Equipment suppliers Nokia and NEC have completed the first phase of interoperability testing of their IP Multimedia Subsystems (IMS). The companies say that they have established voice over IP (VoIP) sessions and sent instant messages on an IP network between Europe and Japan. IMS enables both fixed and mobile devices to set up IP sessions, allowing multimedia services such as real-time video, interactive applications and sharing of content or presence information. Connections can be made via any IP network including fixed broadband, GPRS, W-CDMA or wireless LAN. The firms say they are also trialing international roaming for IMS-based services.