U.S. patent application number 12/522201 was filed with the patent office on 2010-03-04 for method and apparatus for providing circuit switched domain services over a packet switched network.
Invention is credited to Magnus Hallenstal, Jari Tapio Vikberg.
Application Number | 20100054187 12/522201 |
Document ID | / |
Family ID | 39370924 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100054187 |
Kind Code |
A1 |
Hallenstal; Magnus ; et
al. |
March 4, 2010 |
METHOD AND APPARATUS FOR PROVIDING CIRCUIT SWITCHED DOMAIN SERVICES
OVER A PACKET SWITCHED NETWORK
Abstract
A method of determining a domain mode for a mobile station
operating in either a circuit-switched domain or a packet-switched
domain. A first domain mode is determined, and then a determination
is made whether to rove from the first domain mode to a second
domain mode. The determination may be made by a Packet Mobile
Switching Center (PMSC) when, for example, the mobile station moves
between Routing Areas. Alternatively, the mobile station may make
the determination based, for example, on pre-provisioned selection
criteria. The mobile station derives a Fully Qualified Domain Name
(FQDN) based on a cell identifier of a current cell and uses the
FQDN in a DNS query to obtain the IP address of the PMSC.
Inventors: |
Hallenstal; Magnus; (Taby,
SE) ; Vikberg; Jari Tapio; (Jarna, SE) |
Correspondence
Address: |
ERICSSON INC.
6300 LEGACY DRIVE, M/S EVR 1-C-11
PLANO
TX
75024
US
|
Family ID: |
39370924 |
Appl. No.: |
12/522201 |
Filed: |
January 14, 2008 |
PCT Filed: |
January 14, 2008 |
PCT NO: |
PCT/IB08/00074 |
371 Date: |
July 6, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60884914 |
Jan 15, 2007 |
|
|
|
Current U.S.
Class: |
370/328 ;
370/356 |
Current CPC
Class: |
H04L 65/103 20130101;
H04L 65/1016 20130101; H04W 68/00 20130101; H04W 76/00 20130101;
H04L 65/1069 20130101; H04W 80/04 20130101 |
Class at
Publication: |
370/328 ;
370/356 |
International
Class: |
H04W 40/00 20090101
H04W040/00 |
Claims
1. A method of determining a domain mode for a mobile station,
wherein the mobile station accesses a Packet Switched Core Network
through a Long Term Evolution, LTE, radio access network, and
wherein a Packet Mobile Switching Center, PMSC, interfaces the
Packet Switched Core Network with a Circuit Switched Core Network,
said method comprising the steps of: determining a first domain
mode; and determining whether to rove from the first domain mode to
a second domain mode according to predefined roving criteria, said
determining step including determining whether a current serving
cell, location area, routing area, or traffic area requires a
change of domain mode; wherein the first domain mode and the second
domain mode comprise a Circuit Switched domain mode and a 24.008
over 3GPP Packet Switched network mode.
2. The method of claim 1, wherein the roving determination is made
by the PMSC.
3. The method of claim 2, wherein the roving determination is made
when the mobile station is moving between Routing Areas.
4. The method of claim 3, wherein the mobile station connects to
the PMSC using U8-CSR protocol signaling.
5. The method of claim 4, wherein the mobile station sends periodic
U8-CSR KEEP ALIVE messages to the PMSC while the mobile station
operates in 24.008 over 3GPP Packet Switched network mode.
6. The method of claim 4, wherein the mobile station connects to
the PMSC through the steps of: the mobile station sending a U8-CSR
REQUEST message to the PMSC with an establishment cause; the PMSC
requesting a modification of the signaling bearer from a Policy and
Charging Rules Function, if required by the establishment cause;
and the PMSC returning an acceptance to the mobile station.
7. The method of claim 4, further comprising the mobile station
releasing the connection to the PMSC through the steps of: the PMSC
deciding to release the signaling and user plane connection
resources allocated to the mobile station; the PMSC sending a
U8-CSR RELEASE message to the mobile station commanding the mobile
station to release the signaling and user plane connection
resources; the mobile station sending a U8-CSR RELEASE COMPLETE
message to the PMSC; and the mobile station entering idle mode.
8. The method of claim 7, further comprising the steps of: the PMSC
requesting a modification of the signaling bearer from a Policy and
Charging Rules Function; and the PMSC requesting release of a
Secondary PDP Context, if allocated for the user plane.
9. The method of claim 4, further comprising the steps of: the PMSC
sending a U8-CSR CIPHERING MODE COMMAND message to the mobile
station indicating integrity protection and encryption settings;
and the mobile station storing the integrity protection and
encryption settings for use if the mobile station roves to the
Circuit Switched domain mode.
10. The method of claim 4, wherein the mobile station and the PMSC
utilize Circuit Switched signaling in U-B CSR-DEDICATED mode, and
the PMSC encapsulates a NAS/Layer 3 message within a U8-CSR DL
DIRECT TRANSFER message sent to the mobile station.
11. The method of claim 4, wherein the mobile station and the PMSC
utilize Circuit Switched signaling in U-8 CSR-DEDICATED mode, and
the mobile station encapsulates a NAS message or SMS message within
a U8-CSR UL DIRECT TRANSFER message sent to the PMSC.
12. The method of claim 1, wherein the roving determination is made
by the mobile station.
13. The method of claim 12, wherein the mobile station has
pre-provisioned selection criteria.
14. The method of claim 12, wherein the mobile station downloads
roving criteria.
15. The method of claim 1, wherein a Radio Access type indicates to
the mobile station what mode to select.
16. The method of claim 15, wherein the Radio Access type
indication is provided using parameters in System Information
messages.
