4. 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
5. 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
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6. 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
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7. 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.
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9. 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
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11. 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
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17. • Antennas do not need
to have high gain
• Lower-gain antennas
illuminate more trails
• Higher-gain antennas
illuminate weaker
trails
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18. 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
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19. 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
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21. 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.
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22. Should prevent the transmission of data when
no suitable path exists
Two methods
1)Forward error correction code(FEC)
2) Automatic repeat request(ARQ)
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23. 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
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24. 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
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25. 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
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26. 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:
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27. Data rate = 147 characters per second (3 tones/char)
Used for meteor scatter communications
Most activity takes place near 50.270 MHz
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28. JANET by Canada
COMET(COmmunication by MEteor Trails) by NATO
SNOTEL(SNOw pack TELmetry) by united states
AMBCS(Alaskan Meteor Burst Communication System)
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29. 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
30. 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
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31. 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.
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32. ADVANTAGES
Very low error rate about 1/50000
Once the trail burns one cannot know the
location of Transmitter or Receiver.
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33. Low data rate. Not suitable for high
volume users
Limited by distance
Not suitable for voice communication
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