Distributed MIMO Interference Management via QCL Assumptions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wireless communication systems face challenges in reducing interference between cells, particularly for cell-edge UEs, which affects performance due to strong inter-cell interference, and existing methods do not effectively manage this interference to enhance signal quality.
Innovation Solution
The implementation of distributed MIMO techniques, where UEs provide channel estimates and CQI information to cells to enable beamsteering and precoding, allowing cells to direct transmissions towards UEs while minimizing interference to neighboring cells, and cells can concurrently send data streams to UEs to optimize signal-to-noise-and-interference ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cell sends transmission to a UE with high transmit power, then signal quality to the UE is improved, but interference to UEs in neighbor cells increases
Solution Approach 1:
The patent applies local quality by configuring different QCL assumptions for different spatial layers or transmission configurations. Specifically, the network can indicate to the UE that certain DM-RS ports are QCLed with different SSB or CSI-RS resources, allowing the UE to apply appropriate receiving beams for each layer. This enables the system to direct signal quality improvement locally to the intended UE while managing interference characteristics differently for various spatial directions.
Solution Approach 2:
The patent introduces an additional dimension of spatial processing by utilizing multiple receiving beams and QCL assumptions. Instead of simply increasing transmit power in one dimension, the system expands into the angular/spatial dimension by configuring UEs with multiple receive beams that are QCLed with different reference signals. This allows the system to achieve signal quality improvement through spatial diversity and beamforming rather than brute-force power increase.
2Productivity
If multiple cells send concurrent transmissions to a UE, then data rate is improved, but interference management complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the concurrent transmissions from multiple cells into separate transmission configurations or spatial layers, each with its own QCL assumptions. The network can configure different TCI states or QCL relationships for different cells or cell groups, allowing the UE to process each transmission with appropriate beamforming settings. This segmentation simplifies interference management by treating each cell's transmission as a distinct spatial entity with dedicated receive beam processing.
3Measurement precision
If UEs provide detailed channel estimates for multiple cells, then interference cancellation accuracy is improved, but feedback overhead increases
Solution Approach 1:
The patent applies copying by having the network configure UEs to use QCL assumptions where channel estimates from reference signals (SSB or CSI-RS) in one cell can be copied or reused for receiving transmissions from another cell. Instead of requiring completely independent channel estimation for each cell, the system allows UEs to leverage existing channel knowledge through QCL relationships, significantly reducing feedback overhead while maintaining interference cancellation accuracy.
Data Source
AI summary
Techniques for supporting distributed MIMO are described. For multi-user distributed MIMO, a cell directs its transmit power toward a UE while reducing interference to UE(s) in neighbor cell(s). For single-user distributed MIMO, multiple cells concurrently send transmissions to a UE. In an aspect, a UE sends channel estimates for serving and non-serving cells to support multi-user distributed MIMO. Each cell may use the channel estimates to select UEs for data transmission and determine precoding vectors to use for data transmission to the selected UEs. In another aspect, a UE sends CQI information for serving and non-serving cells to support single-user distributed MIMO. Each cell may use the CQI information to select UEs for data transmission and determine modulation and coding schemes to use for the selected UEs. In yet another aspect, a UE determines CQI information for a serving cell by taking into account interference nulling by non-serving cells.