Mobile communication system

Abstract: A mobile communication system comprises a switching station, base stations to constitute respective zones, and mobile stations moving in a service zone formed by the communication zones. Plural base stations exist in one communication zone, and one specific channel among control communication channels is allocated to one of the base stations. The mobile station transmits general communication request using one specific channel during request of the general communication. Or the control communication channel is allocated only to one station among the base stations. The mobile station has a circuit for measuring the signal-to-noise ratio, and if the signal-to-noise ratio is deteriorated, a signal indicating this state is transmitted to the switching station.

Description: The present invention relates to a mobile communication system constituted by a switching station; a plurality of base stations connected to said switching station; and a plurality of mobile stations moving in a service area formed by combination of communication zones constituted by said base stations; wherein each base stations and each mobile stations having a speech radio channel for speech and a control radio channel for communication of control signals, said speech radio channel and said control radio channel being constituted by an upward channel from the mobile station to the base station and a downward channel from the base station to the mobile station, respectively, each communication zones contains a plurality of base stations, and said switching station transmits a general call command to said base stations in accordance with information included in a general call request signal. Such a mobile communication system is known from the European patent application EP-A-0 293 014, for example. This document shows a mobile communication system comprising connecting equipment units functioning as a plurality of base stations for use in carrying out communication with a plurality of radio telephone sets in a service zone by the use of a control channel and a plurality of speech channels. The document shows a control station for use in processing a call in a radio communication network system to carry out communication with a radio telephone set movable in a service area defined by the control station, with a control radio channel and a plurality of speech radio channels preassigned to the control station. The control station comprises first means selectively operable in first and second control modes and a speech mode for selectively accessing the control and the speech radio channels to allow reception of the call in the first control mode, not to allow the reception of the call in the second control mode, and to form a speech pass through a selected one of the speech channels in the speech mode and second means coupled to the first means for successively controlling the first means to switch either one of the first and the second control modes and the speech mode to another. FIG. 1 is a system constitution diagram showing a mobile communication system in the prior art disclosed in Japanese patent application JP-A-60038940. In FIG. 1, the mobile communication system comprises a switching station 1, base stations 2a - 2j connected to the switching station 1, a wired network 3 connecting between the switching station 1 and the base stations 2a - 2j, communication zones 4a - 4j of the base stations 2a - 2j, a crossover zone 5 where the communication zones 4a - 4j intersect each other, and a mobile station 6 moving in a service area 7 formed by the communication zones 4a - 4j. The base stations 2a - 2j and the mobile stations 6 have a speech radio channel (hereinafter referred to as "S-ch") for speech, and a control radio channel (hereinafter referred to as "C-ch") for communication of communication control signals. These channels S-ch and C-ch are constituted by an upward channel from the mobile station 6 to the base stations 2a - 2j, and a downward channel from the base stations 2a - 2j to the mobile station 6, respectively. Next, operation will be described. FIG. 2 is a timing chart showing signals transmitted or received between the base stations 2a - 2j and the mobile stations 6 in the mobile communication system in such constitution. The operation will be described in an example of position registration as follows. When the position information of the mobile station 6 becomes necessary, the base stations 2a - 2j transmit the position registration request signals (a) continuously using the downward channel of C-ch. The mobile station 6 at non-speaking state waits the position registration request signals (a) from the base stations 2a - 2j. When the position registration request signal (a) is received in the communication zone where the mobile station 6 is located at present, for example, in the downward channel of C-ch from the base station 2a of the communication zone 4a, if the base station identification code included in the position registration information signal (a) is different from that stored by the mobile station 6 at the last position registration before then, the downward channel of S-ch with an empty signal (b) transmitted from the base station 2a is detected. When the mobile station 6 detects a signal of the downward channel of S-ch with the empty signal (b) transmitted, the mobile station 6 transmits a position registration signal (c) in the upward channel of S-ch corresponding thereto. The switching station 1 performs the position registration based on the position information. From taking synchronization of the position registration signal (c) until finishing its reception, the base station 2a transmits a transmission inhibiting signal (d) to the downward channel corresponding to the upward channel of S-ch where the position registration signal (c) is transmitted. Thereby the transmission of the position registration signal (c) to the same upward channel from other mobile station 6 can be prevented. In the mobile communication system in the prior art constituted as above described, since only one base station 2a - 2j is installed at the same communication zone 4a - 4j, even if the emergency state occurs during use of the channel S-ch by the base station 2a - 2j, the general call cannot be performed from the mobile station 6 within the corresponding communication zone 4a - 4j. Also even if the mobile station 6 intends to perform the general call using the channel C-ch, the general call cannot be normally performed due to collision of the channel C-ch with other mobile station or other base station. When the communication zones 4a - 4j are constituted simply by a plurality of base stations, the collision of C-ch of these stations causes the communication failure. Even if the