Ihab,
You may want to try replacing the gr-dvbt ofdm_sym_acquisition block
with the gr-isdbt ofdm_sym_acquisition block. A quick test here shows
that it works significantly better. Just leave the freq. error output
unconnected.
The 64QAM 2/3 rate will require a fairly powerful CPU for real-time
decoding.
Ron
On 11/26/2015 09:22 AM, Federico Larroca wrote:
Hi Ihab,
Those "restart aquisition" are generated by the ofdm_sym_acquisition
block when it does not find a peak on the correlation function he uses
to detect the beginning of the OFDM symbol. You should verify there is
indeed a DVB signal precisely at 570 MHz. To do this you may use our
"Sym Align OFDM" block (not a very nice name) available with gr-isdbt
(https://github.com/git-artes/gr-isdbt) and check that you see a
"triangle" (please refer to the readme, the examples, and even the
issues on our git). The symbol alignment is totally equivalent between
DVB-T and ISDB-T.
Moreover, I see several "O"s, meaning that somewhere samples are being
dropped. That does not help either. If you do not have a very fast
machine, you may use at the beginning of the flowgraph a "Stream to
Vector" followed by a "Vector to Stream" with a very big "Num Items"
(some millions).
best
Federico
2015-11-26 12:59 GMT-03:00 Ihab Zine <ihab.zin...@gmail.com
<mailto:ihab.zin...@gmail.com>>:
Hi,
I'm trying to receive a live signal from an antenna on the roof
through a cable connected to my SDR (hackrf one ).The bandwidth of
the DVB-T in ireland is 8 Mhz , and the parametetrs Here in
ireland as following:
Bandwidth: 8 MHz
Stream code rate (hi prio): FEC 2/3
Stream code rate (lo prio): FEC 2/3
Modulation: QAM 64
Transmission mode: 8k mode
Guard interval: 1/32
Hierarchy: none
net_data_rate = 24.128 Mbits/s
I used dvbt_rx_demo_8k_QAM64_rate78.grc flow graph with the
following changes :
*
frequency of hackrf one = 570 Mhz, sampling rate = ((8*8e6)/7).
*
Cyclic Prefix to (8192/32, is this right?)
*
Code Rate HP : 2/3
*
Code Rate LP : 2/3
*
Guard Interval : 1/32
The problem i have is that no output data coming out after the
demod_reference_signals BLOCK(no cancellation map), and got the
following:
restart aquisition
OOrestart aquisition
d_freq_offset: -5
Od_freq_offset: -5
d_freq_offset: -5
d_freq_offset: -5
d_freq_offset: -5
d_freq_offset: -5
d_freq_offset: -5
d_freq_offset: -5
restart aquisition
OOd_freq_offset: -5
d_freq_offset: -5
so I had to add a signal source to shift the signal. After shfting
the signal i got the following :
restart aquisition
restart aquisition
restart aquisition
restart aquisition
Orestart aquisition
I have read a lot about DVB , mapping ,ofdm and others, i have
spent weeks on this but still the same problem, if it is
synchronization problem what i should do?
So please i need a some help with this problem .
Thanks
Ihab
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