| Applicable Versions | Netsim Standard | Netsim Pro |
The Hysteresis margin also called HO margin is the main parameter that governs the HO algorithm between two eNB’s. The handover is initiated if the link quality of another cell is better than the current link quality. The difference in link quality is called the hysteresis value. It is used to avoid ping-pong effects. However, it can increase handover failure since it can also prevent necessary handovers.
In NetSim LTE this difference in link quality is by default fixed to 3 dB. To vary the hysteresis/handover margin in NetSim use the following steps:
| Applicable Release | v12.2 | v13.0 |
1. Open NetSim source code in Visual Studio through Open Simulation -> workspace options -> Open Code
2. Go to the LTE_NR project through the solution explorer and open the file LTENR_GNBRRC.h. The variable HANDOVER_DIFF is the one that governs handover margin in NetSim. It is set to 3 dB by default as shown below:
3. To set a different value for Handover Margin users can specify a different value for the constant HANDOVER_DIFF in dB.
4. After this right click on the LTE_NR module in the solution explorer and select rebuild.
5. Upon a successful build, you will get a new libLTE_NR.dll file in the bin folder of the current workspace.
7. Now upon running LTE simulations involving UE handovers, handover will be initiated only if the difference in signal strength is more than the HANDOVER_DIFF specified by you.
8. You can then run multiple simulations of the same network scenario varying certain parameters such as seed values, the velocity of devices, etc and take the average Number of Handovers and Throughput.
| Applicable Releases | v11 | v12.0 | v12.1 |
- Open NetSim source code in Visual Studio by double-clicking on the NetSim.sln file present in “<NetSim_Install_Directory>/src/Simulation” folder. (from NetSim v11.1 or higher versions, source codes should be opened using Open Code option only)
- Go to LTE project through the solution explorer and open the file NAS.c. The variable HANDOVER_DIFF is the one that governs handover margin in NetSim. It is set to 3 dB by default as shown below:
To set a different value for Handover Margin users can specify a different value for the constant HANDOVER_DIFF in dB.
After this right click on LTE module in the solution explorer and select rebuild.
Upon a successful build, you will get a new libLTE.dll file in the “<NetSim_Install_Directory>/src/Simulation/DLL” folder. (this step can be ignored in case of NetSim v11.1 or higher versions)
Copy this newly created DLL file and replace it in the bin folder of NetSim after you rename the original libLTE.dll file which is already existing there(as a backup). (this step can be ignored in case of NetSim v11.1 or higher versions)
Now upon running LTE simulations involving UE handovers, handover will be initiated only if the difference in signal strength is more than the HANDOVER_DIFF specified by you.
You can then run multiple simulations of the same network scenario varying certain parameters such as seed values, the velocity of devices, etc and take the average Number of Handovers and Throughput.
