LED Reciprocal Channel Estimation for Optical Wireless

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Solution Overview

Problem

Existing optical wireless communication technologies face challenges in efficiently estimating channel characteristics due to the directive nature of light communication and the use of LEDs and photodetectors, which limits the recovery of phase and amplitude information from signals.

Innovation Solution

A wireless communication device uses LEDs as both transmitters and receivers to estimate channel characteristics based on the assumption of channel reciprocity, employing intensity modulation and direct detection, and coherent detection to recover both phase and amplitude information using real-valued and unipolar modulation schemes like DCO-OFDM or advanced phase recovery techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If intensity modulation with direct detection (IM-DD) is used in optical wireless communication, then the system can achieve simple implementation and compatibility with LED transmitters, but phase and amplitude information cannot be recovered from the measured signal

Engineering Contradiction:

Improveimplementation simplicityVSAvoidphase and amplitude information recovery

Core Design Contradiction:

Ease of manufactureVSLoss of information

Solution Approach 1:

The patent replaces the traditional photodetector-based direct detection mechanism with a LED-based reciprocal detection mechanism. By using the LED's photoelectric effect in reverse (detecting incoming light), the system can recover both amplitude and phase information while maintaining implementation simplicity and compatibility with existing LED infrastructure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If channel state information estimation is performed in optical wireless communication, then communication performance can be improved, but the directive nature of light communication and hardware constraints make efficient estimation difficult

Engineering Contradiction:

Improvecommunication performanceVSAvoidchannel estimation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent enables the LED transmitter to perform self-detection of channel characteristics by utilizing its own photoelectric properties. The LED detects incoming reference signals from the receiver, allowing the transmitter to estimate channel state information autonomously without requiring complex receiver-side estimation or additional hardware, thus improving performance while maintaining simplicity.

Inventive Principle:

Principle #25Self-service

3Device complexity

If LEDs are used as both transmitters and receivers, then hardware requirements are reduced and cost is decreased, but the device must perform dual functions that are traditionally separated

Engineering Contradiction:

Improvehardware requirementsVSAvoiddual function operation

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements multi-functionality by enabling the LED to operate in both emission mode (as transmitter) and detection mode (as receiver) through exploitation of the photoelectric effect. This universal design allows a single component to perform both traditional functions, reducing hardware requirements and cost while maintaining full communication capability through reciprocal operation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables accurate and efficient estimation of channel characteristics without requiring feedback, improving the performance and throughput of optical wireless communication systems by allowing for the recovery of both phase and amplitude information, thereby enhancing spectral efficiency and reducing the need for additional hardware.

Implementation Method 1

using the at least one LED as a receiver, the wireless communication device receives incoming optical wireless communication signals

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

using at least one light emitting diode (LED) as a transmitter to send outgoing optical wireless communication signals

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20240297713A1Reciprocity based optical wireless communication

Publication Date: 2024.09.05 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A wireless communication device (11, 100) uses at least one light emitting diode (LED) as a transmitter to send outgoing optical wireless communication signals to a further wireless communication device (11, 100). Further, using the at least one LED as a receiver, the wireless communication device (11, 100) receives incoming optical wireless communication signals from the further wireless communication device (11, 100). Based on at least some of the received incoming optical wireless communication signals, the wireless communication device (11, 100) estimates a channel characteristic for the outgoing optical wireless communication signals.