MU-MIMO Base Station MCS Biasing for RF Correlation

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Solution Overview

Problem

In wireless communication systems, especially in dense urban areas, MU-MIMO service faces interference issues due to RF correlation between UEs, leading to communication errors and retransmissions, despite efforts to group UEs orthogonally for concurrent data transmission.

Innovation Solution

The base station predicts RF correlation between UEs in a MU-MIMO group and adjusts the modulation and coding scheme (MCS) to a lower-order MCS with more error-correction coding and robust modulation, to improve data communication quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If MU-MIMO service is provided to multiple UEs using the same time-frequency resources, then spectral efficiency is improved, but RF correlation between UEs causes interference and communication errors

Engineering Contradiction:

Improvespectral efficiencyVSAvoidcommunication success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The base station dynamically adjusts the MCS parameter based on predicted RF correlation levels. When high RF correlation is predicted between UEs in a MU-MIMO group, the base station selects a lower-order MCS with more robust modulation and error correction, thereby maintaining communication reliability while preserving spectral efficiency through adaptive parameter selection

Inventive Principle:

Principle #35Parameter changes

2Productivity

If orthogonal UE grouping is used for MU-MIMO service, then concurrent data transmission is enabled, but RF correlation still causes interference and retransmissions

Engineering Contradiction:

Improvedata transmission capacityVSAvoidretransmission time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The base station performs preliminary prediction of RF correlation between UEs before allocating them to MU-MIMO groups. By predicting RF correlation in advance and pre-adjusting the MCS accordingly, the system prevents interference-related errors before they occur, eliminating the need for retransmissions and saving time

Inventive Principle:

Principle #10Preliminary action

3Speed

If higher-order MCS is used for data communication, then data rate is increased, but interference from RF correlation causes more communication errors

Engineering Contradiction:

Improvedata rateVSAvoidcommunication robustness

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The base station dynamically selects the MCS order based on real-time prediction of RF correlation between UEs. When RF correlation is low, higher-order MCS is used to maximize data rate; when RF correlation is high, lower-order MCS with better error correction is selected to maintain reliability, creating a dynamic adaptation mechanism that optimizes both speed and robustness

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10862553B1Use of RF correlation between UEs in a MU-MIMO group as a basis to bias MCS

Publication Date: 2020.12.08 SPRINT SPECTRUM LLC

AI summary

When a base station groups a given user equipment device (UE) together with one or more other UEs for multi-user multiple-input-multiple-output (MU-MIMO) service, the base station will predict a level of RF correlation between the given UE and the one or more other UEs of the group (e.g., based angular separation between beam direction of the UE and beam direction of each of the one or more other UEs). And the base station will use that predicted level of RF correlation as a basis to adjust a modulation and coding scheme (MCS) that the base station and the given UE will use for data communication with each other, so as to help improve data communication between the base station and the given UE in the presence of the predicted RF correlation.