november 2008 soo-young chang, csus slide 1 doc.: ieee 15-08-0790-00-0vlc sg-vlc project: ieee...

November 2008

Soo-Young Chang, CSUSSlide 1

doc.: IEEE 15-08-0790-00-0vlc

SG-VLC

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

Submission Title: Some Technical Issues on VLCDate Submitted: November 2008Source: Soo-Young Chang, CSUSContact: Soo-Young Chang, CSUSVoice: E-Mail: [email protected]: Some technical issues on VLCAbstract: To discuss some technical issues on VLC, communication types and up and downlink categories related to these types are defined. Some relevant issues are introduced.Purpose: To Introduce some technical issues on visible light communicationsNotice: 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.

November 2008


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Some Technical Issues on VLC

Soo-Young ChangCSUS

Nov. 2008

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Contents

• Types of Comm. Systems

• Multiplexing/Multiple Access

• Up/Down Link Categories

• Duplexing

• Multi-Hop VLC

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TYPES OF COMM SYSTEMS (1)

A. Indoor short range (10m)1. Infra & fixed/mobile, bidirectional, asymmetric, with illumination, PTP

• Downlink: 100 Mbps, uplink: 10 Mbps2. Infra & fixed/mobile, bidirectional, asymmetric, with illumination,

PTMP (broadcast)• Downlink: 100 Mbps, uplink: 10 Mbps• Multiple access required

3. Infra to fixed/mobile, unidirectional, with illumination, PTP or PTMP (broadcast): same contents to all receivers

• Downlink: 100 Mbps4. Infra to fixed/mobile, unidirectional, with illumination, PTP or PTMP

(broadcast): different content to each receiver• Downlink: 100 Mbps

5. Mobile & fixed/mobile, bidirectional, symmetric, PTP• Up/downlink: 100 Mbps

6. Mobile & fixed/mobile, unidirectional, PTP• Downlink: 100 Mbps

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B. Outdoor short range (10m)1. Mobile-to-mobile, bidirectional, symmetric, PTP

• Up/downlink: 100 Mbps2. Mobile-to-fixed, bidirectional, asymmetric, PTP

• Downlink: 100 Mbps, uplink: 100 Kbps3. Mobile-to-mobile, unidirectional, PTP

• Up/downlink: 100 Mbps

C. Outdoor short range (30m)1. Mobile & display/sign board, bidirectional, asymmetric, PTP

• Downlink: 100 Mbps, uplink: 100 Kbps2. Mobile-to-mobile, bidirectional, symmetric, PTP

• Up/downlink: 100 Kbps

Total 11 types of communications are defined to accommodate all applications so far identified.

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Comm. type

link Bi-/uni-direction

symmetry Illumi

/dimm

PTP/PTMP Data rate Type no.

Indoor short range (10 m)

Between infra/base station/access point and mobile/fixed device

Bi- asymmetric yes PTP Down: 100 Mbps

Up: 10 Mbps

A1

Bi- asymmetric yes PTMP

/broadcast

Down: 100 Mbps

Up: 10 Mbps

A2

Uni- yes PTP/PTMP

/broadcast

Down: 100 Mbps A3

Uni- Yes PTP/PTMP

/broadcast

Down: 100 Mbps A4

Between mobile and fixed/mobile devices

Bi- symmetric x PTP Up/Down: 100 Mbps

A5

Uni- x PTP Down: 100 Mbps A6

Summary of VLC communication types

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Comm. type

link Bi-/uni-directio

n

symmetry Illumi

/dimm

PTP/PTMP Data rate Type no.

Outdoor short range (10 m)

Between mobile and mobile devices

Bi- symmetric x PTP Up/Down: 100 Mbps

B1

Between mobile and fixed devices

Bi- asymmetric x PTP Down: 100 Mbps

Up: 100 Kbps

B2


Uni- x PTP Down: 100 Mbps B3

Outdoor short range (30 m)

Between mobile device and display/sign board

Bi- asymmetric x PTP Down: 100 Mbps

Up: 100 Kbps

C1


Bi- symmetric x PTP Up/Down: 100 Kbps

C2

Summary of VLC communication types (cont’d)

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MULTIPLEX/MULTIPLE ACCESS (1)

• Multiplexing– For point-to-multipoint (PTMP) downlink, multiplexing needed– Conventional schemes: TDM and FDM

• Multiple access– For bidirectional PTMP uplink, a multiple access scheme needed– Conventional schemes: TDMA, FDMA, CDMA, etc.

