SmartVLC: When Smart Lighting Meets VLC Hongjia Wu 1 , Qing Wang 1 , 2 , Jie Xiong 3 , Marco Zuniga 1 1 TU Delft 2 KU Leuven 3 Singapore Management University
Background - VLC Visible Light Communication (VLC): transmit data wirelessly using the artificial light (i.e., LED light ) and is flickering-free for users. SmartVLC 2/26
Background - Smart Lighting Smart Lighting: the LED light changes with ambient light, to keep the total illumination constant within an area-of-interest more ambient light less ambient light � → less LED light � → more LED light SmartVLC 3/26
VLC and Smart Lighting in Action Basic requirements ❼ Smart lighting : fine-grained dimming levels ❼ Visible Light Communication (VLC) : optimized throughput State-of-the-Art (SoA) solutions & Objective of this work System throughput This work SoA-2 SoA-1 LED’s brightness (dimming level) Strong ambient light Weak ambient light SmartVLC 4/26
Related Work SoA-1 (OOK-CT): On-Off-Keying (OOK) with Compensation Time Data Compensation time Data Compensation time t t 0 T 0 T Dimming level: 40% Dimming level: 20% SoA-2 (MPPM): Multiple Pulse-Position-Modulation Choose 4 from 10: 210 possibilities Choose 2 from 10: 45 possibilities t t 0 T 0 T Dimming level: 40% Dimming level: 20% SmartVLC 5/26
Next Subsection 1 Motivation 2 SmartVLC Design Implementation 3 Evaluation 4 Conclusion SmartVLC 6/26
Basic Requirements ❼ Smart lighting : fine-grained dimming levels ❼ VLC : optimized throughput SmartVLC 7/26
1. Support Fine-grained Resolutions Increasing the N in MPPM does NOT work! N ↑ � ⇒ Symbol Error Rate ↑ Symbol: N 1 time slots Symbol: N 2 time slots … à large N 10 -3 N=10 6 Symbol Error Rate (SER) N=30 N=50 N=80 N=120 4 2 0 0 0.2 0.4 0.6 0.8 1 Dimming level of the LED SmartVLC 8/26
1. Support Fine-grained Resolutions Proposed solution Use multiplexing to achieve high resolutions. 20% 30% t t 25% t After multiplexing, we are able to capture all the brightness. Before multiplexing ( N = 10 ) After multiplexing ( N = 10 ) 0.7 0.7 Normalized data rate Normalized data rate 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Dimming level of the LED (N=10) Dimming level of the LED (N=10) SmartVLC 9/26
Basic Requirements ❼ Smart lighting : fine-grained dimming levels SOLVED by multiplexing ❼ VLC : optimized throughput SmartVLC 10/26
2. Increase System Throughput Symbol definition ❼ S ∶< N , l > , N is number of slots, l is the brightness e.g. S 1 ∶< 10 , 20% > , S 2 ∶< 10 , 30% > How about S 1 ∶< 9 , 20% > , S 2 ∶< 11 , 30% > ? 20% 30% t t Obtain the dimming level in between of 20% and 30 % SmartVLC 11/26
2. Increase System Throughput Proposed solution Adaptive Multiple Pulse-Position-Modulation (AMPPM): use super-symbols . Super-symbol: ⟨𝑇 " 𝑂 " ,𝑚 " ,𝑛 " ,𝑇 & 𝑂 & ,𝑚 & ,𝑛 & ⟩ … … 𝑢 0 𝑇 " 𝑂 " ,𝑚 " 𝑇 " 𝑂 " ,𝑚 " 𝑇 & 𝑂 & ,𝑚 & 𝑇 & 𝑂 & ,𝑚 & Requirement: find the proper < N 1 , l 1 > and < N 2 , l 2 > to compose super-symbols for each required dimming level. SmartVLC 12/26
2. Increase System Throughput How to find < N 1 , l 1 > and < N 2 , l 2 > ? ❼ Step 1: Collect available symbols 10 -3 N=10 2.5 Symbol Error Rate (SER) N=30 N=50 2 1.5 1 upper bound 0.5 0 0 0.2 0.4 0.6 0.8 1 Dimming level of the LED SmartVLC 13/26
