D beamforming in wireless communication systems.
Innovation Solution
A method and apparatus for performing physical uplink control channel (PUCCH) feedback using beamformed channel state information reference signal (CSI RS) resources, allowing user equipment (UE) to measure and transmit preferred beams and CSI to a base station, including a precoding type indicator (PTI) to distinguish between non-precoded and beamformed CSI RS resources, facilitating 3D MIMO and 3D beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive antenna system with mechanical or electrical tilting is used, then inter-cell interference is reduced and SINR is improved, but beam direction is fixed or limited to vertical range only
Solution Approach 1:
The patent implements dynamic beamforming by allowing the base station to transmit multiple CSI RS resources with different beam directions and enable the UE to select the preferred beam direction based on channel conditions. This transforms the static antenna tilting into a dynamic system that can adapt beam directions in real-time, resolving the contradiction between achieving good SINR and maintaining beam direction adaptability.
Solution Approach 2:
The patent changes the parameter of beam direction from fixed (mechanical tilting) or limited (electrical tilting) to variable by introducing multiple CSI RS resources with different beam directions. The UE measures channel quality for each beam direction and feeds back CSI, enabling the base station to adaptively select the optimal beam direction, thus achieving both good SINR and beam direction adaptability.
2Reliability
If active antenna system with 3D MIMO is implemented, then beamforming performance is improved, but complexity of CSI measurement and feedback increases
Solution Approach 1:
The patent segments the 3D beamforming CSI feedback into two parts: the UE measures multiple CSI RS resources with different beam directions, selects the preferred beam direction, and feeds back only the CSI for that selected beam. This segmentation approach reduces feedback complexity compared to feeding back CSI for all beam directions, while still achieving good 3D beamforming performance.
Solution Approach 2:
The patent extracts only the essential information needed for 3D beamforming by having the UE select and feed back CSI for the preferred beam direction only, rather than transmitting full CSI for all beam directions. This extraction principle reduces feedback overhead and complexity while maintaining the benefits of 3D MIMO beamforming.
3Adaptability or versatility
If multiple CSI RS resources with different beam directions are transmitted, then 3D beamforming capability is achieved, but overhead of reference signals increases
Solution Approach 1:
The patent applies partial action by having the base station transmit multiple CSI RS resources for 3D beamforming, but the UE only measures and feeds back CSI for a subset of these resources (specifically, the preferred beam direction). This partial measurement and feedback approach achieves 3D beamforming capability while reducing the effective reference signal overhead compared to measuring and reporting all CSI RS resources.
Data Source
AI summary
A method and a device for transmitting channel state information (CSI) in a wireless communication system are provided. A terminal performs a measurement on the basis of at least one beamformed CSI reference signal (RS) resource, and transmits, to a base station, the CSI and information relating to preferred beam on the basis of the measurement result, wherein the CSI includes a precoding type indicator (PTI), and the PTI indicates whether the measurement is based on a CSI RS resource which is not precoded, or is based on the beamformed CSI RS resource.