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Alternative Communications : Survey and Idea

Alternative Communications : Survey and Idea. Lee, Gunhee. Contents. Fiber Optical comm . Free-Space Optical comm. (FSO) Visible light comm. Laser comm . Near-Field Induction comm. (NFI) or Magnetic Field Area Network (MFAN). Fiber Optical Comm.

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Alternative Communications : Survey and Idea

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  1. Alternative Communications : Survey and Idea Lee, Gunhee

  2. Contents • Fiber Optical comm. • Free-Space Optical comm. (FSO) • Visible light comm. • Laser comm. • Near-Field Induction comm. (NFI) or Magnetic Field Area Network (MFAN)

  3. Fiber Optical Comm. • In fiber optic comm., the carrier wave is visible light ( at ) • Due to very high frequency, modulating the electric field is very difficult • Nearly all optical comm. systems use intensity modulation • On-off keying (OOK), which only uses two states for encoding, is used

  4. Idea • Can we use a frequency (in this case, the color of light) to increase the efficiency of encoding?

  5. Color-code Intensity Keying • Similar to QAM scheme, but uses colors instead of phase. Constellation diagram would be intensity vs. color in polar coordinates • RGB color diodes (LEDs or lasers) can represent 8 colors – black, red, green, blue, yellow, cyan, magenta, white – by combination. • Modern Bayer-masked CCDs can easily distinguish the color, hence reducing the complexity of the system

  6. Example Constellation Green Cyan Yellow Blue White Black Magenta Red

  7. Color Multiplexing • There is a patent on Color Multiplexing in fiber optic transmission(Quick, 1980) • It is very different from my idea, however. • CIK uses multiple source of colored diodes, but CM uses a prism to disperse white light into spectrums • Also, my idea uses Bayer-masked CCDs to distinguish colors, but their method uses photoelectric detectors.

  8. Another Issue • Optical fiber is unarguably better than UTP cable in terms of interference and throughput • However, optical fiber is made of glass, which is fragile and stiff • Glass fiber is also expensive, so there are two alternatives • Find another material (It’s not my area) • Eliminate the cable

  9. Free-Space Optical Comm. • Compared to conventional wireless comm., • Minimum interference • High speed • Security • There are two main implementations • Visible light comm. (non-directional) • Laser comm. (directional)

  10. Visible Light Comm. • Lighting + Communication (multi-purpose) • Started by Nakagawa Lab., Keio University, Japan (2003). (will be in IEEE 802.15) • Only uses visible light that is not injurious to vision • 10 kbit/s using ordinary fluorescent lamps • 500 Mbit/s using LEDs

  11. Laser Comm. • High speed, directional • This is an experimental implementation • 8-beam laser link, 1 Gbit/s at 2 km.

  12. Networking Viewpoint • Both laser comm. and visible light comm. are not complete technologies • They can make a link, not a network • A novel idea to establish networks is not found yet • Networking using directional comm. • Idea : almost no interference and collisions in these comms, so ways to exploit these can be useful

  13. Near-Field Induction • Core technology of NFI is patented by a company, FreeLinc • FreeLinc made some products • Wireless energy transfer • I found two critical problems of this technology which should be solved, however

  14. n-Body Problem T1 If there are more than three coils, a transmitter cannot properly generate current because of collision R ? T2

  15. Chain Reaction Problem T R1 R2 Even if Tx range of T doesn’t reach R2, R2 get unnecessary current from R1. Also there is a possibility of further propagation.

  16. Conclusion • Using NFI or MFAN as an alternative method for wireless network seemshard • Also, it suffers from heavy decaying compared to far-field radiation

  17. References • H. Willebrand, B. S. Ghuman, Free space optics : enabling optical connectivity in today’s networks, 2005 • A. Mahdy, J. S. Deogun, Wireless optical communication : a survey, 2004 • A. Attarian, A survey of terrestrial and free space based optical communications systems, 2007 • W. H. Quick, Means for sensing and color multiplexing optical data over a compact fiber optic transmission system, 1980

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