17. The method of claim 1, wherein the roving determination is made
by the Packet Switched Core Network.
18. The method of claim 17, wherein the roving determination is
made by a 3GPP Packet Switched Core Network.
19. A method for providing Packet Mobile Switching Center, PMSC,
Discovery for a mobile station, said method comprising the steps
of: deriving by the mobile station, a Fully Qualified Domain Name,
FQDN, based on a cell identifier of a current cell; sending the
FQDN in a query to a Domain Name System, DNS, server; and receiving
from the DNS server, an IP address of a PMSC based on the FQDN.
20. The method of claim 19, wherein an operator specific string
received by the mobile station and the cell identifier of the
current cell are used to derive the FQDN.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/884,914 filed Jan. 15, 2007, the disclosure of
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to circuit switched domain
services. More particularly, the present invention relates to
providing circuit switched (CS) domain services over a packet
switched (PS) network.
[0003] When introducing LTE (Long Term Evolution)--the next
generation radio access in 3GPP--there are only packet bearers
available. This means that the wide range of services currently
offered within the CS domain can not be used by a terminal using
LTE-connectivity, unless the terminal either shifts to another
radio access or is equipped with a second transceiver permitting
parallel access to the CS-domain present in 2G and 3G networks.
Examples of existing services are: [0004] Prepaid [0005] Regularity
equipments for identity signaling [0006] Legal interception [0007]
0800 calls, free calls [0008] Announcements [0009] Premium number
calls [0010] Home Zone [0011] Sound Logo [0012] Call Barrings
[0013] MultiSIM [0014] Standardized supplementary services
[0015] The basic assumption when introducing LTE is that the
telecommunication service will be provided by the IMS (IP
Multimedia Subsystem) system.
BRIEF SUMMARY OF THE INVENTION
[0016] The present invention generally describes a method of
determining a domain mode for a mobile station. In one embodiment,
a first domain node is determined. A determination is made whether
to rove from the first domain mode to a second domain mode
according to predefined roving criteria.
[0017] The present invention also generally describes a method of
performing Packet Mobile Switching Center discovery for a mobile
station. A Fully Qualified Domain Name is derived based on a cell
identifier of a current cell. The derived Fully Qualifed Domain
Name is used to determine an Internet Protocol Address of a Packet
Mobile Switching Center.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In the following section, the invention will be described
with reference to exemplary embodiments illustrated in the figures,
in which:
[0019] FIG. 1 illustrates a system for providing circuit switched
domain services over a packet switched network according to one
embodiment of the present invention;
[0020] FIG. 2 illustrates a 24.008 over 3GPP PS network functional
architecture according to one embodiment of the present
invention;
[0021] FIG. 3 illustrates a control plane PS network protocol
architecture according to one embodiment of the present
invention;
[0022] FIG. 4 illustrates MS architecture for the CS domain control
plane according to one embodiment of the present invention;
[0023] FIG. 5 illustrates a user plane PS network protocol
architecture according to one embodiment of the present
invention;
[0024] FIG. 6 illustrates a state diagram for an MS implementing
the 24.008 over 3GPP PS network functionality according to one
embodiment of the present invention;
[0025] FIG. 7 illustrates a diagram of a roving criteria method
according to one embodiment of the present invention;
[0026] FIG. 8 illustrates a diagram of a Packet Mobile Switching
Center discovery method according to one embodiment of the present
invention;
[0027] FIG. 9 illustrates a Packet Mobile Switching Center
discovery procedure according to one embodiment of the present
invention;
[0028] FIG. 10 illustrates a Keep Alive process according to one
embodiment of the present invention;
[0029] FIG. 11 illustrates a U8-CSR connection establishment
procedure according to one embodiment of the present invention;
[0030] FIG. 12 illustrates a U8-CSR connection release procedure
according to one embodiment of the present invention;
[0031] FIG. 13 illustrates a ciphering configuration flow according
to one embodiment of the present invention;
[0032] FIG. 14 illustrates network initiated Circuit Switched
Signaling according to one embodiment of the present invention;
and
[0033] FIG. 15 illustrates Mobile Station initiated Circuit
Switched Signaling according to one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] As will be recognized by those skilled in the art, the
innovative concepts described in the present application can be
modified and varied over a wide range of applications. Accordingly,
the scope of patented subject matter should not be limited to any
of the specific exemplary teachings discussed above, but is instead
defined by the following claims.
[0035] The novel features that are considered characteristic of
this invention are set forth with particularity in the appended
claims. The invention itself, however, both as to its organization
and method of operation, as well as additional objects and
advantages thereof, will best be understood from the following
description when read in connection with the accompanying
drawing.
[0036] For the purposes of the present invention, the following
terms and definitions apply:
[0037] 24.008 over 3GPP PS network: A service which allows a
terminal to make use of the CS call control also over a 3GPP packet
switched network.
[0038] 24.008 over 3GPP PS network Mode: MS mode of operation where
the NAS layers communicate through the U8-CSR entity.
[0039] 24.008 over 3GPP PS network PMSC: The target MSC, or rather
PMSC when handing over from CS domain to packet domain entering the
24.008 over 3GPP PS network Mode.
[0040] 24.008 over 3GPP PS network supporting PMSC: The PMCS that a
MS will rove into when entering the 24.008 over 3GPP PS network
Mode.
[0041] 3GPP PS network: Radio and core part of the 3GPP Packet
Switched service.
[0042] CS Domain: The domain where Circuit Switched services are
executed. This domain can be based on IP in the core network, but
on the radio access the resources are circuit based.
