doc.: IEEE 15-15-0720-00-007a

Submission

September 2015

Nan Chi, Yu ZengSlide 1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: Channel Model for Outdoor Freespace Transmission

Date Submitted: July 15, 2015

Source: Nan Chi, Fu Dan University, Yu Zeng, China TelecomAddress: Fu Dan University, 220 Handan Rd., Yangpu District, ShanghaiVoice: Tel: 0086-21-65642983, E-Mail: nanchi@fudan.edu.cn, zengyu@ctbri.com.cnAbstract: In response to «Call for Proposals for OWC Channel Models» issued by 802.15.7r1, this contribution proposes LiFi reference channel models for indoor environments such as office, home and hospital.

Purpose: To introduce reference channel models for the evaluation of different PHY proposals.

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 2

Channel Model for Outdoor Free Space Transmission

Nan Chi, Yu Zeng

September 2015

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 3 Nan Chi, Yu Zeng

September 2015

Data R

ate Increasing

Different M

odulation Schem

e

Background

Outdoor VLC case is not as popular as Indoor VLC

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Submission

Slide 4 Nan Chi, Yu Zeng

September 2015

Research Route

Simulation for Outdoor Long Distance VLC Transmision SystemSystem Structure and Simulation

Parameters Simulation Results and Analysis

Key Technique for Outdoor VLC Transmission SystemPPM Modulation Pre Equalization Diversity reception

technology

VLC Free Space Transmission Channel ModelLED Modulation

PropertyLED dimming

propertyAtmospheric

turbulence model Background Noise

100Mbps OOK Realtime Transmission ExperimentsSystem Structure Results and Analysis

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 5 Nan Chi, Yu Zeng

September 2015

Atmospheric turbulence model Negative Exponential Model ： Strong Turbulence Log-Normal Model: Weak Turbulence Gamma-Gamma Model: From weak to strong turbulence

600 800 1000 1200 1400 16000.0

0.1

0.2

0.3

0.4

0.5

0.6

Rytov

S.I.

Distance / m

S.I.

0.0

0.2

0.4

0.6

0.8

1.0

Ryt

ov

300 400 500 600 700 800 900

0.20

0.25

0.30

0.35

1000m

1200m

1100m

S.I.

Wavelength / nm

Rytov 方差

0.50

0.75

1.00

1.25

1.50

Ryt

ov

Scintillation index (S.I.) and Rytov Variation vs distance

Scintillation index (S.I.) and Rytov Variation vs Wavelength

0.0 0.2 0.4 0.6 0.8 1.0

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

PD

F

Light Intensity

Log-normal Exponential Gamma-Gamma

Comparison of 3 Models PDF (Probability density function)

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 6 Nan Chi, Yu Zeng

September 2015

Atmospheric turbulence model Negative Exponential Model ： Strong Turbulence Log-Normal Model: Weak Turbulence Gamma-Gamma Model: From weak to strong Turbulence

0.01 0.02 0.03 0.04

1E-3

0.01

0.1

BE

R

N噪声功率

Ngative exponential Gamma-Gamma Lognormal

BER under different Model

Turbulence affect light intense and BER Gamma-Gamma are preferred over other model 。

Noise Power N

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 7 Nan Chi, Yu Zeng

September 2015

Background Noise

Background Noise Impact ： Saturate Receiver Affect Receiver Sensitivity

Reduce Background Impact ： Reduce Receiver View Angle Reduce Receiver Antenna Size Choose Proper Optical

Bandpass Filter

Sun Noise Model ： Black Body Model 2

0( )2r

B r

DP L

Sun Radiation vs Wavelength

Black Radiation vs Wavelength

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Submission

Slide 8 Nan Chi, Yu Zeng

September 2015

Modulation

PPM ： Immunity to Certain Interference Power Efficient

Bandwidth Requirements

4 6 8 10 12 14

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

BE

R

SNR(dB)

