Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

As long as you look after an overload or an intermodulation condition, I
don't see a problem with the RTL-SDR.  The phase noise wont matter for
low density modulation types like QPSK...

But as Helmut says, looking after the overload or intermod , SFDR
condition will be very important

8 bit is fine for low dynamic range narrowband applications.

if a nice big multi resonator coupled filter is used, the RTL SDR should
be OK / protected..

so , lots of front end filtering...

On 19/09/2017 2:28 AM, Helmut Oeller wrote:
> Hi Adrian,



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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

well, 2.4 GHz (compared to 70-500 MHz), a short delay profile will be
what you are working with, but with a high likelihood of 0dB echos. The
echoes tend to get quite strong due to the large reflective surface
performance. But there tends to be alot of them, rather than 1 or two
dominant echos . There is plenty of data on this in the literature.

Indoors, there is a tendency for flat fading even with very wide
bandwidths, so some sort of diversity (as Greg axwell pointed out) is
required.

g


On 19/09/2017 12:50 AM, Adrian Musceac wrote:
> Hi Glen,
>
> On 9/18/17, glen english  wrote:
>> It would not improve the performance in a low local multipath dominant
>> two tap local delay scenario  like rural/farmland.
>>
>
> I would be very curious about the dB levels vs. frequency. From my
> knowledge, above 400 MHz is highly unusual to have such a long delay
> with such a low ratio. But I'm not a specialist, and my data is mainly
> ~2.4 GHz so I'll try to prove it by eating the cake and providing BER
> stats vs. GPS data (speed etc.) vs. simulation (qradiopredict has
> CLC2006 data and in the future will do other models)
>
> Cheers,
> Adrian
>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Helmut Oeller]

Hi Adrian,

everything better than the 8 Bit RTL-SDR improves the chance for meaningful 
test results. I think all available 12 bit SDRs like  Ettus B200/210, but also 
your LimeSDR-Myriad (LMS7002M) or a configuration using the AD 9364 would be a 
better choice.  

73, Helmut



-Ursprüngliche Nachricht-
Von: Adrian Musceac [mailto:kanto...@gmail.com] 
Gesendet: Montag, 18. September 2017 16:42
An: freetel-codec2@lists.sourceforge.net
Betreff: Re: [Freetel-codec2] Comparison between digital voice and analog 
narrowband FM on weak signals with interference

Hi,

Do you have a particular device in mind? Anything that is supported by Osmosdr 
can be tested, but I only have AD9364 and Lime Micro devices available.

73,
Adrian

On 9/18/17, Helmut Oeller  wrote:
> Hi,
>
> IMO objective and severe comparison in presence of interference can 
> only succeed using appropriate SDR hardware. These USB sticks are not 
> developed for narrow bandwidths due to very low SFDR, phase noise of LO etc.
>
> 73, Helmut
>
> -Ursprüngliche Nachricht-
> Von: Adrian Musceac [mailto:kanto...@gmail.com]
> Gesendet: Montag, 18. September 2017 11:01
> An: freetel-codec2@lists.sourceforge.net
> Betreff: Re: [Freetel-codec2] Comparison between digital voice and 
> analog narrowband FM on weak signals with interference
>
> Hi,
>
> Helmut, for me RTL-SDR support is required. I will not be testing with 
> another SDR hardware for reception as my application is meant to work 
> with the USB stick (small dynamic range or not).
>
> Glen, have a look at
> http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p
> .pdf specifically section 6.2.2 and below. Faces exactly the same 
> issues.
> FM is also affected by fast Rayleigh fading..
> Anyway, Doppler shift will be a bigger issue than multipath.
>
> Cheers,
> Adrian
>
>
> On 9/18/17, glen english  wrote:
>> HI Adrian
>>
>> good stuff!
>>
>> OK, now try the analog versus the digital, with a copy of the TX 
>> signal at 30uS  delay and -10dB with respect to the wanted signal
>> (a common multipath ) , and also 30uS delay and 0dB.
>>
>> Let me know...
>>
>>
>> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>>> Hi,
>>>
>>> I present a three way comparison between narrow band FM (5 kHz), 
>>> QPSK
>>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>>
>>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>>
>>> The comparison is taking place in the ISM band of 433 MHz with 
>>> interference present from some temperature sensors in an adjacent 
>>> channel.
>>>
>>> Conditions: same antenna locations, same RX chain gain, varying 
>>> transmit gain (LCD like number on the top left of the screen)
>>>
>>> Results: both digital modes cope better with interference and are 
>>> more intelligible than FM. The numbers on top left of RX application 
>>> are expressed in dB of amplification in the SDR transmitter chain.
>>>
>>> Hardware: for transmit one USRP B200 with 433 MHz filter installed, 
>>> for RX one RTL-SDR filter with 433 filter installed.
>>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>>> https://github.com/kantooon/qradiolink
>>>
>>> 73,
>>> Adrian YO8RZZ
>>>
>>>
>>> 
>>> -
>>> - Check out the vibrant tech community on one of the world's 
>>> most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>>
>>>
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>>
>>
>>
>> -
>> -
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Adrian Musceac]