2. Increase System Throughput How to find < N 1 , l 1 > and < N 2 , l 2 > ? ❼ Step 2: Calculate the normalized data rate for all the collected symbols SmartVLC 14/26
2. Increase System Throughput How to find < N 1 , l 1 > and < N 2 , l 2 > ? ❼ Step 3: Obtain the optimal combination via multiplexing and slope-based selection. 0.88 S(21,0.524) S(21,0.571) N = 10 AMPPM N = 11 (with multiplexing) N = 12 0.85 Normalized data rate N = 13 N = 14 N = 15 0.8 N = 16 N = 17 N = 18 N = 19 0.75 N = 20 N = 21 without multiplexing 0.7 0.5 0.55 0.6 0.65 0.7 Dimming level of the LED SmartVLC 15/26
Basic Requirements ❼ Smart lighting : fine-grained dimming levels SOLVED by multiplexing ❼ VLC : optimized throughput SOLVED by AMPPM SmartVLC 16/26
Recap LED light Intensity Time Data Compensation Compensation average -based approach Data (decoding unit) Compensation average -free approach Data (decoding unit) Data (decoding unit) Data (decoding unit) Our proposed average approach SmartVLC 17/26
Next Subsection 1 Motivation 2 SmartVLC Design Implementation 3 Evaluation 4 Conclusion SmartVLC 18/26
3. Implementation Available platforms ❼ High-end: USRP (≈ 5000 ✩ ) , WARP ( 4900 ✩ ) ❼ Low-end: Arduino ( ≈ 20 e ), BeagleBone Black (BBB, ≈ 65 e ), Raspberry Pi ( ≈ 40 e ) BBB is selected in this project ❼ PRUs (similar to micro-controllers): BBB has two 200 MHz, 32-bit PRUs. Used for sampling and operating LEDs. ARM PRU Data Bridge SmartVLC 19/26
3. Implementation Diagram of the front-end Transmitter and Receiver Ambient Transmitter Receiver light Photodiode Power Photodiode BBB BBB MOSFET LED Amplifier ADC Snapshot of the prototype Transmitter Receiver SmartVLC 20/26
Next Subsection 1 Motivation 2 SmartVLC Design Implementation 3 Evaluation 4 Conclusion SmartVLC 21/26
Evaluation: Static Scenario Setup: fix the window blind Results: throughput vs. distance 120 100 Throughput (Kbps) 80 60 40 dimming level=0.18 dimming level=0.5 20 dimming level=0.7 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Distance (m) Observations ❼ Reliable communication within 3.6 meters ❼ Maximum throughput is ≈ 107 Kbps (dimming level = 0.5) SmartVLC 22/26
Evaluation: Dynamic Scenario Setup: lift the window blind Results: throughput vs. at a constant speed ambient light changes 110 Throughput (Kbps) 100 90 80 70 60 50 0 10 20 30 40 50 60 70 Time (second) Ambient light: weak � → strong Observations ❼ The ambient light does not change averagely. SmartVLC 23/26
Evaluation: Comparison Comparison with OOK-CT and MPPM 120 100 Throughput (Kbps) 80 60 AMPPM 40 OOK-CT MPPM 20 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Dimming level of the LED Observations ❼ AMPPM outperforms OOK-CT (increases the throughput by 40% on average) ❼ AMPPM outperforms MPPM (provides non-flickering & increases the throughput by 12% on average) SmartVLC 24/26
Conclusion Co-design smart lighting and VLC: 1 AMPPM : fine-grained resolution & high throughput 2 Implementation : low-end platform 1 3 Evaluation : static & dynamic scenarios 4 Others : heuristic coding scheme, brightness adaptation... 1 Cited by OpenVLC 1.2 SmartVLC 25/26
Looking for PhD position! SmartVLC 26/26
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