Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-03-08
2003-03-11
Maung, Nay (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S440000, C455S443000, C455S445000
Reexamination Certificate
active
06532363
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates to a method for transferring special cell information in a communications system and to a cellular system and mobile station that realise the method. The invention can be advantageously applied in cellular systems in which users are assigned cell-specific services such as cell-dependent charging. Such cellular systems may be digital cellular systems such as GSM (Global System for Mobile Communications).
First it will be discussed the prior art by disclosing the call setup and handover procedures in GSM. Then it will be described a known arrangement for implementing a cell-specific service as well as problems involved in the solutions described.
In cellular mobile communication systems a mobile station can move freely in the area of the mobile communication network and choose the best base station signal available at a particular moment. Usually all base stations offer substantially the same services to the mobile stations in the network. Some base stations, however, may be specified so as to offer a special service to all mobile stations in the network, e.g. a call charge rate cheaper than the normal rate. The base station informs on its broadcast control channel (BCCH) about such a special service so that the mobile subscribers in the area will know that they are in a special service area of the network and can utilise the service.
FIG. 1
of the attached drawing shows a simplified block diagram of the pan-European GSM. A mobile station MS is connected by radio with a base transceiver station BTS, in the case depicted by
FIG. 1
to base transceiver station BTS
1
. The mobile station MS receives in the standby mode the transmission of a base station it has selected. A base station system BSS comprises a base station controller BSC which controls base transceiver stations BTS. A mobile services switching centre is connected with other mobile services switching centres, a gateway mobile services switching centre GMSC and possibly with an intelligent network IN. Through the gateway mobile services switching centre GMSC the GSM network is connected with other networks, such as a public switched telephone network PSTN, public land mobile network PLMN, integrated services digital network ISDN or with an intelligent network IN. The operation of the whole system is supervised by an operation and maintenance centre OMC.
A mobile station's subscriber data are permanently stored in the system's home location register HLR and temporarily in the visitor location register VLR in the area of which the mobile station is located at a given moment. The visitor location register VLR contains location information for a mobile station MS with the accuracy of a location area LA. The geographical area controlled by the visitor location register is divided into one or more location areas LA within which a mobile station may move freely without registering in the visitor location register. Each location area may have one or more base transceiver stations BTS operating in it.
Base transceiver stations BTS continuously transmit on their broadcast control channels information about them and their surroundings, such as cell identity CI, information about neighbour cells and the location area identity LAI. The location area identity tells a mobile station, which receives a base transceiver station's transmission on the broadcast control channel, the location area in which it is located at that moment. If a mobile station detects in conjunction with a handover or cell reselection that the base station's location area identity has changed, it sends a location update request to the network.
While moving in the area of a mobile network a mobile station normally listens to the base station having the strongest signal. Thus, as a mobile-terminated or mobile-originated connection is to be set up, it is first attempted to use that base station. If that base station cannot provide a traffic channel for the connection, the mobile station tries to set up the connection via the base station offering the next strongest signal. If, during the connection established, the mobile station moves within the operating areas of more than one base station, handovers are carried out during the connection according to the principle described above.
FIG. 2
a
in the drawing attached hereto shows signalling in GSM between a mobile network and mobile station in mobile-originated call setup. When a mobile station wants to set up a connection, it sends to the network a Channel_Request (message
21
) to which the network responds with an Immediate_assignment message
22
by means of which it assigns a standalone dedicated control channel SDCCH to the mobile station MS for signalling purposes. The mobile station MS sends on the signalling channel assigned a CM_service_request message
23
, indicating the type of the service requested, in this case a call setup on a traffic channel. Subscriber authentication is carried out using an Authentication_request message
24
and Authentication_response message
25
. In the authentication, information stored in the network is compared with information stored in the mobile station MS with the aim of controlling access to the network, among other things, in order to prevent different violations.
After successful authentication a Cipher_mode_command message
26
and Cipher_mode_complete message
27
carry information about the protection algorithm used on the connection. A Setup message and Call_proceeding message
29
carry more detailed information about the connection to be established. Such information includes e.g. the called number transmitted from the mobile station to the network. Then the network assigns a traffic channel to the mobile station using an Assignment_command message
30
, acknowledged by the mobile station MS with an Assignment_complete message
31
. In step
32
ringing tone is transmitted to the mobile station MS and when subscriber B has answered, the call is established using the Connect
33
and Connect_acknowledge
34
messages. The call then proceeds on the traffic channel as usual.
In a like manner
FIG. 2
b
in the drawing attached hereto shows the call setup signalling in GSM in the case of a mobile-terminated connection. Like messages in
FIGS. 2
a
and
2
b
have like reference designators. The network pages a mobile station MS using a Paging_request message
35
to which the mobile station responds by sending to the network a Channel_request (message
21
) for a signalling channel. The network assigns to the mobile station MS a signalling channel using an Immediate_assignment message
22
as described above. The mobile station MS responds to the paging message on the signalling channel assigned to it using a Paging_response message
36
. Messages
24
to
27
are used for subscriber authentication and for transmitting the protection algorithm data in the manner described above. Call setup is initialised in the Setup message
37
and Call_confirmed message
38
, and a traffic channel for the call is assigned to the mobile station MS in the Assignment_command
30
and Assignment_complete 31 messages. In step
39
the mobile station MS indicates that it is alerting and when the mobile subscriber has answered, the call is established using the Connect
40
and Connect_acknowledge
41
messages. The call then proceeds on the traffic channel as usual.
In cellular-type mobile communication systems radio coverage is achieved using several slightly overlapping radio cells. As a mobile station moves from a cell to another, a handover is carried out in accordance with predetermined handover criteria. The handover should as little as possible disturb the existing connection. Normally, a handover is based on radio path criteria but it may be carried out for other reasons, too; in order to distribute load or reduce transmission power, for instance. A handover may also be carried out within a cell, between traffic channels.
A neighbour cell priority list may also be specified for a base transceiver station BTS so
Lele Tanmay
Maung Nay
Nokia Mobile Phones Ltd.
Perman & Green LLP
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