[[Include(WikiToC)]] == GNURadio OFDM tutorial == === Description === This tutorial illustrates the use of GNURadio OFDM blocks for data transfer between a pair of USRPs. The GNURadio flowgraphs used here were obtained from the workshop material provided for [https://gitlab.flux.utah.edu/powderrenewpublic/mww2019 POWDER-RENEW Mobile and Wireless Week 2019]. They are based on the GRC examples available in the [https://github.com/gnuradio/gnuradio/tree/main/gr-digital/examples/ofdm GNURadio repository]. For a good understanding of the flowgraphs and the blocks, please refer to OFDM pages on GNURadio Wiki such as [https://wiki.gnuradio.org/index.php/Basic_OFDM_Tutorial OFDM Basics] and [https://wiki.gnuradio.org/index.php/Schmidl_%26_Cox_OFDM_synch. OFDM Synchronization]. === Prerequisites === In order to access the test bed, create a reservation and have it approved by the reservation service. Access to the resources is granted after the reservation is confirmed. Please follow the process shown on the COSMOS [wiki:GettingStarted getting started] page to get started. === Resources required === 2 USRPs in COSMOS or ORBIT testbed, and 2 host nodes are required. This tutorial uses [https://orbit-lab.org/wiki/Hardware/bDomains/cSandboxes/bSB2 sb2.orbit-lab.org] with 2 host nodes and 2 USRP X310s. === Tutorial Setup === Follow the steps below to gain access to the [https://orbit-lab.org/wiki/Hardware/bDomains/cSandboxes/bSB2 sandbox 2 console] and set up nodes with appropriate images. 1. If you don't have one already, sign up for a [https://www.cosmos-lab.org/portal-2/ COSMOS account] 1. [wiki:/GettingStarted#MakeaReservation Create a resource reservation] on sandbox 2 (ORBIT) 1. [wiki:/GettingStarted#LogintoyourReservation Login] into sandbox 2 console (console.sb2.cosmos-lab.org) with an SSH session. SSH session for ORBIT SB2 with MobaXterm can be setup as shown in the [https://wiki.cosmos-lab.org/wiki/Tutorials/Wireless/Fosphor#ConfigureMobaXtermfornodeaccess Fosphor tutorial], with remote host = console.sb2.orbit-lab.org, and username = your COSMOS username. X11 forwarding is enabled to access GUI. 1. Load gnuradio_ofdm.ndz on both the nodes {{{#!shell omf load -i gnuradio_ofdm.ndz -t node1-1,node1-2 }}} 1. Turn the nodes on and check the status {{{#!shell omf tell -a on -t node1-1,node1-2 }}} {{{#!shell omf stat -t all }}} 1. Open 2 terminal sessions and ssh into the nodes with -Y for X11 forwarding {{{#!shell ssh root@node1-1 -Y ssh root@node1-2 -Y }}} === Experiment Execution === ==== Find the USRPs ==== 1. As mentioned in the [https://orbit-lab.org/wiki/Hardware/bDomains/cSandboxes/bSB2 sb2.orbit] page, the X310s have their port 1 directly connected to their respective nodes, and the IP addresses hardcoded to 192.168.40.2 as given in the [https://files.ettus.com/manual/page_usrp_x3x0.html#x3x0_setup_network X310 manual]. To access the X310s run eth_config_sb2_orbit.sh on both the nodes. It sets a static IP address 192.168.40.1 on the DATA2 interface, and modifies the maximum send and receive socket buffer sizes. {{{#!shell root@node1-2:~# ./eth_config_sb2_orbit.sh net.core.wmem_max = 25000000 net.core.rmem_max = 25000000 root@node1-2:~# ip addr show DATA2 4: DATA2: mtu 9000 qdisc mq state UP group default qlen 1000 link/ether f4:52:14:83:af:80 brd