Hello Alok, the problem here is that you implicitly request a lower sampling rate than your USRP is able to provide: "-r 250e3" specifies the bit rate. For "-m qam" (with a default number of constellation points (-p) of 16=2^4) this means that the symbol rate is 1/4 of that, (250e3 b/s) / (4 b/sym) = 62500 sym/s. Now, the default setting for samples per symbols (-S) is 2, so that you get 125e3 S/s, which is half of what you can minimally do with your USRP. You can either use a constellation with less points, increase your bit rate, or increase your samples per symbol.
Greetings, Marcus PS: can you please generally reply to the mailing list and not to people individually? It's a bit hard for me to keep track of this, and it might be really frustrating for the others that follow these lists ;) On 11/28/2014 11:20 AM, alok ranjan wrote: > Hello Marcus, > > Thank you for your quick response. > > I am running the benchmark_tx.py and benchmark_rx.py for transmission and > reception. Below is the details what i am getting : > > > python benchmark_tx.py -f 986M -m qam -r 250e3 -A TX/RX --tx-gain=30 -a > serial=49270a48 > linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.005.002-0-unknown > > Using Volk machine: sse4_2_64_orc > -- Opening a USRP1 device... > -- Using FPGA clock rate of 64.000000MHz... > > UHD Warning: > The hardware does not support the requested TX sample rate: > Target sample rate: 0.125000 MSps > Actual sample rate: 0.250000 MSps > > Symbol Rate: 62500.000000 > Requested sps: 2.000000 > Given sample rate: 250000.000000 > Actual sps for rate: 4.000000 > > Requested sample rate: 125000.000000 > Actual sample rate: 250000.000000 > > Looking forward for your response. > > Regards!! > Alok > > > > >> Date: Fri, 28 Nov 2014 10:29:39 +0100 >> To: usrp-us...@lists.ettus.com >> Subject: Re: [USRP-users] [Discuss-gnuradio] how to resolve the uhd warning >> of sample rate >> From: usrp-us...@lists.ettus.com >> >> Hi Alok, >> >> usually, it should say something like "actual sampling rate: XXX". What >> does it say? (actually, can you just copy&paste the whole warning?) >> >> What program are you passing "-r" to? >> >> Greetings, >> Marcus >> >> On 11/28/2014 08:57 AM, alok ranjan wrote: >>> Dear All, >>> >>> >>> I am using USRP1 having RF daughterboards WBX (50Mhz -2.2Ghz). I have >>> gone through some basic details of the USRP1 product features but dont >>> know how to resolve the errors oh UHD warning saying the hardware >>> doesnot support the target tx sample rate and same for the rx also. >>> >>> >>> Below is the USRP1 supported features : >>> >>> ADC sample rate: 64MS/s >>> DAC sample rate:128MS/s >>> Host sample rate: 8 for usb2 >>> FPGA clock rate: 64Mhz >>> >>> Please help me to understand that what value of -r i should pass for the >>> both tx and for rx. >>> >>> I >>> have tried with -r 250e3 and 125e3 but it could not work and popping >>> the warning that target tx and rx rate is not supported by hardware. >>> >>> Thank you. >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> _______________________________________________ >> USRP-users mailing list >> usrp-us...@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
