# Call Model and Test-Verification Methods for PS-LTE Core Equipment
## 3 Field Test Scenarios for MCPTT and eMBMS
### MCPTT Field-Test Scenarios  
As for MCPTT test was performed such as group voice, group videos, all call paging, interception, emergency calls and multicall group reception functions. An MCPTT group call operates in a prearranged group call method in which command devices assign members to an affiliated group and call the group. Furthermore, as for floor control, if the push button is pressed, a request for permission to talk is sent to the floor control server, which sets in motion a mechanism for giving the right to transmit to the member with the highest priority among those who request permission to talk within a specific time [14; 15]. According to the requirements for group calls, users select a call group by operating terminal buttons, switches, LCD panel touch, etc., and the terminals which are selected for a specific call group automatically receive all the calls of the corresponding call group. Only one user at a time is allowed to transmit to avoid collisions between transmission and reception during a group call. When a user is pressing the PTT button, it should be displayed as a separate pop-up to ensure that the user can selectively switch the reception mode without automatically disconnecting the group call [16; 17]. Figure 5 shows an example concerning the creation of an MCPTT voice channel of the terminal for a group call, and it can be seen step-by-step as follows. * Step 1 (channel information inquiry): after an originating terminal performs the authentication procedure for a subscriber, it sends an inquiry to the CSC about the channel information under the subscriber's management. * Step 2 (voice channel creation request): a request is made for the creation of a channel by transmitting a SIP:INVITE message containing the channel ID to the CSCF. * Step 3 (voice channel creation request): the CSCF forwards the message to the PTT server. * Step 4 (channel member inquiry): the MCPTT server acquires the member list of the corresponding channel from the CSC server. * Step 5 (voice channel participation request): the MCPTT server requests channel participation to the channel members by transmitting a SIP:INVITE message. CSCF requests the application of quality of service (QoS) for voice channel through a policy and charging rule function (PCRF), and EPC (SAE-GW) and eNB are established by applying MCPTT voice QoS to the bearer for the voice channel. If the button for a group call is pressed from terminals included in a specific group, it is verified whether the voice or video call is maintained without being interrupted for 30 s in all the reception terminals within the group. As for interception, a terminal with a higher priority should be able to terminate an emergency call from a terminal with a low priority and should be able to preempt the right for transmission according to the priority levels preallocated to the terminals, including command devices, within the same group. During emergency calls within the same group, if another user with the same priority requests an emergency call, they are not allowed to preempt the right of transmission of the existing emergency call user. The reception function for a multicall group refers to an ability for one terminal to receive two or more call groups. In this case, the main call group should be able to transmit and receive, whereas the remaining subcall group is configured to only receive. To conduct tests, the PTT keys from a given pair of terminals, A1 and A2, are pressed simultaneously to verify if the respective main channels can communicate. Subsequently, the subchannel should be changed into the main channel to verify whether the call can be made in the same manner as before. As for the criteria for call connection tests, it should be confirmed whether the delay budget for each key performance indicator (KPI) is satisfied in the setup process for an MCPTT call presented in 3 GPP TS 22.179 Release 13 [18].