Patent ID: 11627170

Abstract:
A first UE receives a first Session Initiation Protocol (SIP) INVITE message requesting the first UE to place the RTT call on hold, during an ongoing Real-Time Text (RTT) call with a second UE. In response to the first SIP INVITE message, the first UE sends a first SIP 200 OK message to the second UE, and the first SIP 200 OK message indicates that the first UE is not allowed to send and receive media data. After sending the first SIP 200 OK message, the first UE receives a second SIP INVITE message requesting the first UE to resume the RTT call. In response to the second SIP INVITE message, the first UE sends a third SIP INVITE message to the second UE, and the third SIP INVITE message indicates that the first UE is allowed to send and receive media data.