Hi Glen,

On 9/18/17, glen english  wrote:
>
> It would not improve the performance in a low local multipath dominant
> two tap local delay scenario  like rural/farmland.
>


I would be very curious about the dB levels vs. frequency. From my
knowledge, above 400 MHz is highly unusual to have such a long delay
with such a low ratio. But I'm not a specialist, and my data is mainly
~2.4 GHz so I'll try to prove it by eating the cake and providing BER
stats vs. GPS data (speed etc.) vs. simulation (qradiopredict has
CLC2006 data and in the future will do other models)

Cheers,
Adrian

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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Adrian Musceac]

Hi,

Do you have a particular device in mind? Anything that is supported by
Osmosdr can be tested, but I only have AD9364 and Lime Micro devices
available.

73,
Adrian

On 9/18/17, Helmut Oeller  wrote:
> Hi,
>
> IMO objective and severe comparison in presence of interference can only
> succeed using appropriate SDR hardware. These USB sticks are not developed
> for narrow bandwidths due to very low SFDR, phase noise of LO etc.
>
> 73, Helmut
>
> -Ursprüngliche Nachricht-
> Von: Adrian Musceac [mailto:kanto...@gmail.com]
> Gesendet: Montag, 18. September 2017 11:01
> An: freetel-codec2@lists.sourceforge.net
> Betreff: Re: [Freetel-codec2] Comparison between digital voice and analog
> narrowband FM on weak signals with interference
>
> Hi,
>
> Helmut, for me RTL-SDR support is required. I will not be testing with
> another SDR hardware for reception as my application is meant to work with
> the USB stick (small dynamic range or not).
>
> Glen, have a look at
> http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf
> specifically section 6.2.2 and below. Faces exactly the same issues.
> FM is also affected by fast Rayleigh fading..
> Anyway, Doppler shift will be a bigger issue than multipath.
>
> Cheers,
> Adrian
>
>
> On 9/18/17, glen english  wrote:
>> HI Adrian
>>
>> good stuff!
>>
>> OK, now try the analog versus the digital, with a copy of the TX
>> signal at 30uS  delay and -10dB with respect to the wanted signal
>> (a common multipath ) , and also 30uS delay and 0dB.
>>
>> Let me know...
>>
>>
>> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>>> Hi,
>>>
>>> I present a three way comparison between narrow band FM (5 kHz), QPSK
>>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>>
>>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>>
>>> The comparison is taking place in the ISM band of 433 MHz with
>>> interference present from some temperature sensors in an adjacent
>>> channel.
>>>
>>> Conditions: same antenna locations, same RX chain gain, varying
>>> transmit gain (LCD like number on the top left of the screen)
>>>
>>> Results: both digital modes cope better with interference and are
>>> more intelligible than FM. The numbers on top left of RX application
>>> are expressed in dB of amplification in the SDR transmitter chain.
>>>
>>> Hardware: for transmit one USRP B200 with 433 MHz filter installed,
>>> for RX one RTL-SDR filter with 433 filter installed.
>>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>>> https://github.com/kantooon/qradiolink
>>>
>>> 73,
>>> Adrian YO8RZZ
>>>
>>>
>>> -
>>> - Check out the vibrant tech community on one of the world's
>>> most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>>
>>>
>>> ___
>>> Freetel-codec2 mailing list
>>> Freetel-codec2@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2
>>
>>
>>
>> --
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

Hi Greg

True diversity (2 x omni) receiver wont fix the long echo scenario
it is likely in that scenario both diversity branches will cop the same
(bad) delay profile .

