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Mbc system

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Mbc system Mbc system Presentation Transcript

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  • METEOR BURST COMMUNICATION A SEMINAR ON: 2
  • •Introduction •Meteor •Principle •Why now? •Procedure for MBC • Error correction •Meteor scatter modes •Technological advancements •Advantages •Shortcomings •Applications •Conclusion •Future scope •References •Thanks 3
  • 4 Communication is very much significant in today's environment Meteor burst communication is a type of communication technique Basic idea is to bounce radio signals by using meteor trails created Attractive option for application including secure independent reliable and low data rate communication
  • Those having orbit around sun in a path that coincides with earth Occur at a rate of 2 to 8 billion daily or roughly 50,000 per second Enters at a speed of 75-80 kms per second Friction between meteor and earth atmosphere cause it to vapourise 5
  • Vaporization/burning causes formation of trail of ionized particles in E layer This meteor trail is used for communication called meteor burst communication It is also called as meteor scatter communication or meteor trail communication Meteor shower from space 6
  • The rate at which meteors enter the Earth’s atmosphere peaks at around 6:00 AM local time Between midnight and 6:00 AM the Earth is turning into the path of oncoming meteors Meteors strike with higher velocity during this time. 7
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  • The meteor strike rate also varies annually. Meteor rates are greater in summer than winter The frequency that can be reflected by the trail depends upon intensity of ionization which depend upon the relative size of meteor Typical range is between 30 MHz and 50 MHz 9
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  • As meteors are vaporized in the upper atmosphere, they leave behind ionized trails sufficiently dense to reflect radio waves in the HF and VHF range. A long trail lasts only 15 seconds – most trails are less than 1 second long 11
  • Trails are classified as: Under dense (n < 2*1014 m-1) Over dense (n >= 2*1014 m-1) 12
  • Over dense: Reflection Under dense: excitation Geminids meteor shower of 2010 13
  • This system have low error rate and safer than satellite communication Safety of data transfer Available resource 14
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  • •Master station, receiving station/sensors •Transmitter-receiver and Antenna •Small laptop for storage with message buffering •Transmission can be simplex half duplex or full duplex 16
  • • Antennas do not need to have high gain • Lower-gain antennas illuminate more trails • Higher-gain antennas illuminate weaker trails 17
  • Master station sends a probe of simple continuous tone of fixed frequency signals When receiver receives probe it gives an acknowledgment Transmission of data occurs 18
  •  The period of searching between usable trails is known as the wait time. communications are buffered into storage If more remote stations are present the probe will contain address code of intended receiver If any other stations receive this probe it will remain idle 19
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  • Since individual trails last for only a short time, information must be sent in small packets The exact time a trail will occur is unknown, so the information must be sent repeatedly. To keep the SNR high, the signal bandwidth should be as narrow as possible. 21
  • Should prevent the transmission of data when no suitable path exists Two methods 1)Forward error correction code(FEC) 2) Automatic repeat request(ARQ) 22
  • The earliest experiments with MS communications used CW and AM phone. Today, the following modes are used: HSCW SSB FSK-441 Most of the meteor Scatter communication now uses FSK-441 23
  • CW sent at high speeds (200 wpm or more) HSCW activity occurs primarily in the following band segments: 50.250 – 50.300 MHz 144.100 – 144.150 MHz 222.000 – 222.200 MHz 24
  • Used primarily on 6 m Can be used with random meteors, but generally works better during a meteor shower SSB activity occurs primarily in the following band segments: 50.125 – 50.250 MHz 144.200 – 144.250 MHz 25
  • Uses triplets of 4 tones to transmit data 882, 1323, 1764, 2205 Hz Each character is sent as a 3 tone sequence 43 Character alphabet (letters, numbers . , / ? # $ <sp>) Single tone characters used for shorthand messages: 26
  • Data rate = 147 characters per second (3 tones/char) Used for meteor scatter communications Most activity takes place near 50.270 MHz 27
  •  JANET by Canada  COMET(COmmunication by MEteor Trails) by NATO  SNOTEL(SNOw pack TELmetry) by united states  AMBCS(Alaskan Meteor Burst Communication System) 28
  • 29 VHF convertors: converts any radio terminal into a MBC terminal ADAPTIVE SIGNAL RATES: signal rates can be varied according to SNR from trail to trail and within the trail ADAPTIVE FILTERING: filtering allows high efficiency at receiver side
  • Independent :user owns the system. Less likely to compromised Uses only one frequency: Advantages over high frequency system. Light and durable equipment and easily deployed Able to survive nuclear war 30
  • Strong confidentiality Easy to prevent the influence of interference station  Communication, good stability, less affected by the ionosphere disturbances and Aurora Sunspot activity is relatively small. 31
  • ADVANTAGES Very low error rate about 1/50000 Once the trail burns one cannot know the location of Transmitter or Receiver. 32
  •  Low data rate. Not suitable for high volume users Limited by distance Not suitable for voice communication 33
  • 1.Natural satellite:  Equivalent to natural satellite But less expensive No need to launch satellite 34
  • 2.During war Communication during war Not affected by nuclear explosion or interference Stations are remote 35
  • 3.Civil:- Aircraft and vehicle scheduling Forest fire alarm Harsh environment communication Data acquisition Broadcasting 36
  • Very effective mode of communication By using advanced technologies data rate can be improved Can replace satellite 37
  • A naturally occurring phenomenon, can improve the network performance. Able to replace existing communication technique 38
  • National communication system –Technical information bulletin Wikipedia http://prezi.com/nmconopethm-/meteor-burst/ www.nsa.gov/public_info 39
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