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Difference between TDMA and ASTRO DIGITALS

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Aboulfad

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Please, can anybody help me by this question;what is the Diffrence between Astro Digital system and TDMA Digital? Thx.
 

loumaag

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Moved to it's own thread.
Please don't post off topic in an existing thread, thanks.
 

SCPD

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Hi Aboulfad;
Please, can anybody help me by this question;what is the Diffrence between Astro Digital system and TDMA Digital? Thx.
Astro is FDMA - multiple calls must use different frequencies.
TDMA calls can share the same frequency by taking turns - using alternating time slots.

P25 is moving towards TDMA so in the future you may see Astro 25 support TDMA slotted voice channels.
 

kb1ipd

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Please, can anybody help me by this question;what is the Diffrence between Astro Digital system and TDMA Digital? Thx.
TDMA = Time Division Multiple Access

Basic digital systems on ASTRO use a simple "FDMA" scheme where each conversation gets its own frequency. This is not really a multiple access method but simply assigns individual frequency channels. TDMA means that multiple transmissions can be on the same frequency. Each one gets its own time slot.

For example: if you had a simple TDMA setup where there were four transmissions per frequency channel you would have a system where one transmission broadcasts for a few milliseconds and then stops to allow the second channel to transmit for a few milliseconds and then the next. Each is assigned a "time slot." Of course these are short enough that the fact that the transmission is cut up into slots and not continuous is not enough to cause any problems with the sound being continuous to the human ear.

TDMA is a lot more complicated to decode because it's not just one data stream on a given frequency but as far as multiple access methods go it's actually pretty simple. Much more complex are CDMA (code division multiple access) and some of the newer versions that combine aspects of CDMA and TDMA or have dynamically assigned time slots and frequencies or those which incorporate spread-spectrum techniques.
 
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