OOK 2PPM 4PPM

Average Power Comparison of PPM and OOK

Bandwidth Requirements Comparison of OOD and PPMOOK 、 2PPM 、 4PPM BER vs SNR

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 9 Nan Chi, Yu Zeng

September 2015

Pre equalization

analog circuit digital circuit

Pre - equalizer based on FIR filter

Original Signal LED Modulated Signal

Pre-Equalized Transmission Signal

Pre-Equalized Received Signal

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Submission

Slide 10 Nan Chi, Yu Zeng

September 2015

6 8 10 12

1E-3

0.01

0.1

BE

R

SNR

预均衡 没有预均衡

@BER=3.810-3

After pre-equalization BER is significantly reduced, when the

signal to noise ratio is less than 10 the 7% FEC error threshold

cna still met

Equalized

Un-Equalized

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 11 Nan Chi, Yu Zeng

September 2015

Diversity reception technology

Space Linear diversity ：MRC ： High Gain, High ComplexityEGC ： Gain less than MRC ， lower

complexitySC ： Minimum Complexity ， worst Gain

Optical receiver1

Optical receiverN

Data in

VL

C channel

Optical

transmitter

A1 AN

...Optical receiver2

PPM

modulation

A2

Data out

PPM demodulation

� 0 2 4 6

1E-3

0.01

0.1

BE

R

SNR1/SNR2

MRC EGC SC

2 3 4 5

1E-3

0.01

BE

R支路个数

@3.810-3

BER comparison

MRC sub path vs BER

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 12 Nan Chi, Yu Zeng

September 2015

Simulation

背景光噪声

大气湍流

Pre

-eq

ual

izat

ion

Up

sam

ple

PIN

ĂĂ

PP

M m

odu

lati

on

Do

wn

sam

ple

A1

An

i branch

ĂĂ ě

PP

M d

emo

du

lati

on

Merge output D

ata

ou

t

Da

ta i

n

发射端 接收端传输信道

Pre-Equalization ： FIR pre-equ

Diversity and number paths ： 4 MRC

Turbulence Model ： Gamma-Gamma

Modulation ： 4-PPM

Transmitter Channel Model Receiver

Turbulence

Background Noise

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 13 Nan Chi, Yu Zeng

September 2015

Background vs Minimum Transmission Power

Angle of Half(deg) 45

LED Number 3600

Distance(m) 1000

Order of Pre-Equ 5

Bandwidth （ MHz）

400

0.010 0.015 0.020 0.025 0.030 0.035

1E-4

1E-3

0.01

0.1

BE

R

W发射功率（ ）

30uW 40uW 50uW

@BER=3.810-3

0.0 0.1 0.2 0.3 0.4 0.5 0.6

1E-5

1E-4

1E-3

0.01

0.1

@BER=3.810-3

BE

R

W发射功率（ ）

300uW 400uW 500uW 600uW 700uW 800uW

Receiver angle of 33° ， BER vs Transmission Power under

different Interference

Receiver angle 115° ， BER vs Transmission Power under

different Interference

33.8 10BER ，Every 10μW Noise power increase will

results individual LED minimum

Transmission Power increase 5mW

Transmission Power Transmission Power

doc.: IEEE 15-15-0720-00-007a

Submission

Slide 14 Nan Chi, Yu Zeng

September 2015

Equalization circuit

Pattern generator

Error detector

Cl ock

Data out

EA

Bi as Tee

Power supplier LED Lens Pi n

AWG

Pre-amplifier

EA

Vari abl e attenuatorSpl i tter

OSC

BER Testset

OOK

Red LED

Pre-Equalized

LED

Realtime

Transmission

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Submission

Slide 15 Nan Chi, Yu Zeng

September 2015

（ a ） Eye diagram no Equalization

（ b ） Eye diagram with Equalization

Effective Results

1.95 2.00 2.05 2.10

1E-5

1E-4

1E-3

0.01

0.1

1

BE

R

300M 400M

V驱动电压（ ）

@3.810-3

Higher Driver voltage Reduce BER, but should under safe LED driver voltage limit

-6 -4 -2 0 2 4 61E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

BE

R

°接收端偏移角度（ ）

300M 400M

@BER=3.810-3 300MHz ， variation angel 5° ；400MHz ， variation angel 3° 。

Receiver Angel

Driving Voltage

doc.: IEEE 15-15-0720-00-007a

Submission

September 2015

Conclusion

Creative Points

Results

Simulation ： VLC Outdoor

Transmission Model

Transmission Key poings

VLC Outdoor Free Space Transmission Model

Experiment： 100Mbps OOK

Realtime transmission system

Future work ： More

improvement Setup long

distance VLC Platform

Pilot study on Outdoor Free Space VLC Transmission

Paper:Jiayi Zhao, Nan Chi. Indoor LED location technique comparison study[J]. Light and lighting ,2015,01:34-41

Slide 16 Nan Chi, Yu Zeng