Visible Light Communications

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1 Mobile and Vehicular Network Lab Visible Light Communications Hsin- Mu (Michael) Tsai ( 蔡欣穆 ) Computer Science and Information Engineering National Taiwan University 前瞻資訊科技 2013/3/29

2 Borrowing the slides Mobile and Vehicular Network Lab Slides from Dr. Rick Robert s talk at NTU

3 An LED a diode that emits IR, VIS or UV light and modulation via on-off keying seems simple enough 3 Dec 2012 Rick Roberts, Intel Labs

4 What is LED-CP and why should we be interested? LED-CP is taking advantage of the modulation bandwidth of an LED to accomplish both illumination, data transmission and position determination. LED lighting is becoming pervasive. 4 Dec 2012 Rick Roberts, Intel Labs

5 Basic Modulation: On- Off Keying (OOK) Mobile and Vehicular Network Lab Bit 1 Bit 0 Bit 1 Bit 1 Bit 0 Bit 0 Bit 0 Transmit 1 : transmit the carrier Transmit 0 : transmit a constant amplitude signal (DC) What happened to the lighting level that human eyes can perceive?

6 Visible Light Communications Got an LED light? Let s modulate it to send data! 6 Dec 2012 Rick Roberts, Intel Labs

7 Let s start with Visible Light Communications Got an LED light? Let s modulate it to send data! But maybe it is not that easy. 7 Dec 2012 Rick Roberts, Intel Labs

The VLC ecosystem is complicated - split

solution and can t justify increased costs

8 Consider the business case Who pays to modulate the light? What is the return on investment? Who pays to modify the phone? What is the return on investment? The VLC ecosystem is complicated - split between vendors who only have half the solution and can t justify increased costs until the other half is present! 8 Dec 2012 Rick Roberts, Intel Labs

9 So why care? Because the High Brightness LED market is projected to be a $15 billon market by There is certainly an applied research opportunity! 9 Dec 2012 Rick Roberts, Intel Labs

10 What can we do to maximize the chance of commercial success for VLC? Leverage unique LED communication properties and try not to duplicate what WiFi can do! 10 Dec 2012 Rick Roberts, Intel Labs

11 Multipath Propagation Mobile and Vehicular Network Lab 接收端接收到的訊號是所有經不同長度路徑的到達的訊號加總

12 Power delay profile Mobile and Vehicular Network Lab h b (t, ) t 同一個訊號, 經不同路徑傳遞後, 會在不同時間到達接收端, 且強度不同 t (t 0 )

13 真實世界的 power delay profile Cellular (RF) Mobile and Vehicular Network Lab

14 Inter- Symbol Interference Mobile and Vehicular Network Lab T s < σ τ P(t;τ) σ τ T s t t T s These will become inter- symbol interference! 14

15 隨時間變化的無線通道 Mobile and Vehicular Network Lab h b (t, ) t 1 t 2 t 3 t 不管是傳輸端接收端或是反射物體的位置變化 ( 移動, 甚至是震動 ) 都會造成環境變化! 經過一段時間後, 環境又略有不同, 造成到達強度 & 時間又有不同 (t 1 ) (t 3 ) (t 2 ) t (t 0 ) 同一個訊號, 經不同路徑傳遞後, 會在不同時間到達接收端, 且強度不同

16 Very Directional : Less multipath Mobile and Vehicular Network Lab Receiver Field- of- View (FOV) Eliminates most large- delay multipath components!

17 Mobile and Vehicular Network Lab

18 Mobile and Vehicular Network Lab

19 Mobile and Vehicular Network Lab

20 Video demonstrations Mobile and Vehicular Network Lab

21 Four Identified Markets Lens LES Location Enhanced Information BC Sensor Array Moderate Resolution Positioning Determine Relative Location Positioning ω 1 ~ τ 1 Car A ω 2 ~ LA τ 2 τ 3 sensor s1 LB Processor Car B VLAN τ 4 sensor s2 High Resolution Positioning Visible LAN Communications 21 Dec 2012 Rick Roberts, Intel Labs

22 Location Enhanced Information BC 22 Dec 2012 Rick Roberts, Intel Labs

Location Enhanced Information Broadcast:

data that a 30 fps camera can see without the

23 Location Enhanced Information Broadcast: downloading restaurant menu from LED signage Smartphone VLC sensor Intel Lab s NTU Presentation The challenge here is transmitting data that a 30 fps camera can see without the human eye detecting flicker. 23 Dec 2012 Rick Roberts, Intel Labs

