3GPP TSG-T2 SWG5#1
Malmö, Sweden, 28-30 July 1999	TSGT2MT#1(99)005	

Agenda Item:	5

Source:	Telia AB

Title:	References and text for the later sections to inspire for production of text

Document for:	Discussion and production

___________________________________________________________________________

The intention of this input is to give an example of how the text in the later part of the report “Multi-mode issues” can look like and also to give some inspiration for production of further text. First of all some relevant references are included under the headlines and the intention is to look at the references and try to summarise them and write an evaluation of them. In this work the scenarios can be helpful to see how the terminals shall function in different situations, and from that the evaluation can tell if something is missing or if all functionality already is included.

A general question in this work is how closely the situations in the report have to be described. The best way forward would be to try to keep the text rather general that it can be applied for other systems too, as well as for UMTS and GSM/GPRS. Even though the text may not be too general that it is missing central functionality that needs to be included in the specifications. This has to be elaborated for every section of the report. It might happen that different parts need to be described differently. 

Abbreviations
MM		Mobility Management
RR		Radio Resource
RRC		Radio Resource Control
URA		UTRAN Registration Area

5	Procedures in connected mode
[TS 25.303: UE Functions and Interlayer Procedures in Connected Mode]
[The reference used here only deal with the UMTS UE. It could be sufficient to see if there are any changes using a multi-mode terminal and in that case if anything is already done and in what stage it is in.]
5.1	General description
A terminal is considered to be in connected mode when at least one signalling/RRC connection is active in one ore several of the modes/systems.

In the connecting state of a multi-mode terminal it is important to have connections between the different states in which the terminal can be active. This is the case in [25.303] where the case of UMTS connected with GSM is considered. In this specification a division between CS- and PS-connections is made and this might be a good division for further systems as well, as different entities in the backbone network is utilised. Anyhow, it might not be interesting to perform an handover for a PS connection onto a CS connection. One case when this might be interesting though is when the subscriber have very high demands on a reliable connection that should stay connected whatever happens. In this case it might be the only possibility to handover e.g.g a PS connection in UMTS to a CS connection in GSM.

5.2	Connecting State
The corresponding chapter in [25.303] is 5.4. This chapter does not only deal with the UMTS terminal but have the alternative of GSM/GPRS included as well. The GSM/GPRS modes are not very well described, but the transition to them are and that is the scope of that document.

[Shall the pictures from this document be included or just referred to?]
The following figures describe the connecting states in UMTS and GSM/GPRS and the interworking between them.
In Figure 1 the connecting states for a terminal capable of CS connections is shown. It includes the CS part of UTMS and the part of GSM that is connected to PSTN/ISDN only.

Figure 1: UE RRC States and State Transitions including GSM (PSTN/ISDN only)

In Figure 2 the connecting states for PS connections is depicted. The figure depicts both the case as it appears in UTRAN and in GPRS. 

Figure 2: UE RRC states and State Transitions including GSM/GPRS  (IP only)
[1: The indicated “Radio access modes” in Idle Mode are only included for clarification and shall not be interpreted as states.]

5.2.1	Transition to Connected Mode
Can only be initiated by the terminal that either by pagings or by initiating a service starts the initiative to transfer from idle mode to connected mode.
5.2.2	Transition to Idle Mode

5.3	Inter system Handover
Generally: TS [23.920], ch 9.13 – New HO functionalities
TS [25.303] 5.6 – Intersystem handover with simultanous IP and PSTN/IGSN domain services

Handover may be initiated by:
•	A service demanding a sertain mode/system
•	The terminal loosing coverage of the registered/active mode
•	The terminal coming into coverage of a higher preferred mode/system.
•	…

5.3.1	UMTS to GSM
Things to examine:
•	Maintenance of neighbour cell list 
•	Handover Measurement Reporting

The requirements say that this handover shall be included in R99. As seen at the available specifications this seems to be a though mission. From the architectural view, the desired functionality only resides in a report and not a specification. 

