Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-07-30
2002-10-08
Urban, Edward F. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432300, C455S435100, C455S436000, C455S439000, C455S560000
Reexamination Certificate
active
06463286
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 198 34 674.3 filed in Germany on Jul. 31, 1998; the entire content of which is hereby incorporated by reference.
BACKGROUND
The invention generally relates to the provision of a temporary selective national roaming at predetermined network operation conditions, e.g. at network overload in a mobile radio communication system. In particular, the invention relates to a method, an exchange, a telecommunication system and a mobile station of a mobile radio communication network, wherein one or more mobile stations of a first mobile radio communication network are transferred to a second mobile radio communication network, when an overload condition occurs in the first mobile radio communication network. There is also the possibility that the mechanism is invoked by maintenance personnel, e.g. due to some very severe maintenance activities or at an exchange or network failure.
FIG. 4
shows an overview of a nationwide telecommunication system TELE, where several mobile radio communication networks HPLMN, VPLMN
1
, VPLMN
2
. . . VPLMNn (e.g. a D
1
, D
2
or E-Plus network) can co-exist. Whilst
FIG. 4
shows the co-existence of the networks, it should be understood that, of course, geographically the networks may cover the same geographical areas. Each mobile station MS (or generally a subscriber station) has a particular subscription to one of the networks. Such subscription data is stored in the home location register HLR. The mobile stations MS are served by respective switching means MSC/VLR within the networks. The switching means comprises the mobile switching center MSC and a visitor location register VLR. Other means necessary for forming the communications between the mobile station MS and the switching center MSC/VLR, like the base station controllers BSCs, the base transmitter stations BTS and the base stations BS, of the individual networks are not illustrated in
FIG. 4
, however, of course, it is assumed that the communication between the mobile station MS and the switching means MSC/VLR and the home location register HLR is performed as in any standard GSM network. Since all mobile radio communication networks and the mobile stations themselves must comply with the GSM standard (or any other nationwide standard), of course, the mobile stations MS, MS′ can in principle perform communications in every network.
When quality of service of a mobile network is below an acceptable level due to lack of resources in the network, the network is considered to be in an overload condition. The resources can consist of processing power, memory, switching, radio or other resources. In such an overload condition, two serious traffic conditions can occur. Firstly, the complete network traffic handling capability may collapse such that all mobile stations currently registered within this network will have very poor grade of service from the network. Secondly, if a mobile station is just about to register in the network, its call setup request may be rejected. In this condition, the mobile stations can normally only perform emergency calls (
112
) and nothing else. In one alternative solution, currently supported by GSM, it is conceivable that the mobile station is adapted to select one of several networks through a key and a display on the mobile station, in which case the operator of the mobile station may manually select a new network once its call setup request has been rejected by the network. If the other network does not support the mobile station even temporarily then no further communication is provided for said mobile station, since either national roaming is not allowed or the second network has a high load due to many mobile stations attempting to select this network.
In a conventional mobile radio communication network according to the GSM standard, some provisions to handle overload conditions are made.
Firstly, there is the possibility to reduce the load in the network simply by restricting accesses from mobile stations, e.g. to simply reject further call setup requests by mobile stations which would cause a collapse of the network. The procedure as described in the ETSI GSM standard 08.08 (digital cellular telecommunication system (phase 2+), mobile-services switching center-base station system (MSC-BSS) interface; layer 3 specification) section 3.1.12.3, November 1996 and ETSI GSM 02.11 version 5.0.0 (digital cellular telecommunication system; service accessibility) section 4, November 1996, can be used. In such a procedure, an access of mobile stations to the network is restricted based on the so-called access classes of the subscribers. The ETSI GSM standards define access classes for particular groups of subscribers in accordance with the defined subscriptions. For example, access classes can be grouped according to the subscribed tariffs, such that an access to the network may be blocked for the group of private users whilst a group of business users may still obtain an access. Other definitions of the groups of subscribers or access classes are possible. During an overload condition, the subscribers belonging to one particular access class will not receive a service, if they are registered in their home public land mobile network HPLMN (see FIG.
4
). If in such a situation there are no further services offered to this group of subscribers, they will not have service, sometimes not even an emergency service, since in GSM it is possible to define with the above-stated mechanism whether normal users are allowed to make emergency calls or not.
Rather than just completely rejecting an access to the network, another option to use in GSM is the national roaming option described in the ETSI GSM standard 03.22 version 5.2.0 (digital cellular telecommunications system (phase 2+); functions related to mobile stations (MS) in idle mode and group receive mode), August 1997. By contrast to the international roaming service, which is a service whereby a mobile station from a mobile network is able to obtain a service from a mobile network of another country that has a roaming agreement with the home network (when the roaming is allowed for the subscriber) the national roaming service is a service, whereby a mobile station of a given mobile network is able to obtain a service from another mobile network in the same country, anywhere or even on a regional basis. The availability of national roaming depends on the home mobile network and the visited mobile network and does not depend on the subscription arrangements.
Essentially, as is shown in
FIG. 4
, during an overload condition the mobile station MS can roam to another network VPLMN
1
(hereinafter called the visited or second network) in the home PLMN country. When this mobile station MS′ is temporarily served by the switching means MSC/VLR of the visited network VPLMN
1
, the mobile station will periodically perform attempts to register back to its home network HPLMN. If several visited networks VPLMN
1
, VPLMN
2
. . . VPLMNn exist, the mobile station MS may attempt to gain an access in a particular network.
FIG. 5
shows the national roaming service for a group of mobile stations MS
1
, MS
2
, MS
3
, MS
4
served by a switching means MSC
1
of the network HPLMN. As shown in
FIG. 5
, two switching means MSC
1
, MSC
2
of two location areas LA
1
, LA
2
respectively serve a number of mobile stations. The location area LA of the visited network VPLMN geographically overlaps with some of the location areas of the home network HPLMN. If a mobile station does not get service in the home network HPLMN, e.g. in the overload area OVLD-AR, the mobile stations MS
1
-MS
4
attempt to roam into one of the switching means MSC
1
′, MSC
2
′ of the visited network VPLMN, depending on at which location area of the VPLMN they are at the moment. Of course, the switching means MSC
1
′, MSC
2
′ may already be serving some mobile stations MS
1
′-MS
4
′, which have a subscription in the visited network VPLMN (It is note
Burns Doane Swecker & Mathis L.L.P.
Telefonaktiebolaget L M Ericsson (publ)
Urban Edward F.
Zewdu Meless
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