24 Photogrammetric Positioning 24 Dec 2012 Rick Roberts, Intel Labs

25 Overhead LED Lighting (Photogrammetry) app: indoor navigation within a large shopping area ID Code Modulated Overhead LED lighting Smartphone camera 25 Dec 2012 Rick Roberts, Intel Labs

26 Intel Lab s NTU Presentation Complements current WiFi based location research Analogy: indoor GPS (lights instead of satellites) reading sufficient number of lights determines position ID#2 ID#1 ID#3 Camera PG VLCP INS WiFi SLAM WiFi 26 Dec 2012 Rick Roberts, Intel Labs Position

27 Phase Difference of Arrival High Resolution Positioning 27 Dec 2012 Rick Roberts, Intel Labs

28 LED-CP auto use case: Using LED lighting for communications, ranging and positioning Enhanced driver safety by using LED lighting to do localization (via light -wave carrier, amplitude modulated, ranging tones). Determine Relative Location ω 1 ~ τ 1 Car A L A τ 2 sensor s 1 ω 2 ~ τ 3 L B Processor Car B τ 4 sensor s 2 Measuring the time differences 1-2 and 3-4 allows this geometric problem to be solved in a manner similar to GPS. The target precision is sub-decimeter at several car lengths. 28 Dec 2012 Rick Roberts, Intel Labs

29 Auto VLP app: dynamic mapping of surrounding LOS vehicles 29 Dec 2012 Rick Roberts, Intel Labs

30 Hi-res positioning enables cooperative driving! 30 Dec 2012 Rick Roberts, Intel Labs

31 The advantage of a lens! The function of the visible light lens is to map 3-dimensional angle of arrival to a 2-dimensional photo-detector planar array. In the process, any multipath energy is physically mapped to a different point in the detector array than the line-of-sight path; hence, the LOS is physically separated from the multipath. 31 Dec 2012 Rick Roberts, Intel Labs

32 The imaging receiver has remarkable ability to spatially separate transmitter signal sources (but we knew that from digital photography). Having the ability to extract the LOS path (i.e. reject multipath) via spatial separation opens up interesting applications such as positioning. 32 Dec 2012 Rick Roberts, Intel Labs

33 Using infrared instead of visible light potentially offers better system performance LED vehicular safety lighting each car is surrounded by an IR sensor bubble Intel Lab s NTU Presentation 33 Dec 2012 Rick Roberts, Intel Labs

34 Visible Light LAN 34 Dec 2012 Rick Roberts, Intel Labs

35 The lightwave LAN use case (offers security) Some serious issues: - how to do uplink - light intensity induced data rate asymmetry - how to support light dimming 35 Dec 2012 Rick Roberts, Intel Labs

36 Use Case Comparison to other technologies Use Case LES Info BC (location enhanced information broadcasts) PG-VLCP 2 (indoor navigation) HiRes VLCP 1 (auto positioning) VLAN Comms Competing Technology WiFi, Bluetooth, NFC UWB, RFID, NFC GPS, Sonar, Radar, Lidar WiFi, ZigBee Bluetooth, IRDA 1 Visible Light Communications/Positioning Visible Light Advantage Highly Directional, Location Dependent BC VLCP: comparable performance at lower cost VLCP: better performance at lower cost None Deployment issues Complex infrastructure (multiple owners) Line-of-sight operation, complex infrastructure (multiple owners) Line-of-sight operation, single ownership of infrastructure (auto OEMs) Complex infrastructure for VLC Difficult uplink problem WiFi & IRDA already available 2 Photogrammetry Visible Light Communications/Positioning 36 Dec 2012 Rick Roberts, Intel Labs

37 Ranking of Opportunities (most opportunity) 1. High Resolution Positioning Car A ω 1 ω 2 ~ ~ LA Determine Relative Location τ 1 τ 2 τ 3 sensor s1 LB Processor Car B Example: auto positioning with 10 cm accuracy τ 4 sensor s2 2. Photogrammetry Positioning Example: indoor navigation with 1 meter accuracy 3. Location Enhanced Info Broadcast Example: smart signage information broadcast Interest cutoff line 4. Visible LAN Communications (lest opportunity) Example: secure conference room VLAN 37 Dec 2012 Rick Roberts, Intel Labs

38 Color Shi) Keying 38

39 Frequency Shi) Keying 39

40 Pulse Posi8on Modula8on 40

41 Conclusion Mobile and Vehicular Network Lab VLC: LED deployment brings us a new opportunity (low- cost and pervasive infrastructure)! Smart lighting: illumination + communications + positioning Not to beat RF techs, but to complement them (business aspects need to be considered) Needs to leverage optical propagation properties in the applications

Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Title: What is Optical Camera Communications (OCC) Date Submitted: January 2015 Source: Rick Roberts Company: Intel Labs