add ocp/frf/enhanced basic simulator sources

targets/ARCH/rfsimulator/README.md

+#General
+This is a RF simulator that allows to test OAI without a RF board.
+It replaces a actual RF board driver.
+
+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
+
+## From build_oai
+You can build it the same way, and together with actual RF driver
+
+Example:
+```bash
+./build_oai --ue-nas-use-tun --UE --eNB -w SIMU
+```
+It is also possible to build actual RF and use choose on each run:
+```bash
+./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 to use 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
+```bash
+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 "enb" in the eNB
+
+## 4G case
+For the UE, it should be set to the IP address of the eNB
+example: 
+```bash
+sudo RFSIMULATOR=192.168.2.200 ./lte-uesoftmodem -C 2685000000 -r 50 
+```
+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
+```bash
+$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)
+```bash
+cd ran_build/build
+make rfsimulator
+```
+### Launch gNB in one window
+```bash
+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
+```bash
+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
+
+#Caveacts
+Still issues in power control: txgain, rxgain are not used
+
+no S1 mode is currently broken, so we were not able to test the simulator in noS1 mode