meteor burst communication - techinal seminar for electronics students prepared by ajai

METEOR BURST METEOR BURST COMMUNICATIONCOMMUNICATION

BY BY AJAI KRISHNA.VAJAI KRISHNA.V

1MV08EC0051MV08EC005

CONTENTCONTENTS S

What are meteoroids ?What are meteoroids ?

Role of Meteor trials in communicationRole of Meteor trials in communication

Procedure of Meteor Burst Procedure of Meteor Burst CommunicationCommunication

AdvantagesAdvantages

DisadvantagesDisadvantages

Developments and its Technological Developments and its Technological BreakthroughsBreakthroughs

ConclusionConclusion

What are Meteoroids???What are Meteoroids??? Meteoroids are small sand Meteoroids are small sand

like particles of debris in like particles of debris in the solar system.the solar system.

These particles orbit These particles orbit around the sun and around the sun and coincide with the earth’s coincide with the earth’s orbit. orbit.

Thousands enter the atmosphere with a very high velocity and get vaporized into ions

Role of Meteor Trails in Role of Meteor Trails in communicationcommunication

Meteor trails are created Meteor trails are created due to friction when due to friction when meteoroids enter earth’s meteoroids enter earth’s atmosphere.atmosphere.

Trail of positive-charged Trail of positive-charged ions and free electrons are ions and free electrons are left behind which last for a left behind which last for a short duration of time.short duration of time.

Meteor trails redirect the radio waves using Meteor trails redirect the radio waves using overdense trail and underdense trail.overdense trail and underdense trail.

Overdense trails contain free electron density Overdense trails contain free electron density great enough to reflect wave back to the earth great enough to reflect wave back to the earth much like a light reflecting from a mirror.much like a light reflecting from a mirror.

Occur rarely.Occur rarely.

Underdense trails allow penetration of the waves Underdense trails allow penetration of the waves and electrons act like small dipole antennas and and electrons act like small dipole antennas and reflect the wave back .reflect the wave back .

Occur frequently.Occur frequently.

Occurrence of number of meteor trails depend on Occurrence of number of meteor trails depend on the time of day and month of the year.the time of day and month of the year.

Early Morning have more number of trails than evening.

MBC have more effect from July to September

Trail length is anywhere between 10 to 20 miles long and with average radius of about 1 meter at head of the trail.

Meteor rate against Time Meteor rate against Time and Monthand Month

Procedure of Meteor Burst Procedure of Meteor Burst CommunicationCommunication

Frequency of range between 20 and 120 MHz.Frequency of range between 20 and 120 MHz. Transmissions can be either simplex , half duplex Transmissions can be either simplex , half duplex

or full duplex.or full duplex.

Master Station transmits a probe which the remote Master Station transmits a probe which the remote receiver station tuned to same frequency. receiver station tuned to same frequency.

Probe bounces against meteor trails until suitable path Probe bounces against meteor trails until suitable path exists for transmission.exists for transmission.

Receiver sends acknowledgement with same frequency.Receiver sends acknowledgement with same frequency.

The period of searching between usable trails is known as The period of searching between usable trails is known as wait time.wait time.

Wait times vary in proportion to the usable time of the trial. Wait times vary in proportion to the usable time of the trial.

Use of Forward Error Correction (FEC) and Automatic Use of Forward Error Correction (FEC) and Automatic Repeat RequestRepeat Request

(ARQ) is responsible for data transmission when no (ARQ) is responsible for data transmission when no suitable path exists.suitable path exists. Data rates range between 75 to 100 words per Data rates range between 75 to 100 words per minute if it is unencrypted.minute if it is unencrypted.

Upto 15 words per minute if encrypted.Upto 15 words per minute if encrypted.

Useful for low volume users who depend on Useful for low volume users who depend on accurate data.accurate data.

ADVANTAGESADVANTAGES

Independent of Satellites for systems which Independent of Satellites for systems which depend on satellite for communication.depend on satellite for communication.

Communication between two stations unlikely to Communication between two stations unlikely to be compromised.be compromised.

MBC is advantageous MBC is advantageous over High Frequency over High Frequency systems.systems.

MBC equipment is MBC equipment is light and durable and light and durable and manpack is manpack is deployable.deployable.

MBC has the ability to MBC has the ability to survive a nuclear war survive a nuclear war when satellites and when satellites and ground stations are off ground stations are off high priority targets.high priority targets.

DISADVANTAGESDISADVANTAGES

Low Data Rate where large data cant be sent in a Low Data Rate where large data cant be sent in a short span of time.short span of time.

Short distance coverage of 1200 miles max.Short distance coverage of 1200 miles max.

It is incompatible to voice signal .It is incompatible to voice signal .

DEVELOPMENTS AND TECHNOLOGICAL DEVELOPMENTS AND TECHNOLOGICAL BREAKTHROUGHSBREAKTHROUGHS

The first ever MBC system was JANET y a canadian The first ever MBC system was JANET y a canadian system in 1954. ARQ was not used and had 0.1 to 4 system in 1954. ARQ was not used and had 0.1 to 4 percent error rate.percent error rate.

In 1965 ,NATO developed MBC system which used ARQ In 1965 ,NATO developed MBC system which used ARQ and error rates reduced dramatically.and error rates reduced dramatically.

In 1970’s AMBCS (Alaskan Meteor Burst In 1970’s AMBCS (Alaskan Meteor Burst Communications Systems) was used by some Communications Systems) was used by some government agencies where it was of great use due to government agencies where it was of great use due to the fact that MBC did not experience the auroral the fact that MBC did not experience the auroral interference common to high frequency interference common to high frequency communications.communications.

IA Research Corporation, an american company IA Research Corporation, an american company developed a VHF converter which converts VHF radio developed a VHF converter which converts VHF radio to an MBC terminal. to an MBC terminal.

An equipment that allows Adaptive Signaling Rates An equipment that allows Adaptive Signaling Rates senses SNR and sets the signal rate accordingly, senses SNR and sets the signal rate accordingly, which in turn allows transmission of larger volumes of which in turn allows transmission of larger volumes of data.data.

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