[0043] CS Domain mode: MS mode of operation where the CS related
NAS layers communicate through either the GERAN RR or the UTRAN RRC
entities, thus operating in the normal CS Domain. When GERAN RR is
used, the BSS is connected to the CN using the standardized
A-interface. When UTRAN RRC is used, the RNS is connected to the CN
using the standardized Iu-CS interface.
[0044] Discovery procedure: The process by which the MS discovers
which PMSC to Rove into.
[0045] Handover: Mobile station engaged in a call moves between
3GPP CS access networks and 24.008 over 3GPP PS networks.
[0046] Handover in: mobile station moves from 3GPP CS access
network to 24.008 over 3GPP PS network
[0047] Handover out: mobile station moves from 24.008 over 3GPP PS
network to 3GPP CS access network
[0048] PMSC: Packet MSC, the network function needed to support the
24.008 over 3GPP PS network service.
[0049] Supporting PMSC: The PMSC the MS Roves into
[0050] Rove in: mobile station reselects from 3GPP CS access
network to 24.008 over 3GPP PS network
[0051] Rove out: mobile station reselects from 24.008 over 3GPP PS
network to 3GPP CS access networks
[0052] Roving: action of re-selection between 3GPP CS access and
24.008 over 3GPP PS network for a mobile station in idle mode
[0053] Seamless: free from noticeable transitions (i.e. no end-user
action is required; speech interruptions are short; service
interruptions are short; incoming calls are not missed; packet
sessions are maintained; services work identically)
[0054] For the purposes of the present invention, the following
abbreviations apply:
[0055] AMR Adaptive Multi-Rate
[0056] AS Access Stratum
[0057] BSS Base Station Subsystem
[0058] BSSGP Base Station System GPRS Protocol
[0059] BSSMAP Base Station System Management Application Part
[0060] CC Call Control
[0061] CGI Cell Global Identity
[0062] CM Connection Management
[0063] CN Core Network
[0064] CS Circuit Switched
[0065] CSR Circuit Switched Resources
[0066] CTM Cellular Text Telephone Modem
[0067] DNS Domain Name System
[0068] DTM Dual Transfer Mode
[0069] ETSI European Telecommunications Standards Institute
[0070] FQDN Fully Qualified Domain Name
[0071] GAD Geographical Area Description
[0072] GAN Generic Access Network
[0073] GERAN GSM EDGE Radio Access Network
[0074] GGSN Gateway GPRS Support Node
[0075] GMM/SM GPRS Mobility Management and Session Management
[0076] GPRS General Packet Radio Service
[0077] GSM Global System for Mobile communications
[0078] GSN GPRS Support Node
[0079] HLR Home Location Register
[0080] HPLMN Home PLMN
[0081] HSPA High Speed Packet Access
[0082] IETF Internet Engineering Task Force
[0083] IMEISV International Mobile station Equipment Identity and
Software Version number
[0084] IMS IP Multimedia Subsystem
[0085] IMSI International Mobile Subscriber Identity
[0086] IP Internet Protocol
[0087] ISIM IMS Subscriber Identity Module
[0088] LA Location Area
[0089] LAI Location Area Identity
[0090] LLC Logical Link Control
[0091] LTE Long Term Evolution
[0092] MAC Medium Access Control
[0093] MM Mobility Management
[0094] MS Mobile Station
[0095] MSC Mobile Switching Center
[0096] MTP1 Message Transfer Part layer 1
[0097] MTP2 Message Transfer Part layer 2
[0098] MTP3 Message Transfer Part layer 3
[0099] NAS Non-Access Stratum
[0100] PDP Packet Data Protocol
[0101] PDU Protocol Data Unit
[0102] PLMN Public Land Mobile Network
[0103] PMSC Packet MSC
[0104] PSAP Public Safety Answering Point
[0105] NOTE: A PSAP is an emergency services network element that
is responsible for answering emergency calls.
[0106] PSTN Public Switched Telephone Network
[0107] QoS Quality of Service
[0108] RA Routing Area
[0109] RAC Routing Area Code
[0110] RAI Routing Area Identity
[0111] RAT Radio Access Technology
[0112] RLC Radio Link Control
[0113] ROHC Robust Header Compression
[0114] RRC Radio Resource Control
[0115] RTCP Real Time Control Protocol
[0116] RTP Real Time Protocol
[0117] SCCP Signaling Connection Control Part
[0118] SGSN Serving GPRS Support Node
[0119] SIM Subscriber Identity Module
[0120] SMLC Serving Mobile Location Center
[0121] SMS Short Message Service
[0122] SNDCP Sub-Network Dependent Convergence Protocol
[0123] SS Signaling Subsystem
[0124] TFO Tandem Free Operation
[0125] TrFO Transcoder Free Operation
[0126] TTY Text Telephone or TeletYpewriter
[0127] UDP User Datagram Protocol
[0128] UMTS Universal Mobile Telecommunication System
[0129] VLR Visited Location Register
[0130] VPLMN Visited Public Land Mobile Network
[0131] FIG. 1 illustrates a system 100 for providing circuit
switched domain services over a packet switched network.
Previously, a mobile station 110 using a long term evolution radio
access 130 needed to access another network, e.g. 2G/3G network
120, in order to use MSC based CS domain services. The present
invention allows a mobile station 110 to use the MSC based CS
domain services also when on a long term evolution (LTE) network
130, or other packet based accesses is used. This invention
description uses Third Generation Partnership Project (3GPP)
accesses as example. It should be noted that other access types
also is applicable to the invention, for example 3GPP2 and WiMax
accesses. This means that all the control plane 180 and user plane
190 information for the CS domain, e.g., circuit switched core
network CS CN 160, is tunneled through the 3GPP PS network 140.
Services related to public switched telephone network (PSTN) 170
may also be accessed via CS CN 160.
