2. Contents
OFDM
Visible light Communication
MIMO systems
Optical Spatial Modulation
Optical Spatial Multiplexing
Micro LEDs
OSM-OFDM using Micro LEDs
Inference
References
2
3. Modulation Vs Multiplexing
3
₪ Modulation – Mapping of the information on
changes in the carrier phase,
frequency or amplitude or
combination
₪ Multiplexing – Method of sharing a bandwidth
with other independent data
channels
4. Orthogonal Frequency Division
Multiplexing
OFDM is a combination of Modulation and Multiplexing
Digital data encoded on multiple carrier frequencies
Sub-carriers are orthogonal to each other
Used in Asymmetric Digital Subscriber Line connections
Need not be wireless 4
11. Visible Light Communication
systems
€ Uses visible light between 400 and 800 THz (780–375 nm)
€ Fluorescent lamps ( 10 Kbit/s ) , LEDs ( 500 Mbit/s )
€ Organic LEDs (OLED) as optical transceivers achieve 10 Mbit/s
€ Modulation transforms data into a series of light pulses
€ Frequency of light pulses is modulated & not the frequency of light
11
12. VLC - Motivation
∞ Visible light does not cause health problems
∞ Expensive patent-license is not needed
∞ No Electromagnetic Interference
∞ Safe to use in hospitals
∞ LEDs -the predominant choice - very short switching time 12
13. Multiple Input Multiple Output
system
13
Source: https://en.wikipedia.org/wiki/File:MIMO.png
16. Optical Spatial Multiplexing
(OSMX)
Each spatial channel carries independent information
Increases the data rate of the system
No additional cost on bandwidth or power
Bit Error Rate is more
Higher computational complexity
Inter-antenna synchronization is required
16
17. Micro LEDs
Diameter of about 12 µm
Can flicker 1,000 times faster than commercial LEDs
Enhanced quantum efficiencies for the same area
17
Source: www.element14.com
26. Inference
₪ OSM-OFDM using µLEDs
Better than OSMX-OFDM in terms of computational complexity
Achieves data rate up to 5.5 Gb/s
₪ OSMX OFDM
Data rates of up to 6 Gb/s are feasible
₪ BER depends largely on spatial separation between the transmitters(ds)
and on the half- power semi-angle of the µLEDs (φ1/2)
₪ Optimum conditions :- larger spatial separation, a smaller half
power semi-angle
26
27. References
1. M. Ijaz et al., "Optical spatial modulation OFDM using micro
LEDs," 2014 48th Asilomar Conference on Signals, Systems and
Computers, Pacific Grove, CA, 2014, pp. 1734-1738.
doi: 10.1109/ACSSC.2014.7094764
2. M. Ijaz et al., "Experimental proof-of-concept of optical spatial
modulation OFDM using micro LEDs," 2015 IEEE International
Conference on Communication Workshop (ICCW), London, 2015, pp.
1338-1343.
doi: 10.1109/ICCW.2015.7247364
3. R. Mesleh, H. Elgala and H. Haas, "Optical Spatial Modulation,"
in IEEE/OSA Journal of Optical Communications and Networking,
vol. 3, no. 3, pp. 234-244, March 2011.
doi: 10.1364/JOCN.3.000234
4. R. Mesleh, R. Mehmood, H. Elgala and H. Haas, "Indoor MIMO Optical Wireless
Communication Using Spatial Modulation," Communications (ICC), 2010 IEEE
International Conference on, Cape Town, 2010, pp. 1-5.
doi: 10.1109/ICC.2010.5502062
27
