# Communication problems between 2 USRP's **URL:** \ **Category:** GNU Radio\ **Created:** [July 31, 2015, 12:30am UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820 "2015-07-31T00:30:31Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\ **Post date:** [July 31, 2015, 12:30am UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/1 "2015-07-31T00:30:31Z")
Hi all, I want to transmit the data between two USRP’s and make them communicate with each other. But I guess the packets are not being received properly… My USRP daughterboard model is XCVR2450. When I am running ./benchmark\_tx.py -f 2.435G, it is starting to transmit the packets but a small error occured given below, linux; GNU C++ version 4.8.4; Boost\_105500; UHD\_003.009.git-144-g407e3086 Using Volk machine: avx\_64\_mmx – Opening a USRP1 device… – Using FPGA clock rate of 64.000000MHz… No gain specified. Setting gain to 7.500000 (from [-20.000000, 35.000000]) UHD Warning: The hardware does not support the requested TX sample rate: Target sample rate: 0.050000 MSps Actual sample rate: 0.250000 MSps Symbol Rate: 25000.000000 Requested sps: 2.000000 Given sample rate: 250000.000000 Actual sps for rate: 10.000000 Requested sample rate: 50000.000000 Actual sample rate: 250000.000000 …U…terminate called after throwing an instance of ‘uhd::runtime\_error’ what(): RuntimeError: usb tx2 transfer status: 1 Aborted (core dumped). But towards the receiver side, I gave the command ./benchmark\_rx.py -f 2.435GG,it has shown the result given below with n\_right=0. linux; GNU C++ version 4.8.4; Boost\_105500; UHD\_003.009.git-144-g407e3086 Using Volk machine: avx\_64\_mmx – Opening a USRP1 device… – Using FPGA clock rate of 64.000000MHz… No gain specified. Setting gain to 56.250000 (from [0.000000, 112.500000]) UHD Warning: The hardware does not support the requested RX sample rate: Target sample rate: 0.050000 MSps Actual sample rate: 0.250000 MSps Symbol Rate: 25000.000000 Requested sps: 2.000000 Given sample rate: 250000.000000 Actual sps for rate: 10.000000 Requested sample rate: 50000.000000 Actual sample rate: 250000.000000 ok = False pktno = 53034 n\_rcvd = 1 n\_right = 0 ok = False pktno = 24 n\_rcvd = 2 n\_right = 0 ok = False pktno = 35 n\_rcvd = 3 n\_right = 0 ok = False pktno = 44 n\_rcvd = 4 n\_right = 0 ok = False pktno = 46 n\_rcvd = 5 n\_right = 0 ok = False pktno = 46 n\_rcvd = 6 n\_right = 0 ok = False pktno = 3872 n\_rcvd = 7 n\_right = 0 ok = False pktno = 12304 n\_rcvd = 8 n\_right = 0 ok = False pktno = 49 n\_rcvd = 9 n\_right = 0 ok = False pktno = 50 n\_rcvd = 10 n\_right = 0 ok = False pktno = 54 n\_rcvd = 11 n\_right = 0 ok = False pktno = 200 n\_rcvd = 12 n\_right = 0 ok = False pktno = 63 n\_rcvd = 13 n\_right = 0 My USRP can access in the range of 2.4GHZ to 5GHZ. Please advice as to what I can do. Thanks Regards, John ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [July 31, 2015, 4:24pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/2 "2015-07-31T16:24:15Z")
On Thu, Jul 30, 2015 at 6:30 PM, John G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > Actual sample rate: 0.250000 MSps > > ``` > > called after throwing an instance of ‘uhd::runtime\_error’ > > ``` > Actual sample rate: 0.250000 MSps > > ``` > > ok = False pktno = 35 n\_rcvd = 3 n\_right = 0 > > My USRP can access in the range of 2.4GHZ to 5GHZ. Please advice as to > what I can do. Thanks > > Regards, > John John, There’s lots of things that can go wrong here. You didn’t set the gains or transmit amplitude. Do you know if you have a significant frequency offset between your two radios? You might need to adjust that. The fact that you are getting “ok = False” means that the receiver saw a packet, but there were too many errors and the CRC check failed. Note there is no FEC applied to the benchmark scripts. So this could be due to low SNR, a bad channel, or, frankly, many other possibilities. Tom ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 1, 2015, 7:52pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/3 "2015-08-01T19:52:13Z")
Hi Tom, So can you please advice what I can do next for them to be right? Regards, John ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 3, 2015, 5:08pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/4 "2015-08-03T17:08:57Z")