[0132] Control plane information 180 is tunneled through packet
switched network 140 to network controller 194. Network controller
194 may be a stand-alone unit or may be a component of mobile
switching center server (MSC-S) 196. User plane information 190 is
tunneled through packet switched network 140 to inter working unit
(IWU) 192. IWU 192 may be a stand-alone unit or may be a component
of circuit switch domain media gateway (CS-MGW) 198. Network
controller 194, MSC-S 196, IWU 192, and CS-MGW 198 are all located
in a packet mobile switching center (not shown).
[0133] All other possible PS traffic 182 would be transported
towards packet data network 150. The figure shows LTE 130 as an
example for the 3GPP PS access being used. Other possibilities are
e.g. Evolved GSM/GPRS, UMTS/HSPA and WiMax. The LTE example of FIG.
1 also shows Access Gateway (AGW) 144. It should be noted that
although the present invention refers to 3GPP accesses, those
skilled in the art will realize that any packet based access may be
utilized. AGW 144 is the node corresponding to the GGSN in the
Evolved GSM/GPRS and UMTS/HSPA cases. In current standards (3GPP
23.401) the AGW consists of a Serving Gateway and a PDN Gateway
(Packet Data Network Gateway).
[0134] FIG. 2 illustrates one embodiment of a 24.008 over 3GPP PS
network functional architecture 200. Mobile station (MS) 205
contains functions to access the 24.008 over 3GPP packet switched
(PS) network 220.
[0135] Packet mobile switching center (PMSC) 225 has new
functionality as compared with a mobile switching center (MSC).
PMSC 225 is able to handle the 24.008 over 3GPP PS network service.
In one embodiment, PMSC 225 handles interface (U8) 217, which is an
interface between mobile station 205 and PMSC 225 over PS network
220. In one embodiment, PMSC 225 is able to request certain IP
Quality of service class from the PS network. PMSC 225 may be
divided into 4 functional components: the MSC server 240, a network
controller 230, e.g., 24.008 over 3GPP network Controller (8PSC),
an Inter Working Unit (IWU) 235 and a media gateway 245, e.g., CS
domain Media Gateway (CS-MGW). Network controller 230 and IWU 235
may be stand alone units or may be part of MSC-Server 240 and
CS-MGW 245, respectively.
[0136] Network controller 194, 230 terminates the control plane
part of the U8 interface (i.e. the U8c interface). Network
controller 230 optionally authenticates the user, e.g., MS 205,
before any signaling towards the Iu-CS interface is attempted.
Network controller 230 is also responsible for requesting resources
from Policy and Charging Rules Function (PCRF) 250.
[0137] IWU 192, 235 terminates the user plane part of the U8
interface (i.e. the U8u interface) and is responsible for repacking
of the media stream from Real Time Protocol (RTP) to Nb (Nb is the
interface between media gateways in the 3GPP CS domain) framing in
RTP. Optionally, if an Asynchronous Transfer Mode (ATM) based
interface on Iu-CS is used, IWU 235 will also do media gatewaying
between ATM and IP.
[0138] In addition to handling control information from network
controller 230, MSC server 240 operates to handle control
information from a mobile station via CS-core 215 and CS access 210
and media control information, Mc, from CS-MGW 245 as detailed in
related specifications of the 3GPP standard. In addition to
handling user plane information from IWU 235, Circuit Switched
domain Media Gateway (CS-MGW) 245 also operates to handle media
information as detailed in related specifications of the 3GPP
standard.
[0139] MS 205 interfaces to network 210 using Um for GERAN and Uu
for UMTS Terrestrial Radio Access Network (UTRAN). The term U(x) is
used to denote both Um and Uu without excluding even more
interfaces.
[0140] The A and Iu interfaces are the two standard CS domain
interfaces between Access Network 210 and Core Network 215. The
A-interface is used between GERAN 210 and MSC 240 and the Iu-CS
interface can be used either between GERAN 210 and MSC 240 or
between UTRAN 210 and MSC 240.
[0141] The Rx interface is the interface used by applications
towards PCRF 250. It is not foreseen that this application will
have any additional functionality needs on the interface.
[0142] Interface 217, i.e., U8-interface, is divided on user plane
U8u 180 and control plane U8c 190. Interface 217 carries all the
control and user plane information needed to e.g. Rove; and set-up,
maintain, and clear 24.008 CS calls over a 3GPP PS network, e.g.
network 140, 220. U8-interface 217 is between the MS 110, 205 and
the PMSC 225. The interface supports all CS defined services within
3GPP 24.008, such as mobility, basic call and supplementary
services.
[0143] The Gi interface is the IP-based interface coming out from
the 3GPP PS network. Another name for the Gi interface is SGi and
is used in the SAE/LTE 3GPP specifications. On functional level
there is no real difference between Gi and SGi. In one embodiment,
the Gi interface (or the SGi) is implemented using AGW 144 (which
can be broken up into S GW and PDN GW according to current
standardisation). In another embodiment using a GPRS PS network,
the Gi interface is implemented using GGSN. In yet another
embodiment using WiMAX, architecture the AGW can be translated into
the Access Service Network Gateway and Home Agent. In the WiMAX
architecture there are no name corresponding to the Gi and SGi
reference points.
[0144] FIG. 3 illustrates a control plane PS network protocol
architecture. One embodiment of a 24.008 over 3GPP PS network
protocol architecture for the control plane in LTE is shown. In
GPRS and UMTS the protocol stack will look very similar, however
some different node entities exists.
[0145] The embodiment shown in FIG. 3 illustrates features of the
U8c interface for the 24.008 over 3GPP PS network service. The 3GPP
PS network provides the generic IP connectivity between the MS and
the PMSC. In this embodiment, the PMSC is connected via the
SGi/Gi-interface.
