Slide
A Multi-‐Element VLC Architecture for High Spatial Reuse
Prabath Palathingal1, Murat Yuksel1, Ismail Guvenc2, and Nezih Pala2 1 University of Nevada, Reno 2 Florida International University [email protected]
Project website: https://sites.google.com/site/nsfvlc/
VLCS 2015
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Why Multi-‐Element/Stream VLC?
Unused space
V i si b
le lig ht do
wnlo ad
LED Array
Photo-‐ detector
Single data stream PHY solu9on Large divergence – for smooth ligh9ng
Mul9ple data streams Narrow divergence – for higher spa9al reuse Spherical structures – to retain smooth ligh9ng VLCS 2015
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Problem Statement Ø Develop an efficient spatial reuse mechanism that – takes full advantage of the directionality of LEDs – provides simultaneous uniform lighting and mobile communication across a room
Ø Challenges – – – –
Handle the line-‐of-‐sight (LOS) alignment management Implement seamless communication across the room Resolve inter-‐LED interference Balance the tradeoff: uniform lighting and high spatial reuse
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The Architecture
le lig ht do V i si b
ad wnlo
Photo-‐ detector
ht do le lig
Data upload
Router with soEware-‐ defined LOS management
V i si b
A transmiIer: LED board
wnlo ad
The Internet
Data upload
RF upload
Photo-‐ detector
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The Architecture Ø Main features – Allows multi-‐user communication in a room. – Seamless handling of mobility of receivers for seamless communication. – Hybrid RF/VLC communication mechanism. VLC is used for download and RF for upload.
Ø Main components – The Bulb – RF/FSO LOS management protocol VLCS 2015
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The Bulb (as an AP) Ø Provides uniform lighting and simultaneous multiple data downloads Ø Hemisphere with multiple circular layers of LED transmitters Ø The transmitters are arranged so as to increase the spatial reuse Ø Each transmitter is connected to the router to achieve seamless steering of data across the bulb
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The Bulb (as an AP) Ø Transmitter placement on the
The bulb
bulb – θ, Angle of placement of the transmitter from the normal of the bulb – α, Angle between the transmitters in the same layer. – Φ, Divergence angle of the transmitter. – Ln , Range of the transmitter where communication is possible.
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α ϑ
Slanted Normal
Ø
Ln
N(x,y) Coverage Area
ϑ
Z
Perpendicular Normal
O(x,y) Normal Distance (DN)
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RF/VLC Hybrid LOS Management Ø Association Mechanisms – Join with LED-‐RAT – Maintain – Leave
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Join with LED-‐RAT LED-‐RAT Tx B
SECAoR nCnHe c Frtaem d es
es radm CneHc Fte SECAoRn
ACK|Rx A|Tx A
Rx A
Tx B
Rx B
Router with soEware-‐ defined LOS management
Tx A
Tx A
ACK|Rx B|Tx B
Rx B
Rx A
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Join with LED-‐RAT Ø Every bulb sends SEARCH frames Ø Receivers filter the frame with the maximum intensity Ø ACK verification Ø Updating LED-‐RAT
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Maintaining the Link
LED-‐RAT
Tx B
Rx AB
Tx B
Rx BA
Router with soEware-‐ defined LOS management
SECAoR nCnHe c Frtaem d es
ACK|Rx B|Tx A
Tx A
es eradm CneHc Ft SECAoRn
A transmiIer: LED board
Tx A
ACK|Rx A|Tx B
Rx B
Rx A
Trade off exists on the time interval between the SEARCH frame transmissions VLCS 2015
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Partitioning Algorithm Ø Divide the transmitters into sections with respect to receiver positions Ø Each “section” serves the same data stream to the respective receiver
Y-axis
Ø Facilitates mobility
X1,Y1 Xmid,Ymid X2,Y2
X,0
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X-axis 12
