Section: 5.3.4.3.1 Initiation of in-call modification
Content: The procedure is initiated by the requesting originating side in the "active" state of the call. It shall send a MODIFY message including the new mode to be changed to. The requesting originating side shall also start timer T323 and enter the "mobile originating modify" state (mobile station side) or the "mobile terminating modify" state (network side). The new mode given in the MODIFY message shall be one of those already negotiated and agreed during the establishment phase of the call. If the data call direction is different from the direction of the call setup a reverse call setup direction IE shall be included in the MODIFY message; otherwise this IE shall not be included. If the in-call modification is originated by the mobile station, the mobile station shall reserve any internal resources necessary to support the next call mode, stop sending Bm-channel information; and stop interpreting received Bm-channel information according to the old call mode. If the in-call modification is originated by the network, the network may reserve any internal resources necessary to support the next call mode. The network shall stop sending Bm-channel information and stop interpreting received Bm-channel information according to the old call mode at the latest when it changes the channel configuration. Upon receipt of the MODIFY message, the destination side shall check to ensure that the requested call mode can still be supported and if so, it shall initiate the reservation of any resources necessary to support the next call mode; start T324 (mobile station side only) if the in-call modification procedure is triggered as a result of a service change from speech to UDI/RDI multimedia modes; and enter the "mobile originating modify" (network side) or "mobile terminating modify" state (mobile station side).