LED-Based MIMO Reception in Optical Wireless Communication

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Solution Overview

Problem

Existing optical wireless communication (OWC) systems face challenges in enhancing performance without increasing device complexity, particularly in devices with small form factors.

Innovation Solution

The use of LEDs for receiving MIMO OWC signals, in conjunction with photodetectors (PDs), allows for efficient MIMO reception processing by detecting and linearizing electrical responses to optical communication signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional PDs are added to enhance MIMO capabilities, then MIMO performance is improved, but device complexity and form factor are worsened

Engineering Contradiction:

ImproveMIMO performanceVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent enables LEDs to perform dual functions: transmitting optical signals and receiving optical signals for MIMO detection. By making the LED receiver universal (capable of both transmission and reception), the system achieves MIMO functionality without requiring separate dedicated receiver components, thus improving MIMO performance while avoiding increased device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the transmission and reception functions into a single LED component. The LED is used both as an optical transmitter and as an optical receiver (through its capacitance discharge response), merging what would traditionally require separate components into one element, thereby reducing device complexity while maintaining MIMO capabilities

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If additional PDs are added to enhance MIMO capabilities, then MIMO performance is improved, but device form factor is worsened

Engineering Contradiction:

ImproveMIMO performanceVSAvoidform factor

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The LED serves multiple purposes including signal transmission and signal reception, eliminating the need for additional dedicated receiver components that would increase the device form factor

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

By merging the transmission and reception functions into the existing LED structure, the patent avoids adding separate receiver components, thus maintaining a compact form factor while achieving MIMO performance

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If LED electrical response is used for MIMO reception, then device complexity is reduced, but signal linearity is worsened due to non-linear capacitance discharge

Engineering Contradiction:

Improvedevice complexityVSAvoidsignal linearity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent converts the harmful non-linear effect of LED capacitance discharge into a beneficial feature by applying a pre-computed non-linear equalization function. The equalization function is specifically designed to counteract the non-linear discharge characteristics, transforming the distortion into a corrected linear signal suitable for MIMO detection

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent performs preliminary equalization by pre-computing and storing non-linear equalization functions that compensate for the LED's capacitance discharge characteristics. This preliminary correction is applied before MIMO signal processing, ensuring linear signal responses without requiring additional hardware complexity

Inventive Principle:

Principle #10Preliminary action

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 enhances MIMO capabilities and field of view without requiring additional PDs, improving the performance and efficiency of OWC systems, especially in IoT devices with limited space.

Implementation Method 1

detecting a time-varying impulse response generated by discharging of an internal capacitance of the LED according to a monotonic function of time

Methodology Applied

Scientific EffectCapacitance discharge: Capacitance

Implementation Method 2

A receiver may detect the changes of the emitted light intensity, e.g., using Photo Detectors (PDs)

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS20250119213A1MIMO Processing with LED based Reception of Optical Communication Signals

Publication Date: 2025.04.10 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A wireless communication device (200), which is equipped with a photodetector (202) and a light-emitting diode (201), detects a first electrical response of the light-emitting diode (201) to an optical communication signal and a second electrical response of the photodetector (202) to the optical communication signal. Based on the detected first electrical response and the detected second electrical response, the wireless communication device (210) performs Multiple-Input Multiple-Output reception processing to receive data from at least one further wireless communication device (210).