As much as possible, it works like a 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

No specific build is required, use the oai softmodem build procedure

After any regular build, you can compile the driver

cd <the_compilation_dir_from_bouild_oai_script>/build
make rfsimulator

Then, you can use it freely

Usage

Setting the env variable RFSIMULATOR enables the RF board simulator It should the 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 --rfsim

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 it 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 .

This simulator can also be used with the --noS1 option, in this case you must run the eNodeB and the UE on different PCs.

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=enb ./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

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