Re: [Discuss-gnuradio] [USRP-users] how to resolve the uhd warning of sample rate

[Marcus Müller]

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: address@hidden
>> Subject: Re: [USRP-users] [Discuss-gnuradio] how to resolve the uhd warning  
>> of sample rate
>> From: address@hidden
>>
>> 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
>>> address@hidden
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
>> _______________________________________________
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>