| 摘要 |
The invention is concerned generally with packet data transmission in cellular telecommunication system, and more particularly with handling of speech connections transmitted using packet data transmission. According to the invention, the GPRS system is arranged to monitor IP telephony call state change messages, which can be performed by monitoring a transport layer service access point (TSAP), which the IP telephony system uses for call state change signaling. The invention can be used with any IP telephony protocol, such as the H.323 protocol and the SIP protocol. Such a TSAP may be for example a specific UDP (User Datagram Protocol) or TCP (Transmission Control Protocol) port at the IP address corresponding to the mobile station. The monitoring may be performed for example by the GPRS control entities in the mobile station, whereby they are able to determine if a new requested packet connection will be used for a H.323 speech or video connection and negotiate and set up a PDP context having a corresponding level of service. Monitoring in the mobile station is advantageous in mobile originated H.323 calls. The monitoring may as well be performed by a GSN, which is advantageous for mobile terminated H.323 connections.
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