3GPP TSGN & TSGS Multimedia and Multicall joint meeting      Tdoc N1-99-640

29.Jun.-1.Jul.1999, Oulu, Finland

Agenda item	:	Multimedia, Multimedia Service Inter-Working	
Source	:	NTT DoCoMo, NTC	
Title	:	Circuit Switched Multimedia Telephony Inter-Working 	
Document for	:	Discussion	

1. Introduction
One the basic principles of the 3GPP/UMTS is to provide multimedia services (multimedia telephony) in both CS domain and PS domain. 3G-H.324/M will be used to provide the multimedia telephony services in CS domain and H.323 will be used to provide such multimedia telephony services in PS domain.
This document would like to describe the following points.
a)	The basic concept of the multimedia services are provided to the user.
b)	The interconnection between the different multimedia systems.
c)	CS domain Multimedia Telephony Inter-Working
(a) and (b) deals with both CS domain and PS domain multimedia telephony, (c) deals with only CS domain multimedia telephony to simplify the discussion.

2. The basic concept of multimedia services are provided to the user
From the users’ point of view, Multimedia telephony service to be same as the enhanced voice telephony service. Therefore, the following requirements to be satisfied when multimedia telephony services are provided to the user.
a)	Users can dial the destination number directly
It is currently realized in CS domain and PS domain. But this is not realized when the interconnection between CS domain and PS domain. In this case, user dials the gateway number first, then gateway dials the destination number after the user informed the gateway of the destination number.
b)	Users should not aware of multimedia system in the destination
In Voice Telephony, users are unaware of speech codec type in the destination(ex, full rate codec, half rate codec and G.711). Therefore, also in multimedia telephony, users should not aware of multimedia systems in the destination(ex, H.324, H.320 and H.323).

3. The interconnection between the different multimedia systems
3G-H.324/M in CS domain and H.323 in PS domain will supported as a multimedia telephony system in the 3GPP/UMTS. H.320 on ISND, H.310 and H.321 on B-ISDN, H.322 on Guaranteed Quality of Service LANs and H.324 on PSTN are supported on each network.
In order to the multimedia services to be attractive for the users in 3GPP/UMTS, these multimedia services provided by various multimedia systems should be seen as the same multimedia telephony service from the 3GPP/UMTS user. Therefore, when seeing from the system point of view, 3GPP/UMTS to support the interconnection between the different multimedia systems(ex, 3G-H.324/M and H.323, 3G-H324/M and H.320) because users not to aware the multimedia systems in the NW.

Figure 3.1: User’s view and System’s view on Multimedia telephony

H.320 on ISDN is already popular in Japan. Therefore, we would like to support especially the interconnection between H.320 and 3G-multimedia systems. And in the specification, TS26.112 describes the interconnection between 3G-H.324/M~3G-H.324/M, H.324 on PSTN~3G-H.324/M and H.324/I~3G-H.324/M. 
The interconnection between H.324 on PSTN~3G-H.324/M, H.324/I~3G-H.324/M and H.320~3G-H.324/M to be concerned in 3GPP/UMTS CS domain. The interconnection with H.323 to be concerned, but the scope of this document is the multimedia services in CS domain, this document dose not explain the detail of PS domain multimedia telephony service.

3. CS domain Multimedia Telephony Inter-Working
3.1 The interconnecting patterns in 3GPP/UMTS CS domain
The following interconnecting patterns to be concerned in 3GPP/UMTS CS domain.

	The interconnecting pattern	IWF	
A (note 1)	3G-H.324/M to/from 3G-H.324/M	Not required	
B	3G-H.324/M to/fromH.320 on ISDN	Required(note 2)	
C (note 1)	3G-H.324/M to/form H.324 on PSTN	Required(note 3)	
Note1: The call setup procedures of the pattern A and C are described in TS26.112 v1.1.0.
Note2:3G-H.324 is different multimedia system form H.320 completely. Therefore, IWF is needed in order to interconnect between 3G-H.324/M and H.320.
	3G-H.324/M	H.320	
audio CODEC	GSM-AMR	G.711	
Video CODEC	H.263	H.261	
System control	H.245	H.242	
Mux/Demux	H.223	H.221	
Table; The comparison of codec types between 3G-H.324/M and H.320
Note3: IWF is modem pole. IWF is not the multimedia protocol converter. 

4. The IWF location
In order for 3GPP/UMTS Multimedia Telephony service to become widespread in telecommunication markets, multimedia telephony services should be attractive for the users. Because of the above reason, the following requirements to be satisfied.
(1)	Mobile users can dial the destination number directly.
If IWF is located outside the 3GPP/UMTS network, users have to recognize the service specific numbers for the IWF located outside the 3GPP/UMTS network and then dial the destination number.
(2)	Mobile users are unaware of multimedia system type in the destination.
Network should insert IWF to the connection between different multimedia systems automatically. That is possible if IWF is located within the network. If IWF is located outside network, network dose not know the existence of IWF and network dose not insert IWF to the connection automatically.
Therefore, 3GPP standard should allow the IWF to be located within 3GPP/UMTS network.

5. Proposal
This paper proposes that;
The call setup procedure of the interconnection between 3G-H.324/M and H.320 with IWF within network to be added to UMTS 26.112.