Session processing method and system

A session processing system, comprising:

• an Access Terminal (AT) supporting wireless video, a conference control centre, a Push To Talk Dispatch Server (PDS) and a cluster terminal, wherein
• the AT is configured to send a cluster user participation command to the conference control centre, wherein the cluster user participation command comprises an identifier of a cluster user which is invited to participate in a video conference, and the AT has an administration authority of adding a user into the conference which is convinced;
• the conference control centre is configured to send an invitation to a cluster terminal corresponding to the identifier of the cluster user through the PDS;
• the cluster terminal is configured to return an Acknowledgement (ACK) response to the PDS when the cluster terminal agrees to participate in the video conference, and establish a link with the PDS;
• the PDS is configured to forward the invitation from the conference control centre to the cluster terminal, establish the link with the cluster terminal after receiving the ACK response from the cluster terminal, and return an ACK response to the conference control centre after establishing the link successfully;
• and
• the AT and the cluster terminal are also configured to perform session interaction based on the link;
• wherein the cluster terminal is further configured to return a Negative Acknowledgement (NACK) response to the PDS when receiving the invitation but disagreeing to participate in the video conference;
• correspondingly, the PDS is further configured to forward the NACK response to the conference control centre;
• and
• the conference control centre is further configured to send the NACK response to the AT through the IP network, the PCN and the RAN in turn.