1. Project: IEEE P802.15 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 E-Mail: sychang@ecs.csus.edu, mhson@etri.re.kr 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 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 1 doc.: IEEE 802.15-09-0557-00 Submission

2. VLC COEXISTENCE WITH LIGHTING CONTROL July 2009 Soo-Young Chang, CSUS, Myunghee Son, Jong-Hyun Park, and Sung Won Sohn, ETRI July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 2 doc.: IEEE 802.15-09-0557-00 Submission

3. INTRODUCTION Rick Roberts et al. questioned about hardware partitioning of the PHY layer into two parts - communication part and light control part - in IEEE802.15-09-0204-00-0007, 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 3 doc.: IEEE 802.15-09-0557-00 Submission

4. HARDWARE PARTITIONING QUESTIONED BY RICK ROBERTS ET AL. [1] Hardware partitioning against the protocol stack for LED infrastructure lighting LED Light Panel Upper PHY (FEC, etc.) PHY Layer MAC 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. The standard specifies the air interface at the transmission source. This includes the LED light source. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 4 doc.: IEEE 802.15-09-0557-00 Submission

5. 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 5 doc.: IEEE 802.15-09-0557-00 Submission

6. 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 802.15.7 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 6 doc.: IEEE 802.15-09-0557-00 Submission

7. 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 802.15.7 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 802.15.7.  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]. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 7 doc.: IEEE 802.15-09-0557-00 Submission

8. SOME THOUGHTS ON THIS ISSUE 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 8 doc.: IEEE 802.15-09-0557-00 Submission

9. VLC SYSTEM STRUCTURE WITH PHY PARTITIONING LED Light Panel Upper PHY (FEC, etc.) PHY Layer MAC Light sensor The standard specifies the air interface at the transmission source. This includes the LED light source. 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. Case that the light control module is a part of PHY of VLC (a typical case) [1] July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 9 doc.: IEEE 802.15-09-0557-00 Submission

10. PROPOSED VLC SYSTEM STRUCTURE 1 Structure 1-1: with light control performed through VLC higher layers : control through VLC MAC PHY Light drive Covered by 802.15.7 standard Higher layers Light control input from outside Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 10 doc.: IEEE 802.15-09-0557-00 Submission

11. PROPOSED VLC SYSTEM STRUCTURE 1 Structure 1-2: with light control performed through VLC higher layers : control through VLC with light abstraction layer (LAL) MAC PHY Light drive Covered by 802.15.7 standard Higher layers Light control input from outside Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 11 doc.: IEEE 802.15-09-0557-00 Submission LAL

12. PROPOSED VLC SYSTEM STRUCTURE 2 Structure 2-1: with light control performed through VLC MAC layer : control through VLC MAC PHY Light drive Covered by 802.15.7 standard Higher layers Light control input from outside Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 12 doc.: IEEE 802.15-09-0557-00 Submission

13. PROPOSED VLC SYSTEM STRUCTURE 2 Structure 2-2: with light control performed through VLC MAC layer : control through VLC with light abstraction layer (LAL) MAC PHY Light drive Covered by 802.15.7 standard Higher layers Light control input from outside Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 13 doc.: IEEE 802.15-09-0557-00 Submission LAL

14. PROPOSED VLC SYSTEM STRUCTURE 3 Structure 3-1: with separate outside digital light control: input from VLC to light drive only for comm. MAC PHY Light drive Light control input from outside Covered by 802.15.7 standard Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed with digital control. Digital or analog control July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 14 doc.: IEEE 802.15-09-0557-00 Submission

15. PROPOSED VLC SYSTEM STRUCTURE 3 Structure 3-2: with separate outside digital light control: input from VLC to light drive only for comm. with light abstraction layer (LAL) MAC PHY Light drive Light control input from outside Covered by 802.15.7 standard Light sensor Lighting system is not a part of VLC: a stand-alone lighting system already deployed with digital control. Digital or analog control July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 15 doc.: IEEE 802.15-09-0557-00 Submission LAL

16. PROPOSED VLC SYSTEM STRUCTURE 4 Structure 4-1: with separate outside light control and lighting/VLC interface : only input from VLC to interface module for comm. MAC PHY Light drive Light control input from outside Lighting/VLC Interface (optional) Light sensor Covered by 802.15.7 standard Lighting system is not a part of VLC: a stand-alone lighting system already deployed with control. Digital or analog control July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 16 doc.: IEEE 802.15-09-0557-00 Submission

17. PROPOSED VLC SYSTEM STRUCTURE 4 Structure 4-2: with separate outside light control inputted to light adaptor: only input from VLC to light abstraction layer (LAL) for comm. MAC PHY Light drive Light control input from outside Light sensor Covered by 802.15.7 standard Lighting system is not a part of VLC: a stand-alone lighting system already deployed with control. Digital or analog control July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 17 doc.: IEEE 802.15-09-0557-00 Submission LAL

18. FUNCTIONS OF EACH LEVEL OF LAYERS MAC PHY LAL - Provide power to drive LEDs - Brightness control if needed - Flexible selection of light sensors as PD, IS, etc - 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 - MAC level control for PHY and VLC communications - Communication with next higher layer - Lighting control (optional) -Emission of light controlled by light drive -Detecting of light controlled by light sensor LEDs Light drive July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 18 doc.: IEEE 802.15-09-0557-00 Submission Light sensor - Less PHY overhead incurred by lighting - Easy to combine signals from VLC and lighting

19. 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). Four possible structures for VLC implementation using lighting systems are being proposed: Structures 1, 2, 3, and 4. The standard will define MAC and PHY as shown in Structures 1, 2, 3, and 4. The TCD should define minimum requirements for lighting drive and /or LEDs or other lighting devices. –Research on lighting drives existing and available and lighting devices including LEDs is a prerequisite to be done for this work. 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 19 doc.: IEEE 802.15-09-0557-00 Submission

20. 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 July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 20 doc.: IEEE 802.15-09-0557-00 Submission

21. POINTS TO BE CONSIDERED FOR PROPOSALS (3) The minimum requirements to accommodate existing and future lighting drive systems 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 section on ” Coexistence with ambient light and other lighting systems” to the TCD [3]. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 21 doc.: IEEE 802.15-09-0557-00 Submission

22. OBSERVATIONS/CONCLUSIONS 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. July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 22 doc.: IEEE 802.15-09-0557-00 Submission

23. REFERENCES 1.Rick Roberts, Intel Corp. and Tom Matsumura, VLCC, A standardized LED infrastructure lighting interface, IEEE802.15-09-0204-00-0007, Mar. 2009 2.LM3445 Triac Dimmable Offline LED Driver, National Semiconductors, http://www.national.com/ds/LM/LM3445.pdf, Mar. 2009 http://www.national.com/ds/LM/LM3445.pdf 3.Sridhar Rajagopal, Samsung Electronics (Editor), TG7 Technical Considerations Document (TCD), IEEE802.15-09-0115-07-0007, July 2009 July 2009 S.-Y. Chang, CSUS, Myunghee Son, et al., ETRISlide 23 doc.: IEEE 802.15-09-0557-00 Submission