# Call Model and Test-Verification Methods for PS-LTE Core Equipment
## 2 Call Model and Test Result for Core Equipment
### MCPTT Core System Test Model  
The NE comprising MCPTT services consists of command devices, CSC servers, and MCPTT servers. Representative services are group voice/video calling and group character services, and for these services, the control plane is processed by linking with terminals, CSCF, and HSS. MCPTT is provided as a virtualization system, and the software structure comprises VOMA, VISA, VECA, VIDA, and VEPA. The requirements for the MCPTT system capacity in Korea are 480,000 busy hour register attempts (BHRA) for registering and 82.4 million busy hour call attempts (BHCA) for service.  
Based on the above requirements, the load conditions of the simulator for MCPTT system testing approve full performance traffic according to the call model shown in Table 1. The conversion to Regi BHRA per subscriber is calculated by initial registration (INIT-REG) + refresh registration + deregistration (DE-REG). The conversion to service BHCA per subscriber is calculated as short message service (SMS) BHCA + MCPTT BHCA. As shown in Figure 2, the call operating conditions for instant message service (IMS) INIT-REG, DE-REG, and MCPTT voice/video/message simulator are as follows:  
* MCPTT voice outgoing call of 320,000 BHCA, incoming call of 320,000 BHCA, and 40,000 simultaneous-access call approvals (average holding time = 225 s);
* MCPTT video outgoing call of 3.2 million BHCA, incoming call of 3.2 million BHCA, and 40,000 simultaneous call approvals (average holding time = 225 s);
* MCPTT MSG of 200,000 BHCA and incoming of 200,000 BHCA call approvals;
* MCPTT linkage of 240,000 BHRA INIT-REG and 240,000 BHRA DE-REG approval.  
Figure 1: Block diagram of core equipment test environment.  
The operating condition according to the proposed call model processes is [INIT-REG (40,009) + DE-REG (40,005)] \(\times\) 6 = 480,084 BHRA, which is repeated to perform the connection/disconnection of subscribers. The outgoing/incoming messages of the instant message (IM) are occurring as much as [originating participant function call session (OPFCS) (33,334: group outgoing call) + terminating participant function call session (TPFCS) (33,334: group incoming call)] \(\times\) 6 = 400,008 BHCA. PTT voice/video call generation confirms [OPFCS (voice of 33,333 + videos of 5333) + TPFCS (voice of 53,335 + videos of 5339)] \(\times\) 6 = 704,040 BHCA. Because the message load ratio per MCPTT 1 call is 0.3 compared to VoLTE, it is calculated as 400,008 \(\times\) 0.3 = 120,002 BHCA, and the results of 700,400 BHCA + 120,002 BHCA = 824,002 BHCA are confirmed. As the test results are derived from the call model  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Items** & **BHCA/User** & \begin{tabular}{c} **VoLTE 1 Call** \\ **Comparison** \\ \end{tabular} & \
\begin{tabular}{c} **VoLTE 1 Call** \\ **Conversion to** \\ **BHCA** \\ \end{tabular} \\ \hline \multirow{4}{*}{Registration} &
\begin{tabular}{c} Initial registration \\ (MCPTT basis) \\ Refresh registration \\ (MCPTT basis) \\ Deregistration \\ (MCPTT basis) \\ \end{tabular} & 0.1 BHRA & & & \\ \hline \multirow{2}{*}{Service BHCA} & SMS BHCA & 1 BHCA & 30\% & 0.3 BHCA \\  & MCPTT BHCA & 1.76 BHCA & 100\% & 1.76 BHCA \\ \hline \multirow{4}{*}{Service BHCA} & Regi BHRA per subscriber & & 1.2 BHRA \\ \cline{2-5}  & Service BHCA per subscriber & & 2.06 BHCA \\ \hline \multirow{2}{*}{Regi BHRA based on 400,000 subscribers} & \multicolumn{2}{c}{480,000 BHCA} \\ \cline{2-5}  & Service BHCA based on 400,000 subscribers & & 824,000 BHCA \\ \hline \hline \end{tabular}
\end{table}
Table 1: MCPTT call model: assuming 400,000 subscriber base.  
Figure 2: Operating condition of MCPTT simulator.  
defined in Table 1, it can be confirmed that an appropriate call model was calculated, which can test the MCPTT service requirements of 82.4 million BHCA.