[0146] UDP provides transport for the U8 Circuit Switched Resources
(U8-CSR) 217 between MS 110, 205 and PMSC 225. In one embodiment,
U8-CSR is based on GAN (Generic Access Network) tunneling protocols
as defined in 3GPP TS 43.318 and 44.318. The U8-CSR protocol
manages the IP connection and performs functionality equivalent to
the GSM-RR protocol. Protocols, such as mobility management (MM)
and above, e.g., CC/SS/SMS, are carried transparently between MS
110, 205 and PMSC 225. The IP address of MS 110, 205 is used by
PMSC 225 to communicate with the MS 110, 205 for the 24.008 over
3GPP PS network service.
[0147] FIG. 4 illustrates MS architecture for the CS domain control
plane in MS 110, 205. A Connection Management (CM) layer comprises
call control (CC), signaling subsystem (SS), and short message
service (SMS) services. Mobility Management (MM) layer interfaces
with CC, SS, and SMS services of the CM layer using corresponding
service access points (SAPs). The Radio Resource SAP (RR-SAP)
interface to the UMTS/GSM-MM layer is preserved identically for
GSM, UMTS and 24.008 over 3GPP PS network (and for GAN if present)
access. An access mode switch is provided to switch between
UTRAN/GERAN and 24.008 over 3GPP PS network modes (and GAN if
present). U8-CSR peers with UTRAN-RRC/GSM-RR to provide
coordination for handover. Note: The RLC/MAC/L1 can be the same in
some cases, e.g. in the UMTS CS and PS radio interfaces.
[0148] FIG. 5 illustrates a user plane PS network protocol
architecture. The embodiment shown in FIG. 6 illustrates features
of the U8u interface for the 24.008 over 3GPP PS network service.
The 3GPP PS network provides the generic connectivity between the
MS and the IP network. CS domain user plane is transported over
RTP/UDP between MS and PMSC. Standard 3GPP codecs, e.g. AMR, as
specified e.g. in 3GPP TS 26.071, are supported when operating in
24.008 over 3GPP PS network mode. CS-data is transported over
RTP/UDP, by defining a new RTP frame format to carry the TAF
(Terminal Adaptation Function)-TRAU (Transcoder and Rate Adaptation
Unit) (V.110 like) frames over RTP TTY is transported using CTM
over GSM codec over RTP/UDP. Header compression (such as ROHC) for
efficient voice transport over the radio access network can
optionally be supported by 3GPP PS access and PS core nodes.
[0149] The U8-CSR protocol provides a resource management layer,
which is equivalent to the GSM-RR or UTRAN-RRC and provides the
following functions: discovery, i.e. selecting the 24.008 over 3GPP
PS network supporting PMSC; setup of IP bearer resources for CS
service between the MS and PMSC (8PSC functional entity); handover
support between UTRAN/GERAN and 24.008 over 3GPP PS network; and
functions such as paging, ciphering configuration, classmark
change, etc.
[0150] FIG. 6 illustrates an exemplary state diagram for an MS
implementing the 24.008 over 3GPP PS network mode. The U8-CSR
sub-layer in the MS can be in two states U8-CSR-IDLE or
U8-CSR-DEDICATED and moves between these states as defined
below.
[0151] The MS enters 24.008 over PS network mode when the MS
switches the serving RR entity to U8-CSR and the SAP between the MM
and the U8-CSR is activated. While the MS remains in 24.008 over
3GPP PS network mode it performs normal and periodic Location
Updates and application level keep-alive with the 24.008 over 3GPP
PS network supporting PMSC.
[0152] The MS moves from the U8-CSR-IDLE state to the
U8-CSR-DEDICATED state when the U8-CSR connection is established
and returns to U8-CSR-IDLE state when the U8-CSR connection is
released. Upon U8-CSR connection release an indication that no
dedicated resources exist is passed to the upper layers.
[0153] The MS may also enter U8-CSR-DEDICATED state in 24.008 over
PS network mode to from CS Domain mode when Handover to 24.008 over
3GPP PS network is being performed. In the same way, the MS enters
CS Domain mode from U8-CSR-DEDICATED when Handover from 24.008 over
3GPP PS network.
[0154] The 24.008 over 3GPP PS network supports security mechanisms
at different levels and interfaces. It is assumed that the 3GPP PS
access is secure enough for the service (using the security
mechanism specified for the PS service). Optionally IPsec (IPsec is
used by IMS) may be utilized to secure the signaling.
Authentication will be done on MM layer, and controlled by the PMSC
(normal SIM and ISIM authentication procedures).
[0155] In addition, it may be desirable to provide security between
the AGW and the PMSC. For example, the AGW resides in the HPLMN and
the PMSC resides in the VPLMN in the roaming case and it might be
appropriate to provide some low-level security (e.g. IPsec tunnels)
for the traffic between the AGW and the PMSC.
[0156] FIG. 7 illustrates a diagram of a roving criteria method
according to one embodiment. Method 700 starts at step 705 and
proceeds to step 710. At step 710, a first domain mode is
determined. Once a first mode is determined there must be a way for
the MS, e.g. MS 110, 205 to determine if it shall be in CS domain
mode or if it shall be in the 24.008 over 3GPP PS network mode.
[0157] At step 715, a determination whether to rove from the first
domain mode to a second domain mode is made according to predefined
roving criteria. The decision to rove may be made by the following
entities: the PMSC, the MS, the Radio Access or the 3GPP PS CN
network. The decision to rove may be made by one entity alone or in
combination with one or more of the other entities.
