modBulb: A modular Light Bulb for Visible Light Communication Kasun - PowerPoint PPT Presentation

modBulb: A modular Light Bulb for Visible Light Communication Kasun Hewage 1 , Ambuj Varshney 1 , Abdalah Hilmia 1 , Thiemo Voigt 1 , 2 1 Uppsala University, Sweden 2 SICS Swedish ICT, Sweden October 3, 2016

Embedded Visible Light Communication VLC has been mainly researched as an alternative to WiFi – High bitrates in the orders of GBit/s Embedded Visible Light Communication – Not all applications require high bitrates – Internet connectivity is only one application Embedded VLC applications – Localization – Gesture Recognition – Camera Flash Synchronization K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 2

Motivation Light transmitter is a key component in VLC – Decides light intensity, data rate, etc Lack of truly open source hardware – Repeatability of experiments Existing solutions: OpenVLC [HotWireless 2015], Linux Light Bulbs[VLCS 2015] – Limited bandwidth – Not very flexible (eg: multiple LEDs, LEDs with different wavelengths) Can we design an open VLC hardware to enable a wide spectrum of applications? K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 3

Contributions: modBulb Flexible baseband generator – MCU, FPGA or a hybrid architecture Wireless connectivity – Over-the-air updates for MCU and FPGA through WiFi Exchangeable light source – Efficient LED driving, flexibility to change LEDs Open hardware & software K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 4

Modular Design Baseband Generator – Modulated signal is digital LED Driver - Constant current driving – Non-linear IV characteristics LED(s) – Multiple LEDs – LEDs with different wavelengths K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 5

Baseband Generators: MCU & FPGA MCU baseband generator FPGA baseband generator CC3200 - ARM Cortex-M4 Core at 80 Microsemi AGLN060 at 20 MHz ( ∼ MHz 200 MHz) Over-the-air updates through Wi-Fi Over-the-air updates through MCU Dedicated WiFi network processor Parallel processing Constrained by clock frequency Precise control over the timing Easy to program Complex to program K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 6

Modulation overhead 35 30 Processing time (ms) 25 20 15 10 5 0 0 200 400 600 800 1000 Throughput (KBit/s) The modulation affects on the ability of performing additional processing. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 7

Achievable Throughput MCU 20 FPGA Throughput (MBit/s) 15 10 5 0 OOK FSK PPM Modulation scheme The FPGA based baseband generator allows higher throughput at the expense of ease of use. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 8

LED Drivers: Linear Regulator & Switching Regulator Linear regulator based driver Switching regulator based driver Controls the current linearly Controls the current by switching High heat dissipation, inefficient Very low heat dissipation, efficient Simple to prototype Switching noise can appear in modulated light Bulky due to the attached heat sink Widely used in commercial lighting K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 9

Noise comparison 1.0 Signal (V) 0.5 0.0 Time (us) Linear Regulator 1.0 Signal (V) 0.5 0.0 Time (us) Switching Regulator 5 Signal (V) 0 0 10 20 30 40 Time (us) Baseband Signal The switching regulator introduces noise at the benefit of power efficiency. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 10

Efficiency of the Driver Circuits LED driver LED Input Output Efficiency current power power (%) (A) (W) (W) Linear 0.566 6.79 3.47 51.10 Switching 0.508 3.48 3.04 87.36 The linear regulator based driver is less efficient than the switching regulator based driver circuit. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 11

Multiple LEDs 1400 500 KBit/s OOK Without modulation 1200 Light Intensity (Lux) 1000 800 600 400 200 0 1 2 3 Number of LEDs Since modBulb controls current, multiple LEDs can be added to increase the light intensity. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 12

Sent & Received Waveforms Sent Sent Received Received 1 1 0 0 Signal Signal 1 1 0 0 0 10 20 30 40 50 0 5 10 15 20 25 30 35 40 Time (us) Time (us) OOK modulation at 1 MBit/s BFSK modulation at 500 KBit/s modBulb achieves a superior datarate than existing open embedded VLC hardware. K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 13

All Together FPGA & MCU baseband generators, Switching LED driver K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 14

Conclusions & Future work modBulb is an open tool to be used with embeded VLC Can be used beyond prototyping applications Future work modBulb as a VLC receiver Analog modulations such as OFDM modBulb will be truly open source Schematics & PCBs Other design files Visit our demo to see modBulb in action K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 15

Thank You Thank You Q & A K. Hewage, A. Varshney, A. Hilmia, T. Voigt modBulb: A modular Light Bulb for VLC 16