OTA MIMO Channel Emulator with Pilot Signal Equalization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In large-scale Multi-User Multiple-Input Multiple-Output (MU-MIMO) wireless communication systems, existing technologies face challenges in acquiring and maintaining Over-The-Air (OTA) Channel State Information (CSI) due to the lack of antenna ports for cable connections, leading to increased channel estimation overhead and reduced performance.

Innovation Solution

A MIMO RF channel emulator that utilizes OTA channels to connect with Base Stations (BS) and User Equipments (UEs), employing reflectors and diffusers to maintain channel reciprocity and equalize the OTA channel, allowing for real-time channel simulations and reduced overhead through pilot signal transmission and compensation matrices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If cable connections are used to connect BS RF paths to the channel emulator, then channel estimation overhead is reduced, but the system becomes inapplicable when antenna ports are not reserved or cable connections become impractical in massive MIMO systems with tens to hundreds of antennas

Engineering Contradiction:

Improvechannel estimation overheadVSAvoidapplicability to massive MIMO systems

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical cable connection system with an electromagnetic wave-based OTA connection system. Instead of using physical cables to connect BS RF paths to the channel emulator, the system uses wireless electromagnetic channels, thereby eliminating the need for physical connectors and making the system applicable to massive MIMO configurations where cable management becomes impractical.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a wireless channel as an intermediary between the BS and the channel emulator. Rather than direct cable connections, the electromagnetic propagation medium serves as the connection path, enabling flexible OTA testing while maintaining channel emulation functionality through intermediate signal processing and calibration procedures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If OTA channels are used to connect BS and channel emulator, then the system becomes applicable to massive MIMO systems without cable connections, but channel estimation overhead increases and performance degrades due to the need for additional pilot signals and equalization

Engineering Contradiction:

Improveapplicability to massive MIMO systemsVSAvoidchannel estimation overhead

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs channel calibration and reciprocity verification in advance before actual channel estimation. By pre-characterizing the OTA channel properties and establishing calibration matrices beforehand, the system reduces the overhead required during actual channel estimation operations, as much of the channel information is already known from preliminary measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent discards redundant channel information that can be inferred from reciprocity principles and recovers only the essential independent parameters. In TDD systems where channel reciprocity holds, the patent estimates only the downlink channel from uplink measurements, discarding the need for separate downlink pilot signals and recovering the channel state through mathematical transformations of the uplink channel estimates.

Inventive Principle:

Principle #34Discarding and recovering

3Loss of time

If antenna ports are reserved for cable connections in massive MIMO systems, then channel estimation overhead is reduced, but the number of antennas available for spatial reuse decreases

Engineering Contradiction:

Improvechannel estimation overheadVSAvoidspatial reuse capacity

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The patent replaces the mechanical cable connection requirement with wireless OTA connections, eliminating the need to reserve antenna ports for physical connectors. This substitution allows all antennas to be used for spatial reuse while maintaining channel estimation functionality through wireless measurement and calibration procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11489598B2Over-the-air channel state information acquirement for a massive MIMO channel emulator with over-the-air connection

Publication Date: 2022.11.01 RF DSP INC

AI summary

This invention presents a channel emulator for testing a multi-user multiple input multiple output (MU-MIMO) wireless communication system using an over-the-air (OTA) connection between the antennas of a base station (BS) and the channel emulator. It uses pilot signals with special structures to estimate the channel matrix between the BS and the channel emulator, equalizes the channel when performing emulation of the channels between the BS and a plural of user equipment (UEs) in MU-MIMO communication.