# Call Model and Test-Verification Methods for PS-LTE Core Equipment
## 2 Call Model and Test Result for Core Equipment
### Core Equipment Test Environment  
Core equipment comprises MCPTT, eMBMS, evolved packet core (EPC), RAN, sharing internetworking equipment, information management system (IMS), L3 switch, and others. As the core services of PS-LTE among the components above, the MCPTT entity performing the function of group communication for mission-critical services comprises common services core (CSC) servers, MCPTT servers, command servers, and command devices. Moreover, the eMBMS entity, which is an LTE-based mobile broadcasting technology for resolving call congestions, comprises a broadcast/multicast service center (BM-SC), multimedia broadcast and multicast service gateway (MBMS GW), and multicall/multicast coordination entity (MCE). Among the components of EPC, mobility management equipment (MME) is one of the network entities (NEs) that constitute the LTE core. It processes the mobility management and session management of the terminal; authentication of the terminal; handover control; control plane, which is connected to evolved node B (eNB); system architecture evolution gateway (SAE-GW); and home subscriber server (HSS) [12; 13]. Core equipment must be tested for the required capacity and performance before establishment to smoothly perform the planned services. This paper proposes a performance test call model of MME and SAE-GW systems among core equipment for MCPTT which is a representative service of PS-LTE.  
Figure 1 shows the composition of the core equipment, measuring instrument, and simulator environment for performance tests. The main VNF configuration as a component of core networks comprises (i) a virtual operation and management application (VOMA) for system operation maintenance, (ii) a virtual interface and protocol distribution application (VIPA) for stream control transmission protocol (SCTP)/diameter call distribution with connection with HSS/eNB, (iii) a virtually established call-processing application (VECA) for session-initiation protocol (SIP)/media gateway control (Megaco) call distribution and PTT call-processing functions, (iv) a virtual interface and distribution application (VIDA) for physical linking with external NE and Layer 4 (L4) load distribution, (v) a virtual interface of session application (VISA) for diameter/HTTP call distribution and subscriber/session information management, and (vi) a virtually established packet processing application (VEPA) for processing PTT media. The components of HSS comprise a UPN (user data convergence (UDC) proxy node) for connection with external NE and L4 load distribution, a UDC function node (UFN) for HSS call processing and connection with the MME/call session control function (CSCF)/MCPTT, and a UDC database node (UDN) for subscriber information database management. MCE is a nonvirtualized system and is installed as separate hardware and software configurations. MCE comprises MCE processing software for base station resource allocation, MCE access control block for session management, MCE transmission control block for SCTP connection management, MCE management block for eMBMS service area management, and MCE connection admission control for session admission load management. In PS-LTE systems, VECA, UDN, and UFN for important services operate in an active-active mode, and the rest of the configurations operate in an active-standby mode.