Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-29 Thread mleech 
 

Your center frequency is in the 2.4GHz WiFi band. So, yeah, you could be
seeing lots of interference. 

On 2015-10-29 11:41, Washbourne, Logan wrote: 

> So I decimated both sides, right in front of the constellation plots. The TX 
> side looks a lot better, no zero groupings. The RX side still looks very 
> noisy. Could this be a product of my environment? 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Tue, Oct 27, 2015 at 11:33 AM, Richard Bell  
> wrote:
> 
> To sanity check the transmitter, instead of showing the constellation of 
> every sample, show every other sample, i.e. decimate by 2 going into the 
> constellation plot. The two comes from the fact you use 2 samples/symbol. We 
> don't want to see the every sample on a constellation, only symbols. That's 
> why the transmitter block has the grouping it does. Once you've confirmed you 
> see the expected BPSK constellation, you can move on to the receiver. 
> 
> On Tue, Oct 27, 2015 at 9:08 AM,  wrote:
> 
> Try cranking your RX gain up/down 5dB and see how that affects your 
> constellation. 
> 
> On 2015-10-27 11:55, Washbourne, Logan wrote: 
> Ok, that sampling rate mismatch was my fault. The RX spectrum looks better 
> after that fix. The unpacked to packed bits didn't seem to remove the zero 
> grouping on the constellation plot. Here are pictures of the setup now.
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Tue, Oct 27, 2015 at 10:34 AM, Richard Bell  
> wrote:
> 
> Logan, make sure you're feeding packed bytes into the DPSK Mod block. That's 
> probably why you're seeing a constellation point at zero, you're feeding in 
> unpacked bytes. That might fix everything. 
> 
> Rich
> 
> Sent from my iPad 
> 
> On Oct 27, 2015, at 8:16 AM, mle...@ripnet.com wrote:
> 
> What does the spectral plot look like? It should look very similar to the TX 
> side of the house. 
> 
> On 2015-10-27 11:10, Washbourne, Logan wrote: 
> 
> Thanks for the info guys! They are both using antennas btw. I came in this 
> morning and turned the RX gain up pretty high, roughly 45dB, and the 
> constellation plot on the RX side is starting to look pretty square, which I 
> think is a bad sign. My thoughts are that with the increase in gain, there is 
> too much noise coming through.
> 
> I've been toying with adding in a frequency offset on the TX side. I've been 
> adding and subtracting up to 30kHz from the center frequency and I haven't 
> seen any improvement in the constellation plot on the RX side.
> 
> Another thing that is confusing me, on the TX constellation plot, before it 
> gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure where 
> the 0 points are coming from. Since this is DBPSK, there should only be -.5 
> and .5 groupings right?
> 
> Should this exercise be pretty straightforward? 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
> 
> Consulting now, the book of armaments, errr, UHD manual: 
> 
> http://files.ettus.com/manual/page_dboards.html#dboards_rfx [2] 
> 
> The RFX series has no TX RF gain control, output magnitude is entirely 
> dependent on baseband magnitude. 
> 
> There's 70dB of gain range on RX, however. So, crank up the RX gain. 
> 
> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is probably 
> putting out 5dBm, so at the RX end, that's maybe as much as -35dBm. If your 
> RX is set properly, should be enough to see the signal. 
> 
> On 2015-10-26 15:46, Marcus Müller wrote: Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [3] TX
> http://imgur.com/DBy8gqs [4] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
>

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-29 Thread Richard Bell 
Hey Logan,

There are sum fundamental principals I think you're overlooking when you
say "the Rx side still looks very noisy". You cannot just pipe the output
of the USRP into a sink and expect to get anywhere near a perfect
constellation ever. There are a lot of effects that need to be fixed before
a perfect constellation exists. The DPSK Demod block is supposed to do
these things for you. But only after this block should you expect to see
anything you're used to seeing. Out of the USRP, all bets are off.

I still don't see a Tx side constellation that looks correct. And I
emphasize to you that until you get a perfect BPSK constellation plot on
the Tx side, don't debug the Rx side. One because you could waste your time
trying to fix a problem on the Rx that exists on the Tx. Two, because if
you don't have the understanding needed to make the Tx work, you don't have
much hope with the Rx.

You shouldn't just be decimating into the constellation on the Tx side.
It's true that I said that in the previous email, but I assumed you knew
what I really meant. You should be aware that pulse shaping has occurred in
the DPSK Mod block using a root raised cosine. If you don't undue this,
your Tx constellation is going to look very noisy, not because it is, but
because it's been shaped. To do the decimation on the Tx side that feeds
into the Constellation sink, you should use a root raised cosine filter to
undue the shaping. This will decimate for you as well. Going this route,
get two perfect BPSK constellation points to come out.

v/r,
Rich

On Thu, Oct 29, 2015 at 8:48 AM,  wrote:

> Your center frequency is in the 2.4GHz WiFi band.  So, yeah, you could be
> seeing lots of interference.
>
>
>
>
>
>
> On 2015-10-29 11:41, Washbourne, Logan wrote:
>
> So I decimated both sides, right in front of the constellation plots. The
> TX side looks a lot better, no zero groupings. The RX side still looks very
> noisy. Could this be a product of my environment?
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
> On Tue, Oct 27, 2015 at 11:33 AM, Richard Bell 
> wrote:
>
>> To sanity check the transmitter, instead of showing the constellation of
>> every sample, show every other sample, i.e. decimate by 2 going into the
>> constellation plot. The two comes from the fact you use 2 samples/symbol.
>> We don't want to see the every sample on a constellation, only symbols.
>> That's why the transmitter block has the grouping it does. Once you've
>> confirmed you see the expected BPSK constellation, you can move on to the
>> receiver.
>>
>> On Tue, Oct 27, 2015 at 9:08 AM,  wrote:
>>
>>> Try cranking your RX gain up/down 5dB and see how that affects your
>>> constellation.
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 2015-10-27 11:55, Washbourne, Logan wrote:
>>>
>>> Ok, that sampling rate mismatch was my fault. The RX spectrum looks
>>> better after that fix. The unpacked to packed bits didn't seem to remove
>>> the zero grouping on the constellation plot. Here are pictures of the setup
>>> now.
>>>
>>>
>>>
>>> Logan Washbourne
>>> Electrical Engineering Graduate Student
>>> (Electromagnetics)
>>>
>>> On Tue, Oct 27, 2015 at 10:34 AM, Richard Bell 
>>> wrote:
>>>
 Logan, make sure you're feeding packed bytes into the DPSK Mod block.
 That's probably why you're seeing a constellation point at zero, you're
 feeding in unpacked bytes. That might fix everything.

