[Hackrf-dev] Cell Extender Concept?

[Michael Ossmann]

On Wed, Jul 03, 2013 at 02:14:24AM -0400, Russell Hande wrote:

>

> I am kicking around the idea of perhaps trying to make a cellular

> network extender (right now VZW LTE would be the target). I'm not sure

> if it is even possible.


It might be possible with four Jawbreakers, but even then it would be
quite tricky.  LTE is bi-directional, and Jawbreaker is half-duplex.
You would need a TX Jawbreaker and RX Jawbreaker facing the base station
and another TX Jawbreaker and RX Jawbreaker facing the mobile.  And you
would need to somehow keep them from interfering with each other.

I imagine that there are better solutions than SDR and certainly better
than Jawbreaker.


> Concept 1 would use an RTL Dongle to receive, and the HackRF to

> transmit. Problem is, LTE is about 9MHZ wide here, so I doubt RTL can

> help with its 2MSPS sampling rate.


Correct.


> Concept 2 would use the HackRF for both, but switch between RX and TX

> extremely fast. How fast can we switch back and forth?


We haven't pushed the limits, but my guess is that the minimum (with
some work) would be somewhere between 50 and 500 microseconds.  Since
LTE carries data simultaneously in both directions it's irrelevant
anyway.

It might be interesting to experiment with relaying other technologies,
though.  I suggest starting with something simple like remote keyless
entry systems, radio controlled toys, pagers, etc.