Wideband Channel Sounding with USRP X310s

Description

This tutorial shows how to use the RFNoC Correlator block(CE) for channel sounding. This experiment is conducted using USRP X310s on ORBIT grid.

Set Up

Make a reservation on the ​Orbit Scheduler for using the grid.

Prepare Receive Node

• Load channel_sounder_x310.ndz on an ORBIT node.

  prasanthi@console.grid:~$ omf load -i channel_sounder_x310.ndz -t node1-19
  

• Once imaging is done, turn the node on and log in

  prasanthi@console.grid:~$ omf tell -a on -t node1-19
  prasanthi@console.grid:~$ ssh root@node1-19
  

Prepare Receive USRPs

• Pick USRP X310s from the MIMO racks 23-1…8, 23-11…18, 24-1…8, 24-11…18 and load correlator FPGA image on them. The USRPs are programmed one at a time.

  root@node1-19:~# uhd_image_loader --args="addr=10.10.24.12" --fpga-path="/root/bit/corrmag63avg8k_v2_8_7.bit"
  

• Power cycle USRPs so that the new FPGA image is active

  prasanthi@console.grid:~$ omf tell -a offh -t node24-12,node24-13
  prasanthi@console.grid:~$ omf tell -a on -t node24-12,node24-13
  

• Running uhd_usrp_probe on the X310s with spectrum sensing FPGA image should give the following

  |   |    /
  |   |   |       RFNoC blocks on this device:
  |   |   |
  |   |   |   * DmaFIFO_0
  |   |   |   * Radio_0
  |   |   |   * Radio_1
  |   |   |   * DDC_0
  |   |   |   * DUC_0
  |   |   |   * Corrmag63avg8k_0
  |   |   |   * FIFO_0
  
  

Prepare Transmit Node

A spectrum spreader RFNoC block is being used to generate wideband PN signal.

• Load prasanthi-channel-sounder.ndz on an ORBIT node.

  prasanthi@console.grid:~$ omf load -i prasanthi-channel-sounder.ndz -t node14-20
  

• Once imaging is done, turn the node on and log in

  prasanthi@console.grid:~$ omf tell -a on -t node14-20
  prasanthi@console.grid:~$ ssh root@node14-20
  

Prepare Transmit USRP

• Pick a USRP X310 for transmitting, and load the spectrum spreader FPGA image

  root@node1-20:~# uhd_image_loader --args="addr=10.10.24.11" --fpga-path="/root/bit/x310_spreader_4_28.bit"
  

• Power cycle the USRP so that the new FPGA image is active

  prasanthi@console.grid:~$ omf tell -a offh -t node24-11
  prasanthi@console.grid:~$ omf tell -a on -t node24-11
  

• Running uhd_usrp_probe on the X310 with spectrum spreader FPGA image should give the following

  |   |     _____________________________________________________
  |   |    /
  |   |   |       RFNoC blocks on this device:
  |   |   |
  |   |   |   * DmaFIFO_0
  |   |   |   * Radio_0
  |   |   |   * Radio_1
  |   |   |   * DUC_0
  |   |   |   * Spreader_0
  |   |   |   * FIFO_0
  |   |   |   * FIFO_1
  

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

Use run-websock command to set up the proxy (this is required for remote web based streaming)

prasanthi@console.grid:~$ run-websock 5100 10.10.1.19:5100 --daemon
WARNING: no 'numpy' module, HyBi protocol will be slower
WebSocket server settings:
  - Listen on :5100
  - Flash security policy server
  - No SSL/TLS support (no cert file)
  - Backgrounding (daemon)

Run the experiment

• Run rfnoc_spec_sense_display on the receive node. The command below starts the application to receive spectrum sensing samples from 4 USRP X310s at 100MSPS.

  root@node1-19:~/uhd/host/build/examples# ./rfnoc_spec_sense_display --args="addr0=10.10.23.11,addr1=10.10.23.12,addr2=10.10.23.13,addr3=10.10.23.14,skip_ddc,skip_duc" --freq 5e9 --gain 15 --ddc-args="input_rate=200000000.0,output_rate=100000000.0" --num-usrp 4 --spec-sense-args="avg_size=256"
  

• Run rfnoc_spreader on the transmit node. The command below starts the application to send a 50MHz wide PN signal on node23-17.

  root@node1-20:~/uhd/host/build/examples# ./rfnoc_spreader --args="addr=10.10.23.17,skip_ddc,skip_duc" --freq 5e9 --gain 15 --duc-args="input_rate=50000000.0,output_rate=200000000.0"
  

• Download spec_sense_display.html and open it in your browser. Once you click the Start button, you should see power spectrum display as shown below.