• Duplexing– For bidirectional communications, duplex schemes needed to provide

both direction communication links– Conventional schemes: TDD and FDD– In this document, full duplex is assumed.

• System design with these issues– For each comm. type defined, a system concept can be established.

• Multiplexing from an infra/base station/access point• Multiple access from each unit/device for PTMP uplinks• Duplexing between uplink and downlink

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MULTIPLEX/MULTIPLE ACCESS (2)

• Multiplexing– For point-to-multipoint (PTMP) communications, multiplexing

needed– Using OFDM in this document

• Multiple access– For bidirectional uplink, multiple access schemes needed– Using OFDMA in this document

• Duplexing– For bidirectional communications, duplex schemes needed to

provide both directional communication links– A few of possible schemes described in this document

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UP/DOWN LINK CATEGORIES (1)

Various up/down link categories identified• Links between an infra/base station/access point and a

mobile/fixed device– Downlink PTMP multiplexing :

with illumination and possibly dimming control

– Downlink PTP or broadcast no multiplexing : with illumination and possibly dimming control

– Uplink PTMP or (two-way) broadcast multiple access

– Uplink PTP no multiple access

• Links between two mobile/fixed devices– Uplink and downlink PTP no multiplexing, no multiple access

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Link type Up/down PTP/PTMP Mux/MA Illumi

/dimm

Category no.

Between infra/base station/access point and mobile/fixed device

down PTMP Mux yes L1

down PTP or broadcast

no Mux yes L2

up PTMP or broadcast

MA x L3

up PTP no MA x L4

Between two mobile/fixed devices

Up and down

PTP no Mux

/no MA

x L5

Summary of categories of VLC links

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• Transmitter and receiver configurations– Between an infra/base station/access point and a mobile/fixed

– Between two mobile/fixed devices

TxRx

Tx Rx

Infra/base station/access point

Mobile/fixedDevice 1

Tx Rx Tx Rx


Mobile/fixedDevice n

Tx RxMobile/fixed

Device 1 Tx RxMobile/fixed

Device 2

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Link Category L1: PTMP down link (transmitter)– MUX: Using OFDM

Subset1

Subset2

Subsetn

IFFT

Modulator n

LED driver LED

From information source

Infra/base station/access point block diagram (transmitter)

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Link Category L1: PTMP down link (receiver)– MA: Using OFDMA

Subseti

FFT

demodulator i

amplifier Photo detector

to information sink

Mobile/fixed device block diagram (receiver)

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Link Category L2: PTP or broadcast down link (transmitter)– No MUX: merely modulation using OFDM

IFFT

Modulator

LED driver LED


Infra/base station/access point block diagram (transmitter)

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Link Category L2: PTP or broadcast down link (receiver)– No MUX: merely modulation using OFDM

FFT

demodulator


to information sink


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Link Category L3: PTMP or broadcast uplink (transmitter)– MA: Using OFDMA

Subseti

IFFT

Modulator i

LED driver LED


Mobile/fixed device block diagram (transmitter)

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Link Category L3: PTMP or broadcast uplink (receiver)– MA: Using OFDMA

Subset1

Subset2

Subsetn

FFT

demodulator n


to information sink

Infra/base station/access point block diagram (receiver)

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Link Category L4: PTP uplink (transmitter)– No MA: Merely Modulation using OFDM

IFFT

Modulator

LED driver LED



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Link Category L4: PTP uplink (receiver)– No MA: Merely Modulation using OFDM

FFT

demodulator


to information sink

Infra/base station/access point block diagram (receiver)

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Link Category L5: PTP uplink or downlink (transmitter)– No MA: Merely Modulation using OFDM

