Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-08-26
2002-06-04
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S437000, C455S439000, C455S513000
Reexamination Certificate
active
06400951
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a handover method and a call setup method in a mobile communication system that consists of base stations and mobile stations, and in which, at least for some of the mobile stations a mobile station-specific special cell list has been created, which contains the identifier for at least one cell that offers special service to the mobile station. The handover method comprises the following steps: setting at least one handover criterion, measuring the quality and signal level of the radio link in the base station and mobile station, measuring the signal level of the neighboring base stations in the mobile station, transmitting the measurement results acquired by the mobile station from the mobile station to the base station as a report message, and performing the handover to the target cell, when the handover criteria are met. The call setup method comprises the following steps: measuring in the mobile station the signal level of the base station of the camping cell and that of the neighboring base stations, establishing the signaling link between the base station and the mobile station, transmitting the measurement results from the mobile station to the base station as a report message, and performing the call setup in the traffic channel assigned to the mobile station.
Additionally, the invention relates to the mobile station and the arrangement for the selection of the base station.
BACKGROUND OF THE INVENTION
In cellular mobile communication networks the mobile station can move freely within the mobile communication network and connect to the best base station signal available at the time. Usually all base stations offer essentially identical services to the mobile stations in the network. However, some base stations can be configured to offer a special service to all mobile stations in the network, for example, a special tariff. The base station transmits information about such special service in its broadcast channel so that the subscribers in this region of the network notice the fact and can make use of this service.
The FI patent application publication #970034 describes offering tailored special services from some mobile communication network cells to individual mobile stations or a group of mobile stations by using subscriber-or subscriber group-specific local service regions. Such special services include, for example, special tariffs and data services. In a method according to the publication, a mobile station-specific priority cell list (MPCL) is composed from the selected network cells and the operation of the mobile station is controlled according to this priority cell list. Priority cell information can be stored in the list to be composed by using, for example, CI (Cell Identity) and LAI (Location Area Identifier), or only the CI. An priority cell list consisting of the local service cell data of the mobile station is transmitted to the mobile station MS during location update. On the basis of the priority cell list, the mobile station recognizes the priority cells from which it can receive special services to which the other mobile stations are not entitled. The publication does not describe the use of an priority cell list in base station selection.
FIG. 1
of the attached drawing shows a simplified block diagram of the Pan-European GSM mobile communication system. The MS (Mobile Station) is connected via a radio path to a BTS (Base Transceiver Station), in
FIG. 1
, to the base station BTS
1
. An idle mobile station MS receives the broadcast from the base station it has selected. A BSS (Base Station Subsystem) consists of a BSC (Base Station Controller) and base stations BTS controlled by it. An MSC (Mobile Services Switching Center) usually controls several base station controllers BSC. The mobile services switching center MSC is connected to other mobile services switching centers, to a GMSC (Gateway Mobile Services Switching Center), and possibly to an intelligent network IN. Via the GMSC, the GSM network is connected to other networks, such as the PSTN (Public Service Telephone Network), PLMN (another mobile communication network), ISDN network or the intelligent network IN. The operation of the entire system is monitored by the OMC (Operation and Maintenance Center).
The subscriber data of the mobile station MS is permanently stored in the HLR (Home Location Register) of the system and temporarily in the VLR (Visitor Location Register) of the area, in which the mobile station MS is located at the time. The VLR contains the location data for the mobile station MS at the accuracy of the LA (Location Area). The geographic area monitored by the VLR is divided into one or more location areas LA within which the mobile station MS can move freely without notifying the VLR. There can be one or more base stations BTS operating in each location area.
The base stations BTS continuously broadcast information about themselves and their surroundings in their broadcast channel, such as the CI (Cell Identity), information about the neighboring cells, and the location area information LAI. According to the LAI the mobile station MS receiving the broadcast channel from the base station BTS can recognize the location area LA in which the mobile station is located. If the mobile station MS notices, when changing the base station BTS, that the location area information LAI of the base station has changed, the mobile station transmits a location update request into the network.
When moving within the area of the mobile communication network, the mobile station MS normally switches to listen to the base station BTS with the strongest signal. The system tries to establish any mobile station MS originated or terminated calls via this base station BTS. If the base station BTS into which the mobile station MS is connected, cannot provide a traffic channel for the call setup, the mobile station MS attempts the call setup with the base station that provides the next strongest signal. This method is called directed retry
FIG. 2
a
of the attached drawing shows the signaling of the GSM system between the mobile communication network and the mobile station MS in the establishment of a mobile station MS originated call. When the mobile station MS wants to establish a call, it transmits a signaling channel request Channel_request (message
21
) to the network which the network answers by assigning the mobile station MS an SDCCH (Stand alone Dedicated Control Channel) by using the message Immediate_assignment (message
22
). The mobile station MS uses the assigned channel to transmit a service request message CM_service_request (message
23
) which indicates the quality of the requested service which is, in this case, the call setup in the traffic channel. The authentication of the subscriber for controlling the network access and to prevent different misuses is performed by using the messages Authentication_request (message
24
) and Authentication_response (message
25
). The authentication is performed by comparing the data stored in the network to the data stored in the mobile station MS. After successful authentication the messages Cipher_mode_command (message
26
) and Cipher_mode_complete (message
27
) are used to convey data about the ciphering algorithm used for the connection. The messages Setup (message
28
) and Call_proceeding (message
29
) are used to convey more detailed information about the call to be set up, among other things, the mobile station MS transmits to the network the telephone number which the caller wants to call. The network assigns the mobile station MS a traffic channel for the call by using the message Assignment_command (message
30
) which is acknowledged by the mobile station MS by the message Assignment_complete (message
31
). At item
32
the mobile station MS receives a line alert tone and when subscriber B answers the call, the connection is established by using the messages Connect (message
33
) and Connect_acknowledge (message
34
). After this the call is continued in a normal fashion in t
Altera Law Group LLC
Nokia Telecommunications Oy
Tran Congvan
Trost William
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