[0158] In one embodiment, the PMSC determines whether to rove from
a first domain mode to a second domain mode. The MS will always be
GPRS or PS domain attached. At Routing Area Update (or equivalent
other concept for LTE) when the MS is moving between Routing Areas,
i.e. not at periodic RA updates, the MS will connect to the
supporting PMSC and ask what mode of operation it shall be in using
U8-CSR signaling. The PMSC may have a database, or some other means
to determine what mode the MS should be in.
[0159] In one embodiment, the MS determines whether to rove from a
first domain mode to a second domain mode. The MS may have
pre-provisioned selection criteria. E.g. it shall always be in
24.008 over 3GPP PS network mode when on LTE or HSPA access. Or,
the MS contacts the network (PMSC e.g. or a special database) and
downloads Roving criteria, such as certain cells, LAs, RAs or TAs
or ranges there of. The Roving criteria will be used when the MS
determines which mode to enter, and where to rove in.
[0160] In one embodiment, the Radio Access determines whether to
rove from a first domain mode to a second domain mode. The Radio
Access may indicate to the MS what mode to select, e.g. via
parameters in the System Information messages.
[0161] In one embodiment, the 3GPP PS CN network determines whether
to rove from a first domain mode to a second domain mode. The MS
receives responses from the 3GPP PS CN network while performing
e.g. Routing Area Updates and PDP Context activations and
modifications. These responses can also be used to indicate if the
3GPP PS network operator wishes the MS to enter 24.008 over 3GPP PS
network mode.
[0162] Re-selection between CS Domain Mode and 24.008 over 3GPP PS
network modes will now be described. Re-selection comprises Rove-in
(from CS Domain mode to 24.008 over 3GPP PS network mode) and
Rove-out (from 24.008 over 3GPP PS network mode to CS Domain mode)
procedures.
[0163] The Rove-in procedure is applicable when it is determined
that the MS shall use the 24.008 over 3GPP PS network service. The
access mode in the MS is switched to 24.008 over 3GPP PS network
mode. The prerequisites for the Rove-in are the following: [0164]
The MS is aware of the appropriate supporting PMSC i.e. the MS has
performed the discovery procedure; and; [0165] The MS has performed
successful registration towards the PMSC. The registration process
is described later in this description.
[0166] When all the above prerequisites are filled, the MS may
decide to perform Rove-in to the 24.008 over 3GPP PS network mode
(i.e. the MS switches the serving RR entity to U8-CSR and the SAP
between the MM and the U8-CSR is activated). As part of this, the
U8-CSR indicates that CS service is available and passes the
relevant NAS-level system information for the CS domain to the
NAS-layers (i.e. MM).
[0167] After this normal MM operations follow, e.g. if the LAI
indicated to the NAS is different from the previous LAI indicated
to NAS or if CS service was not previously available, then the
NAS-layers in the MS will trigger Location Updating procedures
towards the PMSC as following: [0168] The MS establishes the U8-CSR
signaling connection, with the 24.008 over 3GPP PS network
supporting PMSC that approved the MS registration previously.
[0169] The PMSC (or very likely the 8PSC entity of the PMSC) is
aware of the cell identity of the current PS cell and either uses
that or another cell identity (as returned to the MS as part of
registration) when indicating the current cell identity towards the
MSC-service entity of the PMSC.
[0170] While in 24.008 over 3GPP PS network mode, UTRAN RRC and
GERAN-RR entities are detached from the RR-SAP in the MS, as a
result the entities do not act on any paging request message for
the CS domain in UTRAN or GERAN.
[0171] If the 24.008 over 3GPP PS network supporting PMSC rejects
the registration, and does not provide redirection to another
Serving 24.008 over 3GPP PS network supporting PMSC, the MS shall
revert to 3GPP CS access network, and start a re-attempt timer.
When the timer has timed out, a new registration is attempted,
starting with the Discovery procedure. If the MS can not revert to
CS access network the MS is no longer reachable for CS domain
services.
[0172] The Rove-out procedure is applicable when MS determines that
it can not be in the 24.008 over PS network mode, or it needs to
detach from the 3GPP PS network.
[0173] The MS detaches U8-CSR from the RR-SAP and re-attaches UTRAN
RRC or GERAN-RR to RR-SAP and restores normal CS domain UTRAN RRC
or GERAN-RR functionality. There after may follow a normal CS
domain Location Update if CS service is available after
rove-out.
[0174] FIG. 8 illustrates a diagram of a Packet Mobile Switching
Center discovery procedure according to one embodiment. Method 800
starts at step 805 and proceeds to step 810. At step 810, a Fully
Qualified Domain Name is derived based on a cell identifier of a
current cell. At step 815, the derived Fully Qualified Domain Name
is used to determine an Internet Protocol Address of a Packet
Mobile Switching Center.
[0175] FIG. 9 illustrates a Packet Mobile Switching Center
discovery procedure according to one embodiment. When an MS
supporting 24.008 over 3GPP PS network attempts to connect to a
24.008 over 3GPP PS network, the MS needs to identify a PMSC that
supports the 24.008 over 3GPP PS network service, a so called
24.008 over 3GPP PS network supporting PMSC. The PMSC will be
identified with a Fully Qualified Domain Name (FQDN) or only an IP
address. The MS can derive the FQDN of the PMSC based on
information received on a DNS lookup using the unique identifier of
the current cell (e.g. Cell Global Identity, CGI, for GERAN cells;
or LAI and the 28-bit Cell identity, as described in 3GPP TS
25.331, for UTRAN cells) of current PS cell. The important parts of
this cell identifier are the Private Land Mobile Network Identifier
(PLMN-ID) (consisting of Mobile Country Code, MCC, and Mobile
Network Code, MNC), Location Area Code (LAC) and the Cell identity
part. The Location Area Identity (LAI) consists of PLMN-ID and LAC
and can be used to uniquely point to an MSC (or MSC pool) in the
network. In addition, the Routing Area Code (RAC) might also be
used in any combination with the above identifiers. The MS will
construct a FQDN (other than the FQDN of the PMSC) based on the
cell identifier of the current PS cell.
