# Practical Performance Analyses of 5G Sharing Voice Solution
## 5 Performance Analysis
### SA Sharing EPS Fallback Performance Analysis  
We conducted EPS fallback call setup tests based on handover and redirection in Section 4.2 separately. The test results are as follows.  
* EPS fallback based on handover UE1 initiates a voice service request to UE2, which can be seen in the IRAT NR\(\rightarrow\)LTE HO request message ARFCN: 629952(5G) to 1850(4G), PCI:122(5G) to 125(4G), after which IRAT NR\(\rightarrow\)LTE HO success and outgoing call are received. For the operator A user, based on the handover back to the LTE network of operator A, voice service is established successfully, and the call is normal. The UE supports the normal fallback of voice services  
Figure 13: Share 5G access inter-frequency handover.  
based on different PLMNs to their respective 4G networks through PSHO. The signaling flow is shown in Figure 14.  
* EPS fallback based on redirection  
UE1 initiates a voice service request to UE2, which can be seen in the IRAT NR\(\rightarrow\) L redirection request message EUREA frequency: 1850 (carrier A 4G), after which IRAT NR\(\rightarrow\) L redirection success and outgoing call are received. In the established message, it can be seen that the user of operator A can fall back to the LTE network of operator A based on redirection under the 5G network of operator B. The voice service is established successfully, and the call is normal. The signaling flow is shown in Figure 15.  
Voice services are established on the SA sharing 5G network, and UE can fall back to the 4G network by handover/redirection. Both options are achievable.  
Due to the different handover and redirection processes, experiments were conducted to compare the call setup delay, and the results are shown in Table 3.  
Figure 14: EPS fallback test process based on the handover.  
Figure 15: EPS fallback test process based on redirection.  
As can be seen in the Figure 6 comparison, there is an RRC release process for redirection. The handover process is that the RRC is always in the connected state, and the redirection is that when the RRC is in the connected state, it needs to be released first and then reconnected on another frequency through the redirected frequency and initiates random access again. This is also the main reason why the delay of the redirection process is longer than that of the handover.  
In contrast, the handover-based EPS fallback scheme can save the process of returning to the idle state and then access, which can greatly shorten call setup delay and can improve voice service experience in the early stage of 5G SA network construction.  
The average call setup delay for the handover-based EPS fallback is longer than the NSA delay investigated in Section 4.2: about 850 ms. The 4G network fallback is more complicated than the handover process when setup voice service by VoLTE, thus increasing the voice setup call duration. At the same time, data traffic will also be transmitted over LTE, which will significantly reduce the data rate and affect the user experience.  
This shows that EPS fallback can only play a transitional role in terms of voice continuity assurance in the early stages of 5G SA deployment based on 5 GC. However, the high setup delay and reducing data rate will affect the user experience to a certain extent.