[Discuss-gnuradio] About MIMO-cable
Hello everyone, I'm curious about synchronising 2 USRP2 boards using MIMO-cable. Is there any firmware code, which supports transmitting and receiving signals from two USRP2s connected by MIMO-cable? Which blocks do I need to use in GNURadio companion for it? By the way, compared to setting ref. and PPS clock, which is the best way for setting up MIMO system? Thanks in advance. :clap: Best wishes, Hongliang -- View this message in context: http://old.nabble.com/About-MIMO-cable-tp30189888p30189888.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Problem of using UHD blocks as Tx & Rx
Thanks Jason, Sorry, I told you wrong reference clock. I have used 10MHz reference clocks for the test again, and I still got the same results as the previous post. Could you please give me some suggestions about the problem? Cheers, Hongliang Jason Abele wrote: > >> I used a signal generator and a spliter to provide two identical 100MHz >> ref. >> clocks for the boards. > > The ref clock needs to be 10MHz rather than 100MHz > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Problem-of-using-UHD-blocks-as-Tx---Rx-tp30069825p30094576.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Problem of using UHD blocks as Tx & Rx
Dear Jason and Josh, Thanks very much for your reply. I followed your instructions and use the UHD MIMO Sink and Source again. They should be synchronised now. First, I transmitted a constant and observe the received signal. The following figure is my flow graph of GRC: http://old.nabble.com/file/p30086842/FlowGraph.jpg But I got the received signal with large fluctuation (I observe the received signal in a long time period window): http://old.nabble.com/file/p30086842/Result1.jpg The fluctuation increased when I increased the amplitude of the transmitted signal. Then I made a test for transmitting a 10K Hz sine wave http://old.nabble.com/file/p30086842/FlowGraph2.jpg The result seems better : http://old.nabble.com/file/p30086842/Result2.jpg However, if I watch the received signal in real time, I can still find the slight vibration of the period of the signal wave. I used a signal generator and a spliter to provide two identical 100MHz ref. clocks for the boards. In my opinion, the results may imply that there are still frequency difference between transmitter and receiver. And this frequency difference is a random value which may goes from -100 to 100 Hz. May I have your understandings of the results? Would you mind to provide me with some ideas or suggestions about them? Best wishes, Hongliang Jason Abele wrote: > >> Why do I receive a sine wave when I transmit a constant? > > Probably because the 100MHz reference clocks of your two USRP2s are > slightly different > > Here are a few suggestions for being sure that you are locking to your > 10MHz reference clock: > > If you have not modified the generated python code from your GRC > flowgraph, then you are definitely not locked to refclock. The > easiest way to fix this would be: > Use a multi-usrp sink and source from the UHD categorey > Set the number of motherboards and channels to 1 each > Use the Sync to Unknow PPS option > > I know that is a strange interface, we will put an option to use > external ref clock in an update coming soon to git repositories near > you. > > Finally, be sure your refclock meets the power/amplitude requirements > shown here: > http://www.ettus.com/uhd_docs/manual/html/usrp2.html#ref-clock-10mhz >+5dBm to +20dBm (roughly 1Vpp to 5Vpp) > > Jason > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Problem-of-using-UHD-blocks-as-Tx---Rx-tp30069825p30086842.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Problem of using UHD blocks as Tx & Rx
Dear Marcus Leech, Thanks very much for your response. I use RFX2400 daughterboards and their TX/RX ports. A attenuator is added between the transmitter and receiver boards now. And to simplify the test, I use a constant source at the transmitter side. Here is my GRC flow graph: http://old.nabble.com/file/p30077180/flow%2Bgraph.jpg And here are the results I've observed from the scope: http://old.nabble.com/file/p30077180/Result.jpg Why do I receive a sine wave when I transmit a constant? Best wishes, Hongliang Marcus D. Leech wrote: > > On 10/27/2010 02:11 PM, Hongliang Zhang wrote: >> Hi everyone, >> >> I made a test for UHD blocks today, and I found a problem as follows: >> >> I take two USRP2 boards for my test. One is used as transmiter and the >> other >> board is set to be receiver.And I use UHD Simple Sink and UHD Simple >> Source >> blocks for transmiting and receiving respectively. >> >> sampling frequency = 195.312K (which is the minimum sampling frequncy of >> the >> system). >> gain=0 >> The transmitted signal is a AM modulated sine signal. >> The frequency of orignal sine wave (the message signal) is 10K Hz. >> The frequency of carrier signal (center frequency for modulation at >> transmitter board) is 2.42 GHz, and I use the same frequency at the >> receiver >> board for demodulation. >> Amplitude of transmitted signal is 0.05. >> >> I connect the two boards together, and I add a scope to observe the >> period >> of the received demodulated signal. The problem is the period is about >> 0.45, which means the frequency of the signal I received is not 10 >> KHz, >> but about 2.2 KHz. >> >> I have used the same external reference clock and PPS signal for both of >> the >> boards, so I think they are set up correctly. Why do I get a received >> signal >> with different frequency from what I transmit? >> >> Does anyone meet the similar problem before? How may I solve the problem? >> >> Thanks so much for every help and suggestions in advance. >> >> Best regards, >> Hongliang >> >> >> >> > What daughterboards are you using? > > Can you share your (GRC) flow-graphs with us--makes it easier to spot > problems. > > I hope that you're using an attenuator between the transmitter side and > receiver side. > > My guess is that there's a sample-rate issue somewhere on the receive > side, like the scope sink > hasn't been told the correct sample rate, so it's displaying > incorrectly, etc. > > > > > -- > Marcus Leech > Principal Investigator > Shirleys Bay Radio Astronomy Consortium > http://www.sbrac.org > > > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Problem-of-using-UHD-blocks-as-Tx---Rx-tp30069825p30077180.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Problem of using UHD blocks as Tx & Rx
