On 05/23/2014 11:33 AM, xianda wrote: > Hi Martin: > Thank you for your reply. > But, > 1.I see the virual Source(Stream ID:Payload Bits)->Chunks > to Symbols(Symbol Table(-0.707...))(modulate:qpsk)?When I input 800 bits > to the Packet Header Generator,then chunks to symbols.How many symbols > generate in this way?When I input 800 bits to the Repack Bits,then > chunks to symbols.How many symbols generate in this way?Thank you very much.
I'm pretty sure I've answered all of these questions already. > 2.I also see another ofdm in the old version of > gnuradio.And the module structure is attached.And the connect code in > python: Just ignore that. The new stuff is a complete rewrite. > 3.And i use two usrps to run the tx_ofdm.grc and > rx_ofdm.grc.The adjust code I also attached. But in the transmit,so many > U U U display.Why?And in the receive part,I also encouter problem.Can > you help me explain it? Your computer is too slow. M > Thank you very much.I see the ofdm part many days.And the > 3 questions I encounter.Thank you.Sorry for my poor English if you can't > understand.Thank you in advance.Thank you for your patience. > Best regards > > > > > > > At 2014-05-23 16:40:55,"Martin Braun" <[email protected]> wrote: >>On 05/23/2014 02:29 AM, xianda wrote: >>> Hi: >>> Thank you so much. >>> 1.But from "chunks to symbols" I see you use the bpsk and qpsk >>> both.Right?What is the relationship between 800 bits and 17 >>> symbols?Namely,how to calculate the 17 symbols? >>> 17*64=1088.Can you explain? >> >>1 OFDM symbol @ BPSK == 48 bits in this configuration. >>ceil(800/48) == 17. >> >>> 2.I have looked at your ppt about the ofdm.You say now have two >>> version ofdm.Can you give me some links to them?Or some advices?Thank you. >> >>They're both in the tree. If you start working off of rx_ofdm an tx_ofdm >>you're already using the new stuff; no need to worry about this. >> >>M >> >> >>> Best regards >>> At 2014-05-23 04:33:44,"Martin Braun" <[email protected]> wrote: >>>> On 05/22/2014 10:12 PM, eontool wrote: >>>>> IIRC, the tx and rx files are just a very general implementation of the >>>>> OFDM >>>>> model. >>>>> >>>>> Here's my understanding: >>>>> >>>>> - Packet length refers to the data necessary to produce n symbols (48 data >>>>> carriers, 2 symbols = 96). >>>> >>>> Er, no. This is the number of bytes per packet. It's 96 because we add 4 >>>> bytes for CRC, and then the packet number is a round value. >>>> >>>> At 100 bytes per packet, the payload is 800 bits. With BPSK, that would >>>> be 17 OFDM symbols (plus 1 OFDM symbol for header, and 2 for preamble). >>>> >>>> You can set whatever here, but remember that the stock equalizers don't >>>> do a good job on long packets. Also, the length can vary per packet. >>>> >>>>> - The number of total carriers in the systems equals the FFT length. >>>>> In this case, 48 data carriers and 4 pilots, 52 total and the rest are set >>>>> to 0. >>>> >>>> This is correct (compare 802.11a standard). >>>> >>>> M >>>> >>>> >>>> _______________________________________________ >>>> Discuss-gnuradio mailing list >>>> [email protected] >>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >>_______________________________________________ >>Discuss-gnuradio mailing list >>[email protected] >>https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