TS [22.129], 6 – Requirements for Handover from UMTS to GSM 
TR [23.920], 9.9.1.3 – Handover from UMTS to GSM 
TR [23.920], 10.1.1 – UMTS to GSM HO for circuit switched services.
TS [25.303], 5.6.1 – Inter-system handover UTRAN to GSM / BSS

5.3.2	GSM to UMTS
TS [22.129], 7 – Requirements for Handover from GSM to UMTS
TR [23.920], 9.9.1.2 – Handover from GSM to UMTS
TR [23.920], 10.2 – Packet swithced Handover and Roaming Principles 
Treats the transition between UMTS <-> GSM GPRS.
TS [25.303], 5.6.2 – Inter-system handover GSM / BSS to UTRAN 

5.3.3	UMTS to other systems
TS [23.121], 7.7 – Alternate Access technologies to UTRAN (BRAN/HiperLAN)

5.4	Support of Localised Service Area (LSA) 
In case of a network-controlled handover procedure, UTRAN shall take into account the local support of LSA service and the eventual subscription information of the UE to those LSA regarding the provision of service to the UE.
TS [22.129], 4.1.1 – Supprot of localised service area (SoLSA)

TR [23.920], 9.18 – UMTS Simultaneous Mode
Parallell PS- and CS-connection.

5.5	Evaluation
Most work associated with handover between UMTS and GMS/GPRS is already initiated in the standardisation. The work progresses but it is not sure that it will be finalised for R99. 

6	Procedures in idle mode 
[TS 25.304: UE Procedures in Idle Mode]
[The reference used here only deal with the UMTS UE. It could be sufficient to see if there are any changes using a multi-mode terminal.]
Definition of idle mode:
The UE is in idle mode when the connection of the UE is closed on all layers, e.g. there is neither an MM connection nor an RRC connetion.

6.1	General description of idle mode
6.1.1	Overview

The box at the bottom of the picture (Radio access mode Selection and Reselection) is taken away in version 1.2.0 of TS [25.304]. 

6.1.2	Functional division between AS and NAS in idle mode
AS – Access Stratum
NAS – Non Access Stratum
6.1.3	Service type in idle mode
The list identifies different types of cells that includes different services. Compare with GSM/GPRS and see if the services for the similar situations/cells are the same.
•	Acceptable cell
•	High priority suitable cell
•	Barred cell
•	“Operator only” cell
6.2	Radio access mode selection and reselection
6.2.1	Mode selection
6.2.1.1	Manual
Mode selection after power on

6.2.1.2	Automatic
Mode selection after power on
Mode selection when roaming
Mode selection at incoming call
Mode selection at outgoing call

6.2.2	Mode reselection
6.2.2.1	Terminal initiated
Manual and/or automatic

6.2.2.2	Network initiated
Automatic

6.3	PLMN selection and reselection
Ch 5.1 is the corresponding chapter in [25.304].
Here a comparison with GSM/GPRS could be included to identify similarities and differentiation’s between the procedures.
Corresponding document can be found in GSM [03.22] v 5.2.1, chapter 3. This applies also for cell selection and reselection.
Alternatively this can section be excluded, as the PLMN selection/reselection shall behave as defined for the included modes/systems.
6.4	Cell selection and reselection
Ch 5.2 is the corresponding chapter in [25.304].
Here you could compare with GSM/GPRS and see if the procedures are the same. 
Alternative this can section be excluded, as the cell selection/reselection should behave as defined in the included modes/systems.

6.5	Evaluation
In the referenced document, created by RAN1, the choice of mode/system is still FFS and in this area there need to be some work done. This group should be the right one to perform that work. 

7	Signalling
TS [23.121], 7.3.12 – Signalling procedures
“By default the combined procedures ac defined in GSM 03.60 are also applicable when using Gs.”