[0176] For the following example, it is assumed that the MS has
determined that 24.008 over 3GPP PS network mode shall be
entered.
[0177] 1. The MS derives a FQDN based on the cell identifier of the
current cell. This FQDN could for example take the following
format. As an example, the MS has received the cell identifier of
the current cell in e.g. the broadcasted system information in the
current cell and it consists of the following information: PLMN-ID
is 012-123 (i.e. MCC is 012 and MNC is 123), LAC has value 34567,
Cell Identity has value of 4567. In this case the built FQDN could
for example be: [0178] lac34567.mnc123.mcc012.pub.3gppnetwork.org
or [0179] ci4567.1ac34567.mnc123.mcc012.pub.3gppnetwork.org Once
the FQDN is derived, the MS performs a DNS query (via the IP
network) to resolve the FQDN to an IP address.
[0180] 2. The DNS Server returns a response including the IP
Address of the relevant 24.008 over 3GPP PS network supporting
PMSC.
[0181] Still another possibility for building the FQDN is the
following two step approach. The MS will first receive an operator
specific string during PS Attachment or PDP Context
activation/modification procedures. This operator specific string
is valid in the current network until the MS receives another
operator string. This string could be e.g. "operatorX.com". The MS
uses that string together with the cell identity of the current
cell to build an FQDN for the PMSC. For example, using the example
from above where LAC of the current cell has value 34567, then
"lac34567.operatorX.com" would be built and used towards the DNS to
retrieve the IP address of the PMSC.
[0182] In one embodiment, the MS performs registration to the
appropriate PMSC. The Registration to the PMSC procedure serves the
following functions: [0183] Ensures the MS is registered to the
appropriate PMSC entity i.e. with use of the redirection process;
[0184] MS informs the PMSC that it is now connected through a 3GPP
PS access network and is available at a particular IP address and
UDP port. The PMSC maintains the registration context for the
purposes of e.g. Paging for mobile-terminated calling; and [0185]
Provides the MS with the NAS system information for the CS domain.
This "NAS System Information for CS" is delivered to the MS during
the Registration to the PMSC process. This enables the MS to
rove-in, and following the Registration procedure trigger NAS
procedures with the core network (such as Location Area Update,
mobile originated calls, mobile terminated calls, etc.).
[0186] The registration is performed as described in the following
steps: [0187] The MS is aware of the appropriate supporting PMSC
i.e. the MS has performed the discovery procedure [0188] The MS
initiates registration to the PMSC and informs the PMSC about the
current PS cell identity e.g. LAI and cell identifier. The details
of this information may vary depending on the 3GPP PS RAT being
used (e.g. there are some differences between cell identities in
GERAN and UTRAN). The MS also informs whether CS service is
available in the current cell and some other relevant information
e.g. the current PS RAT (GPRS/UMTS/HSPA/LTE) and the known
capabilities of the current PS RAT. [0189] The PMSC which accepts
the registration and provides the MS with the relevant NAS-level
system information for the CS domain (e.g. MSC Release Indicator,
Attach/Detach allowed, T3212 timeout value (used for Periodic
Location Updates) and whether Call re-establishment is allowed).
Note that this NAS-level system information for the CS domain is
normally broadcasted in the RAN to the MS. As the MS may now be
operating in a PS-only 3GPP access network, the PMSC provides the
needed information to the MS as part of a successful
registration.
[0190] Note: The PMSC may also provide the MS with the Rove-in
criteria or reject the registration based on the current 3GPP PS
RAT or cell identity (or parts of it) or other information provided
by the MS and/or configured in the PMSC. E.g. some LAIs of a
specific PS RAT are not to be used for 24.008 over 3GPP PS network
mode and the registration is rejected. [0191] In addition, the PMSC
may provide the MS with the Location Area Indicator (LAI) and Cell
Identity to be used as the cell identity for the 24.008 over 3GPP
PS network mode. If this information is not provided from the PMSC,
then the MS uses the identifiers of the current PS cell as the LAI
and CI also for the 24.008 over 3GPP PS network mode. [0192] The
PMSC may also redirect the MS to another PMSC based on the current
3GPP PS RAT or cell identity (or parts of it) or other information
provided by the MS and/or configured in the PMSC. The PMSC may also
rediret the MS to another PMSC for load-balancing reasons.
[0193] FIG. 10 illustrates a Keep Alive procedure according to one
embodiment. The Keep Alive process is a mechanism between the peer
U8-CSR entities to indicate that the MS is still in the 24.008 over
3GPP PS network mode (i.e. either in state U8-CSR-IDLE or in state
U8-CSR-DEDICATED) and wishes to maintain the registration state in
the PMSC (i.e. stay registered and attached) for e.g. mobile
terminated calls and so paging. Using periodic transmissions of the
U8-CSR KEEP ALIVE message the MS in turn determines that the 24.008
over 3GPP PS network supporting PMSC is still available using the
currently established lower layer connectivity.
[0194] 1. The MS sends U8-CSR KEEP ALIVE to the 24.008 over 3GPP PS
network supporting PMSC. The MS includes TMSI in the message as the
identification or if no TMSI is available, then IMSI is used.
[0195] 2. The PMSC acknowledges the U8-CSR KEEP ALIVE message by
sending the U8-CSR KEEP ALIVE ACK message to the MS. This
acknowledgement is needed as UDP is used as the underlaying
transmission mechanism.