However it would likely improve the performance if there was a very high
level of local multipath, as such decorrelating the two antennas.

That is to say, there would be a long delay profile applied to both
antennas, and there would also but, superimposed, a short delay (local
multipath) delay profile. If you are lucky, the two antennas will see a
different composite delay profile.

It would not improve the performance in a low local multipath dominant
two tap local delay scenario  like rural/farmland.

There are some other mitigation strategies.  1) dynamic directivity by
use of a steerable antenna, there at least two antennas are used in a
beam steering scenario, and the strong (trouble) reflections are
nulled.  2) reduce the symbol rate/ reduce the SNR requirement

cheers


On 18/09/2017 7:19 PM, Gregory Maxwell wrote:
> On Mon, Sep 18, 2017 at 9:14 AM, glen english  wrote:
>> The only real fix is slowing down the symbol rate.
> A true diversity receiver is also a real fix.
>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Helmut Oeller]

Hi, 

IMO objective and severe comparison in presence of interference can only
succeed using appropriate SDR hardware. These USB sticks are not developed
for narrow bandwidths due to very low SFDR, phase noise of LO etc.

73, Helmut

-Ursprüngliche Nachricht-
Von: Adrian Musceac [mailto:kanto...@gmail.com] 
Gesendet: Montag, 18. September 2017 11:01
An: freetel-codec2@lists.sourceforge.net
Betreff: Re: [Freetel-codec2] Comparison between digital voice and analog
narrowband FM on weak signals with interference

Hi,

Helmut, for me RTL-SDR support is required. I will not be testing with
another SDR hardware for reception as my application is meant to work with
the USB stick (small dynamic range or not).

Glen, have a look at
http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf
specifically section 6.2.2 and below. Faces exactly the same issues.
FM is also affected by fast Rayleigh fading..
Anyway, Doppler shift will be a bigger issue than multipath.

Cheers,
Adrian


On 9/18/17, glen english  wrote:
> HI Adrian
>
> good stuff!
>
> OK, now try the analog versus the digital, with a copy of the TX 
> signal at 30uS  delay and -10dB with respect to the wanted signal 
> (a common multipath ) , and also 30uS delay and 0dB.
>
> Let me know...
>
>
> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>> Hi,
>>
>> I present a three way comparison between narrow band FM (5 kHz), QPSK
>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>
>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>
>> The comparison is taking place in the ISM band of 433 MHz with 
>> interference present from some temperature sensors in an adjacent 
>> channel.
>>
>> Conditions: same antenna locations, same RX chain gain, varying 
>> transmit gain (LCD like number on the top left of the screen)
>>
>> Results: both digital modes cope better with interference and are 
>> more intelligible than FM. The numbers on top left of RX application 
>> are expressed in dB of amplification in the SDR transmitter chain.
>>
>> Hardware: for transmit one USRP B200 with 433 MHz filter installed, 
>> for RX one RTL-SDR filter with 433 filter installed.
>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>> https://github.com/kantooon/qradiolink
>>
>> 73,
>> Adrian YO8RZZ
>>
>>
>> -
>> - Check out the vibrant tech community on one of the world's 
>> most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>
>>
>> ___
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>
>
>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

Hi Alex

so the ETSI HTx 6.2.2.4 propagation profile is specified as :

two taps, ratio 8.6dB
tap delay : 1/4 TETRA symbol (12.5uS)

In my opinion, this is completely insufficient. Any arse can pass that.