On Sat, Aug 1, 2015 at 1:52 PM, John G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi Tom, > So can you please advice what I can do next for them to be right? > > Regards, > John Too many things; you’ll have to go through it step-by-step. Best thing to start with is to transmit and use uhd\_fft at the receiver end to look at the signal. Make sure everything looks ok and try to find a gain setting that maximizes the SNR. Tom ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 3, 2015, 11:09pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/5 "2015-08-03T23:09:02Z")
Hi Tom, I have actually added a jpg file which shows the output when given the command of uhd\_fft. Actually,my experiment is to transmit different data packets to the receiver with minimized errors with ./benchmark\_tx.py -f 2.435G and ./benchmark\_rx.py -f 2.435G as commands . May I please know of how can to set the gain in this picture and also how this picture is useful for the reception of data packets. Please help as I am new to using GNU Radio and USRP. Thank you. Regards, John ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 7, 2015, 11:53pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/6 "2015-08-07T23:53:17Z")
Hi Tom, Attached is the picture that I have sent you previously. I have somewhat adjusted the receiver gain for the signal to be a flat one. As you have mentioned before about how to apply the gain settings to the benchmark scripts, how do you suggest I do that? Also, how do I change the transmitting gain setting. If I do this, will I be able to receive the data packet correctly?. I mean, I need to get n\_right=1, that is the CRC check needs to be right. Please suggest as to what I can do. Thanks. Regards, John ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 4, 2015, 4:33pm UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/7 "2015-08-04T16:33:21Z")
On Mon, Aug 3, 2015 at 5:09 PM, John G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > John > > Attachments: [![](https://www.ruby-forum.com/attachment/10951/Screenshot_from_2015-08-03_16_03_15.png) ](https://www.ruby-forum.com/attachment/10951/Screenshot_from_2015-08-03_16_03_15.png) Hi John, That PNG you sent doesn’t show any signal that I can tell, which indicates that your gain settings are either too low to not see it or too high causing nonlinear effects. In this case, I’d guess the former. You can adjust the gain directly on the uhd\_fft app there with the RX Gain slider. Play with that to see if you can see the signal better. Then use the gain setting as an option to the benchmark scripts. You may also want to adjust the transmit gain setting, as well. But the issue here isn’t GNU Radio or USRP. This is now radio. You have to have good enough signal power to receive data, and so you need to adjust the gains of the radio to make that happen. Tom ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 12, 2015, 2:05am UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/8 "2015-08-12T02:05:02Z")
On Fri, Aug 7, 2015 at 5:53 PM, John G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Regards, > John > > Attachments: [![](https://www.ruby-forum.com/attachment/10970/Screenshot_from_2015-08-07_16_49_26.png) ](https://www.ruby-forum.com/attachment/10970/Screenshot_from_2015-08-07_16_49_26.png) The problem is that I still don’t see a signal in that screen shot you’re sending me. To adjust the gains and amplitudes, in the benchmark scripts, use the ‘-h’ flag to get help to see what options you can pass to it. I cannot tell you if you will get the packets received correctly, and certainly not all of them will be. There is no error correction on that link, so even 1 bit wrong in a packet will force that entire packet to be marked as false because the CRC check will fail. In the end, these aren’t so much GNU Radio questions but radio questions, so then it’s how you work with GNU Radio to address them. You have to work on sample rate, frequency offset, gains, etc. etc. The tools are all there with the sliders in the GUI apps and the command-line arguments for the benchmark programs. Tom ---
**Author:** ![softf5ajivanet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9f8e36/32.png) [@softf5ajivanet](https://www.ruby-forum.com/u/softf5ajivanet)\ **Post date:** [August 23, 2015, 1:43am UTC](https://www.ruby-forum.com/t/communication-problems-between-2-usrps/242820/9 "2015-08-23T01:43:28Z")
Hi Tom, Thanks for the reply. I have been trying to import ./benchmark\_tx.py -f 2.435G and ./benchmark\_rxpy -f 2.435G commands and I have not yet been able to resolve the problem. I am attaching the files of the benchmark scripts. What do I need to change in order for my packet to receive correctly? Please help as I am new to GNU Radio. Regards, John