 Rich

 Sent from my iPad

 On Oct 27, 2015, at 8:16 AM, mle...@ripnet.com wrote:

 What does the spectral plot look like?  It should look very similar to
 the TX side of the house.






 On 2015-10-27 11:10, Washbourne, Logan wrote:

 Thanks for the info guys! They are both using antennas btw. I came in
 this morning and turned the RX gain up pretty high, roughly 45dB, and the
 constellation plot on the RX side is starting to look pretty square, which
 I think is a bad sign. My thoughts are that with the increase in gain,
 there is too much noise coming through.

 I've been toying with adding in a frequency offset on the TX side. I've
 been adding and subtracting up to 30kHz from the center frequency and I
 haven't seen any improvement in the constellation plot on the RX side.

 Another thing that is confusing me, on the TX constellation plot,
 before it gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not
 sure where the 0 points are coming from. Since this is DBPSK, there should
 only be -.5 and .5 groupings right?

 Should this exercise be pretty straightforward?

 Logan Washbourne
 Electrical Engineering Graduate Student
 (Electromagnetics)

 On Mon, Oct 26, 2015 at 3:12 PM,  wrote:

> Consulting now, the book of armaments, errr, UHD manual:
>
>

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread mleech 
 

What does the spectral plot look like? It should look very similar to
the TX side of the house. 

On 2015-10-27 11:10, Washbourne, Logan wrote: 

> Thanks for the info guys! They are both using antennas btw. I came in this 
> morning and turned the RX gain up pretty high, roughly 45dB, and the 
> constellation plot on the RX side is starting to look pretty square, which I 
> think is a bad sign. My thoughts are that with the increase in gain, there is 
> too much noise coming through.
> 
> I've been toying with adding in a frequency offset on the TX side. I've been 
> adding and subtracting up to 30kHz from the center frequency and I haven't 
> seen any improvement in the constellation plot on the RX side.
> 
> Another thing that is confusing me, on the TX constellation plot, before it 
> gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure where 
> the 0 points are coming from. Since this is DBPSK, there should only be -.5 
> and .5 groupings right?
> 
> Should this exercise be pretty straightforward? 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
> 
> Consulting now, the book of armaments, errr, UHD manual: 
> 
> http://files.ettus.com/manual/page_dboards.html#dboards_rfx [2] 
> 
> The RFX series has no TX RF gain control, output magnitude is entirely 
> dependent on baseband magnitude. 
> 
> There's 70dB of gain range on RX, however. So, crank up the RX gain. 
> 
> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is probably 
> putting out 5dBm, so at the RX end, that's maybe as much as -35dBm. If your 
> RX is set properly, should be enough to see the signal. 
> 
> On 2015-10-26 15:46, Marcus Müller wrote: Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [3] TX
> http://imgur.com/DBy8gqs [4] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK 
> Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz 
> center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK 
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
> 
> I'm checking the progress of the communication by looking at a constellation 
> plot that is connected directly to the USRP SOURCE block on the receiver 
> side. I'm getting a very elliptical shape, more spread out in the horizontal 
> direction but not by much. I'm also looking at the bits from the receiver 
> side in matlab and my preamble is not showing up.
> 
> These were the same problems I had when trying to use a correlated system for 
> OTA communications. I feel like I'm missing something really simple.
> 
>

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread mleech 
 

Try cranking your RX gain up/down 5dB and see how that affects your
constellation. 

On 2015-10-27 11:55, Washbourne, Logan wrote: 

> Ok, that sampling rate mismatch was my fault. The RX spectrum looks better 
> after that fix. The unpacked to packed bits didn't seem to remove the zero 
> grouping on the constellation plot. Here are pictures of the setup now.
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Tue, Oct 27, 2015 at 10:34 AM, Richard Bell  
> wrote:
> 
> Logan, make sure you're feeding packed bytes into the DPSK Mod block. That's 
> probably why you're seeing a constellation point at zero, you're feeding in 
> unpacked bytes. That might fix everything. 
> 
> Rich
> 
> Sent from my iPad 
> 
> On Oct 27, 2015, at 8:16 AM, mle...@ripnet.com wrote:
> 
> What does the spectral plot look like? It should look very similar to the TX 
> side of the house. 
> 
> On 2015-10-27 11:10, Washbourne, Logan wrote: 
> 
> Thanks for the info guys! They are both using antennas btw. I came in this 
> morning and turned the RX gain up pretty high, roughly 45dB, and the 
> constellation plot on the RX side is starting to look pretty square, which I 
> think is a bad sign. My thoughts are that with the increase in gain, there is 
> too much noise coming through.
> 
> I've been toying with adding in a frequency offset on the TX side. I've been 
> adding and subtracting up to 30kHz from the center frequency and I haven't 
> seen any improvement in the constellation plot on the RX side.
> 
> Another thing that is confusing me, on the TX constellation plot, before it 
> gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure where 
> the 0 points are coming from. Since this is DBPSK, there should only be -.5 
> and .5 groupings right?
> 
> Should this exercise be pretty straightforward? 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
> 
> Consulting now, the book of armaments, errr, UHD manual: 
> 
> http://files.ettus.com/manual/page_dboards.html#dboards_rfx [2] 
> 
> The RFX series has no TX RF gain control, output magnitude is entirely 
> dependent on baseband magnitude. 
> 
> There's 70dB of gain range on RX, however. So, crank up the RX gain. 
> 
> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is probably 
> putting out 5dBm, so at the RX end, that's maybe as much as -35dBm. If your 
> RX is set properly, should be enough to see the signal. 
> 
> On 2015-10-26 15:46, Marcus Müller wrote: Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [3] TX
> http://imgur.com/DBy8gqs [4] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread Richard Bell 
Logan, make sure you're feeding packed bytes into the DPSK Mod block. That's 
probably why you're seeing a constellation point at zero, you're feeding in 
unpacked bytes. That might fix everything. 