A more realistic test would be two taps 0dB, and 25uS delay. That's
reality

Their EQx model is closer to the mark but excluded from usual testing...
it is too hard !

THE PROBLEM IS most of the digital systems like DMR and P25 are not BER
driven, especially at the terminal, they are mostly RSSI driven for
voting.  The base can site-vote but the mobile has to do better.

cheers


On 18/09/2017 7:00 PM, Adrian Musceac wrote:
> Hi,
>
> Helmut, for me RTL-SDR support is required. I will not be testing with
> another SDR hardware for reception as my application is meant to work
> with the USB stick (small dynamic range or not).
>
> Glen, have a look at
> http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf
> specifically section 6.2.2 and below. Faces exactly the same issues.
> FM is also affected by fast Rayleigh fading..
> Anyway, Doppler shift will be a bigger issue than multipath.
>
> Cheers,
> Adrian
>
>
> On 9/18/17, glen english  wrote:
>> HI Adrian
>>
>> good stuff!
>>
>> OK, now try the analog versus the digital, with a copy of the TX signal
>> at 30uS  delay and -10dB with respect to the wanted signal (a common
>> multipath ) , and also 30uS delay and 0dB.
>>
>> Let me know...
>>
>>
>> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>>> Hi,
>>>
>>> I present a three way comparison between narrow band FM (5 kHz), QPSK
>>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>>
>>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>>
>>> The comparison is taking place in the ISM band of 433 MHz with
>>> interference present from some temperature sensors in an adjacent
>>> channel.
>>>
>>> Conditions: same antenna locations, same RX chain gain, varying
>>> transmit gain (LCD like number on the top left of the screen)
>>>
>>> Results: both digital modes cope better with interference and are more
>>> intelligible than FM. The numbers on top left of RX application are
>>> expressed in dB of amplification in the SDR transmitter chain.
>>>
>>> Hardware: for transmit one USRP B200 with 433 MHz filter installed,
>>> for RX one RTL-SDR filter with 433 filter installed.
>>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>>> https://github.com/kantooon/qradiolink
>>>
>>> 73,
>>> Adrian YO8RZZ
>>>
>>>
>>> --
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>>
>>>
>>> ___
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>>> Freetel-codec2@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/freetel-codec2
>>
>>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Gregory Maxwell]

On Mon, Sep 18, 2017 at 9:14 AM, glen english  wrote:
> The only real fix is slowing down the symbol rate.

A true diversity receiver is also a real fix.

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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

Hi ALex

well ETSI can say what they like, but unless the system is long delay
multipath tolerant, it will be a poor performer with respect to analog
if a hill gets in the way with another hill behind it...

This is not a rayleigh flat fading scenario, this is a frequency
selective fast fading scenario.

I see it in all the narrowband digital systems, P25, DMR, Tetra.

It is VERY difficult to fix with an equaliser in a narrow band
environment . If the multipath was stationary, then it is fixable, but
in a mobile environment,  the results are poor unless there is alot of
overhead.

The only real fix is slowing down the symbol rate. 
The 700 sps I think is slow enough,  anything more than 2000 sps is trouble

So, if you want to go faster  than say 2000 sps, use of OFDM ! lots of
low symbol rate carriers...

as for doppler shift, well that depends on the frequency, speed etc sure.

cheers

glen.




