System and method of providing required quality of service (QOS) level for mobile-originated call routed through packet-switched network

A system and method of providing a required quality of sercice (QOS) level for a call that is originated in a mobile radio telecommunications network and is routed through a Voice-Over-Internet-Protocol (VOIP) network(3). Signaling connections are established between a mobile switching center (MSC) (4) in the mobile network and at least one VOIP gateway (6). The MSC sends an Initial Address Message (IAM) (11) to the VOIP gateway and includes a new QOS Required parameter (12). The gateway confers with a gate keeper (8) in the VOIP network to determine whether the required QOS can be provided. If the required QOS can be provided, an indication that the required QOS can be provided is sent from the packet-switched network to the mobile network. If the required QOS cannot be provided, an indication (16) that the required QOS cannot be provided is sent from the packet-switched network to the mobile network.