IFFT

Modulator

LED driver LED



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Link Category L5: PTP uplink or downlink (receiver)– No MA: Merely Modulation using OFDM

FFT

demodulator


to information sink


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DUPLEXING (1)

• Conventional duplex schemes for full duplex– TDD (Time Division Duplex)– FDD (Frequency Division Duplex)

• A couple of duplex schemes for VLC– Duplex 1: Using OFDM/OFDMA assumed

• A subset of frequency components for downlink

• Another subset of frequency components for uplink

– Duplex 2: Direction Division Duplex (DDD)• Using directional LEDs

– Duplex 3: Code Division Duplex (CDD)• Using orthogonal PN sequences

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DUPLEXING (2)

• Duplex 1: Orthogonal Frequency Division Duplex (OFDD)– If MUX/MA required: Using OFDM/OFDMA assumed

• A subset of frequency components for downlink to a single device or multiple devices

• Another subset of frequency components for uplink

TxRx

Tx Rx



Tx Rx Tx Rx



Downlink:Using subset i

Uplink:Using subset j

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DUPLEXING (3)

• Duplex 2: (Direction Division Duplex, DDD) – Duplex: using isolation between uplink and downlink through

directivity of transmitter and receiver LEDs

LEDPD

LED PD



LED PD LED PD



Each LED has asmall beam width.

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DUPLEXING (4)

• Duplex 2: (Direction Division Duplex, DDD) (cont’d)– For downlink, a broad beam is used to broadcast light signals while for

uplink a narrower (pencil) beam is used to dedicate the signal to a specific receiver of a base station (or access point or infra).

TransmitterLight source

Infra system(base station,access point)

User unit (mobile or fixed)

Infra receiver

Directed narrow beam

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DUPLEXING (5)• Duplex 3: Code Division Duplex (CDD)

– For downlink and uplink, different orthogonal PN sequences are assigned.

• For downlink: PN sequence i• For uplink: PN sequence j for User Unit j

– With this scheme, multiplexing and multiple access can also be achieved.

TransmitterLight source

Infra system(base station,access point)

User unit(s) (mobile or fixed)

Infra receiver

PN sequence jused for uplinkfor User j

PN sequence iused for downlink

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MULTI-HOP VLC (1)

• To cover broader area in indoor environment or to overcome short range problem

– An in-building space is divided into multiple cells.– Each cell has its own base station (or access point).

• It is assumed that these base stations do not communicate with each other through an infra network.

– To connect all base stations, some relays/repeaters are to be deployed to connect all base stations.

– A mobile/fixed unit in a cell can communicate with a unit in another cell through a multiple hop connection.

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MULTI-HOP VLC (2)

• To cover broader area in indoor environment and to increase communication ranges

– A server/gateway can be connected to only one base station.– Other base stations are connected with other base stations

through multiple hop links. small mesh network

Base station

Relay/repeater

Server/gateway

Outsidenetwork

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MULTI-HOP VLC (3)

• Advantages with multi-hop VLC:• Simple infrastructure to form a network among base

stations• Ubiquity can be easily realized.• Quick deployment and flexible network configuration

without additional infra networks.– For temporary events and places

• Easy installation for places where frequent configuration changes are required

• Short range can be overcome with multiple cells (or hops).• Line-of-sight problem can be overcome with dynamic

routing scheme.• Abrupt blocking problem can be solved by switching routes

– by changing to an alternative route.

Slide 30

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SUMMARY

• VLC communication types are defined by reviewing applications suggested by all documents submitted so far.

– 11 comm. types

• All uplinks and downlinks are categorized for all comm. types defined.

– 5 links

• Multiplexing, multiple access, and duplexing for VLC are discussed.

• Multi-hop VLC for indoor environment is introduced to overcome some VLC problems.

Slide 31

november 2008 soo-young chang, csus slide 1 doc.: ieee 15-08-0790-00-0vlc sg-vlc project: ieee...

Documents

mbps slide

vlc sgvlc project

csus slide

vlc sooyoung chang csus

vlc sgvlc contents types

downlink slide

vlc abstract

vlc date