Connecting to External MME
The purpose of this tutorial is to show you how to run multiple MME and let multiple eNB get connected to different MME. Motivation for this tutorial was for the case where non-Amarisoft RAN and Amarisoft Core are used, but I don't have any non-Amarisoft RAN to play with and I tried with Amarisoft RAN and Amarisoft Core but they are in different location. However, you can apply the concept of this tutorial to the case for Amarisoft RAN + Non-Amarisoft Core and for Non-Amarisoft RAN + Amarisoft Core. It is relatively simple to combine the heterogenious components, the only parameters that you need to pay attention to are amf_addr and gtp_addr.
Table of Contents
- Connecting to External MME
Test Setup
In this setup, I installed callbox software on an external PC with fedora to use it as the external MME.
Configuration
I used gnb-sa-external-mme.cfg which is copied and modified from gnb-sa.cfg.
I used mme-ims-external.cfg on the external MME PC which is copied from mme-ims.cfg.
I used ots.default.cfg file in /root/ots/config directory on the external MME PC. I haven't created any additional config file for this because the change will be very minor and may not be mandatory.
In gnb-sa-external-mme.cfg on Callbox, I made the following modification. Note that I changed amf_addr to point to the external MME PC IP address and gtp_addr to point to the IP address of NIC on Callbox which has access to external PC.
Configure as follows in /root/mme/config/mme.cfg (mme-ims-external.cfg ) on the external MME PC. gtp_addr here is the IP address of NIC which has access to other PCs.
Configure as follows in /root/ots/config/ots.cfg on the external MME PC
Perform the test
On Callbox (enb) screen, run the command : ng. this shows the IP address of the MME IP which the gNB is connected to.
On the external MME PC, you can check the IP address of gNB which the MME is connected to using the command ng_ran in (mme) screen window.
On the Callbox, confirm the gNB (cell) is configured as intended using 'cell' and 'cell phy' command. The defailed configuration is not important for this tutorial. You may use any kind of SA configuration for this tutorial.
Now Power On UE and let it complete the attach process and check if UE is successfully registerred to the external MME and IP address is assigned to the UE
Try ping from the external MME PC to UE and confirm that ping goes through.
Log Analysis
Since the MME is running on external PC, I changed IP address of MME as shown below and increased the Max size of all the components to capture the full header of data traffic.
Increase the max size of all the components on eNB for troubleshooting
You can check if the gNB is successfully connected to the external MME
Power on UE and check if all the protocol sequence is properly going through
