Spectrum sensing with USRP2 and wiserd

Description

This tutorial will utilize Wiserd to set up USRPs for signal transmission and reception.

Hardware / Software Resources utilized

1. Grid nodes with a USRP2 connect via Ethernet.
2. baseline-sdr.ndz: disk image loaded onto nodes.
3. ​Wiserd - interface to configure and stream data to/from USRPs.
4. octave - generate transmit data file and plot received data file.

Set up

• To get started first make a reservation on the ​Orbit Scheduler for using the Grid.

• After logging into grid console, make sure all nodes are turned off

  nilanjan@console.grid:~$ omf tell -a offh -t system:topo:all
  

• Verify state of node before continuing. Make sure all nodes are in the POWEROFF state.

  nilanjan@console.grid:~$ omf stat -t system:topo:all
  

• Image nodes

  nilanjan@console.grid:~$ omf load -i baseline-sdr.ndz -t node20-20,node19-19,node8-8 -r 20
  

• After nodes are imaged, verify that nodes are in POWEROFF state. Otherwise issue the following to turn them off for a reboot

  nilanjan@console.grid:~$ omf tell -a offh -t system:topo:all
  

• Turn nodes back on and verify they are in POWERON state

  nilanjan@console.grid:~$ omf tell -a on -t node20-20,node19-19,node8-8
  

In this example node8-8 and node19-19 is used as the transmitting nodes and the node20-20 as the receiver

Generate signal source file using octave

On each transmiting node, create a signal file using octave. You can use the scripts provided here as an example. On node8-8 create a file s1.bin using the lines below

root@node8-8:~# cd wiserd
root@node8-8:~/wiserd# octave
octave:1> signal = fGenFDSignal(256,50,10,'1half');
octave:2> saveToWiserdFile(signal,'s1.bin');
octave:3> exit

The signal will look something like the following in the frequency domain - notice the first half of the spectrum is populated:

Create a similar signal on node19-19 but with the 2nd half of the spectrum populated

octave:1> signal = fGenFDSignal(256,50,10,'2half');
octave:2> saveToWiserdFile(signal,'s2.bin');

Set up transmitting node

• ssh into each node and start the wiserd interface:

  root@node8-8> wiserd
  linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.008.002-86-g566dbc2b
  
  -- Opening a USRP2/N-Series device...
  -- Current recv frame size: 1472 bytes
  -- Current send frame size: 1472 bytes
  -- Detecting internal GPSDO.... No GPSDO found
  -- Successfully tuned to 900.000000 MHz
  --
  -- Successfully tuned to 900.000000 MHz
  --
  Ready!
  >
  

• At the wiserd prompt set the carrier frequency, sampling rate & gain. Then link the transmitter to the signal source which is the binary file generated in octave from prior step:

  > --uhd_tx_freq 700e6 --uhd_tx_rate 5e6 --uhd_tx_gain 20 --tran_wavefilename s1.bin
  -- Successfully tuned to 700.000000 MHz
  uhd_tx_freq 700000000
  uhd_tx_gain 20
  uhd_tx_rate 5000000
  > --addmodule signalfromfile
  Consumer signalfromfile added
  LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  >
  

In order to set parameter values, multiple arguments can be used in one line:

--uhd_tx_freq set carrier frequenct to 700MHz

--uhd_tx_rate set sampling rate to 5M samples/sec

--uhd_tx_gain set transmit gain to 20dB.

--tran_wavefilename tells the links the transmitter source to a binary filename.

--addmodule signalfromfile opens the above filename, reads the samples and streams to the usrp.

At this point the USRP will continuously transmit the signal util the delete command is issued:

--delmodule signalfromfile stops tranmitting signal.

Now set up the transmitter on node19-19 using similar commands.

Set up receiving node(s)

On the receiving node (node20-20), run wiserd to capture a snapshot of the signal from both transmitters.

root@node20-20> wiserd
linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.008.002-86-g566dbc2b

-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Detecting internal GPSDO.... No GPSDO found
-- Successfully tuned to 900.000000 MHz
--
-- Successfully tuned to 900.000000 MHz
--
Ready!
> --uhd_rx_freq 700e6 --uhd_rx_rate 5e6 --uhd_rx_gain 20 --recv_running_time 1000 --recv_output_filename rx_signal
-- Successfully tuned to 700.000000 MHz
--
recv_output_filename rx_signal
recv_running_time 1000
uhd_rx_freq 700000000
uhd_rx_gain 20
uhd_rx_rate 5000000
> --addmodule timesamplestofile --timed
Consumer timesamplestofile added
Consumer timesamplestofile finished

> exit

Here the set command has an additional argument to limit capturing to 1000 milliseconds:

--recv_output_filename set receiving signal filename.

--recv_running_time set receiver run time in milliseconds. (optional)

The --addmodule command options

--addmodule timesamplestofile streams data from receiver to file

--timed runs receiver for the specified amount of time. (optional)

Received signal file name will automatically be appended with the frequency, rate and gain:

root@node20-20> ls -ltr *.bin
-rw-r--r-- 1 root root 40003072 May 21 10:56 rx_signal_freq700000000_rate5000000_gain20.bin

Use octave to view the spectrum image:

octave:1> fReconFDSignal(readWiserdFile('rx_signal_freq700000000_rate5000000_gain20.bin', 256*500), 256);

Received signal should look simiar to