DMR Repeater Talk-Around

[notwenif]

This is not accurate.

some radios are capable of 2 slot simplex operation. there is also some radios that can act as a repeater on a somplex channel as well.

Some radios do exist where the hardware could do this. Motorola has updated some of it's firmware to allow this. In the world of DMR tier 2 however, this isnt found. Not to mention the complexityof configuration all while offering little benefit and tons of risks with tdma slot timing, bandwidth masking etc.

This is not accurate.

some radios are capable of 2 slot simplex operation. there is also some radios that can act as a repeater on a somplex channel as well.

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[kayn1n32008]

Some radios do exist where the hardware could do this. Motorola has updated some of it's firmware to allow this. In the world of DMR tier 2 however, this isnt found. Not to mention the complexityof configuration all while offering little benefit and tons of risks with tdma slot timing, bandwidth masking etc.



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Both Hytera and Motorola offer 2 slot simplex, for their tier 2 gear, so to say that simplex can only be one slot is not accurate.

I beleive Hytera also now offers a simplex repeater option as well. Basically it parrots one time slot to the other on a simplex frequency, with the radio that is doing the repeating provids the timing reference for the other radios.

 

[JRayfield]

And I think I remember seeing that '2 slot simplex' is also part of the Tier 2 ETSI DMR standard now.

John Rayfield, Jr.

Both Hytera and Motorola offer 2 slot simplex, for their tier 2 gear, so to say that simplex can only be one slot is not accurate.

I beleive Hytera also now offers a simplex repeater option as well. Basically it parrots one time slot to the other on a simplex frequency, with the radio that is doing the repeating provids the timing reference for the other radios.

 

[notwenif]

And I think I remember seeing that '2 slot simplex' is also part of the Tier 2 ETSI DMR standard now.

John Rayfield, Jr.

That's awesome, do you have link to the standard? I am having trouble locating one so that I may correct my inaccuracies

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[nd5y]

do you have link to the standard?

Digital Mobile Radio Association | The DMR Standards
I'm not sure if the links are to the current documents but they link to the ETSI web site. You can find the current documents at
ETSI - Digital Mobile Radio
Click on the Standards tab.

 

[notwenif]

I think their may need to be some clarification regarding the OPs question

According to The Motorola Patent regarding Talkaround*

“A subscriber unit automatically selects repeater access mode, if a repeater is available, or talk-around mode, if a repeater is not available (500).

The subscriber unit initiates a call by transmitting a call setup request on the outbound channel used by the repeater (510), and by monitoring the outbound channel to detect a response from the repeater (520). If a response is received within a timeout period, the subscriber unit continues the call by transmitting on the inbound channel (530, 540).

Otherwise, the subscriber unit continues the call using talk-around mode, by transmitting on the outbound channel (530, 550). In this process, the repeater monitors the outbound channel to determine when a call setup request is transmitted by the subscriber unit (610), and responds accordingly on the outbound channel (620, 630), thereby indicating its availability. The repeater then monitors the inbound channel and retransmits, or repeats, signals received via the inbound channel, on the outbound channel (640, 650, 660).”


Further, what i found on another website regarding what i think we are now talking about regarding Dual-slot TDMA simplex operation.Motorola refers to this as Dual Capacity Direct mode, and this is very different then Talkaround detailed above.

Dual Capacity Direct Mode

From Wayne Holmes (DJ0WH)


“a feature available in all second generation MOTOTRBO radios which allows two slot operation on simplex. Not only does it offer two slot operation but is also currently the only product which complies with ETSI TS102-361 §1-4 v2.1.1 for 6.25e operation on simplex.
DCDM - also known as 6.25 kHz Equivalency Direct Mode (6.25e DM) - provides additional spectral efficiency by supporting up to two simultaneous Direct Radio-to-Radio Mode subscriber calls within a 12,5kHz allocation of spectrum.”

Now, i have looked at the ETSI TS102-361-1(2) standard and i am sure if the (Rx) frequency is identical to the (Tx) Frequency.

I am not sure about everyone else but i have learned one heck of alot during this short time researching this topic.

 

[chief21]

According to The Motorola Patent regarding Talkaround*

“A subscriber unit automatically selects repeater access mode, if a repeater is available, or talk-around mode, if a repeater is not available (500).

The subscriber unit initiates a call by transmitting a call setup request on the outbound channel used by the repeater (510), and by monitoring the outbound channel to detect a response from the repeater (520). If a response is received within a timeout period, the subscriber unit continues the call by transmitting on the inbound channel (530, 540).

Otherwise, the subscriber unit continues the call using talk-around mode, by transmitting on the outbound channel (530, 550). In this process, the repeater monitors the outbound channel to determine when a call setup request is transmitted by the subscriber unit (610), and responds accordingly on the outbound channel (620, 630), thereby indicating its availability. The repeater then monitors the inbound channel and retransmits, or repeats, signals received via the inbound channel, on the outbound channel (640, 650, 660).”

Notwenif -

The info you uncovered is most interesting, especially the blurb about the Motorola version of talk-around. It appears as if DMR talk-around is NOT similar to conventional talk-around as many of us thought it was.

The way I read this information suggests that DMR repeaters actually have two receivers... one for the inbound frequency (typical) and another monitoring the outbound frequency (quite different). This could explain why some posters have indicated that signals on the repeater talk-out frequency could interfere with other users of the repeater. Those posters never explained how this might occur and others (including myself) could not understand how a low-power signal on the repeater talk-out frequency could disturb the repeater itself.

Thanks for posting your findings. DMR is truly another world. Very interesting, indeed!

John AC4JK