On 18/09/2017 7:00 PM, Adrian Musceac wrote:
> Hi,
>
> Helmut, for me RTL-SDR support is required. I will not be testing with
> another SDR hardware for reception as my application is meant to work
> with the USB stick (small dynamic range or not).
>
> Glen, have a look at
> http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf
> specifically section 6.2.2 and below. Faces exactly the same issues.
> FM is also affected by fast Rayleigh fading..
> Anyway, Doppler shift will be a bigger issue than multipath.
>
> Cheers,
> Adrian
>
>
> On 9/18/17, glen english  wrote:
>> HI Adrian
>>
>> good stuff!
>>
>> OK, now try the analog versus the digital, with a copy of the TX signal
>> at 30uS  delay and -10dB with respect to the wanted signal (a common
>> multipath ) , and also 30uS delay and 0dB.
>>
>> Let me know...
>>
>>
>> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>>> Hi,
>>>
>>> I present a three way comparison between narrow band FM (5 kHz), QPSK
>>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>>
>>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>>
>>> The comparison is taking place in the ISM band of 433 MHz with
>>> interference present from some temperature sensors in an adjacent
>>> channel.
>>>
>>> Conditions: same antenna locations, same RX chain gain, varying
>>> transmit gain (LCD like number on the top left of the screen)
>>>
>>> Results: both digital modes cope better with interference and are more
>>> intelligible than FM. The numbers on top left of RX application are
>>> expressed in dB of amplification in the SDR transmitter chain.
>>>
>>> Hardware: for transmit one USRP B200 with 433 MHz filter installed,
>>> for RX one RTL-SDR filter with 433 filter installed.
>>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>>> https://github.com/kantooon/qradiolink
>>>
>>> 73,
>>> Adrian YO8RZZ
>>>
>>>
>>> --
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>>>
>>>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[Adrian Musceac]

Hi,

Helmut, for me RTL-SDR support is required. I will not be testing with
another SDR hardware for reception as my application is meant to work
with the USB stick (small dynamic range or not).

Glen, have a look at
http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf
specifically section 6.2.2 and below. Faces exactly the same issues.
FM is also affected by fast Rayleigh fading..
Anyway, Doppler shift will be a bigger issue than multipath.

Cheers,
Adrian


On 9/18/17, glen english  wrote:
> HI Adrian
>
> good stuff!
>
> OK, now try the analog versus the digital, with a copy of the TX signal
> at 30uS  delay and -10dB with respect to the wanted signal (a common
> multipath ) , and also 30uS delay and 0dB.
>
> Let me know...
>
>
> On 15/09/2017 9:10 PM, Adrian Musceac wrote:
>> Hi,
>>
>> I present a three way comparison between narrow band FM (5 kHz), QPSK
>> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>>
>> https://www.youtube.com/watch?v=vApRe6R1gnk
>>
>> The comparison is taking place in the ISM band of 433 MHz with
>> interference present from some temperature sensors in an adjacent
>> channel.
>>
>> Conditions: same antenna locations, same RX chain gain, varying
>> transmit gain (LCD like number on the top left of the screen)
>>
>> Results: both digital modes cope better with interference and are more
>> intelligible than FM. The numbers on top left of RX application are
>> expressed in dB of amplification in the SDR transmitter chain.
>>
>> Hardware: for transmit one USRP B200 with 433 MHz filter installed,
>> for RX one RTL-SDR filter with 433 filter installed.
>> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
>> https://github.com/kantooon/qradiolink
>>
>> 73,
>> Adrian YO8RZZ
>>
>>
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>
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Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference

[glen english]

HI Adrian

good stuff!

OK, now try the analog versus the digital, with a copy of the TX signal
at 30uS  delay and -10dB with respect to the wanted signal (a common
multipath ) , and also 30uS delay and 0dB.

Let me know...


On 15/09/2017 9:10 PM, Adrian Musceac wrote:
> Hi,
>
> I present a three way comparison between narrow band FM (5 kHz), QPSK
> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz):
>
> https://www.youtube.com/watch?v=vApRe6R1gnk
>
> The comparison is taking place in the ISM band of 433 MHz with
> interference present from some temperature sensors in an adjacent
> channel.
>
> Conditions: same antenna locations, same RX chain gain, varying
> transmit gain (LCD like number on the top left of the screen)
>
> Results: both digital modes cope better with interference and are more
> intelligible than FM. The numbers on top left of RX application are
> expressed in dB of amplification in the SDR transmitter chain.
>
> Hardware: for transmit one USRP B200 with 433 MHz filter installed,
> for RX one RTL-SDR filter with 433 filter installed.
> Software: QRadioLink running on top of Gnuradio (GNU/Linux):
> https://github.com/kantooon/qradiolink
>
> 73,
> Adrian YO8RZZ
>
>
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>
>
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