Hi Sara, On 23.06.2014 18:31, Sara Chérif wrote: > I plot the signal before the tx and after the rx on same graph to compare > between them while increasing noise to know how much noise can affect it > for different types of channel & frequency offset . But when I set noise to > zero , I find that the 2 signals are not the same ! why ?! They may be the > same but they are not synchronized . How to solve this problem ? > (Attached the loopback.grc & the graph) If one is delayed longer than the other, use the delay block to compensate for this.
> Second , There is a variable called sync word , I know that it is for > synchronization using schmidl and cox algorithm & I know that is takes > fft length & occupied carriers & pilot carriers > as it is written in "ofdm_rxrx.py > "if sync_word1 is None: > self.sync_word1 = _make_sync_word1(fft_len, occupied_carriers, > pilot_carriers)" > > But why I get an error syaying that " sync words must be fft length" when I > write in sync word 1 & sync word 2 fields in the tx & rx block : (128, > (range(-61,-42)+range(-41, -14) + range(-13, -7) + range(-6, 0) + range(1, > 7) + range(7, 14) + range(15, 42)+range(43,62),) , ((-42, -14, 14, 42,),) > ) ? Ok, this is a little much python parsing to do it in my head. Have you verified that len(<your range concatenation>) is actually correct? For my python interpreter, it's 117, not 128, just like the error said. > Third , I tried my parameters in loopback example & I got no error , but I > want to try tx_ofdm.grc with my parameters & put file sink after each block > to understand , but I got an error in tx_ofdm.grc . Why I got an error > while the same parameters don't give an error in loopback ?!! > Only I changed these parameters to be mine in tx & rx : > fft len=128 , CP =fft_len/8=16 , packet length=87 > occupied carriers = (range(-61,-42)+range(-41, -14) + range(-13, -7) + > range(-6, 0) + range(1, 7) + range(7, 14) + range(15, 42)+range(43,62),) > pilot carriers : ((-42, -14, 14, 42,),) > pilot symbols : (((-1+1j),(1-1j),(-1+1j),(-1-1j),),) > sync_word1=None , sync_word2=None > > Here is the full output when executing : > Using Volk machine: sse4_2_64_orc > Traceback (most recent call last): > File "/home/sara/trials/tx_ofdm.py", line 241, in <module> > tb = tx_ofdm() > File "/home/sara/trials/tx_ofdm.py", line 100, in __init__ > self.digital_ofdm_carrier_allocator_cvc_0 = > digital.ofdm_carrier_allocator_cvc(fft_len, occupied_carriers, > pilot_carriers, pilot_symbols, (sync_word1, sync_word2), length_tag_key) > File > "/usr/local/lib/python2.7/dist-packages/gnuradio/digital/digital_swig.py", > line 4312, in make > return _digital_swig.ofdm_carrier_allocator_cvc_make(*args, **kwargs) > TypeError: in method 'ofdm_carrier_allocator_cvc_make', argument 5 of type > 'std::vector< std::vector< gr_complex,std::allocator< gr_complex > >> ,std::allocator< std::vector< gr_complex,std::allocator< gr_complex > > > >> const &' Again, this is a type error which has to do with the content and/or shape of your parameters. You'll have to figure this one out yourself. > Thanks is advance No problem! However, I feel that you tend to ask questions that, with a little more investigative vigor, you would have answered yourself, so maybe it would pay to work a little more thoroughly before mailing the list. That being said, whenever you're stuck, feel absolutely free and encouraged to ask! Greetings, Marcus _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
