openairinterface5g/targets/ARCH/rfsimulator/README.md

#General This is an RF simulator that allows to test OAI without an RF board.

It replaces an actual RF board driver.

As much as possible, it works like an RF board, but not in realtime: It can run faster than realtime if there is enough CPU or slower (it is CPU bound instead of real time RF sampling bound)

#build

From build_oai

You can build it the same way, and together with actual RF driver

Example:

./build_oai --ue-nas-use-tun --UE --eNB -w SIMU

It is also possible to build actual RF and use choose on each run:

./build_oai --ue-nas-use-tun --UE --eNB -w USRP --rfsimulator

Will build both the eNB (lte-softmodem) and the UE (lte-uesoftmodem) We recommend using the option --ue-nas-use-tun that is much simpler to use than the OAI kernel driver.

Add the rfsimulator after initial build

After any regular build, you can compile the driver

cd <the_compilation_dir_from_build_oai_script>/build
make rfsimulator

Then, you can use it freely

Usage

Setting the env variable RFSIMULATOR enables the RF board simulator. It should be set to "server" in the eNB or gNB.

4G case

For the UE, it should be set to the IP address of the eNB example:

sudo RFSIMULATOR=192.168.2.200 ./lte-uesoftmodem -C 2685000000 -r 50 

For the eNodeB, use a valid configuration file setup for USRP board tests and start the softmodem as usual, but adding the --rfsim option.

sudo RFSIMULATOR=enb ./lte-softmodem -O <config file> --rfsim

Except this, the UE and the eNB can be used as if the RF is real

If you reach 'RA not active' on UE, be careful to generate a valid SIM

$OPENAIR_DIR/targets/bin/conf2uedata -c $OPENAIR_DIR/openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf -o .

5G case

After regular build, add the simulation driver (don't use ./build_oai -w SIMU until we merge 4G and 5G branches)

cd ran_build/build
make rfsimulator

Launch gNB in one window

sudo RFSIMULATOR=server ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-LTE-EPC/CONF/gnb.band78.tm1.106PRB.usrpn300.conf --parallel-config PARALLEL_SINGLE_THREAD

Launch UE in another window

sudo RFSIMULATOR=127.0.0.1 ./nr-uesoftmodem --numerology 1 -r 106 -C 3510000000 

Of course, set the gNB machine IP address if the UE and the gNB are not on the same machine.

In UE, you can add "-d" to get the softscope

Store and replay

You can store emitted I/Q samples:

If you set the environment variable: saveIQfile to a file name The simulator will write all IQ samples into this file

Then, you can replay with the executable "replay_node"

First compile it, as the other binaries

make replay_node

You can use this binary as I/Q data source to feed whatever UE or NB with recorded I/Q samples.

The file format is successive blocks of a header followed by the I/Q array. If you have existing stored I/Q, you can adpat the tool "replay_node" to convert your format to the rfsimulator format.

The format intend to be compatible with the OAI store/replay feature on USRP

Channel simulation

The RF channel simulator is called. In current version all channel paramters are hard coded in the call to:

new_channel_desc_scm(bridge->tx_num_channels,
                     bridge->rx_num_channels,
                     AWGN,
                     bridge->sample_rate,
                     bridge->tx_bw,
                     0.0, // forgetting_factor
                     0, // maybe used for TA
                     0); // path_loss in dB

Only the input noise can be changed on command line with -s parameter.

With path loss = 0 set "-s 5" to see a little noise.

Caveats

Still issues in power control: txgain, rxgain are not used