Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-12-14
2003-03-04
Vo, Nguyen T. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S552100, C370S328000
Reexamination Certificate
active
06529732
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and a service providing means for supporting services, to which a subscriber of a first telecommunication network has subscribed, in a second telecommunication network, when a mobile station roams from said first to said second telecommunication network. The invention also relates to a telecommunication network comprising such a service providing means.
In particular, the invention relates to a situation, where a subscriber has subscribed to specific services in the first telecommunication network and part of the services or a complete service is differently implemented in the second telecommunication network, when the mobile station roams to the second telecommunication network or when a call is to be routed to the second network.
BACKGROUND OF THE INVENTION
FIG. 5
a
shows a telecommunication system TELE, which comprises at least two different telecommunication networks HPLMN, VPLMN. Both networks HPLMN, VPLMN are, for example, mobile radio communication networks, for example according to a GSM specification, NMT (Nordic Mobile Telephony) specification, a TACS specification or a DECT specification. The first network HPLMN could, for example, be constituted by the D
1
or D
2
network in Germany and the second visiting network VPLMN could be the TELECOM network in Italy. In this case, the two networks HPLMN, VPLMN are geographically separated. However, it is also possible that a mobile station MS is provided with the option of using two different networks in one country. Hereinafter, the first network will be called the home network HPLMN and the second network will be called the visiting network VPLMN, independently as to whether the two networks geographically overlap or not.
FIG. 5
a
shows that each of the mobile radio communication networks comprises the usual functionalities of a home data base, formed by a home location register HLR, HLR′, switching means, formed by a mobile switching center/visitor location register MSC/VLR, MSC/VLR′, and gateway mobile switching centers GMSC, GMSC′, which basically link the two networks. It should be noted that the units GMSC′, HLR′, SN′ (a service node which will be explained below) are not used by a mobile station MS roaming from the home network HPLMN, but will be used of course by a mobile station MS which belongs to VPLMN (i.e. which regards VPLMN as home network). Furthermore, it is possible that the GMSC′ is part of an IPLMN (interrogating PLMN) network in case of optimal routing which is indicated with the x-x-x line in
FIG. 5
a.
Normal routing (used in today's networks) and optimal routing (contemplated for future use) will be explained below with reference to
FIGS. 5
b,
5
c.
Different procedures are invoked when the mobile station MS (belonging to the home network HPLMN) roams from cell to cell in the home network HPLMN and when the mobile station MS roams to the visiting network VPLMN. When in the first case, as shown in the home network HPLMN, the mobile station MS just roams from cell to cell, e.g. from one MSC/VLR to another MSC/VLR in the same home network (indicated with the dotted arrow in HPLMN), a location updating procedure is performed with respect to the subscriber data stored in the home location register HLR, such that each MSC/VLR is always provided with the relevant subscriber data of the subscriber whose card has been inserted into the respective mobile station MS. In this case, a roaming detection means for detecting when said mobile station MS roams from one cell to another cell can be viewed as being constituted by parts of the base station system and parts of the mobile station. For example, during an on-going call a handover of the mobile station is carried out when the roaming detection means detects that the signal strength has decreased below an acceptable level such that another MSC/VLR should take over the communication. On the other hand, if the mobile station does not participate in call and is merely switched on, then at least the location updating procedure is carried out.
In the second case the mobile station MS roams to the visiting network VPLMN (indicated with the dashed arrows in
FIG. 5
a
) in a state where it is switched on or in a case where it is only switched on after having entered the visiting network. In this case, the mobile station MS must register at the respective MSC/VLR′ of the visiting network VPLMN which will request a copy of the relevant subscriber data to be sent from the home location register HLR of the home networks HPLMN, where the mobile station MS (more precisely the subscriber whose card is inserted into the mobile station) is registered.
A similar situation occurs when a call is to be routed to a mobile station MS which has roamed to a visiting network VPLMN.
FIG. 5
b
shows the case of a normal routing and
FIG. 5
c
shows the case of an optimal routing.
If e.g. in
FIG. 5
b
a call is to be routed from MS
1
to MS
2
(a terminating call for MS
2
) then the GMSC will request HLR to provide routing information (step ST
1
). The HLR requests this information from MSC′ (step ST
2
) which provides the information to HLR (step ST
3
). Then the information is forwarded to GMSC (step ST
4
) which can—on the basis of the received routing information—route the call to MS
2
(step ST
5
). It should be noted that the call terminating scenario in
FIG. 5
b
is in principle also valid if a call is originated from a terminal of a fixed network connected to the home HPLMN. Also in this case the call is first routed to the GMSC of the network HPLMN which then requests the routing information from MSC′.
Optimal routing as in
FIG. 5
c
alway relates to terminating calls (IPLMN does not exist for originating calls). When the further network IPLMN (IPLMN: interrogating network for terminating calls) is provided, in case of optimal routing, the routing principle is exactly the same as in the case of normal routing, the difference being that the gateway MSC GMSC′ resides in a different PLMN (i.e. IPLMN) That is, also in this case, terminating calls are always routed to the GMSC′ which requests HLR for the routing information of MS
2
. HLR always knows where the MS
2
is roaming and requests as in the case of
FIG. 5
b
the respective MSC′ in the visting network to provide e.g the roaming number (steps ST
1
-ST
5
; note that the x-x-x line in
FIG. 5
c
corresponds to the x-x-x line in the general diagram in
FIG. 5
a
). The difference between
FIG. 5
b
, and
FIG. 5
c
is that in
FIG. 5
c
the terminating call is directly routed from the GMSC′ to the MSC′ in the visiting network (VPLMN) where the mobile station MS
2
is registered.
If both networks only provide the normal GSM services to the mobile station MS and the subscriber has only subscribed to these normal services in the home network HPLMN, then no problem with the roaming to the visiting network VPLMN and the terminating of calls to the mobile station MS in VPLMN occurs in all cases in
FIG. 5
a
,
5
b
,
5
c
, since the format of the subscriber data and/or service data which are stored in the home location register HLR in HPLMN and the format which the VPLMN can handle is the same. For example, a call forwarding number specified by the subscriber in the home network HPLMN will immediately be understood and can be processed also in the visiting network VPLMN, so that such types of information can immediately be copied and used in the MSC/VLR′ of the visiting network VPLMN.
However, problems exist if some services, to which the subscriber has subscribed in the first network HPLMN, or an additional service are/is differently implemented in the visiting network VPLMN. For example, when the service is not supported in the visiting network VPLMN, of course any format of data relating to such services will not be understood can not be processed in the visiting network VPLMN. Indeed, such a situation can arise, since nowadays a subscriber in the home networks HPLMN h
Maekiniemi Petri
Vainiomäki Hannu
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
Vo Nguyen T.
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