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  • 4 months later...

You have 2 options:

1) Use 2x HackRFs (1x receiver, 1x transmitter) - due to the 1/2 duplex nature

2) Use a bladeRF - as its full-duplex

Edited by midnitesnake
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  • 1 month later...

I can think of another option but not with an analog GSM radio.

Use a single HackRF1 and set it to time division multiplex once a carrier is detected (46 mS receive or transmit and 4 mS idle) on a single frequency to sync with another HackRF1 on the opposite cycle. It's like having two, two stroke engines exactly operating exactly 180 degrees out of phase. The antenna ports (RX/TX) can either have their own antenna but will have better performance with a circulator in between them to feed a single antenna.

DMR radios do a form of this today, albiet on two different frequencies to offer two voice paths. But a simplex DMR repeater sits in the receive mode and will sync with the first carrier to come up when an operator accesses it. The repeater starts cycling and listens for DMR packets on the receive cycle. Once a payload is recovered it is then fed to the input buffer of the transmitter output cycle and wraps the output in the repeater output protocol to announce the output to the other receivers, all on the same frequency.

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  • 1 month later...

You have 2 options:

1) Use 2x HackRFs (1x receiver, 1x transmitter) - due to the 1/2 duplex nature

2) Use a bladeRF - as its full-duplex

I can think of another option but not with an analog GSM radio.

Use a single HackRF1 and set it to time division multiplex once a carrier is detected (46 mS receive or transmit and 4 mS idle) on a single frequency to sync with another HackRF1 on the opposite cycle. It's like having two, two stroke engines exactly operating exactly 180 degrees out of phase. The antenna ports (RX/TX) can either have their own antenna but will have better performance with a circulator in between them to feed a single antenna.

DMR radios do a form of this today, albiet on two different frequencies to offer two voice paths. But a simplex DMR repeater sits in the receive mode and will sync with the first carrier to come up when an operator accesses it. The repeater starts cycling and listens for DMR packets on the receive cycle. Once a payload is recovered it is then fed to the input buffer of the transmitter output cycle and wraps the output in the repeater output protocol to announce the output to the other receivers, all on the same frequency.

The solution was demonstrated this past weekend before TadHack 2015 @ IIT and I've posted about it here: https://forums.hak5.org/index.php?/topic/36044-wideband-sdr-successfully-demonstrated-before-tadhack-2015/

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  • 5 weeks later...

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