Hi everyone, I made a test for UHD blocks today, and I found a problem as follows: I take two USRP2 boards for my test. One is used as transmiter and the other board is set to be receiver.And I use UHD Simple Sink and UHD Simple Source blocks for transmiting and receiving respectively. sampling frequency = 195.312K (which is the minimum sampling frequncy of the system). gain=0 The transmitted signal is a AM modulated sine signal. The frequency of orignal sine wave (the message signal) is 10K Hz. The frequency of carrier signal (center frequency for modulation at transmitter board) is 2.42 GHz, and I use the same frequency at the receiver board for demodulation. Amplitude of transmitted signal is 0.05. I connect the two boards together, and I add a scope to observe the period of the received demodulated signal. The problem is the period is about 0.45, which means the frequency of the signal I received is not 10 KHz, but about 2.2 KHz. I have used the same external reference clock and PPS signal for both of the boards, so I think they are set up correctly. Why do I get a received signal with different frequency from what I transmit? Does anyone meet the similar problem before? How may I solve the problem? Thanks so much for every help and suggestions in advance. Best regards, Hongliang -- View this message in context: http://old.nabble.com/Problem-of-using-UHD-blocks-as-Tx---Rx-tp30069825p30069825.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Need help: How to extract timestamps of data for UHD mimo source block?
Hi Josh, Thanks so much for your reply. I have some questions about the metadata. 1). I read the codes in the work function. The metadata is defined by: uhd::rx_metadata_t metadata; Does "uhd::rx_metadata_t" define the data type or give values to metadata? And in which C++ file may I find that the "uhd::rx_metadata_t" is created ? 2). Is metadata a scaler or vector? I use 4 USRP2 boards for MIMO receiver system. Does metadata contain 4 groups of timestamps for each 4 USRP2 boards or just 1 group of timestamps for the whole synchronised data? 3). When I use the UHD MIMO Source block, GNU Radio Companion shows the following sentences: Current recv sock buff size: 5000 bytes Current recv sock buff size: 5000 bytes Current recv sock buff size: 5000 bytes Current recv sock buff size: 5000 bytes Using: Flex 2400 MIMO B RX (0x0027) Using: Flex 2400 MIMO B TX (0x002b) Using: Flex 2400 MIMO B RX (0x0027) Using: Flex 2400 MIMO B TX (0x002b) Using: Flex 2400 MIMO B RX (0x0027) Using: Flex 2400 MIMO B TX (0x002b) Using: Flex 2400 MIMO B RX (0x0027) Using: Flex 2400 MIMO B TX (0x002b) RX samples per packet: 362 TX samples per packet: 363 Recv pirate num frames: 33967 Set time with unknown pps edge: 1) set times next pps (race condition) 2) catch seconds rollover at pps edge 3) set times next pps (synchronously) Time was reset successfully on board 1 relative to board 0 Time was reset successfully on board 2 relative to board 0 Time was reset successfully on board 3 relative to board 0 Do they mean that 4 boards are synchronised and have the same timestamps? In which C++ script may I find this sentence :" Time was reset successfully on board 1 relative to board 0" ? Many thanks in advance. Best wishes, Hongliang Josh Blum-2 wrote: > > > > On 10/06/2010 04:24 AM, Hongliang Zhang wrote: >> >> Hi everyone, >> >> I set up 4 USRP2 boards for MIMO receiver system for array antennas, and >> use >> the PPS signal to synchronise them. I wish to collect the data from the >> boards as well as the associated timestamps for the four boards. >> >> Could someone teach me how to read the time stamps from a UHD mimo source >> block? Do I need to modify the block in C++ or Python scripts? >> > > The timestamps are inside the metadata, they are discarded in the work > function: > http://gnuradio.org/cgit/gnuradio.git/tree/gr-uhd/lib/uhd_mimo_source.cc?h=next#n127 > > You will need to modify the mimo source c++ and find a place to store > the timestamps, or write a c++ app that calls into the UHD mimo_usrp > interface directly. > > -Josh > >> Thanks so much for every help and suggestions.:clap: >> >> Best regards, >> Hongliang > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Need-help%3A-How-to-extract-timestamps-of-data-for-UHD-mimo-source-block--tp29886484p29908883.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Need help: How to extract timestamps of data for UHD mimo source block?
Hi everyone, I set up 4 USRP2 boards for MIMO receiver system for array antennas, and use the PPS signal to synchronise them. I wish to collect the data from the boards as well as the associated timestamps for the four boards. Could someone teach me how to read the time stamps from a UHD mimo source block? Do I need to modify the block in C++ or Python scripts? Thanks so much for every help and suggestions.:clap: Best regards, Hongliang -- View this message in context: http://old.nabble.com/Need-help%3A-How-to-extract-timestamps-of-data-for-UHD-mimo-source-block--tp29886484p29886484.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