Rich

Sent from my iPad

> On Oct 27, 2015, at 8:16 AM, mle...@ripnet.com wrote:
> 
> What does the spectral plot look like?  It should look very similar to the TX 
> side of the house.
> 
>  
> 
>  
> 
>  
>> On 2015-10-27 11:10, Washbourne, Logan wrote:
>> 
>> Thanks for the info guys! They are both using antennas btw. I came in this 
>> morning and turned the RX gain up pretty high, roughly 45dB, and the 
>> constellation plot on the RX side is starting to look pretty square, which I 
>> think is a bad sign. My thoughts are that with the increase in gain, there 
>> is too much noise coming through.
>> 
>> I've been toying with adding in a frequency offset on the TX side. I've been 
>> adding and subtracting up to 30kHz from the center frequency and I haven't 
>> seen any improvement in the constellation plot on the RX side.
>> 
>> Another thing that is confusing me, on the TX constellation plot, before it 
>> gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure where 
>> the 0 points are coming from. Since this is DBPSK, there should only be -.5 
>> and .5 groupings right?
>> 
>> Should this exercise be pretty straightforward?
>> 
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>> 
>>> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
>>> Consulting now, the book of armaments, errr, UHD manual:
>>> 
>>>  
>>> 
>>> http://files.ettus.com/manual/page_dboards.html#dboards_rfx
>>> 
>>>  
>>> 
>>> The RFX series has no TX RF gain control, output magnitude is entirely 
>>> dependent on baseband magnitude.
>>> 
>>> There's 70dB of gain range on RX, however.  So, crank up the RX gain.
>>> 
>>> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is probably 
>>> putting out 5dBm, so at the RX end, that's maybe as much as -35dBm. If your 
>>> RX is set properly, should be enough to see the signal.
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  
>>> On 2015-10-26 15:46, Marcus Müller wrote:
>>> 
>>> Hi!
>>> 
>>> * looking at your constellation, relief comes setting in: It looks pretty 
>>> circular to me; notice how the axes are scaled differently. So no 
>>> catastrophic IQ imbalance.
>>> * the fact that it's circular and not a line is probably the result of the 
>>> constellation sink not being able to achieve timing synchronization, i.e. 
>>> it doesn't "know" when a symbol starts
>>> * You're right, RX SNR is terrible. However, RX power is very little indeed
>>>   * Rule of thumb: if(not clipping && in doubt) increase gain;
>>>   * What exactly is your "RF channel": antennas, direct cable with 
>>> attenuator?
>>>   * The mistake I do every few months: Did you connect the antenna/cable to 
>>> the wrong SMA port?
>>> 
>>> Best regards,
>>> Marcus 
>>> On 26.10.2015 20:33, Washbourne, Logan wrote:
>>> I looked at the spectrums of both sides and the RX side looks to be 
>>> inundated with a lot of noise. I'm not sure if its my environment or my 
>>> USRPs, but I really expected to see some resemblance of a signal. I am 
>>> posting links to screencaps of the TX and RX sides.
>>> 
>>> http://imgur.com/GBTHw8T- TX
>>> http://imgur.com/DBy8gqs - RX
>>> 
>>> Logan Washbourne
>>> Electrical Engineering Graduate Student
>>> (Electromagnetics)
>>> 
 On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
 wrote:
 Can you compare the TX spectrum with the RX spectrum? Maybe it'd 
 worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether, 
 due to frequency offset, some of the wanted signal simply gets cut off; 
 admittedly, with 2S/sym that's not too likely...
 
 Best regards,
 Marcus
 
 
 On 26.10.2015 19:16, Washbourne, Logan wrote:
 I am using 250k!
  
  
 
 Logan Washbourne
 Electrical Engineering Graduate Student
 (Electromagnetics)
 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus
> 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote:
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications 
> with the USRPs. Let me know if it would be better to post this in the 
> USRPs-Users list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector 
> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply 
> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread Washbourne, Logan 
Thanks for the info guys! They are both using antennas btw. I came in this
morning and turned the RX gain up pretty high, roughly 45dB, and the
constellation plot on the RX side is starting to look pretty square, which
I think is a bad sign. My thoughts are that with the increase in gain,
there is too much noise coming through.

I've been toying with adding in a frequency offset on the TX side. I've
been adding and subtracting up to 30kHz from the center frequency and I
haven't seen any improvement in the constellation plot on the RX side.

Another thing that is confusing me, on the TX constellation plot, before it
gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure
where the 0 points are coming from. Since this is DBPSK, there should only
be -.5 and .5 groupings right?

Should this exercise be pretty straightforward?

Logan Washbourne
Electrical Engineering Graduate Student
(Electromagnetics)


On Mon, Oct 26, 2015 at 3:12 PM,  wrote:

