Alternative Communications : Survey and Idea

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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.
Alternative Communications : Survey and IdeaLee, GunheeContents
  • 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.
  • 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
  • Idea
  • Can we use a frequency (in this case, the color of light) to increase the efficiency of encoding?
  • 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
  • Example ConstellationGreenCyanYellowBlueWhiteBlackMagentaRedColor 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.
  • 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
  • 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)
  • 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
  • Laser Comm.
  • High speed, directional
  • This is an experimental implementation
  • 8-beam laser link, 1 Gbit/s at 2 km.
  • 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
  • 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
  • n-Body ProblemT1If there are more than three coils, a transmitter cannot properly generate current because of collisionR?T2Chain Reaction ProblemTR1R2Even if Tx range of T doesn’t reach R2, R2 get unnecessary current from R1. Also there is a possibility of further propagation.Conclusion
  • Using NFI or MFAN as an alternative method for wireless network seemshard
  • Also, it suffers from heavy decaying compared to far-field radiation
  • 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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