Mobile communication system making use of

Base stations are connected to subscriber lines of neighboring ISDN local switches, and mobile subscriber connection control equipment connected to the subscriber line of a particular ISDN local switch manages mobile subscriber data register equipment. Connection of a call which originates from or terminates at a mobile station, registration of the location of the mobile station, and channel switching process during service are performed by way of the mobile subscriber connection control equipment using an ISDN subscriber interface.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a mobile communication system, and more 
particularly to a digital mobile communication system which makes use of 
an ISDN switched network. 
2. Description of the Prior Art 
Conventionally, a mobile communication system is constructed with a switch 
for exclusive use for mobile subscribers. For instance, in order to 
perform a connection process of a call which is originated or terminated 
between a mobile subscriber which uses a mobile station and another 
subscriber of a fixed network, a switch for exclusive use (visitor mobile 
telephone switch) is first provided for each of the base stations located 
in a prescribed area, and these switches are connected to the fixed 
network (routing switched network) by way of gateway mobile telephone 
switches (Document 1 and Document 2). 
Document 1: Kota Kinoshita, "Technique Supporting Digital Mobile Telephones 
- System Network Implementation Technique," Journal of the Electronic 
Information Communication Society of Japan, Vol. 73, No. 8, pp. 812-818, 
1990. 
Document 2: Minoru Tanaka, "Mobile Radiocommunication System," Japanese 
Patent Laid-Open No. 151136/83. 
FIG. 6 is a block diagram showing an example of a conventional mobile 
telephone system disclosed in Document 1. Referring to FIG. 6, mobile 
station 11 has radio transmission and reception functions. Base stations 
12a and 12b are connected to visitor mobile telephone switch 13 and 
perform radio communication with mobile station 11, and further per-form 
call connection with visitor mobile telephone switch 13. Visitor mobile 
telephone switch 13 has visitor control and connection functions for 
mobile station 11. Gateway mobile telephone switch 14 has a routing 
function between visitor mobile telephone switch 13 and public telephone 
switched network 15 including local switch 16 to which fixed subscriber 17 
is connected. Home memory station 18 is connected to visitor mobile 
telephone switch 13 and gateway mobile telephone switch 14, and registers 
the specific numbers of mobile stations and location registration 
information. 
The system of Document 2 is proposed to allow a subscriber to perform 
communication by way of a same terminal between different mobile 
radiocommunication systems such as a mobile telephone system, a portable 
telephone system and a cordless telephone system. Claim 1 recites a mobile 
telephone radio base station and a portable telephone radio base station 
connected to a wire communication switched network. According to an 
embodiment, however, base stations of the mobile telephone system and the 
portable telephone system are connected to switches for exclusive use for 
mobile telephones, and all base stations are not connected to a local 
switch of an ISDN switched network. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a mobile communication 
system wherein all base stations are connected to neighboring local 
switches of an ISDN switched network, and connection of a call originated 
from or terminated at a mobile station, registration of the location of 
the mobile station and channel switching during service are controlled by 
mobile subscriber connection control equipment (MSCC) which is connected 
to a particular one or more of the local switches of the same ISDN 
switched network and which controls mobile subscriber data register 
equipment (MSDR), or in other words, a mobile communication system which 
is constructed in an ISDN switched network making use of an existing ISDN 
fixed switched network without providing a switch for exclusive use for 
mobile communication. 
To achieve the above object, there is provided a mobile communication 
system which makes use of an ISDN switched network, comprising: 
mobile subscriber data register equipment for registering information 
regarding mobile subscribers including subscriber numbers of the mobile 
subscribers, subscriber data of the mobile subscribers, identification 
numbers of mobile stations, and location information of the mobile 
stations; 
a base station connected to a subscriber line of an ISDN local switch for 
performing radio link control of a mobile station to connect a call which 
is originated from or terminated at the mobile station to said ISDN 
switched network by way of the subscriber line; and 
mobile subscriber connection control equipment connected to a subscriber 
line of the ISDN local switch for managing the mobile subscriber data 
register equipment and controlling connection of a call which is 
originated from or terminated at a mobile station, registration of the 
location of a mobile station, and a channel switching process during 
service by way of the subscriber line.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention is described below with reference to 
the drawings. 
Referring to FIG. 1, mobile station 1 is an equipment unit for a mobile 
subscriber having radio transmission and reception functions and is in use 
under required registration by a mobile subscriber. Base stations 2a and 
2b perform radiocommunication with mobile station 1 and are connected to 
subscriber lines of neighboring ISDN local switch 3a so that they perform 
call connection with mobile subscriber connection control equipment 
(hereinafter referred to MSCC) 4 by way of ISDN switched network 6. Mobile 
subscriber data register equipment 5 is connected to MSCC 4 and registers 
various information regarding mobile subscribers including subscriber 
numbers of the mobile subscribers, subscriber data, and identification 
numbers and location information of mobile stations. Mobile MSCC 4 is 
connected to a subscriber line of ISDN local switch 3b and controls the 
mobile subscriber data register equipment 5 and controls connection of a 
call originated from or terminated at the mobile station 1. Fixed 
subscriber 7 is connected to local switch 3c, and the local switches 3a, 
3b and 3c are connected to ISDN switched network 6, 
Operation of the mobile communication system of FIG. 1 is described below 
referring to FIGS. 2-5. 
