MU-MIMO Beam Orthogonality via Dynamic Null Placement

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In Multi-User Multiple-Input-Multiple-Output (MU-MIMO) radio systems, existing technologies fail to ensure full orthogonality between beams, leading to interference due to overlapping side and main lobes, and static beam weighting factors do not improve Signal to Interference plus Noise Ratio (SINR) in uplink scenarios.

Innovation Solution

A radio system with a processing unit that determines initial null locations for beams and adjusts them based on other beams to be used simultaneously, computing new beam weighting factors to ensure nulls are at the main lobe directions of other beams, thereby providing full orthogonality and improving SINR through dynamic beam weighting factor calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If ordinary beamforming techniques with uniform phase variation are used, then the beamforming process is simple, but full orthogonality among beams is not provided and side lobe overlap with main lobe of other beams occurs

Engineering Contradiction:

Improvebeamforming implementation simplicityVSAvoidbeam orthogonality

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the phase variation pattern from uniform to non-uniform by introducing specific phase shifts across antenna elements. The beamforming weights are designed with progressive phase changes that force nulls to align with main lobes of other beams, achieving full orthogonality while maintaining practical implementation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent proactively designs beamforming weights that create nulls in the directions of main lobes of other beams before transmission occurs. By pre-positioning these nulls through careful weight design, the system prevents interference from occurring in the first place, ensuring orthogonality is built into the beam structure itself

Inventive Principle:

Principle #9Preliminary anti-action

2Object-affected harmful factors

If tapering function with window function is used to suppress side lobe, then interference between beams is mitigated, but beam gain is reduced

Engineering Contradiction:

Improveinterference between beamsVSAvoidbeam gain

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The patent extracts and removes the harmful side lobe energy by forcing nulls in the directions of other beams' main lobes. Instead of suppressing side lobes with tapering functions, the design directly eliminates interference paths by positioning nulls at critical locations, achieving interference mitigation without the gain penalty of windowing functions

Inventive Principle:

Principle #2Taking out (Extraction)

3Device complexity

If static beam weighting factors are used, then the system is simple to implement, but SINR is not improved in uplink scenarios

Engineering Contradiction:

Improvebeam weighting factor calculationVSAvoidSINR performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent transitions from static to dynamic beam weighting factors. The weights are calculated adaptively based on the specific set of simultaneously active beams, allowing the system to optimize orthogonality for each scheduling instance. This dynamic approach ensures SINR improvement in uplink by continuously adapting to the current beam configuration

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a feedback mechanism where the system determines which beams are simultaneously active and uses this information to calculate appropriate beamforming weights. The weights are then applied and the process repeats for the next scheduling instance, creating a closed-loop system that adapts to changing conditions and maintains optimal SINR performance

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11533094B2Systems and methods for providing forced full orthogonality for beams in a MU/MIMO radio system

Publication Date: 2022.12.20 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Systems and methods are disclosed herein for providing full orthogonality between simultaneously used beams, e.g., in a Multi-User Multiple-Input-Multiple-Output (MU-MIMO) radio system. In some embodiments, a radio system comprises an antenna system and a processing unit. The processing unit is adapted to determine an initial set of null locations for a particular beam based on an initial set of beam weighting factors for the particular beam, and change one or more of the initial null locations based on one or more other beams to be used simultaneously with the particular beam, thereby providing a new set of null locations for the particular beam. The processing unit is further adapted to compute a new set of beam weighting factors for the particular beam based on the new set of null locations, and utilize the new set of beam weighting factors to transmit or receive on the particular beam.