A.6 IMS Emergency Voice Call / 5GS

34.229-53GPPInternet Protocol (IP) multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP)Part 5: Protocol conformance specification using 5G System (5GS)Release 16TSUser Equipment (UE) conformance specification

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

Expected sequence

Step	Direction		Message	Comment
	UE	SS
1	🡪		INVITE	UE sends INVITE with the first SDP offer.
2	🡨		100 Trying	SS sends a 100 Trying provisional response.
3	🡨		180 Ringing	SS sends a 180 Ringing.
4	🡨		200 OK	SS responds INVITE with 200 OK.
5	🡪		ACK	UE acknowledges.

Specific Message Contents

INVITE (Step 1)

Use the default message "INVITE for MO Call" in Annex A.2.1 of TS 34.229-1 [2] with condition A28 and the following exceptions:

Header/param

Value/remark

Message-body

The following SDP types and values.

Session description:

v=0

o=(username) (sess-id) (sess-version) IN (addrtype) (unicast-address for UE)

s=(session name)

c=IN (addrtype) (connection-address for UE) [Note 1]

Time description:

t=(start-time) (stop-time)

Media description:

m=audio (transport port) [Note 2]

c=IN (addrtype) (connection-address for UE) [Note 1]

b=AS: (bandwidth-value)

Note 1: At least one "c=" field shall be present.

Note 2: AMR-WB/16000 codec shall be present in the media attributes, optionally including channel number "/1".

180 Ringing for INVITE (Step 3)

Use the default message "180 Ringing for INVITE" in Annex A.2.6 of TS 34.229-1 [2] with conditions A4 and A14.

200 OK for INVITE (Step 4)

Use the default message "200 OK for other requests than REGISTER or SUBSCRIBE" in Annex A.3.1 of TS 34.229-1 [2] with conditions A6 and A22 and the following exceptions:

Header/param	Value/remark
Content-Type
media-type	application/sdp
Content-Length
value	length of message-body
Message-body	The following SDP types and values. Session description: v=0 o=- 1111111111 1111111111 IN (addrtype) (unicast-address for SS)s=- c=IN (addrtype) (connection-address for SS)b=AS:37 Time description: t=0 0 Media description: m=audio (transport port) RTP/AVP (fmt) [Note 1]b=AS:37 b=RS:0 b=RR:0 Attributes for media: a=rtpmap: (payload type) AMR-WB/16000/1 [Note 1]a=fmtp: (format) mode-change-capability=2; max-red=220a=ptime:20 a=maxptime:240 Note 1: The values for fmt, payload type and format are copied from step 1.