1. Submission Title: VLC Coexistence with Lighting Control
July 2009
doc.: IEEE
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: VLC Coexistence with Lighting Control
Date Submitted: July 15, 2009
Source: Soo-Young Chang, CSUS, Myunghee Son, Jong-Hyun Park, and Sung Won Sohn, ETRI
Re: Some technical system structures on VLC
Abstract: To discuss and solve a problem incurred by outside light control drives of existing lighting systems, some thoughts are addressed and some relevant system structures are introduced.
Purpose: To Introduce some technical issues on visible light communications
Notice: This document has been prepared to assist the IEEE P 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 P
Submission
Slide 1
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

2. VLC COEXISTENCE WITH LIGHTING CONTROL
July 2009
doc.: IEEE
VLC COEXISTENCE WITH LIGHTING CONTROL
July 2009
Soo-Young Chang, CSUS,
Myunghee Son,
Jong-Hyun Park, and Sung Won Sohn, ETRI
Submission
Slide 2
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

3. INTRODUCTION
July 2009
doc.: IEEE
Rick Roberts et al. questioned about hardware partitioning of the PHY layer into two parts - communication part and light control part - in IEEE , Mar. 2009
to allow most of on-the-shelf LED control modules provided by LED manufacturers to be used for VLC without modification
to ease LED manufacturers’ burden to facilitate interface to communication part.
In this document a few structures by which splitting PHY is not needed to make communication features be independent of outside lighting control.
Submission
Slide 3
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

4. HARDWARE PARTITIONING QUESTIONED BY RICK ROBERTS ET AL. [1]
July 2009
doc.: IEEE
HARDWARE PARTITIONING QUESTIONED BY RICK ROBERTS ET AL. [1]
Hardware partitioning against the protocol stack for LED infrastructure lighting
Upper PHY
(FEC, etc.)
LED Light Panel
MAC
The standard specifies the air interface at the transmission source. This includes the LED light source.
PHY Layer
The PHY layer is split between the upper PHY (FEC, etc.) - which is supplied by the VLC vendor – and the lower PHY which is the LED light panel, which may NOT be supplied by the VLC vendor.
Submission
Slide 4
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

5. POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (1)
July 2009
doc.: IEEE
POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (1)
PHY partitioning suggested in [1]
The PHY layer is split between
the upper PHY (FEC, etc.), which is supplied by the VLC vendor, and
the lower PHY (LED light panel), which may NOT be supplied by the VLC vendor.
Comments
Basic assumption: the “LED light panel” may not recognize the existence of VLC and may not be affected by VLC.  more desirable
Without splitting into two PHYs, it is more desirable for VLC to have only two traditional layers – MAC and PHY.
The VLC can have simple control/input to the LED light panel for communications. This simple control/input should be able to be applied to any LED systems through which VLC can be achieved.
The requirements for these LED systems (or any other lighting systems) for VLC should be minimal to allow more LEDs (or other light sources) available to be used with no or simple modifications.
Submission
Slide 5
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

6. POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (2)
July 2009
doc.: IEEE
POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (2)
The splitting of the PHY layer proposes a potential problem for the infrastructure VLC model: [1]
Existing LED lighting will have to be retrofitted to support VLC.
 This problem can be solved by simplifying control so as not to affect lighting control format for lighting systems by VLC control/processing.
Ideally, new LED lighting would be manufactured with an VLC interface in place.
 This VLC interface features should be minimized to minimize burden for VLC to LED industries.
So what assumptions should make about the light panel interface? What kind of “modulation” will be supported at the light panel? OOK? PWM? OFDM? At what data rate? What about dimmers?
 Through 15.7 proposal procedure, the best technology including modulation scheme(s) should be identified and adopted so that this interface can be simplified and minimized while lighting performance is not degraded.
What we need is a functional interface specification to the light panel. But how do we get that?
 By defining a set of specifications so as not to affect lighting control while performing communications, this can definitely be achieved.
Submission
Slide 6
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

7. POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (3)
July 2009
doc.: IEEE
POSSIBLE PHY PARTITIONING AND COMMENTS ON IT (3)
It could be a two part process for infrastructure lighting … [1]
Part 1: specification of MAC and Upper PHY by
Part 2: specification of the Lower PHY interface by ????
PHY does not need to be split and both of the above two parts should be specified by
Even the air interface which can be a part of lighting control such as in forms of voltage or current control can be specified while lighting control does not recognize this communication function.
LED lighting that is installed without a VLC interface will require TBD modifications to accommodate VLC. And LED lighting lasts a long time. It could be years before the next generation of LED lighting is installed due to product churn. [1]
It is more desirable that existing lighting systems can be utilized with no or minimal modification or addition to them for VLC.
Rick Roberts recommended the group to look at a document on LM3445 “Triac Dimmable Offline LED Driver” [2] to get some help to clarify some issues he suggested in [1].
Submission
Slide 7
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

