在 2012-07-19Thu的 11:38 -0700，Josh Blum写道： > > On 07/17/2012 08:31 PM, King Qiu wrote: > > Hi Josh, > > I have done the same work as Alex. I modified the code in > > gr_message_source. I added a tx_sob tag and a tx_time tag to the first > > byte of the message, and a tx_eob tag to the last byte of the message. > > Assuming: > > 1. there are 100 bytes in a message(or we call it a packet) > > 2. bpsk modulation is employed > > 3. set samples_per_symbol to 2 > > So there are 800 symbols or 1600 samples in the packet. > > In the output of the gr_message_source block, the 0 byte is tagged with > > the tx_sob and the tx_time, and the 99 byte is tagged with the tx_eob. > > > > Then in the output of the symbol map block, the 0 symbol is tagged with > > the tx_sob and the tx_time, and the 792 symbol is tagged with the > > tx_eob. > > > > After pulse shaping filter, the 0 sample is tagged with the tx_sob and > > the tx_time, and the 1584 sample is tagged with the tx_eob. > > > > I think its important to note that certain gnuradio blocks do not pass > tags because it is undecided how to interpolate the sample index. Tom > would have more to say about this. > > > My questions are as follow: > > 1. The 1599 sample is the last sample in the packet, but the tx_eob tag > > are added to the 1584 sample. So, what will happen to the 1585-1599 > > samples in the usrp? Are they transmitted by the usrp immediately after > > the 1584 sample? > > > > Yes, these samples will be send ASAP, and they will not have an EOB, so > the device will regard this as underflow > > > 2. Is it necessary to adding the tx_eob tag exactly to the last (1599) > > sample? How can I do this? > > > > The sample index is one of the parameters of the tag > > -josh
_______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
