The Internet protocol multimedia subsystem (IMS) is a key technology for integrating voice services in an LTE network (voice over LTE, VoLTE). IMS offers a framework that supports IP-based multimedia services.
The session initiation protocol (SIP) is the base protocol of IMS. SIP uses an IP network to establish the connection between subscribers. To ensure a consistently high quality of service (QoS), network operators have started to roll out VoLTE services for voice and video telephony based on IMS – with a guaranteed seamless transition to circuit-switched services, i.e. to 2G and 3G networks.
Voice over WLAN (VoWLAN) is a network operator driven technology that ensures seamless multimedia service coverage within buildings. VoWLAN also uses SIP/IMS to route voice over WLAN access points. Instead of using the closest base station, the voice packets are tunneled through the Internet to a gateway provided by the network operator. This evolved packet data gateway (ePDG) creates a link between the LTE network and WLAN. IMS and upcoming generations of mobile devices that support all of these mechanisms as standard need to ensure uninterrupted and high-quality voice services for all available access technologies to meet user expectations.
Based on the R&S®CMW500 wideband radio communication tester, Rohde & Schwarz offers comprehensive solutions for IMS, VoLTE and rich communictions services (RCS) functional testing on mobile devices as well as for device to device interoperability testing. On the data application unit, the tester provides all access technologies and all necessary servers, such as an ePDG and an IMS server, to test, for example, the handover between LTE and WLAN as well as single radio voice call continuity (SRVCC), i.e. the handover between LTE and legacy networks such as GSM and UMTS.