8. SOME THOUGHTS ON THIS ISSUE
July 2009
doc.: IEEE
It totally depends on what technologies will be used for the 15.7 standard.
Including modulation techniques
What happens if modulation technique applied is not dependent on technical characteristics of LED deployed?
What problem if only simple current or voltage control is needed to the LED control panel for VLC? This control can be implemented even for existing LED lighting systems already deployed.
Basically it is more desirable that the standard for VLC be independent of lighting systems.
The VLC should be coexistent with or adapted to any (infrastructure) lighting systems. To do this, simple inputs are allowed to be inputted to the lighting controller.
Submission
Slide 8
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

9. VLC SYSTEM STRUCTURE WITH PHY PARTITIONING
July 2009
doc.: IEEE
VLC SYSTEM STRUCTURE WITH PHY PARTITIONING
Case that the light control module is a part of PHY of VLC (a typical case) [1]
Upper PHY
(FEC, etc.)
LED Light Panel
MAC
Light sensor
The standard specifies the air interface at the transmission source. This includes the LED light source.
PHY Layer
With this structure there is a problem to specify the 15.7 standard for VLC because of uncertainty of lighting system specifications applied: to overcome this problem, four structures are being proposed in the following slides.
Submission
Slide 9
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

10. PROPOSED VLC SYSTEM STRUCTURE 1
July 2009
doc.: IEEE
Structure 1-1: with light control performed through VLC higher layers : control through VLC
Higher
layers
MAC
PHY
Light drive
Covered by standard
Light sensor
Light control input from outside
Lighting system is not a part of VLC: a stand-alone lighting system already deployed.
Submission
Slide 10
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

11. PROPOSED VLC SYSTEM STRUCTURE 1
July 2009
doc.: IEEE
Structure 1-2: with light control performed through VLC higher layers : control through VLC with light abstraction layer (LAL)
Higher
layers
MAC
PHY
LAL
Light drive
Covered by standard
Light sensor
Light control input from outside
Lighting system is not a part of VLC: a stand-alone lighting system already deployed.
Submission
Slide 11
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

12. PROPOSED VLC SYSTEM STRUCTURE 2
July 2009
doc.: IEEE
Structure 2-1: with light control performed through VLC MAC layer : control through VLC
Covered by standard
Higher
layers
MAC
PHY
Light drive
Light
sensor
Light control input from outside
Lighting system is not a part of VLC: a stand-alone lighting system already deployed.
Submission
Slide 12
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

13. PROPOSED VLC SYSTEM STRUCTURE 2
July 2009
doc.: IEEE
Structure 2-2: with light control performed through VLC MAC layer : control through VLC with light abstraction layer (LAL)
Covered by standard
Higher
layers
MAC
PHY
LAL
Light drive
Light sensor
Light control input from outside
Lighting system is not a part of VLC: a stand-alone lighting system already deployed.
Submission
Slide 13
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

14. PROPOSED VLC SYSTEM STRUCTURE 3
July 2009
doc.: IEEE
Structure 3-1: with separate outside light control: input from VLC to light drive only for comm.
Digital or analog control
Light control input from outside
Light drive
MAC
PHY
Light sensor
Covered by standard
Lighting system is not a part of VLC: a stand-alone lighting system already deployed with digital or analog control.
Submission
Slide 14
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

15. PROPOSED VLC SYSTEM STRUCTURE 3
July 2009
doc.: IEEE
Structure 3-2: with separate outside light control: input from VLC to light drive only for comm. with light abstraction layer (LAL)
Digital or analog control
Light control input from outside
Light drive
MAC
PHY
LAL
Light sensor
Covered by standard
Lighting system is not a part of VLC: a stand-alone lighting system already deployed with digital or analog control.
Submission
Slide 15
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

16. PROPOSED VLC SYSTEM STRUCTURE 4
July 2009
doc.: IEEE
Structure 4-1: with separate outside light control and lighting/VLC interface : only input from VLC to interface module for comm.
Light control input
from outside
Digital or analog control
Lighting/VLC
Interface
(optional)
Light drive
Covered by standard
MAC
PHY
Light
sensor
Lighting system is not a part of VLC: a stand-alone lighting system already deployed with control.
Submission
Slide 16
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

