How do you measure the channel impulse response?

GNU Radio
1

Hello,

I’m trying to figure out how to measure the impulse response of a
channel
its coefficients.

If you have any information on how to do that, please let me know.

Thank you.

2

On Tue, Oct 05, 2010 at 11:43:53AM -0700, sirjanselot wrote:

Hello,

I’m trying to figure out how to measure the impulse response of a channel
its coefficients.

Hello sirjanselot,

the channel sounder which is part of GNU Radio works, but has no
synchronisation or anything–so you have no direct means of averaging
taps. Perhaps you can give it a bash, though.

Cheers,
MB

–
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin B.
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-3790
Fax: +49 721 608-6071
www.cel.kit.edu

KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

3

Thank you for your response.

I’ve tried gr sounder but from the looks of it, it is only accurate when
you
use the LFRX/TX or the RFX boards.

I have a WBX transciever and when I tried it on my first shot measuring
the
channel coefficients by directly connecting the output of my TXA to my
RXA,
the length of the channel was 32760 coefficients!!!

I haven’t been able to figure out how to read the output.dat of the
gr-sounder yet but this is what is showing me on debugging mode.

It also keeps giving me this warning message:
gr_buffer::allocate_buffer:
warning: tried to allocate
4 items of size 32760. Due to alignment requirements
512 were allocated. If this isn’t OK, consider padding
your structure to a power-of-two bytes.
On this platform, our allocation granularity is 4096 bytes.

Any thoughts?

Thank you.

Martin B.-4 wrote:

synchronisation or anything–so you have no direct means of averaging
Research Associate
National Laboratory of the Helmholtz Association

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4

On 10/06/2010 11:41 AM, sirjanselot wrote:

the channel coefficients by directly connecting the output of my TXA to my
RXA, the length of the channel was 32760 coefficients!!!

When you say "directly’, you mean through a minimum 30dB attenuator,
correct? The output power of
the transmitter can easily damage the LNA in the receiver if directly
connected, and at the
very least, will cause serious clipping.

Any thoughts?

I’m trying to figure out how to measure the impulse response of a
MB
76131 Karlsruhe

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Principal Investigator
Shirleys Bay Radio Astronomy Consortium

5

I meant TXA to RXB.

sirjanselot wrote:

I haven’t been able to figure out how to read the output.dat of the

its coefficients.
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Phone: +49 721 608-3790
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6

Thank you for your response.

I’ve tried using gr-sounder, but I think it only works well for any of
the
LXRX and RFX family.

I only have a WBX and when I tried to hook it up straight from my TXA to
RXB, it gave me 32760 coefficients.

I haven’t figured out how to open the file output of gr-sounder.py, but
that
is what the debugger told me.

Any thoughts on this or comments?

Also can someone please show me how to open the file output of
gr-sounder.py
using python?

Thanks!

  • Jan

Martin B.-4 wrote:

synchronisation or anything–so you have no direct means of averaging
Research Associate
National Laboratory of the Helmholtz Association

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7

Yes with 40 dB attenuation.

Somehow I didn’t see your post.

Marcus D. Leech wrote:

On this platform, our allocation granularity is 4096 bytes.

Hello,

Kaiserstraße 12

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