ff:ff:ff:ff:ff:ff inet 192.168.40.1/24 scope global DATA2 valid_lft forever preferred_lft forever inet6 fe80::f652:14ff:fe83:af80/64 scope link valid_lft forever preferred_lft forever }}} 1. Run uhd_find_devices and uhd_usrp_probe to detect the X310s and to make sure they have a compatible firmware installed. {{{#!shell root@node1-2:~# uhd_find_devices [INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; UHD_4.4.0.0-0ubuntu1~focal1 -------------------------------------------------- -- UHD Device 0 -------------------------------------------------- Device Address: serial: 30F10F9 addr: 192.168.40.2 fpga: XG name: product: X310 type: x300 root@node1-2:~# uhd_usrp_probe --args="addr=192.168.40.2" [INFO] [UHD] linux; GNU C++ version 9.4.0; Boost_107100; UHD_4.4.0.0-0ubuntu1~focal1 [INFO] [X300] X300 initialization sequence... [INFO] [X300] Maximum frame size: 8000 bytes. [INFO] [GPS] No GPSDO found [INFO] [X300] Radio 1x clock: 200 MHz _____________________________________________________ / | Device: X-Series Device | _____________________________________________________ | / | | Mboard: X310 | | revision: 8 | | revision_compat: 7 | | product: 30818 . . . . | | / | | | RX Frontend: 0 | | | Name: UBX RX | | | Antennas: TX/RX, RX2, CAL | | | Sensors: lo_locked | | | Freq range: 10.000 to 6000.000 MHz | | | Gain range PGA0: 0.0 to 31.5 step 0.5 dB | | | Bandwidth range: 160000000.0 to 160000000.0 step 0.0 Hz | | | Connection Type: IQ | | | Uses LO offset: No }}} {{{#!box note width=600px In case of firmware mismatch, follow the directions displayed in the error message and use uhd_image_loader to update the firmware. }}} ==== Run the GRC application ==== 1. Open OFDM receiver on node1-2. With X11 forwarding enabled, GRC should show up as below. {{{#!td {{{#!shell root@node1-2:~# cd GNURadioOFDMExample/ root@node1-2:~/GNURadioOFDMExample# gnuradio-companion RX_OFDM_GUI.grc <<< Welcome to GNU Radio Companion 3.9.8.0 >>> Block paths: /usr/local/share/gnuradio/grc/blocks Loading: "/root/GNURadioOFDMExample/RX_OFDM_GUI.grc" >>> Done }}} }}} {{{#!td [[Image(RX_OFDM_grc.PNG, width=800px)]] }}} 2. Open OFDM transmitter on node1-1 {{{#!td {{{#!shell root@node1-1:~# cd GNURadioOFDMExample/ root@node1-1:~/GNURadioOFDMExample# gnuradio-companion TX_OFDM.grc <<< Welcome to GNU Radio Companion 3.9.8.0 >>> Block paths: /usr/local/share/gnuradio/grc/blocks Loading: "/root/GNURadioOFDMExample/TX_OFDM.grc" >>> Done }}} }}} {{{#!td [[Image(TX_OFDM_grc.PNG, width=800px)]] }}} 3. Make sure the device arguments on both nodes are correctly set as shown below. Check the center frequencies and sample rates, and make sure they match. TX_OFDM.grc has a "File Source" block which reads the text file to be transmitted. RX_OFDM.grc stores the received data in a local file that is specified in the "File Sink" block. {{{#!td [[Image(OFDM_SB2_args.PNG, width=300px)]] }}} {{{#!td [[Image(FileSource.PNG, width=400px)]] }}} {{{#!td [[Image(FileSink.PNG, width=400px)]] }}} 4. Run the receive flowgraph followed by the transmit flowgraph. The following display window with received IQ samples and constellation can be seen. Stop the flowgraph and check the received text file. [[Image(RX_OFDM_samples.PNG, width=500px)]] 5. The receive GNURadio application can also be run without GUI, by generating the