gnbsim

gnbsim is a 5G SA gNB/UE (Rel. 16) simulator for testing 5G System. The project is aimed to understand 5GC more efficiently than just reading 3GPP standard documents.

Getting Started

Prerequisites

• golang environment on linux host.

  • root previledge is required to set an IP address which is dynamically assigned by SMF.
  • GTP kernel module capability is required for using wmnsk/go-gtp
    • To check if GTP kernel module is present in your system, try the following command

      find /lib/modules/`uname -r` -name gtp.ko
      

      If you get something like:

      /lib/modules/5.4.0-42-generic/kernel/drivers/net/gtp.ko
      

      it means that the module is present in your system. You may also want to try modinfo gtp. Otherwise, you need to install the GTP kernel module by following instructions here: https://osmocom.org/projects/openggsn/wiki/Kernel_GTP
  • If you would like to use 'Raspberry Pi' to run gnbsim, Kernel Compiling is required for activating GTP kernel module (gtp.ko).

• running free5gc somewhere.

  • subscriber has been registered by free5gc web console.
  • change 'ngapIPList' to external ip address in config/amfcfg.conf.

        ngapIpList:
          #- 127.0.0.1
          - 192.168.1.17      # extern IP address fot N1/N2 address.
    

  • change 'gtpu.addr' to external ip address in src/upf/build/config/upfcfg.yaml.

      gtpu:
        #- addr: 127.0.0.8
        - addr: 192.168.1.18  # external IP address for GTP-U (N3) address.
    

  • free5gc/free5gc v3.0.4 is used in my test environment.

Installing and testing

• Download the related files.

$ git clone https://github.com/hhorai/gnbsim.git
$ cd gnbsim

• Build example binary.

$ make test		# test for each libary.
$ make			# building example binary.

• Edit the configuration file.
  • imeisv replace with the registered value of IMSI in free5gc web console (e.g. 208930000000003)
  • msin replace with last 10 digits of the IMSI (e.g. 0000000003)
  • GTPuAddr for the IP address of gnbsim
  • GTPuIFname for the network interface of gnbsim
  • UE.url is access URL for testing U-Plane.

$ cd example
$ vi example.json

• run 'example' with 'ip' option and specify the AMF IP address.

$ sudo ./example -ip <AMF NGAP listen ip address set above>

• Then you can find the following line in the debug message. In this case, your configuration for OPc and K are both correct.

***** Integrity check passed

• And you could also find your UE in 'subscriber' page of free5gc web console.

Progress

• Initial Registration
• PDU Session Establishment
• User Plane functionality
• Deregistration