RFsimulator stopped with oai_device coldn't be loaded error

Hi'll

well i just used

https://open-cells.com/index.php/2017/08/22/all-in-one-openairinterface-august-22nd/

open-cells tutorial to run EPC & eNB on ubuntu 18.04 also used

https://gitlab.eurecom.fr/oai/openairinterface5g/tree/develop/targets/ARCH/rfsimulator

eurecom RFSIMULATOR tutorial instead of UE & eNB compilation of open-cells part

( i mean just used

<path to oai sources>/openairinterface5g/cmake_targets/build_oai --UE --eNB

** * PLUS * **

cd <path to oai sources>/openairinterface5g/cmake_targets/lte_build_oai/build
make rfsimulator

*** PLUS THIS***** **

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

** **INSTEAD OF * **

./cmake_targets/build_oai -w USRP --eNB --UE **) **

but got an oai_device couldn't be loaded error

library liboai_device.so is not loaded: liboai_device.so: cannot open shared object file: No such file or directory [HW] Library oai_device couldn't be loaded [PHY]
/openairinterface5g-1/targets/RT/USER/lte-ue.c:367 init_UE() Exiting OAI softmodem: Error loading device library

what should i do?