An Initial Evaluation Ø 6m x 6m x 3m Ø The bulb in the middle of the ceiling Ø 25 transmitters on 3 layers: 30⁰, 45⁰, 70⁰ Ø 8 transmitters per layer Ø Two receivers at random positions on the floor – 80K runs Ø Any signal received from the transmitters assigned to the other receiver is considered as noise Ø Transmitter radius: 4cm PD radius: 3.75cm Bulb radius: ~11cm Ø 12W transmitter, e.g., 600 LEDs with 20mW each Ø 25 transmitters on the bulb VLCS 2015
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Divergence angle = 45⁰ 15
High interference
SNR (dB)
10
High spa>al reuse
5
0
Max. SNR Min. SNR Avg. SNR
Low signal strength
−5
−10 0
1
2
3
4
5
6
7
8
Distance between laptops (meter)
3-‐region behavior! VLCS 2015
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Effect of Divergence angle 450
200
Large divergence angle increases the distribution of light across the room but can create sizable interference
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Spatial reuse is better as expected from narrower divergence angles For smooth lighting: need more LEDs with narrower divergence 15
Three Regions Region 3 Region 2
Region 1 High interference
Low signal strength VLCS 2015
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Effect of Divergence angle 8 7
SNR (dB)
6 5 4 1 degree 20 degree 45 degree
3 2 1 0 0
2
4
6
8
10
Distance between laptops (meter)
Is there an op>mal divergence angle? VLCS 2015
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Effect of Divergence angle 12 50 W 25 W 20 W 10 W 5W
100-‐160
10
Avg. SNR (dB)
seems to be the best
8
6
4
2
0 5
10
15
20
25
30
35
40
Divergence Angle (degree) VLCS 2015
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Effect of Room Size
Room height is 3m. Floor’s edge is varied.
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SNR in region 1 reduces much slower than the floor area
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SNR in region 3 reduces along with the floor area
SNR (dB)
LED divergence: 200 Tx power: 20W
1x 4m 8m 12 m 16 m 20 m
6
2
4x 9x
0 −2 −4 −6 0
5
10
15
20
25
30
Distance between laptops (meter) VLCS 2015
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Effect of Room Size & Tx Power
Increase tx power along with the floor size.
LED divergence: 200
12
10
6
25x
4x
8
SNR (dB)
SNR in region 1 saturates but does not reduce
16x
1x 9x
4m 8m 12 m 16 m 20 m
4
SNR in region 3 consistently increases but sublinearly tx power
2
0 0
5
10
15
20
25
30
Distance between laptops (meter) VLCS 2015
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Summary Ø A multi-‐element VLC architecture that – supports multiple simultaneous data streams and illumination – use an RF/FSO hybrid LOS management protocol
Ø Reasonably high SNRs observed Ø A heuristic to partition the LEDs on the bulb/AP Ø 3 regions: a guide to organize room layouts
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Future Work Ø Test the architecture with – More LEDs – More receivers – Varying Tx power of LEDs
Ø The Bulb: Optimize the # of LEDs and their placements Ø Use multiple bulbs/APs in a room Ø Joint optimization of illumination and communication in a room
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Other or Upcoming VLC Work Ø Extended results (with wall reflections): – Y. S. Eroglu, A. Sahin, I. Guvenc, N. Pala, and M. Yuksel, Multi-‐Element Transmitter Design and Performance Evaluation for Visible Light Communication, to appear in Proceedings of IEEE GLOBECOM Workshop on Optical Wireless Communication (OWC), San Diego, CA, December 2015.
Ø VLC localization: – A. Sahin, Y. S. Eroglu, I. Guvenc, N. Pala, and M. Yuksel, Hybrid 3D Localization for Visible Light Communication Systems, to appear in IEEE/ OSA Journal of Lightwave Technology. – A. Sahin, Y. S. Eroglu, I. Guvenc, N. Pala, and M. Yuksel, Accuracy of AOA-‐ Based and RSS-‐Based 3D Localization for Visible Light Communications, Proceedings of IEEE VTC, Boston, MA, September 2015. – Y. S. Eroglu, I. Guvenc, N. Pala, and M. Yuksel, AOA-‐Based Localization and Tracking in Multi-‐Element VLC Systems, Proceedings of IEEE Wireless and Microwave Technology Conference (WAMICON), Cocoa Beach, FL, April 2015. VLCS 2015
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Questions?
Project website: https://sites.google.com/site/nsfvlc/
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