RFNoC Spectrum Sensing

=== Description ===
This tutorial shows how to use the RFNoC Spectrum Sensing block(CE) to plot receive power spectrum from multiple USRP X310s on ORBIT grid.

=== Set Up ===
Make a reservation on the [https://www.orbit-lab.org/schedule/ Orbit Scheduler] for using the grid.
==== Prepare Receive Node ====
* Load prasanthi-rfnoc-specsense-9-14.ndz on an ORBIT node. 
{{{
omf load -i prasanthi-rfnoc-specsense-9-14.ndz -t node1-19
}}}
* Once imaging is done, turn the node on
{{{
omf tell -a on -t node1-19
}}}
* Wait for the node to turn on and log in
{{{
ssh root@node1-19
}}}
==== Prepare Receive USRPs ====
* Pick USRP X310s from the MIMO racks 23-1...8, 23-11...18 and load spectrum sensing FPGA image on them.
{{{
uhd_image_loader --args="addr0=10.10.23.11,addr1=10.10.23.12,addr2=10.10.23.13,add4=10.10.23.14" --fpga-path="/root/bit/x310_spec_sense_2ddc_1duc_7_14.bit"
}}}
* Power cycle USRPs so that the new FPGA image is active
{{{
omf tell -a offh -t node23-11
omf tell -a on -t node23-11
}}}
==== Prepare Transmit Node ====
Any source can be used to transmit a test waveform. In this tutorial, a spectrum spreader RFNoC block is being used to generate wideband PN signal.
* Load prasanthi-channel-sounder.ndz on an ORBIT node.
{{{
omf load -i prasanthi-channel-sounder.ndz -t node1-20
}}}
* Once imaging is done, turn the node on
{{{
omf tell -a on -t node1-20
}}}
* Wait for the node to turn on and log in
{{{
ssh root@node1-20
}}}
==== Prepare Transmit USRP ====
* Pick a USRP X310 for transmitting, and load the spectrum spreader FPGA image
{{{
uhd_image_loader --args="addr=10.10.23.17" --fpga-path="/root/bit/x310_spreader_4_28.bit"
}}}
* Power cycle the USRP so that the new FPGA image is active
{{{
omf tell -a offh -t node23-17
omf tell -a on -t node23-17
}}}
==== Set up SSH tunnel from your local port 5100 to grid.orbit-lab.org:5100 ====
{{{
ssh -L 5100:grid.orbit-lab.org:5100 username@grid.orbit-lab.org
}}}
==== Set up a web proxy for the receive node ====
Verify that Webproxy is running (this is required for remote web based streaming)
{{{
nilanjan@.grid:~$ run-websock 5100 10.10.1.19:5100 --daemon
WebSocket server settings:
  - Listen on :5100
  - Flash security policy server
  - No SSL/TLS support (no cert file)
  - Backgrounding (daemon)
}}}