TR [23.920], 9.3 – Benefits of the Gs interface applied to UMTS

[EN 301 344] v 6.1.1 (also called [GSM 03.60]).
Gs is the interface in the GPRS structure that combines the MSC/VLR with the SGSN. It is mainly used for co-ordinating MS:s that are both GPRS-attached and IMSI-attached. This association is defined to facilitate the following actions:
•	IMSI attach and detach via SGSN. This makes combined GPRS/IMSI attach and combined GPRS/IMSI detach possible, thus saving radio resources.
•	Co-ordination of LA update and RA update. Including periodic updates, thus saving radio resources. A combined RA/LA update is sent from the MS to the SGSN. SGSN forwards the LA update to the VLR.
•	Paging for a CS connection via the SGSN.
•	Alert procedures for non-GPRS services.
•	Identification procedure.
•	MM Information procedure.

This interface ought to be adapted to UMTS identities.

Gs is not mandatory in GPRS, but this interface ought to be mandatory for UMTS backbone, as it is to be built on GPRS, as it utilise the use of multi-mode terminals essentially. Multi-mode terminals shall be supported in the first release of UMTS and the first terminals are expected to be rather basic and therefor this interface is more important than ever. This is addressed in [23.121] (ch 7.3.1.1) and in [23.920] (ch 10).

GENERAL QUESTIONS: How much has the radio network to do with Mobility Management? There is a difference between GMS and UTRAN where in UTRAN more functionality is placed in the RNC.
7.1	Terminal Capability Information
It should be possible to transfer terminal capability information in connected mode as well as in idle mode.
Some work has been done in RAN1 on how what and how much to signal of the terminal capabilities. No conclusion has been reached and the discussion is at the moment non-existing, as is also the case with the document that treats this issue. Although this is something that the terminal has to be able to communicate to the network/HLR. The signalling of capabilities can be referred to the ongoing work in T2 SWG6 too.

FFS.
7.2	Paging
Support of GSM paging when camping in a UTRA cell and vice versa
Supported by Gs. 
Situations to consider to make sure as few pagings as possible are missed.
•	In connected mode: an update in the other mode/system may have to be done right after the connection is terminated
•	In idle mode

7.3	Location Registration
Definitions applied for UMTS and GSM/GPRS:
RA		Registration Area, for PS-services
LA		Location Area, for CS-services
The definitions of the registration areas and corresponding areas in GSM has to be explained. 

TR [23.920], 9.19 – GSM & UMTS cells in the same registration area

7.4	Location update
A LU from one mode may be made valid in other modes as well.
Combining LU for different systems/networks, e.g. the terminal is registered in GSM and UTRA but still it is enough with one LU.
Combined updates: 	TS [23.121], 7.3.6.3 - for 2G and 3G
			TS [23.121], 7.3.13 - for 3G-configuration
Combined LA or signalling between entities that makes it possible to direct a call or ask the terminal/user to change mode.
[Editors note: The interface Gs has a lot to do in this case. Lots of situations are described in [23.121] on how this could be implemented both in the CN and in the terminal (at least on a protocol level).]
8	Identities
TS [23.121],	7.3.10 – Requirements on Identifiers for UMTS and GSM
		7.3.11 – Use of TMSI signature
TR [23.920], 	9.5 – Management of ciphering keys
Multiple identities
One identity for several modes/networks
8.1	Signalling of multiple identities

8.2	Treatment of multiple identities
[Editors note: In what entity are the identities combined and in what way?]
The HLR or an evolved HLR seems to be the common denominator for treatment of identities in UMTS. Both the 3G_MSC/VLR and the 3G_SGSN collects MM information from this entity.
9	Conclusions
9.1	General
In the work with this report several issues have been found that need additional treatment to make multi-mode terminals usage efficient. 
9.2	Identified requirements

9.3	Identified work items
Idle mode – mode selection/reselection