> Consulting now, the book of armaments, errr, UHD manual:
>
>
>
> http://files.ettus.com/manual/page_dboards.html#dboards_rfx
>
>
>
> The RFX series has no TX RF gain control, output magnitude is entirely
> dependent on baseband magnitude.
>
> There's 70dB of gain range on RX, however.  So, crank up the RX gain.
>
> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is
> probably putting out 5dBm, so at the RX end, that's maybe as much as
> -35dBm. If your RX is set properly, should be enough to see the signal.
>
>
>
>
>
>
> On 2015-10-26 15:46, Marcus Müller wrote:
>
> Hi!
>
> * looking at your constellation, relief comes setting in: It looks pretty
> circular to me; notice how the axes are scaled differently. So no
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the
> constellation sink not being able to achieve timing synchronization, i.e.
> it doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
>   * Rule of thumb: if(not clipping && in doubt) increase gain;
>   * What exactly is your "RF channel": antennas, direct cable with
> attenuator?
>   * The mistake I do every few months: Did you connect the antenna/cable
> to the wrong SMA port?
>
> Best regards,
> Marcus
> On 26.10.2015 20:33, Washbourne, Logan wrote:
>
> I looked at the spectrums of both sides and the RX side looks to be
> inundated with a lot of noise. I'm not sure if its my environment or my
> USRPs, but I really expected to see some resemblance of a signal. I am
> posting links to screencaps of the TX and RX sides.
>
> http://imgur.com/GBTHw8T- TX
> http://imgur.com/DBy8gqs - RX
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller 
> wrote:
>
>> Can you compare the TX spectrum with the RX spectrum? Maybe it'd
>> worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether,
>> due to frequency offset, some of the wanted signal simply gets cut off;
>> admittedly, with 2S/sym that's not too likely...
>>
>> Best regards,
>> Marcus
>>
>>
>> On 26.10.2015 19:16, Washbourne, Logan wrote:
>>
>> I am using 250k!
>>
>>
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller 
>> wrote:
>>
>>> Hello!
>>> what's the sampling rate you're using?
>>>
>>> Best regards,
>>> Marcus
>>>
>>>
>>> On 26.10.2015 18:38, Washbourne, Logan wrote:
>>>
>>> Hello all,
>>>
>>> I'm trying to take a step back from my previous postings and try a
>>> simple approach to try and understand working with over the air
>>> communications with the USRPs. Let me know if it would be better to post
>>> this in the USRPs-Users list.
>>>
>>> I'm trying to have a simple TX and simple RX side so I can eliminate and
>>> unnecessary complications.
>>>
>>> The TX side has the following flowgraph: Vector
>>> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
>>> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>>>
>>> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) ->
>>> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
>>>
>>> I'm checking the progress of the communication by looking at a
>>> constellation plot that is connected directly to the USRP SOURCE block on
>>> the receiver side. I'm getting a very elliptical shape, more spread out in
>>> the horizontal direction but not by much. I'm also looking at the bits from
>>> the receiver side in matlab and my preamble is not showing up.
>>>
>>> These were the same problems I had when trying to use a correlated
>>> system for OTA communications. I feel like I'm missing something really
>>> simple.
>>>
>>> Does anyone know of a simple TX, RX grc setup that I can use to test my
>>> USRPs?
>>>
>>> Again, I really appreciate the help you guys

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread Richard Bell 
To sanity check the transmitter, instead of showing the constellation of
every sample, show every other sample, i.e. decimate by 2 going into the
constellation plot. The two comes from the fact you use 2 samples/symbol.
We don't want to see the every sample on a constellation, only symbols.
That's why the transmitter block has the grouping it does. Once you've
confirmed you see the expected BPSK constellation, you can move on to the
receiver.

On Tue, Oct 27, 2015 at 9:08 AM,  wrote:

> Try cranking your RX gain up/down 5dB and see how that affects your
> constellation.
>
>
>
>
>
>
> On 2015-10-27 11:55, Washbourne, Logan wrote:
>
> Ok, that sampling rate mismatch was my fault. The RX spectrum looks better
> after that fix. The unpacked to packed bits didn't seem to remove the zero
> grouping on the constellation plot. Here are pictures of the setup now.
>
>
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
> On Tue, Oct 27, 2015 at 10:34 AM, Richard Bell 
> wrote:
>
>> Logan, make sure you're feeding packed bytes into the DPSK Mod block.
>> That's probably why you're seeing a constellation point at zero, you're
>> feeding in unpacked bytes. That might fix everything.
>>
>> Rich
>>
>> Sent from my iPad
>>
>> On Oct 27, 2015, at 8:16 AM, mle...@ripnet.com wrote:
>>
>> What does the spectral plot look like?  It should look very similar to
>> the TX side of the house.
>>
>>
>>
>>
>>
>>
>> On 2015-10-27 11:10, Washbourne, Logan wrote:
>>
>> Thanks for the info guys! They are both using antennas btw. I came in
>> this morning and turned the RX gain up pretty high, roughly 45dB, and the
>> constellation plot on the RX side is starting to look pretty square, which
>> I think is a bad sign. My thoughts are that with the increase in gain,
>> there is too much noise coming through.
>>
>> I've been toying with adding in a frequency offset on the TX side. I've
>> been adding and subtracting up to 30kHz from the center frequency and I
>> haven't seen any improvement in the constellation plot on the RX side.
>>
>> Another thing that is confusing me, on the TX constellation plot, before
>> it gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure
>> where the 0 points are coming from. Since this is DBPSK, there should only
>> be -.5 and .5 groupings right?
>>
>> Should this exercise be pretty straightforward?
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
>>
>>> Consulting now, the book of armaments, errr, UHD manual:
>>>
>>>
>>>
>>> http://files.ettus.com/manual/page_dboards.html#dboards_rfx
>>>
>>>
>>>
>>> The RFX series has no TX RF gain control, output magnitude is entirely
>>> dependent on baseband magnitude.
>>>
>>> There's 70dB of gain range on RX, however.  So, crank up the RX gain.
>>>
>>> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is
>>> probably putting out 5dBm, so at the RX end, that's maybe as much as
>>> -35dBm. If your RX is set properly, should be enough to see the signal.
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 2015-10-26 15:46, Marcus Müller wrote:
>>>
>>> Hi!
>>>
>>> * looking at your constellation, relief comes setting in: It looks
>>> pretty circular to me; notice how the axes are scaled differently. So no
>>> catastrophic IQ imbalance.
>>> * the fact that it's circular and not a line is probably the result of
>>> the constellation sink not being able to achieve timing synchronization,
>>> i.e. it doesn't "know" when a symbol starts
>>> * You're right, RX SNR is terrible. However, RX power is very little
>>> indeed
>>>   * Rule of thumb: if(not clipping && in doubt) increase gain;
>>>   * What exactly is your "RF channel": antennas, direct cable with
>>> attenuator?
>>>   * The mistake I do every few months: Did you connect the antenna/cable
>>> to the wrong SMA port?
>>>
>>> Best regards,
>>> Marcus
>>> On 26.10.2015 20:33, Washbourne, Logan wrote:
>>>
>>> I looked at the spectrums of both sides and the RX side looks to be
>>> inundated with a lot of noise. I'm not sure if its my environment or my
>>> USRPs, but I really expected to see some resemblance of a signal. I am
>>> posting links to screencaps of the TX and RX sides.
>>>
>>> http://imgur.com/GBTHw8T- TX
>>> http://imgur.com/DBy8gqs - RX
>>>
>>> Logan Washbourne
>>> Electrical Engineering Graduate Student
>>> (Electromagnetics)
>>>
>>> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller >> > wrote:
>>>
 Can you compare the TX spectrum with the RX spectrum? Maybe it'd
 worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether,
 due to frequency offset, some of the wanted signal simply gets cut off;
 admittedly, with 2S/sym that's not too likely...

