Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-04-12
2004-09-07
Nguyen, Tony T. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432100, C455S456100
Reexamination Certificate
active
06788936
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Description of Related Art
Not Applicable
2. Field of the Invention
The present invention relates to mobile communications systems, and more specifically, to recovery of a gateway location register from a fault.
FIG. 1
illustrates a wireless communication system in accordance with the Global System for Mobile communication (GSM) standard. The GSM standard is designed to provide a uniform interface which allows mobile communication subscribers of various countries to operate their mobile devices regardless of the current location of the mobile subscriber. A mobile subscriber typically has a subscription with a network which is designated as the mobile subscriber's home public land mobile network
110
(HPLMN). The HPLMN
110
has a home location register (HLR)
115
which contains, among other things, various information regarding the services provided to the mobile subscriber. When a mobile subscriber roams into a different network, which is referred to as a visited public land mobile network
120
(VPLMN), the VPLMN requires certain data regarding the mobile subscriber's subscription. The data regarding the mobile subscribers subscription is also known as the mobile subscriber's profile. The mobile subscriber's profile is transferred from the HLR to a visitor location register (VLR) in the VPLMN
120
.
In a GSM system mobile subscriber data is stored within the VLR that is associated with the mobile services switching center (MSC) that currently serves the mobile subscriber in order to reduce internetwork signaling between VLRs and HLRs. The decentralization of the VLRs within a GSM system (i.e., each MSC being equipped with a VLR) reduces internetwork signaling as well. So, for example, if the mobile subscriber is roaming in an area of the VPLMN
120
which is controlled by the MSC/VLR
130
, the HLR
115
will transfer the mobile subscriber's profile to MSC/VLR
130
. Similarly, if the mobile subscriber is roaming in an area controlled by MSC/VLR
135
, the HLR
115
will transfer the mobile subscriber's profile to MSC/VLR
135
. Although
FIG. 1
illustrates the MSC/VLR as a single network node, one skilled in the art will recognize that the MSC and VLR can be implemented as separate network elements.
To increase the compatibility of GSM with other types of systems, it is anticipated that future versions of the GSM standard, also called Universal Mobile Telecommunications System (UMTS) will incorporate elements of other mobile communications systems. For example, the Japanese Personal Digital Cellular (PDC) system includes a network node which is used to reduce internetwork signaling known as a gateway location register (GLR).
FIG. 2
illustrates an exemplary mobile communications system in accordance with the PDC system. Like a GSM system, a home network
210
includes an HLR
215
which contains the mobile subscriber's profile. When a mobile subscriber roams into a visited network
220
the mobile subscriber's profile is transferred to GLR
225
. In GSM terms, the GLR can be described as a VLR for all mobile subscribers roaming from other networks. Hence, only one GLR is needed in each network.
FIG. 3
illustrates an exemplary UMTS system which incorporates the GLR of the PDC system. When a mobile subscriber of HPLMN
310
roams into VPLMN
320
, the HLR
315
will transfer the mobile subscriber's profile to GLR
325
. Then, depending upon which area within the VPLMN
320
the mobile subscriber is roaming, the GLR
325
will transfer the mobile subscriber's profile to the respective MSCNLR
330
,
335
or
340
. The introduction of the GLR
325
into a GSM/UMTS system reduces internetwork signaling because once the mobile subscriber roams into VPLMN
320
, the HLR will only need to transfer the mobile subscriber's profile to GLR
325
. GLR
325
will be responsible for transferring the mobile subscriber's profile to the proper MSC/VLR within VPLMN
320
as the mobile subscriber travels around the VPLMN
320
.
The protocol used by GSM/UMTS systems for transferring data between VLRs and HLRs is the mobile applications part (MAP). Since GLRs are optional elements within the UMTS system, MAP procedures must be completely independent of the presence or absence of GLRs in a network. Accordingly, by using an HLR interface towards the VLRs and a VLR interface towards the HLRs, the GLR should be completely transparent. However, because of the dual nature of the GLR in the network it may be difficult for the GLR to behave in a way which simultaneously will be perceived as VLR behavior by the HLRs, and as HLR behavior by the VLRs. One such case is the fault recovery behavior of the GLR.
FIG. 4
illustrates a conventional method in a GSM system when an HLR is recovering from a fault. In step
405
the HLR loads the contents of its non-volatile backup memory into its dynamic memory. Next the HLR sends a MAP_RESET message to the VLRs to which the HLR's subscribers are currently associated as indicated by the information in the backup memory in accordance with step
410
. The MAP_RESET message triggers the VLRs to initiate a location update procedure towards the HLR at the next authenticated radio contact with a concerned mobile subscriber. Accordingly, in step
415
the VLR waits for an authenticated radio contact from the concerned mobile subscriber. In step
420
the VLR determines whether it has received an authenticated radio contact from the concerned mobile subscriber. If the VLR has not received an authenticated radio contact from the concerned mobile subscriber, in accordance with the “No” path out of decision step
420
, the VLR continues to wait in accordance with step
415
. If the VLR receives an authenticated radio contact from the concerned mobile subscriber the VLR sends a MAP_UPDATE_LOCATION message to the HLR indicating that the VLR is serving the concerned subscriber in accordance with step
425
. The location updates sent from the VLRs to the HLR will gradually restore and confirm the subscriber data of the restarted HLR.
FIG. 5
illustrates a conventional method in a GSM system when a VLR is recovering from a fault. In step
505
the VLR, which does not have a non-volatile backup memory for its dynamic subscriber data, deletes all IMSI records which remain in its dynamic memory. In step
510
the VLR waits for contact from either a mobile subscriber or from the HLR associated with a mobile subscriber. In step
515
, the VLR determines whether it has received a location update request from a mobile subscriber. If the VLR receives a location update request from a mobile subscriber, in accordance with the “Yes” path out of decision step
515
, the VLR initiates the MAP_UPDATE_LOCATION procedure with the HLR associated with the mobile subscriber in accordance with step
520
. The MAP_UPDATE_LOCATION procedure is used to send data associated with a mobile subscriber from an HLR to a VLR. Specifically, this data is sent in the framed MAP_INSERT_SUBSCRIBER_DATA indication message.
If the VLR has not received a location update request from a mobile subscriber, in accordance with the “No” path out of decision step
515
, the VLR determines whether it has received a roaming number request from an HLR in accordance with step
525
. If a VLR has not received a roaming number request from an HLR, in accordance with the “No” path out of decision step
525
, then the VLR continues to wait for a contact from either a mobile subscriber or from an HLR in accordance with step
510
. If the VLR has received a request for roaming number from an HLR, in accordance with the “Yes” path out of decision step
525
, then the VLR sends a MAP_RESTORE_DATA message, including an indication of the concerned subscriber whose data is being restored, to the HLR indicating that the VLR has experienced a fault in accordance with step
530
. In response to the MAP_RESTORE_DATA message the HLR
Hu Yun Chao
Noguera-Rodriguez Juan
Rune Johan
Nguyen Tony T.
Telefonaktiebolaget LM Ericsson
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