When attempting to originate a call from mobile station 1 toward fixed 
subscriber 7, as shown in FIG. 2, mobile station 1 sends a call request to 
base station 2a, which controls mobile station 1, designating the called 
subscriber number N(7) and an identification number PN(1) of mobile 
station 1. Upon reception of the call request, base station 2a seizes 
local switch 3a and originates a call designating the subscriber number 
N(4) allocated to MSCC 4 as a terminating address and designating the 
designated called subscriber number N(7) as the terminating sub-address 
and the mobile station identification number PN(1) as the originating 
sub-address. MSCC 4 holds a communication line set by way of local switch 
3a, ISDN switched network 6 and local switch 3b, and reads out subscriber 
data corresponding to the received mobile station identification number 
PN(1) from the mobile subscriber data register equipment 5. MSCC 4 then 
analyzes the thus read out subscriber data and, after it confirms that the 
service is available with the mobile subscriber, it originates a call to 
ISDN local switch 3c designating the called subscriber number N(7) as a 
called number. 
When a call is to be originated from the fixed subscriber and terminated at 
the mobile station as shown in FIG. 3, fixed subscriber 7 originates a 
call designating the subscriber number N(1) of the mobile subscriber as a 
destination number. ISDN switched network 6 seizes ISDN local switch 3b 
with the mobile subscriber number N(1), and ISDN local switch 3b seizes 
MSCC 4. Holding a communication line set by way of the local switch 3c, 
ISDN switched network 6 and local switch 3b, and using the mobile 
subscriber number N(1) which was designated upon seizure, MSCC 4 reads out 
and analyzes subscriber data of the mobile subscriber, the identification 
number PN(1) and location information of the mobile station 1 in use, 
determines at least one or more base stations 2a to be seized from the 
analyzed location information, and originates a call designating the 
mobile station identification number PN(1) as the destination sub-address 
and the subscriber number N(2a) allocated to base station 2a as the 
destination address. Base station 2a alerts mobile station 1 with the 
mobile station identification number PN(1) and terminates the call at 
mobile station 1. 
Updating of location registration upon movement of a mobile station 
proceeds in the following manner as shown in FIG. 4. If it is assumed that 
base stations 2a and 2b belong to different location registration areas 
and mobile station 1 detects a changing of the location registration area 
when it moves from the location registration area of base station 2a into 
the location registration area of base station 2b, mobile station 1 
transmits a location registration request signal to base station 2b. Base 
station 2b seizes local switch 3a and originates a location registration 
request signal designating the identification number PN(1) of mobile 
station 1 as an originating sub-address and the subscriber number N(4) 
allocated to MSCC 4 as a terminating address. MSCC 4 calculates location 
information based on the mobile station identification number PN(1) and 
the originating address N(2b) from base station 2b and effects updating of 
the location information in the mobile subscriber data register equipment 
5. 
Switching between channels during communication is performed in accordance 
with the signal sequence illustrated in FIG. 5. It is assumed now that 
base stations 2a and 2b are located adjacent each other and mobile station 
1 moves, during service, from the service area of the control base station 
2a in control to the service area of the adjacent base station 2b. In this 
instance, when mobile station 1 approaches the border of the service area 
of base station 2a and the received electric field becomes weak, mobile 
station 1 transmits a channel switching request signal to the controlling 
base station 2a, to which mobile station 1 is then connected, adding as 
additional information the base station identification number CS(2b) of 
base station 2b to which the channel is to be switched (step A). Base 
station 2a designates the identification number PN(1) of mobile station 1 
as an originating sub-address adding the base station identification 
number CS(2b), and originates a call designating the subscriber number 
N(4) allocated to MSCC 4 as the terminating address, sets a communication 
line from base station 2a to MSCC 4 and notifies the channel switching 
request from mobile station 1 to MSCC 4 (step B). MSCC 4 holds the 
communication line set between base station 2a and MSCC 4, originates a 
call designating the mobile station identification number PN(1) as an 
originating sub-address and the subscriber number N(2b) of base station 2b 
as the terminating address, sets a communication line from MSCC 4 to base 
station 2b and requests base station 2b to secure a new radio channel 
necessary for channel switching (step C). Base station 2b stores the 
identification number PN(1) of mobile station 1 and returns an alerting 
message to MSCC 4 to report information of the radio channel secured for 
channel switching to MSCC 4 (step D). MSCC 4 notifies the information of 
the radio channel secured for channel switching and the identification 
number CS(2b) of base station 2b to base station 2a using the alerting 
message (step E). Upon reception of the alerting message, base station 2a 
transmits a channel switching instruction signal to mobile station 1 to 
notify the information of the radio channel for channel switching to the 
adjacent base station 2b which is the destination of the switching (step 
F). 
Upon reception of the channel switching instruction signal including the 
base station identification number CS(2b), mobile station 1 effects the 
channel switching process based on a re-originating procedure to base 
station 2b (step G). Upon reception of the originating request from mobile 
station 1, base station 2b confirms that the received mobile station 
identification number is identical with the mobile station identification 
number PN(1) stored at step D, and transmits a message of connection 
adding a channel switching completion signal to MSCC 4 (step H). Upon 
reception of the channel switching completion report, MSCC 4 disconnects 
the communication line established at the time of the channel switching 
request from base station 2a at step B (step I), and further disconnects 
the communication line to mobile station 1 which has been in a connected 
condition to base station 2a for service until channel switching Step J. 
While the embodiment of the present invention is described in detail above 
with reference to the drawings, connection of a call originating from or 
terminating at a mobile station, registration of the location of the 
mobile station and channel switching process during service are performed 
by way of mobile subscriber connection control equipment (MSCC) using an 
ISDN subscriber interface, and a mobile communication network is 
constructed in an ISDN switched network without providing a switch for 
exclusive use for mobile communication. 
The present invention can be applied also to systems wherein base stations 
are provided in a private branch or inside ordinary houses.