 Best regards,
 Marcus


 On 26.10.2015 19:16, Washbourne, Logan wrote:

 I am using 250k!

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-27 Thread mleech 
 

You're transmitting at 1MS, and receiving at 250ksps. Your receiver is
only seeing part of your signal. 

On 2015-10-27 11:27, Washbourne, Logan wrote: 

> The RX side looks drowned out, almost like its all noise.
> 
> I'm attaching the pictures, hopefully they make it trough the email filter. 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Tue, Oct 27, 2015 at 10:16 AM,  wrote:
> 
> What does the spectral plot look like? It should look very similar to the TX 
> side of the house. 
> 
> On 2015-10-27 11:10, Washbourne, Logan wrote: 
> 
> Thanks for the info guys! They are both using antennas btw. I came in this 
> morning and turned the RX gain up pretty high, roughly 45dB, and the 
> constellation plot on the RX side is starting to look pretty square, which I 
> think is a bad sign. My thoughts are that with the increase in gain, there is 
> too much noise coming through.
> 
> I've been toying with adding in a frequency offset on the TX side. I've been 
> adding and subtracting up to 30kHz from the center frequency and I haven't 
> seen any improvement in the constellation plot on the RX side.
> 
> Another thing that is confusing me, on the TX constellation plot, before it 
> gets sent to the USRP, there are 3 groupings, -.5, 0, .5. I'm not sure where 
> the 0 points are coming from. Since this is DBPSK, there should only be -.5 
> and .5 groupings right?
> 
> Should this exercise be pretty straightforward? 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 3:12 PM,  wrote:
> 
> Consulting now, the book of armaments, errr, UHD manual: 
> 
> http://files.ettus.com/manual/page_dboards.html#dboards_rfx [2] 
> 
> The RFX series has no TX RF gain control, output magnitude is entirely 
> dependent on baseband magnitude. 
> 
> There's 70dB of gain range on RX, however. So, crank up the RX gain. 
> 
> Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is probably 
> putting out 5dBm, so at the RX end, that's maybe as much as -35dBm. If your 
> RX is set properly, should be enough to see the signal. 
> 
> On 2015-10-26 15:46, Marcus Müller wrote: Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [3] TX
> http://imgur.com/DBy8gqs [4] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK 
> Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz 
> center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK 
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
> 
> I'm checking the progress of the communication by looking at a

Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread mleech 
 

How much attenuation do you have in the path between the TX and RX? What
daughtercards? Two separate USRPs, or a single, looped back? 

If you turn the RX gain up, does the RX FFT change? Are you on the RX2
port on the RX side? 

On 2015-10-26 15:33, Washbourne, Logan wrote: 

> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [2] TX
> http://imgur.com/DBy8gqs [3] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK 
> Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz 
> center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK 
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
> 
> I'm checking the progress of the communication by looking at a constellation 
> plot that is connected directly to the USRP SOURCE block on the receiver 
> side. I'm getting a very elliptical shape, more spread out in the horizontal 
> direction but not by much. I'm also looking at the bits from the receiver 
> side in matlab and my preamble is not showing up.
> 
> These were the same problems I had when trying to use a correlated system for 
> OTA communications. I feel like I'm missing something really simple.
> 
> Does anyone know of a simple TX, RX grc setup that I can use to test my USRPs?
> 
> Again, I really appreciate the help you guys give.
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
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Links:
--
[1] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[2] http://imgur.com/GBTHw8T-
[3] http://imgur.com/DBy8gqs
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Washbourne, Logan 
I looked at the spectrums of both sides and the RX side looks to be
inundated with a lot of noise. I'm not sure if its my environment or my
USRPs, but I really expected to see some resemblance of a signal. I am
posting links to screencaps of the TX and RX sides.

http://imgur.com/GBTHw8T- TX
http://imgur.com/DBy8gqs - RX

Logan Washbourne
Electrical Engineering Graduate Student
(Electromagnetics)


On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller 
wrote:

> Can you compare the TX spectrum with the RX spectrum? Maybe it'd
> worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether,
> due to frequency offset, some of the wanted signal simply gets cut off;
> admittedly, with 2S/sym that's not too likely...
>
> Best regards,
> Marcus
>
>
> On 26.10.2015 19:16, Washbourne, Logan wrote:
>
> I am using 250k!
>
>
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller 
> wrote:
>
>> Hello!
>> what's the sampling rate you're using?
>>
>> Best regards,
>> Marcus
>>
>>
>> On 26.10.2015 18:38, Washbourne, Logan wrote:
>>
>> Hello all,
>>
>> I'm trying to take a step back from my previous postings and try a simple
>> approach to try and understand working with over the air communications
>> with the USRPs. Let me know if it would be better to post this in the
>> USRPs-Users list.
>>
>> I'm trying to have a simple TX and simple RX side so I can eliminate and
>> unnecessary complications.
>>
>> The TX side has the following flowgraph: Vector
>> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
>> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>>
>> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK
>> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
>>
>> I'm checking the progress of the communication by looking at a
>> constellation plot that is connected directly to the USRP SOURCE block on
>> the receiver side. I'm getting a very elliptical shape, more spread out in
>> the horizontal direction but not by much. I'm also looking at the bits from
>> the receiver side in matlab and my preamble is not showing up.
>>
>> These were the same problems I had when trying to use a correlated system
>> for OTA communications. I feel like I'm missing something really simple.
>>
>> Does anyone know of a simple TX, RX grc setup that I can use to test my
>> USRPs?
>>
>> Again, I really appreciate the help you guys give.
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>>
>>
>> ___
>> Discuss-gnuradio mailing 
>> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
>>
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>>
>>
>
>
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Washbourne, Logan 
Tx and Rx are on their own USRP1s, the daughter board is the RFX2400. They
are roughl 3ft apart from each other on a desk. The Rx side is using the
RX2 port.

