Any implementation of Spread Spectrum


#1

Hi,

I want to know if ever any work was done on Spread Spectrum (DSSS) in
Gnuradio?


#2

On Wed, Jan 28, 2009 at 9:31 AM, Mir A. removed_email_address@domain.invalid wrote:

I want to know if ever any work was done on Spread Spectrum (DSSS) in
Gnuradio?

Yes. I have done both host code and FPGA code implementation of DSSS
with the USRP1 and in progress with USRP2.

These will eventually make into the public GNU Radio tree, but it
might be some time before that happens.

Johnathan


#3

These will eventually make into the public GNU Radio tree, but it
might be some time before that happens.

Are there CGRAN projects?


#4

On Tue, Feb 3, 2009 at 4:28 PM, Mark K. removed_email_address@domain.invalid wrote:

So your DSSS code is not yet public? How did you manage waveform
synchronization among multiple USRPs?

Not sure I understand your question. My DSSS implementation is a
unidirectional continuous transmitter and separate receiver,
implementing m-sequence based chipping. The receiver performs code
phase synchronization using early/prompt/late correlation power and
frequency synchronization using a Costas loop on the despread BPSK
signal.

Or perhaps you’re asking about multiple, simultaneous
transmitter/receiver pairs. Right now, this is not optimal, as
m-sequences have poor cross-correlation properties, but I’ll
eventually put in Gold code generators. While this system was
designed with a completely different purpose in mind, one goal I have
is to eventually be able to use the receiver part of the code as a GPS
L1 demodulator.

Johnathan


#5

Johnathan,

So your DSSS code is not yet public? How did you manage waveform
synchronization among multiple USRPs?

Thanks.

Mark


#6

On Mon, Feb 23, 2009 at 8:25 PM, Mir A. removed_email_address@domain.invalid wrote:

can you suggest me a place where I can find more information about the phase
sync and the freq sync methods you used in your work. It will be of great
help to me.

There is plenty of information available via Google. An excellent
reference book is:

“Fundamentals of Global Positioning System Receivers: A Software
Approach”
Wiley Series in Microwave and Optical Engineering
James Bao-Yen Tsui, 2004

Johnathan


#7

Hi Johnathan,

can you suggest me a place where I can find more information about the
phase
sync and the freq sync methods you used in your work. It will be of
great
help to me.

Thanks,
Ali.

On Tue, Feb 3, 2009 at 6:45 PM, Johnathan C. <


#8

Thanks, I will try this out.


#9

Hi Johnathan,
I have a few question regarding implementation. The book that you
referred
earlier was of great help. Thanks.
I am sure this won’t take a lot of your time and I would be really glad
and
thankful to you if you answer them.

In the transmitter the data and the PN code is ex-or and then modulated
and
transmitted. So basically this is a BPSK transmission. At the receiver
the
received signal is first multiplied by the PN code in order to strip it
free
of PN code and this happens at the E/P/L correlation and Costas Loop
block.
Being a BPSK signal this is correct.

  1. My question is can I just use the upsampler and multiply the
    upsampled
    sequence with the received signal samples?
  2. Where will the AGC and the RRC filter go in this arrangement?

Any help would be appreciated.
Thanks.
Ali

On Tue, Feb 24, 2009 at 11:23 AM, Johnathan C. <


#10

Hi Johnathan,
Is your code public yet?