[0196] The Deregistration from the PMSC procedure allows the MS to
explicitly inform the PMSC that it is leaving the 24.008 over 3GPP
PS network mode (e.g. when it is about to enter a network where the
normal CS service is available and the MS is not supposed to use
24.008 over 3GPP PS network anymore), by sending a U8-CSR
DEREGISTER message to the PMSC, allowing the PMSC to free resources
that it assigned to the MS.
[0197] The PMSC may also autonomously release the MS registration
context, and send a U8-CSR DEREGISTER message to the MS. NOTE: At
power-down the U8-CSR sublayer of the MS ensures that the MS
explicitly detaches from the network, where possible, before
completing the Deregistration from the PMSC procedure.
[0198] The MS is authenticated to the 24.008 over 3GPP PS network
service using normal MM level Authentication that may take place
after the Rove-In procedure if the normal Location Update procedure
is triggered.
[0199] 3GPP PS network encryption will be used. Security may also
be provided between the AGW and the PMSC.
[0200] The U8-CSR connection is a logical connection between the MS
and the 24.008 over 3GPP PS network supporting PMSC. It is
established when the upper layers in the MS request U8-CSR to enter
dedicated mode. When a successful response is received from the
network, U8-CSR replies to the upper layer that it has entered
dedicated mode. The upper layers have then the possibility to
request transmission of NAS messages to the network.
[0201] FIG. 11 illustrates a U8-CSR connection establishment
procedure according to one embodiment. FIG. 11 shows successful
establishment of the U8-CSR Connection.
[0202] 1. The MS initiates U8-CSR connection establishment by
sending the U8-CSR REQUEST message to the 24.008 over 3GPP PS
network supporting PMSC. This message contains the Establishment
Cause indicating the reason for U8-CSR connection
establishment.
[0203] 2. Depending on the reason for U8-CSR connection
establishment, the PMSC may request modification of the signaling
bearer from the PCRF to be able to cope with signaling that may
follow.
[0204] 3. Possible response from the PCRF.
[0205] 4. 24.008 over 3GPP PS network supporting PMSC signals the
successful response to the MS by sending the U8-CSR REQUEST ACCEPT
and the MS enters dedicated mode and the U8-CSR state changes to
U8-CSR-DEDICATED.
[0206] 5. Alternatively, the 24.008 over 3GPP PS network supporting
PMSC may return a U8-CSR REQUEST REJECT indicating the reject
cause.
[0207] FIG. 12 illustrates a U8-CSR connection release procedure
according to one embodiment. FIG. 12 shows release of the logical
U8-CSR connection between the MS and the 24.008 over 3GPP PS
network supporting PMSC.
[0208] 1. The 24.008 over 3GPP PS network supporting PMSC decides
to release the signalling and user plane connection resources
allocated to the MS (e.g. in Iu interface that could be seen as an
Iu Release Command).
[0209] 2. The 24.008 over 3GPP PS network supporting PMSC commands
the MS to release the signalling plane and user plane resources,
using the U8-CSR RELEASE message.
[0210] 3. The MS confirms resource release to the 24.008 over 3GPP
PS network supporting PMSC using the U8-CSR RELEASE COMPLETE
message and the MS enters idle mode and the U8-CSR state in the MS
changes to U8-CSR-IDLE.
[0211] 4. If resources has been requested in the U8-CSR connection
Establishment and/or during the traffic channel assignment, the
PMSC will ask for a modification of the signaling bearer from the
PCRF. The PMSC may also ask PCRF to release the Secondary PDP
context if such was allocated for the user plane. This may be
uncorrelated to step 2 and 3.
[0212] 5. Response from the PCRF.
[0213] 6. All the signaling and user plane connection resources
allocated to the MS are released (e.g. in Iu interface that could
be seen as an Iu Release Complete).
[0214] FIG. 13 illustrates a ciphering configuration flow according
to one embodiment. The message flow for ciphering configuration is
shown. The term ciphering configuration is normally used for GSM CS
operations and the corresponding term for UMTS CS (and PS)
operations is Security Mode Command.
[0215] 1. The 24.008 over 3GPP PS network supporting PMSC sends
U8-CSR CIPHERING MODE COMMAND to the MS. This message indicates the
integrity protection and encryption settings (i.e., that may be
applicable after handover/relocation to CS Domain mode). MS stores
the information for possible future use after a handover/relocation
to CS Domain mode. The message may also indicate whether the MS
shall include IMEISV in the U8-CSR CIPHERING MODE COMPLETE
message.
[0216] 2. The MS then sends U8-CSR CIPHERING MODE COMPLETE message
to network and includes the IMEISV, if indicated so in the U8-CSR
CIPHERING MODE COMMAND.
[0217] CS signaling in U8-CSR-DEDICATED state is shown in FIG. 14
and FIG. 15. FIG. 14 illustrates network initiated Circuit Switched
Signaling according to one embodiment in the downlink direction
i.e. from the PMSC to the MS.
[0218] 1. The 24.008 over 3GPP PS network supporting PMSC
encapsulates a NAS/Layer 3 message within a U8-CSR DL DIRECT
TRANSFER message that is sent to the MS.
[0219] FIG. 15 illustrates Mobile Station initiated Circuit
Switched Signaling according to one embodiment in the uplink
direction i.e. from the MS to PMSC.
[0220] 1. For MS initiated signaling the MS U8-CSR layer receives a
request from the NAS layer to transfer an uplink NAS signaling
message or SMS message. The MS U8-CSR encapsulates the message
within a U8-CSR UL DIRECT TRANSFER message and sends the message to
the 24.008 over 3GPP PS network supporting PMSC.
* * * * *