I will definitely try upping the gain when I get back into the office
tomorrow. I will check the SMA ports, I didn't configure these myself so I
should probably double check them anyways.



Logan Washbourne
Electrical Engineering Graduate Student
(Electromagnetics)


On Mon, Oct 26, 2015 at 2:46 PM, Marcus Müller 
wrote:

> Hi!
>
> * looking at your constellation, relief comes setting in: It looks pretty
> circular to me; notice how the axes are scaled differently. So no
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the
> constellation sink not being able to achieve timing synchronization, i.e.
> it doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
>   * Rule of thumb: if(not clipping && in doubt) increase gain;
>   * What exactly is your "RF channel": antennas, direct cable with
> attenuator?
>   * The mistake I do every few months: Did you connect the antenna/cable
> to the wrong SMA port?
>
> Best regards,
> Marcus
> On 26.10.2015 20:33, Washbourne, Logan wrote:
>
> I looked at the spectrums of both sides and the RX side looks to be
> inundated with a lot of noise. I'm not sure if its my environment or my
> USRPs, but I really expected to see some resemblance of a signal. I am
> posting links to screencaps of the TX and RX sides.
>
> http://imgur.com/GBTHw8T- TX
> http://imgur.com/DBy8gqs - RX
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller 
> wrote:
>
>> Can you compare the TX spectrum with the RX spectrum? Maybe it'd
>> worthwhile to first look at at e.g. 500kHz of RX spectrum to see whether,
>> due to frequency offset, some of the wanted signal simply gets cut off;
>> admittedly, with 2S/sym that's not too likely...
>>
>> Best regards,
>> Marcus
>>
>>
>> On 26.10.2015 19:16, Washbourne, Logan wrote:
>>
>> I am using 250k!
>>
>>
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>>
>> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller <
>> marcus.muel...@ettus.com> wrote:
>>
>>> Hello!
>>> what's the sampling rate you're using?
>>>
>>> Best regards,
>>> Marcus
>>>
>>>
>>> On 26.10.2015 18:38, Washbourne, Logan wrote:
>>>
>>> Hello all,
>>>
>>> I'm trying to take a step back from my previous postings and try a
>>> simple approach to try and understand working with over the air
>>> communications with the USRPs. Let me know if it would be better to post
>>> this in the USRPs-Users list.
>>>
>>> I'm trying to have a simple TX and simple RX side so I can eliminate and
>>> unnecessary complications.
>>>
>>> The TX side has the following flowgraph: Vector
>>> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
>>> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>>>
>>> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) ->
>>> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
>>>
>>> I'm checking the progress of the communication by looking at a
>>> constellation plot that is connected directly to the USRP SOURCE block on
>>> the receiver side. I'm getting a very elliptical shape, more spread out in
>>> the horizontal direction but not by much. I'm also looking at the bits from
>>> the receiver side in matlab and my preamble is not showing up.
>>>
>>> These were the same problems I had when trying to use a correlated
>>> system for OTA communications. I feel like I'm missing something really
>>> simple.
>>>
>>> Does anyone know of a simple TX, RX grc setup that I can use to test my
>>> USRPs?
>>>
>>> Again, I really appreciate the help you guys give.
>>>
>>> Logan Washbourne
>>> Electrical Engineering Graduate Student
>>> (Electromagnetics)
>>>
>>>
>>>
>>> ___
>>> Discuss-gnuradio mailing 
>>> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
>>>
>>>
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>>>
>>
>>
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Marcus Müller 
Hi!

* looking at your constellation, relief comes setting in: It looks
pretty circular to me; notice how the axes are scaled differently. So no
catastrophic IQ imbalance.
* the fact that it's circular and not a line is probably the result of
the constellation sink not being able to achieve timing synchronization,
i.e. it doesn't "know" when a symbol starts
* You're right, RX SNR is terrible. However, RX power is very little indeed
  * Rule of thumb: if(not clipping && in doubt) increase gain;
  * What exactly is your "RF channel": antennas, direct cable with
attenuator?
  * The mistake I do every few months: Did you connect the antenna/cable
to the wrong SMA port?

