UE-Specific Reference Signals for Multi-User MIMO Channel Estimation
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Solution Overview
Problem
In multi-user multiple input multiple output (MIMO) systems, the transmission of downlink reference signals is inefficient due to interference and channel distortion, which affects the decoding of data streams and the estimation of channel impulse response.
Innovation Solution
The implementation of a coordinated multi-point (CoMP) transmission system using dedicated UE-specific reference signals (DRS) and precoding vectors, allowing simultaneous data transmission from multiple base stations to a user equipment (UE) with coordinated interference reduction and improved decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If downlink reference signals are transmitted in multi-user MIMO systems, then channel estimation is enabled, but interference and channel distortion occur affecting decoding performance
Solution Approach 1:
The patent segments the reference signal transmission by assigning UE-specific reference signals to different user equipment and different antenna ports. Each UE receives dedicated reference signals that are orthogonal to other UEs' reference signals, allowing independent channel estimation without mutual interference. This segmentation resolves the contradiction by enabling accurate channel estimation while eliminating the harmful interference that would otherwise occur in multi-user MIMO systems.
Solution Approach 2:
The patent implements local quality by transmitting reference signals with specific properties tailored to each UE and antenna port combination. Each UE-specific reference signal is designed with unique orthogonal codes and allocated to specific resource elements, providing localized channel estimation capability for each user and antenna port. This allows the system to maintain high measurement precision for each individual UE while managing interference through localized signal design.
2Productivity
If multiple base stations transmit data streams simultaneously to a UE, then spectral efficiency increases, but interference between signals from different cells occurs
Solution Approach 1:
The patent merges signals from multiple base stations and antenna ports into a unified multi-user MIMO transmission framework. Multiple data streams from different cells and antenna ports are combined and transmitted simultaneously to different UEs using orthogonal UE-specific reference signals. This merging allows the system to achieve high spectral efficiency by utilizing multiple spatial dimensions while the orthogonality of reference signals prevents harmful interference between the combined signals.
Solution Approach 2:
The patent converts the potentially harmful interference from multiple simultaneous transmissions into a beneficial resource by using it to enable spatial multiplexing. Multiple base stations transmit data streams simultaneously, and the system exploits the spatial separation and orthogonal reference signals to turn what would be interference into useful signal diversity. This allows spectral efficiency to increase while interference is managed through the orthogonal structure of UE-specific reference signals.
Data Source
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AI summary
A base station can communicate with a plurality of subscriber stations in a Multi-User (MU) Multiple-Input Multiple-Output (MIMO) system. The base station includes a transmitter and plurality of antenna configured to transmit control information. The base station can transmit a resource block to a first subscriber station. The resource block includes at least two downlink reference signal (DRS) patterns. The base station can assign a first DRS pattern for use by the first subscriber station. The base station informs the subscriber station regarding the assignment by reserving a state in a downlink grant. In response, the subscriber station can utilize the first DRS pattern as a pilot resource element and, optionally, avoid other DRS patterns.