Variable Rate MIMO for Airborne Platform Communications

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Solution Overview

Problem

Airborne communication systems face challenges such as antenna blockage due to platform movement and orientation, interference, and the lack of transmitter channel state information, which hinder reliable high-throughput data transmission in situational awareness missions.

Innovation Solution

A multiple-input multiple-output (MIMO) communication system integrating spatial spreading to counter antenna blockage, temporal spreading to mitigate interference, and a low rate feedback scheme for real-time adaptation, implemented in a Bell Laboratories Layer Space-Time (BLAST) architecture to maintain connectivity and boost signal-to-interference noise ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If MIMO communications are used to achieve linear throughput scaling, then spectrum efficiency is improved, but the system becomes vulnerable to antenna blockage and keyhole effect in airborne platforms

Engineering Contradiction:

ImprovethroughputVSAvoidconnectivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the spatial distribution parameters of transmit antennas by applying spatial spreading codes that distribute signal energy across multiple antennas with different weights and phases. This transforms the concentrated MIMO signal into a spread signal that can bypass blockage effects, maintaining connectivity while preserving throughput capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system applies spatial spreading as a preventive measure before transmission to cushion against potential antenna blockage. By pre-distributing signal energy across multiple spatial paths through spreading codes, the system prepares redundancy that activates automatically when blockage occurs, ensuring continuous connectivity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If spatial spreading is applied to counter antenna blockage, then connectivity is maintained, but signal-to-interference noise ratio degrades

Engineering Contradiction:

ImproveconnectivityVSAvoidsignal-to-interference noise ratio

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements feedback mechanisms where the receiver detects the spread signal characteristics and channel conditions, then sends feedback to the transmitter to adapt the spreading code selection and parameters. This closed-loop control allows the system to optimize the balance between connectivity maintenance and SINR preservation by selecting spreading codes that minimize interference while maintaining spatial diversity.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If temporal spreading is used to mitigate interference, then signal-to-interference noise ratio is improved, but data transmission rate is reduced

Engineering Contradiction:

Improvesignal-to-interference noise ratioVSAvoiddata transmission rate

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent applies temporal spreading selectively and partially rather than uniformly to all data streams. By applying spreading only when and where interference is detected through channel estimation, the system achieves interference mitigation for affected portions of the transmission while maintaining full rate for unaffected portions, thus balancing SINR improvement with data rate preservation.

Inventive Principle:

Principle #16Partial or excessive action

4Productivity

If full transmitter channel state information is obtained for optimal MIMO performance, then throughput is maximized, but feedback overhead and system complexity increase significantly

Engineering Contradiction:

ImprovethroughputVSAvoidfeedback overhead

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent extracts only the essential channel state information needed for spatial spreading code selection rather than transmitting complete CSI. By identifying and transmitting only the critical parameters (such as channel quality indicators and spreading code preferences), the system achieves optimal MIMO performance with minimal feedback overhead, removing unnecessary information transmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS11569871B2Variable rate MIMO for multi-user communications involving airborne platforms

Publication Date: 2023.01.31 THE GOVERNMENT OF THE UNITED STATES AS REPRESENTED BY THE SECRETARY OF THE AIR FORCE

AI summary

A multiple-input multiple-output (MIMO) communication system that addresses three major challenges in airborne MIMO communications, namely, antenna blockage due largely to the movement and orientation of the airborne platforms, the presence of unknown interference inherent to the intended application, and the lack of channel state information (CSI) at the transmitter. The system is implemented on a Diagonal Bell-Labs Layered Space-Time (D-BLAST) MIMO architecture and includes spatial spreading to counter antenna blockage, temporal spreading to mitigate signal to interference and noise ratio degradation due to intended or unintended interference, and a simple low rate feedback scheme to enable real time adaptation in the absence of full transmitter CSI.