9 May
2017
9 May
'17
6:53 p.m.
Dear all,
Most BTS code I have, generate only one or two 200 kHz channels, but I need
to test a receiver using several (multiplexed) 200 kHz channels, composing
approximately 5 MHz of total bandwidth. This should be a "valid" multiplex
signal (correct and "decodable" control channel). Can anyone pointout where
should I start to put together the software to generate a binary file with
such signal? I guess I can inspect the code of a BTS that supports two TRX
(two 200 kHz channels) but I would like to double check whether there is a
more direct approach.
Thanks beforehand,
Marcus Dias
UFPA - Lasse - LaPS
9 May
9 May
8:41 p.m.
Hi Marcus,
On Tue, May 9, 2017 at 9:53 AM, Marcus Dias <vmarcusv(a)gmail.com> wrote:
Most BTS code I have, generate only one or two 200 kHz
channels, but I need
to test a receiver using several (multiplexed) 200 kHz channels, composing
approximately 5 MHz of total bandwidth. This should be a "valid" multiplex
signal (correct and "decodable" control channel). Can anyone pointout where
should I start to put together the software to generate a binary file with
such signal? I guess I can inspect the code of a BTS that supports two TRX
(two 200 kHz channels) but I would like to double check whether there is a
more direct approach.
It sounds like you need a raw IQ sampled binary file at about 5 Msps.
Is that correct?
There are a variety of methods to achieve this depending on your
requirements. You could generate the multiplexed signal live with up
to 3 adjacent ARFCN channels (800 kHz separation) with a B200 and
osmo-trx with multi-ARFCN enabled.
But, it sounds like you just need a test file, so you could
post-process an existing single ARFCN signal file in Octave or Matlab
to carry multiple versions of the same GSM signal. That may or may not
be sufficient depending on your needs.
-TT
11 May
11 May
6:58 p.m.
It sounds like you need a raw IQ sampled binary file at
about 5 Msps.
Is that correct?
Thanks a lot for your hints!
If my math (sampling theorem) is not wrong, because I need a bandwidth
of 5 MHz (assuming only downstream transmission, given I will not use
upstream), it would require 5 Msps in case each sample is a complex number
or 10 Msps in case the samples are real-valued.
There are a variety of methods to achieve this
depending on your
requirements. You could generate the multiplexed signal live with up
to 3 adjacent ARFCN channels (800 kHz separation) with a B200 and
osmo-trx with multi-ARFCN enabled.
That is a good starting point. But I would need to increase the number
of 200 kHz to reach a total of 5 MHz.
But, it sounds like you just need a test file, so you
could
post-process an existing single ARFCN signal file in Octave or Matlab
to carry multiple versions of the same GSM signal. That may or may not
be sufficient depending on your needs.
Yes, exactly: just a test file. I am still studying the GSM PHY and I
suspect if I simply position the ARFCNs in different frequencies I
will end up with an invalid GSM signal (that is, it will not be properly
decoded by the Keysight VSA equipment that I have to interface to).
Marcus Dias
UFPA - Lasse - LaPS
2017-05-09 15:41 GMT-03:00 Tom Tsou <tom(a)tsou.cc>cc>:
Hi Marcus,
On Tue, May 9, 2017 at 9:53 AM, Marcus Dias <vmarcusv(a)gmail.com> wrote:
Most BTS code I have, generate only one or two
200 kHz channels, but I
need
to test a receiver using several (multiplexed)
200 kHz channels,
composing
approximately 5 MHz of total bandwidth. This
should be a "valid"
multiplex
signal (correct and "decodable" control
channel). Can anyone pointout
where
should I start to put together the software to
generate a binary file
with
such signal? I guess I can inspect the code of a
BTS that supports two
TRX
(two 200 kHz channels) but I would like to double
check whether there is
a
more direct approach.
It sounds like you need a raw IQ sampled binary file at about 5 Msps.
Is that correct?
There are a variety of methods to achieve this depending on your
requirements. You could generate the multiplexed signal live with up
to 3 adjacent ARFCN channels (800 kHz separation) with a B200 and
osmo-trx with multi-ARFCN enabled.
But, it sounds like you just need a test file, so you could
post-process an existing single ARFCN signal file in Octave or Matlab
to carry multiple versions of the same GSM signal. That may or may not
be sufficient depending on your needs.
-TT
8:26 p.m.
Hi,
Yes, exactly: just a test file. I am still studying
the GSM PHY and I
suspect if I simply position the ARFCNs in different frequencies I
will end up with an invalid GSM signal (that is, it will not be properly
decoded by the Keysight VSA equipment that I have to interface to).
It should work fine. A GSM broadcast channel doesn't include its own
frequency, so you can just take it and position it anywhere (as long
as it's on an actual possible frequency).
In gr-osmosdr the siggen application even has a small hardcoded burst
sequence that's "good enough" for the E4406 VSA to lock onto.
Cheers,
Sylvain
2566
days inactive
2568
days old
3 comments
3 participants
participants (3)
-
Marcus Dias -
Sylvain Munaut -
Tom Tsou