Best regards,
Marcus
On 26.10.2015 20:33, Washbourne, Logan wrote:
> I looked at the spectrums of both sides and the RX side looks to be
> inundated with a lot of noise. I'm not sure if its my environment or
> my USRPs, but I really expected to see some resemblance of a signal. I
> am posting links to screencaps of the TX and RX sides.
>
> http://imgur.com/GBTHw8T- TX
> http://imgur.com/DBy8gqs - RX
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller
> > wrote:
>
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd
> worthwhile to first look at at e.g. 500kHz of RX spectrum to see
> whether, due to frequency offset, some of the wanted signal simply
> gets cut off; admittedly, with 2S/sym that's not too likely...
>
> Best regards,
> Marcus
>
>
> On 26.10.2015 19:16, Washbourne, Logan wrote:
>> I am using 250k!
>>
>>
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>>
>> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller
>> > wrote:
>>
>> Hello!
>> what's the sampling rate you're using?
>>
>> Best regards,
>> Marcus
>>
>>
>> On 26.10.2015 18:38, Washbourne, Logan wrote:
>>> Hello all,
>>>
>>> I'm trying to take a step back from my previous postings and
>>> try a simple approach to try and understand working with
>>> over the air communications with the USRPs. Let me know if
>>> it would be better to post this in the USRPs-Users list.
>>>
>>> I'm trying to have a simple TX and simple RX side so I can
>>> eliminate and unnecessary complications.
>>>
>>> The TX side has the following flowgraph: Vector
>>> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)->
>>> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz center freq,
>>> 10dB default gain)
>>>
>>> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain
>>> default) -> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest
>>> default values) - > file sink
>>>
>>> I'm checking the progress of the communication by looking at
>>> a constellation plot that is connected directly to the USRP
>>> SOURCE block on the receiver side. I'm getting a very
>>> elliptical shape, more spread out in the horizontal
>>> direction but not by much. I'm also looking at the bits from
>>> the receiver side in matlab and my preamble is not showing up.
>>>
>>> These were the same problems I had when trying to use a
>>> correlated system for OTA communications. I feel like I'm
>>> missing something really simple.
>>>
>>> Does anyone know of a simple TX, RX grc setup that I can use
>>> to test my USRPs?
>>>
>>> Again, I really appreciate the help you guys give.
>>>
>>> Logan Washbourne
>>> Electrical Engineering Graduate Student
>>> (Electromagnetics)
>>>
>>>
>>>
>>> ___
>>> Discuss-gnuradio mailing list
>>> Discuss-gnuradio@gnu.org 
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread mleech 
 

With antennae, or with a cable, and if with a cable, how much
attenuation in the cable system? 

On 2015-10-26 15:54, Washbourne, Logan wrote: 

> Tx and Rx are on their own USRP1s, the daughter board is the RFX2400. They 
> are roughl 3ft apart from each other on a desk. The Rx side is using the RX2 
> port. 
> 
> I will definitely try upping the gain when I get back into the office 
> tomorrow. I will check the SMA ports, I didn't configure these myself so I 
> should probably double check them anyways. 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 2:46 PM, Marcus Müller  
> wrote:
> 
> Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [2] TX
> http://imgur.com/DBy8gqs [3] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK 
> Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz 
> center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK 
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
> 
> I'm checking the progress of the communication by looking at a constellation 
> plot that is connected directly to the USRP SOURCE block on the receiver 
> side. I'm getting a very elliptical shape, more spread out in the horizontal 
> direction but not by much. I'm also looking at the bits from the receiver 
> side in matlab and my preamble is not showing up.
> 
> These were the same problems I had when trying to use a correlated system for 
> OTA communications. I feel like I'm missing something really simple.
> 
> Does anyone know of a simple TX, RX grc setup that I can use to test my USRPs?
> 
> Again, I really appreciate the help you guys give.
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread mleech 
 

Consulting now, the book of armaments, errr, UHD manual: 

http://files.ettus.com/manual/page_dboards.html#dboards_rfx 

The RFX series has no TX RF gain control, output magnitude is entirely
dependent on baseband magnitude. 

There's 70dB of gain range on RX, however. So, crank up the RX gain. 

Also, across 1m, the path loss is about 40dB at 2.5GHz, your TX is
probably putting out 5dBm, so at the RX end, that's maybe as much as
-35dBm. If your RX is set properly, should be enough to see the signal. 

On 2015-10-26 15:46, Marcus Müller wrote: 

> Hi!
> 
> * looking at your constellation, relief comes setting in: It looks pretty 
> circular to me; notice how the axes are scaled differently. So no 
> catastrophic IQ imbalance.
> * the fact that it's circular and not a line is probably the result of the 
> constellation sink not being able to achieve timing synchronization, i.e. it 
> doesn't "know" when a symbol starts
> * You're right, RX SNR is terrible. However, RX power is very little indeed
> * Rule of thumb: if(not clipping && in doubt) increase gain;
> * What exactly is your "RF channel": antennas, direct cable with attenuator?
> * The mistake I do every few months: Did you connect the antenna/cable to the 
> wrong SMA port?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 20:33, Washbourne, Logan wrote: 
> I looked at the spectrums of both sides and the RX side looks to be inundated 
> with a lot of noise. I'm not sure if its my environment or my USRPs, but I 
> really expected to see some resemblance of a signal. I am posting links to 
> screencaps of the TX and RX sides.
> 
> http://imgur.com/GBTHw8T- [2] TX
> http://imgur.com/DBy8gqs [3] - RX
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:31 PM, Marcus Müller  
> wrote:
> 
> Can you compare the TX spectrum with the RX spectrum? Maybe it'd worthwhile 
> to first look at at e.g. 500kHz of RX spectrum to see whether, due to 
> frequency offset, some of the wanted signal simply gets cut off; admittedly, 
> with 2S/sym that's not too likely...
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 19:16, Washbourne, Logan wrote: 
> I am using 250k! 
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller  
> wrote:
> 
> Hello!
> what's the sampling rate you're using?
> 
> Best regards,
> Marcus 
> 
> On 26.10.2015 18:38, Washbourne, Logan wrote: 
> 
> Hello all,
> 
> I'm trying to take a step back from my previous postings and try a simple 
> approach to try and understand working with over the air communications with 
> the USRPs. Let me know if it would be better to post this in the USRPs-Users 
> list.
> 
> I'm trying to have a simple TX and simple RX side so I can eliminate and 
> unnecessary complications.
> 
> The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK 
> Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz 
> center freq, 10dB default gain)
> 
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK 
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
> 
> I'm checking the progress of the communication by looking at a constellation 
> plot that is connected directly to the USRP SOURCE block on the receiver 
> side. I'm getting a very elliptical shape, more spread out in the horizontal 
> direction but not by much. I'm also looking at the bits from the receiver 
> side in matlab and my preamble is not showing up.
> 
> These were the same problems I had when trying to use a correlated system for 
> OTA communications. I feel like I'm missing something really simple.
> 
> Does anyone know of a simple TX, RX grc setup that I can use to test my USRPs?
> 
> Again, I really appreciate the help you guys give.
> 
> Logan Washbourne Electrical Engineering Graduate Student (Electromagnetics) 
> 
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[Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Washbourne, Logan 
Hello all,

I'm trying to take a step back from my previous postings and try a simple
approach to try and understand working with over the air communications
with the USRPs. Let me know if it would be better to post this in the
USRPs-Users list.

