Content for  TS 23.333  Word version:  17.1.0

The following procedure assumes the IMS session has been established and the bearer is through-connected, and the MRFC has received a trigger to play ASR, and the MRFP selected for the call has the capabilities to provide Automatic Speech Recognition.

If the MRFC receives a request to initiate ASR, the MRFC shall extract the SRGS script or the SRGS URI from the received script. If the size of the SRGS script is larger than the transport capability of the Mp interface, the MRFC shall terminate ASR procedure and return error. Otherwise the MRFC initiates the Start ASR procedure; the MRFC shall indicate to the MRFP the SRGS script or the SRGS URI to play ASR to one termination in a context. The MRFC may indicate to the MRFP the recognition mode: Normal Recognition Mode, Hotword Recognition Mode. If the MRFC indicate the Normal Recognition Mode to the MRFP, the MRFP shall match all of the speech against a recognition grammar and returns a no-match status if the input fails to match or the method times out. If the MRFC indicates the Hot-word Recognition Mode to the MRFP, the MRFP shall look for a match against specific speech grammar and ignores speech that does not match. The MRFP shall recognize the subscriber's input speech stream according to the SRGS grammar, and output the result as the EMMA format. If the MRFP does not support an element of the SRGS, the MRFP may ignore the element. The MRFC may request the MRFP to detect DTMF digit while executing ASR, and may request the MRFP to stop ASR when a DTMF digits is detected. For the latter case, only the ASR result is notified. The MRFC may request the MRFP to detect the ASR completion and notify the completion event and cause to the MRFC. The ASR is completed when either of the following has occurred;

• the ASR has been completed successfully,
• a DTMF digit is detected by the MRFP,
• the executing of ASR is not successful or
• the recognition time elapses.

On receipt of a trigger to stop ASR, the MRFC shall request the MRFP to stop the ASR.

When an ASR is completed, if the MRFC has requested the MRFP to notify the ASR completion, the MRFP shall notify the ASR result and the cause to the MRFC. The cause of the ASR completed may be that the ASR has been completed successfully, a DTMF digit is detected by the MRFP, or the executing ASR is not successful. The MRFP shall generate the ASR result as the EMMA format. The EMMA result may include multiple recognition results that are mutually exclusive. Each result may be structured by multiple parts in time sequence with the input time. Each result may include the text token that the value will correspond to tokens as defined by the SRGS grammar. Each result may include the interpretation of application specific markup. Each result may include the confidence score that represents the recognition quality. If the size of the EMMA script is larger than the transport capability of the Mp interface, the MRFP shall return the MRFC the ASR is not successful. Then the MRFC may indicate to the AS that the ASR has been stopped and the ASR result.

Figure 6.2.6.5.1 shows the message sequence chart example for executing ASR.