Re: [Discuss-gnuradio] how to raise the packet error rate in benchmark

[Nathan West]

On Sat, Jul 27, 2013 at 12:03 AM, Adeel Anwar <address@hidden> wrote:
> In ur GR flowgraph, just add a const-multiply block before USRP-Sink and
> multiply the Tx signal with it. Set its value between 0-1.
>
> -Adeel
>
>
> On Fri, Jul 26, 2013 at 5:29 PM, yeran <address@hidden> wrote:
>>
>> Hi Adeel,
>>
>> I'm using RFX 2400 for experiment, there are no parameter
>> tx-dsp-amplitude. So I can't control tx-power linearly, is that what you
>> mean?
>>
>> Thanks!
>> Ada
>>
>> ________________________________
>> Date: Fri, 26 Jul 2013 04:58:18 +0500
>>
>> Subject: Re: [Discuss-gnuradio] how to raise the packet error rate in
>> benchmark
>> From: address@hidden
>> To: address@hidden; address@hidden
>>
>> >>Currently, what I'm doing is keep the tx-amplitude 0.2, and change the
>> >> gain from 35 to 65. You mean in this range, the power is not liner to gain
>> >> change, right? If so, is there any way to control or influence the power
>> >> change?
>> I was mentioning about the that total Tx-Power. U can control Tx-power by
>> varing the value of tx-dsp-amplitude from 0-1 in daughter-boards that don't
>> have variable tx-gain e.g. RFX2400 otherwise its the combination of both
>> tx-dsp-amplitude and tx-gain.
>>
>>
>> -Adeel
>>
>>
>> On Thu, Jul 25, 2013 at 9:10 PM, yeran <address@hidden> wrote:
>>
>> Hi Adeel,
>>
>> Thanks for your prompt reply!
>>
>> I don't quite understand your last email. If I want to test the
>> performance of transmission under different power allocation. What should I
>> do? Can you please be more specific about this?
>>
>> Currently, what I'm doing is keep the tx-amplitude 0.2, and change the
>> gain from 35 to 65. You mean in this range, the power is not liner to gain
>> change, right? If so, is there any way to control or influence the power
>> change?
>>
>> Thank you!
>>
>> Regards,
>> Ada
>>
>> ________________________________
>> Date: Wed, 24 Jul 2013 06:12:15 +0500
>> Subject: Re: [Discuss-gnuradio] how to raise the packet error rate in
>> benchmark
>> From: address@hidden
>> To: address@hidden; address@hidden
>>
>>
>> Ada,
>>
>> >>once the signal has been up converted. Now I'm using 0.2 amplitude and
>> >> 35 gain. But I don't understand, how come that the smaller the power is, 
>> >> the
>> >> better transmission performance there will be. And also, why does power
>> >> should be in the range of 0 to 1.0? How to calculate transmission power
>> >> using the -tx-amplitude and tx-gain?
>> Better performance is not due to smaller power but it is due to the
>> non-linear effects of RF-amplifiers. As per my observations, Tx-Dsp
>> amplitude beyond 0.15 to 0.2 causes the USRP daughter-boards
>> Tx-amplification-stage to go into non-linear region thus error-rate of
>> PSK/QAM  increases. Non-linear modulation e.g. FSK/GMSK are more robust to
>> Amps non-linear effects. so u can experiment increasing TX-amplitude both
>> for FSK-variants & PSK/QAM and observe performance.
>>
>> -Adeel
>>
>>
>> On Tue, Jul 23, 2013 at 9:25 PM, yeran <address@hidden> wrote:
>>
>> Hi everyone,
>>
>> I'm doing a project on joint decode. But my problem is that in the lab
>> environment,  the benchmark transmission is always good, there are hardly
>> any packet loss, so I can not show the advantage of joint decode.
>>
>> I've tried to change the physical distance from transmission to receiver
>> attenna. Still works really well even put in opposite side of the building.
>>
>> I've tried to change the transmission power and transmission rate.
>> Inspired by some previous study, I learned that transmission power is
>> controlled by -tx-amplitude and -tx-gain, in which -tx-amplitude sets the
>> amplitude of the signal going into the DAC.  RF gain is applied in the
>> daughtercard once the signal has been up converted. Now I'm using 0.2
>> amplitude and 35 gain. But I don't understand, how come that the smaller the
>> power is, the better transmission performance there will be. And also, why
>> does power should be in the range of 0 to 1.0? How to calculate transmission
>> power using the -tx-amplitude and tx-gain?
>>
>> Is there any other way that may cause more error in transmission beside
>> the ones I mentioned?
>>
>> Thanks in advance! Any suggestion will be greatly appreciated!
>>
>> Ada
>>
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>>
>>
>>
>
>
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Changing this amplitude is *a* way to change the transmit power, but
that's not really the purpose of this amplitude. The tx-gain is the
better way to change the tx power. At one point you mentioned you were
using 35dB gain. Why don't you lower that to 0 and then increase the
gain until you have sufficient reception?