== Full-Duplex Wireless using USRP N210 ==

=== Description ===
In this tutorial, we'll use node11-10 in the main grid (equipped with a USRP N210) to transmit and receive a single frequency over the air to demonstrate full-duplex wireless capability using the Columbia [http://flexicon.ee.columbia.edu/ FlexICoN]'s Gen-1 Frequency-Flat Amplitude- and Phase-based RF Canceller. Pictures of the FlexICoN RF canceller and node11-10 in the main grid equipped with full-duplex capability are below:
 ||||  Figure 1: The ORBIT-FlexICoN Full-Duplex Node  ||
 || [[Image(FlexICoN-gen1-canceller.jpg, 300px)]] || [[Image(FlexICoN-gen1-node11-10.jpg, 400px)]] || 
 ||  (a) The FlexICoN RF Canceller  ||  (b) Full-Duplex SDR at node11-10 in the ORBIT grid  ||

For more information, please read:


''T. Chen, J. Zhou, N. Grimwood, R. Fogel, J. Marasevic, H. Krishnaswamy, and G. Zussman, “Demo: Full-duplex Wireless based on a Small-Form-Factor Analog Self-Interference Canceller,” in Proc. ACM MobiHoc'16, 2016.'' [http://wimnet.ee.columbia.edu/wp-content/uploads/2016/06/full_duplex_demo_mobihoc16.pdf (PDF)] [https://dl.acm.org/citation.cfm?id=2942397&CFID=829383168&CFTOKEN=81447061 (DOI)]

Please email Tingjun Chen (tingjun [at] ee.columbia.edu) if you are using (or plan to use) the full-duplex node, or if you have any questions. We also thank Mahmood Baraani Dasterjerdi and Steven Alfano for their great contributions.


=== Hardware / Software Resources Utilized ===
1. The Columbia FlexICoN Gen-1 RF Canceller, which is a frequency-flat amplitude- and phase-based RF canceller implemented using discrete components on a PCB. The Gen-1 RF canceller is optimized to have a center operating frequency at 900MHz.
2. USRP N210 with node11-10 in the ORBIT main grid.
3. [http://www.xdimax.com/sub20/sub20.html SUB-20] is a multi-interface USB adapter for providing popular interfaces between PC (USB host) and different hardware devices. Specifically, we use the SUB-20 SPI module to control and configure the Gen-1 RF canceller (see Fig. 1(a)). The user manual can be found [http://www.xdimax.com/sub20/doc/sub20-man.pdf here].
4. [https://github.com/EttusResearch/uhd, UHD] is already installed with the imaged SDR node.
5. The {{{Eigen C++}}} Library is used for basic algebra used in channel estimation and digital self-interference cancellation. The Eigen releases can be found on the [http://eigen.tuxfamily.org/index.php?title=Main_Page this website]. We used the latest stable release Eigen 3.3.4 through our testings and experiments.

All the source code is also publicly available at [https://github.com/Wimnet/flexicon_orbit here].

=== Set Up ===
Before you can access the testbed, you need to [https://www.orbit-lab.org/schedule make a reservation] and get it approved by the [wiki:Documentation/Scheduler reservation service]. After receiving the reservation's confirmation (approval) email:

 * Login into reserved domain: {{{ssh username@conslole.grid.orbit-lab.org}}}
 * Make sure that the full-duplex node is powered down for loading the desired image: {{{omf tell -a offh -t node11-10}}}
 * Load an image on the node (this process can take about a few minutes so please be patient): {{{omf load -i orbit-flexicon.ndz -t node11-10}}}
 * Turn on the node: {{{omf tell -a on -t node11-10}}}
 * Login into the node: {{{ssh root@node11-10}}}
 After login into the node, a {{{flexicon_orbit}}} folder should exist under the home directory of {{{node11-10:~/}}} which contains the source code of this example. You can always retrieve the most recently updated code from [https://github.com/Wimnet/flexicon_orbit here].


=== Run the Experiments ===
You will need to login into the full-duplex node (by {{{ssh root@node11-10}}}) in two separate terminal windows lo for running the experiment: one for the main full-duplex transceiver UHD program and one for controlling the RF canceller

==== In Terminal 1 (UHD) ====
 * Build the example:
{{{
cd ~/flexicon_orbit/fd_transceiver_simple/uhd/
mkdir build
cd build
cmake ../
make
}}}
 * Check the conection and serial number of the USRP N210 using command {{{uhd_find_devices}}}. The serial number should be {{{F331D4}}}.
 * Run the example with IQ rate {{{rate}}}, carrier frequency {{{freq}}}, TX gain {{{tx-gain}}}, and RX gain {{{rx-gain}}}:
{{{
./fd_transceiver_simple --tx-args="serial=F331D4" --rx-args="serial=F331D4" --rate 1e6 --freq 900e6 --tx-gain 10 --rx-gain 10
}}}
 The default sine wave has an amplitude {{{ampl = 0.3}}} and wave frequency of 100kHz {{{wave-freq = 100e3}}}. This terminal window will show the power level at RX baseband, after RF cancellation (before digital) and after digital cancellation, respetively.

==== In Terminal 2 (SUB-20) ====
 * Build the RF canceller configuration code:
{{{
cd ~/flexicon_orbit/fd_transceiver_simple/sub20/
make
}}}
 * Check the connection to the SUB-20 device using command {{{lbusb}}}. You should see a XDIMAX devices connected to the USB hub.
 * Program and configure the RF canceller with the desired values:
{{{
./rf_canc_config ATT PS C1 C2 C3
}}}
 In particular, the {{{ATT = 0, 1, 2, ..., 127}}} and {{{PS = 0, 1, 2, ..., 255}}} codes are for configuring the 7-bit attenuator and 8-bit phase shifter of the Gen-1 RF canceller. It is recommended to use {{{C1 = 16, C2 = 3, C3 = 9}}}. You can play with the values of {{{ATT}}} and {{{PS}}} until you see good cancellation profile (e.g., low residual self-interference power level) in Terminal 1.

==== A Secondary Transmitter Using Node13-8 ====
Once the full-duplex node11-10 is up and running, you can turn on another SDR to transmit to the full-duplex node. Below, we use {{{node13-8}}} as an example in the 3rd terminal window (Terminal 3).
 * Load image, power on, and login into node13-8:
{{{
omf tell -a offh -t node13-8
omf load -i baseline-sdr.ndz -t node13-8
omf tell -a on -t node13-8
ssh root@node13-8
}}}
 * Configure the USRP Ethernet interface: {{{ifconfig eth2 192.168.10.1 netmask 255.255.255.0 up}}}
 * Set up a secondary transmitter sending a sine wave at a different frequency (e.g., 200kHz) than that of the full-duplex node:
{{{
./tx_waveforms --args="serial=F331D4" --rate 1e6 --freq 900e6 gain 10 --wave-type SINE --wave-freq 200e3
}}}
 Now