I'm trying to have a simple TX and simple RX side so I can eliminate and
unnecessary complications.

The TX side has the following flowgraph: Vector Source(preamble+data)->DPSK
Mod(DBPSK,2samples/symbol)-> Multiply Const(.707) -> UHD:USRP SINK(2.448GHz
center freq, 10dB default gain)

RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK
DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink

I'm checking the progress of the communication by looking at a
constellation plot that is connected directly to the USRP SOURCE block on
the receiver side. I'm getting a very elliptical shape, more spread out in
the horizontal direction but not by much. I'm also looking at the bits from
the receiver side in matlab and my preamble is not showing up.

These were the same problems I had when trying to use a correlated system
for OTA communications. I feel like I'm missing something really simple.

Does anyone know of a simple TX, RX grc setup that I can use to test my
USRPs?

Again, I really appreciate the help you guys give.

Logan Washbourne
Electrical Engineering Graduate Student
(Electromagnetics)
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Marcus Müller 
Can you compare the TX spectrum with the RX spectrum? Maybe it'd
worthwhile to first look at at e.g. 500kHz of RX spectrum to see
whether, due to frequency offset, some of the wanted signal simply gets
cut off; admittedly, with 2S/sym that's not too likely...

Best regards,
Marcus

On 26.10.2015 19:16, Washbourne, Logan wrote:
> I am using 250k!
>
>
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
> On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller
> > wrote:
>
> Hello!
> what's the sampling rate you're using?
>
> Best regards,
> Marcus
>
>
> On 26.10.2015 18:38, Washbourne, Logan wrote:
>> Hello all,
>>
>> I'm trying to take a step back from my previous postings and try
>> a simple approach to try and understand working with over the air
>> communications with the USRPs. Let me know if it would be better
>> to post this in the USRPs-Users list.
>>
>> I'm trying to have a simple TX and simple RX side so I can
>> eliminate and unnecessary complications.
>>
>> The TX side has the following flowgraph: Vector
>> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
>> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>>
>> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default)
>> -> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest default values) - >
>> file sink
>>
>> I'm checking the progress of the communication by looking at a
>> constellation plot that is connected directly to the USRP SOURCE
>> block on the receiver side. I'm getting a very elliptical shape,
>> more spread out in the horizontal direction but not by much. I'm
>> also looking at the bits from the receiver side in matlab and my
>> preamble is not showing up.
>>
>> These were the same problems I had when trying to use a
>> correlated system for OTA communications. I feel like I'm missing
>> something really simple.
>>
>> Does anyone know of a simple TX, RX grc setup that I can use to
>> test my USRPs?
>>
>> Again, I really appreciate the help you guys give.
>>
>> Logan Washbourne
>> Electrical Engineering Graduate Student
>> (Electromagnetics)
>>
>>
>>
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Marcus Müller 
Hello!
what's the sampling rate you're using?

Best regards,
Marcus

On 26.10.2015 18:38, Washbourne, Logan wrote:
> Hello all,
>
> I'm trying to take a step back from my previous postings and try a
> simple approach to try and understand working with over the air
> communications with the USRPs. Let me know if it would be better to
> post this in the USRPs-Users list.
>
> I'm trying to have a simple TX and simple RX side so I can eliminate
> and unnecessary complications.
>
> The TX side has the following flowgraph: Vector
> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) ->
> DPSK DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
>
> I'm checking the progress of the communication by looking at a
> constellation plot that is connected directly to the USRP SOURCE block
> on the receiver side. I'm getting a very elliptical shape, more spread
> out in the horizontal direction but not by much. I'm also looking at
> the bits from the receiver side in matlab and my preamble is not
> showing up.
>
> These were the same problems I had when trying to use a correlated
> system for OTA communications. I feel like I'm missing something
> really simple.
>
> Does anyone know of a simple TX, RX grc setup that I can use to test
> my USRPs?
>
> Again, I really appreciate the help you guys give.
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
>
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Re: [Discuss-gnuradio] DBPSK and USRPs

2015-10-26 Thread Washbourne, Logan 
I am using 250k!



Logan Washbourne
Electrical Engineering Graduate Student
(Electromagnetics)


On Mon, Oct 26, 2015 at 1:05 PM, Marcus Müller 
wrote:

> Hello!
> what's the sampling rate you're using?
>
> Best regards,
> Marcus
>
>
> On 26.10.2015 18:38, Washbourne, Logan wrote:
>
> Hello all,
>
> I'm trying to take a step back from my previous postings and try a simple
> approach to try and understand working with over the air communications
> with the USRPs. Let me know if it would be better to post this in the
> USRPs-Users list.
>
> I'm trying to have a simple TX and simple RX side so I can eliminate and
> unnecessary complications.
>
> The TX side has the following flowgraph: Vector
> Source(preamble+data)->DPSK Mod(DBPSK,2samples/symbol)-> Multiply
> Const(.707) -> UHD:USRP SINK(2.448GHz center freq, 10dB default gain)
>
> RX Side: UHD:USRP Source(2.448GHz center freq, 10dB gain default) -> DPSK
> DEMOD(DBPSK, 2 samples/ symbol, rest default values) - > file sink
>
> I'm checking the progress of the communication by looking at a
> constellation plot that is connected directly to the USRP SOURCE block on
> the receiver side. I'm getting a very elliptical shape, more spread out in
> the horizontal direction but not by much. I'm also looking at the bits from
> the receiver side in matlab and my preamble is not showing up.
>
> These were the same problems I had when trying to use a correlated system
> for OTA communications. I feel like I'm missing something really simple.
>
> Does anyone know of a simple TX, RX grc setup that I can use to test my
> USRPs?
>
> Again, I really appreciate the help you guys give.
>
> Logan Washbourne
> Electrical Engineering Graduate Student
> (Electromagnetics)
>
>
>
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