Hi Wee Shinhan, Short answer: The idea is feasible.
Long answer: Using two USRP's is a little more complicated because of the same issue of synchronization. The first step is synchronization of the on-board clocks. The current solution requires some hands-on work using directions here ->(http://www.gnuradio.org/trac/wiki/MultiUsrp). NOTE: This reversible process disables one of the USRP board clocks and so the "slave" USRP can no longer be used as a stand-alone board. The next issue is synchronization of the actual waveforms in TX and RX. This can be accomplished in two ways (that I know of): 1) Using the m-block/inband timestamps: Using M-blocks, you can define timestamps that allow you to control when data is transmitted and appropriately synchronize RX. The m-block/inband code is still in development but is sufficiently stable to start some experiments. The m-block code is all in c++ and does not use gr-flowgraphs so you might have to build your application around it, or find some way to integrate m-blocks into your flowgraphs (hint: SWIG). The m-block code can also be used for many other functions (search the list for more details). Most of the code is available in the trunk. 2) Custom FPGA code: the current gr-flowgraphs can already handle multiple receivers(see http://www.gnuradio.org/trac/wiki/MultiUsrp for multi-USRP description). There is no implemented TX parallel, but it is possible to build a multi-TX FPGA and gr code using the same ideas. So the multi board radios are possible, but it is not necessarily straightforward to implement right now. -Sanmi -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Wee Shinhan Sent: Friday, March 07, 2008 1:27 AM To: jiqun qi Cc: discuss-gnuradio@gnu.org Subject: [Discuss-gnuradio] Re: Simultaneously transmitting on twotransmitters Hi Jiqun, Thanks for your reply, i greatly appreciate the help, I would try your suggestion, another idea is what if i used 2 USRP? is the idea feasible? Thanks again for the help. --- jiqun qi <[EMAIL PROTECTED]> wrote: > > > In principle, in USRP, if these two transmit > daughter boards share "one > common clock", it could not achieve the > "strict-sense simultaneously > transmitting" because your program is executed in > "sequence", not > "parallel". However, you can "first" transmit the > symbol s1 on antenna 1, > "then" transmit s2 on antenna 2 "almost > simultaneously" from the view point > of well programming. > > For example, you can send symbols s1 and s2 to the > transmit buffer first, > then enable the two antennas for transmitting, so > the transmit time cycle > difference \delta_t will be smaller than the way > that you send symbol s1 to > the antenna 1, and enable it for transmitting, then > do the symbol s2, > because there is the time cycle consumption that you > send symbol s2 to the > transmit buffer. > > I am not sure how actually it would be in practice. > And I will try my best > to do it in the following days. > ____________________________________________________________________________ ________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