17. PROPOSED VLC SYSTEM STRUCTURE 4
July 2009
doc.: IEEE
Structure 4-2: with separate outside light control inputted to light abstraction layer: only input from VLC to light abstraction layer (LAL) for comm.
Light control input
from outside
Digital or analog control
Light drive
Covered by standard
MAC
PHY
LAL
Light
sensor
Lighting system is not a part of VLC: a stand-alone lighting system already deployed with control.
Submission
Slide 17
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

18. FUNCTIONS OF EACH LEVEL OF LAYERS
July 2009
doc.: IEEE
MAC level control for PHY and VLC communications
Communication with next higher layer
Lighting control (optional)
MAC
- Simple LED input to deliver information transmitted
Facilitate modulation of light signals
Reception of signal information from photo detectors
Lighting control (optional)
Communication with MAC
PHY
Less PHY overhead incurred by lighting
Easy to combine signals from VLC and lighting
LAL
- Provide power to drive LEDs
Brightness control if needed
Flexible selection of light sensors as PD, IS, etc
Light drive
Light sensor
LEDs
Emission of light controlled by light drive
Detecting of light controlled by light sensor
Submission
Slide 18
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

19. POINTS TO BE CONSIDERED FOR PROPOSALS (1)
July 2009
doc.: IEEE
POINTS TO BE CONSIDERED FOR PROPOSALS (1)
More efforts should be made not to split PHY into two parts and avoid major modification of lighting control panel (or simply lighting panel).
The standard will define MAC and PHY as shown in Structures 1, 2, 3, and 4.
The future proposals/contributions will include technical methodology to implement these structures suggested here.
More considerations should be given to the proposed technologies which facilitate the suggestions so far mentioned. Or more desirably the proposals should facilitate them to avoid unnecessary need to modify the light control modules for VLC.
Submission
Slide 19
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

20. POINTS TO BE CONSIDERED FOR PROPOSALS (2)
July 2009
doc.: IEEE
POINTS TO BE CONSIDERED FOR PROPOSALS (2)
For example, if LM3445 is used [2], one of some of the following pins can be used to manipulate light signals to convey information depending on modulation scheme adopted by the future standard:
Pin 1 ASNS PWM output of the triac dim decoder circuit
Pin 2 FLTR1 First filter input.
Pin 3 DIM Input/output dual function dim pin. This pin can be driven with an external PWM signal to dim the LEDs.
Pin 4 COFF OFF time setting pin.
Pin 5 FLTR2 Second filter input.
It totally depends on what parameters will be used for signal processing (or signal manipulation for information delivery):
Varying currents
Varying voltages
Varying colors (or wavelengths)
Or any other parameters which can be processed with the existing and future lighting systems
Submission
Slide 20
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

21. POINTS TO BE CONSIDERED FOR PROPOSALS (3)
July 2009
doc.: IEEE
POINTS TO BE CONSIDERED FOR PROPOSALS (3)
The minimum requirements to accommodate existing and future lighting drive systems and lighting devices including LEDs should be identified and included in TCD.
To do this, study on lighting drive devices and systems should be performed and common control schemes should be identified.
These common control schemes can be used for VLC light signal processing.
Recommendation to the group
To include a statement in ” Coexistence with ambient light and other lighting systems” of the TCD [3] to inform the proposers of the need of these requirements.
Submission
Slide 21
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

22. OBSERVATIONS/CONCLUSIONS
July 2009
doc.: IEEE
These concepts can be applied for any light sources as well as LEDs.
The concepts can be generalized to be applied for any light sources.
Adaptive data rates should be achieved through these concepts due to the specifications of light sources used.
Achievable data rates (or the amount of information delivered) depend on the type of light sources and their radiant powers – especially when applying brightness (or dimming) control.
Submission
Slide 22
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI

23. REFERENCES
July 2009
doc.: IEEE
Rick Roberts, Intel Corp. and Tom Matsumura, VLCC, A standardized LED infrastructure lighting interface, IEEE , Mar. 2009
LM3445 Triac Dimmable Offline LED Driver, National Semiconductors, Mar. 2009
Sridhar Rajagopal, Samsung Electronics (Editor), TG7 Technical Considerations Document (TCD) , IEEE , July 2009
Submission
Slide 23
S.-Y. Chang, CSUS, Myunghee Son, et al., ETRI