time difference is taken for the transmission of C-ch in order to avoid such collision of C-ch, since the base station identification code is different per each base station, the mobile station 6 even in the same communication zone responds to the position registration request signal from each base station of the communication zone. Also the mobile station 6 storing the base station identification code of the base station of some communication zone waits signals in the communication processing including the base station identification code and does not respond to signals in the same communication processing including the base station identification code from other base station in the same communication zone thereby a long time is required until the execution of the communication processing. FIG. 3 is a system constitution diagram of another mobile communication system in the prior art disclosed, for example, in Japanese patent application JP-A-5214703. In FIG. 3, the mobile communication system comprises a switching station 1, base stations 2a, 2b connected to the switching station 1, a telephone terminal 20 incorporated in the switching station 1, communication zones 4a, 4b of the base stations 2a, 2b, a mobile station 6 moving in a service area formed by the communication zones 4a, 4b, wired networks 3a, 3b connecting the base stations 2a, 2b to the switching station 1, information of signal-to-noise ratio (hereinafter referred to as "SN ratio") 17a, 17b transmitted from the base station 2a or 2b to the switching station 1, base station control signals 18a, 18b for the switching station 1 to control the base stations 2a, 2b, and speech paths 19a, 19b installed in the switching station 1 for connecting the base stations 2a, 2b to the telephone terminal 20. The base stations 2a, 2b and the mobile station 6 have a speech radio channel (hereinafter referred to as "S-ch") for speech, and a control radio channel (hereinafter referred to as "C-ch") for communication of communication control signals. These channels S-ch and C-ch are constituted by an upward channel from the mobile station 6 to the base stations 2a, 2b, and a downward channel from the base stations 2a, 2b to the mobile stations 2a, 2b to the mobile station 6, respectively. Next, operation will be described. Assume now that speech exists between the telephone terminal 20 and the mobile station 6 in the communication zone 4b through the base station 2b. Then the switching station 1 detects the movement of the mobile station 6 in following manner. That is, the base station 2b always measures the SN ratio of signals from the mobile station 6, and if the measured value is the standard value or more, the SN ratio information 17b is transmitted, for example, as "1" to the switching station 1. If the mobile station 6 is moved to the communication zone 4a, the measured value of the SN ratio in the base station 2b becomes the standard value or less. Consequently, the SN ratio information 17b from the base station 2b becomes "0" for example. Since the SN ratio information 17b becomes "0", the switching station 1 detects the movement of the mobile station 6 to the outside of the communication zone of the base station 2b, and executes changing of the channel during speech. The switching station transmits the control signal 18a to the base station 2a adjacent to the communication zone, and commands the reception of the channel S-ch with frequency used by the mobile station 6 in the communication zone 4b. The base station 2a receives the channel S-ch, and if the SN ratio is the standard value or more, the SN ratio information 17a is transmitted as "1" to the switching station 1. On receiving the information, the switching station 1 changes the speech path 19a into the speech path 19b, and realizes the speech in the mobile station 6 - the base station 2a - the switching station 1 - the telephone terminal 20, and restores the base station 2b. Since other mobile communication system in the prior art is constituted as above described, the switching station 1 must always measure and monitor the SN ratio of the received signals from the mobile station 6 regarding all base stations 2a, 2b. Also when the movement of the mobile station between the communication zones 4a, 4b is detected, the SN ratio information must be collected regarding all base stations at the periphery of the communication zone 4b before the movement, simultaneously or in sequence, in matching with the channel S-ch of frequency used by the mobile station 6 and the base station 2b within the communication zone 4b before the movement, until the communication zone 4a of the movement destination can be found. Consequently, problems exist in that large burden is applied to the processing. In view of the above-mentioned problems in the prior art, an object of the invention is to provide a mobile communication system wherein even when speech by channel S-ch between a mobile station and a base station is performed within the same communication zone the general call service can be normally realized. In order to attain the foregoing object, it is provided a mobile communication system as described at the beginning which is characterized in that a radio channel for building up a communication line on receipt of respective general call request signal from a mobile station is dedicated to one base station for each communication zone normally residing in a receiving state, said base station on receipt of said general call request signal from the requesting mobile station within said communication zone at the upward channel of said radio channel transmits the general call request signal to said switching sation, and said base stations on receipt of said command from said switching station transmit general call signal to said mobile stations on the speech radio channel or the control radio channel in use. The base station with the radio channel to be used only in the specific case allocated thereto is in the normally receiving state, and if a general call request signal exists on an upward channel of the radio channel from a mobile station within the communication zone, in accordance with the information included in the general call request signal, the switching station commands the general call to the base stations of all communication zones or the specific communication zone, and the base station receiving the command of the general call towards the general call signal to the mobile station using the upward channel of Cn-ch or S-ch, thereby the mobile communication system is realized in that while ordinary service of the mobile communication system using Cn-ch and S-ch is performed for each mobile station within the corresponding communication zone, performing of service such as the general call with higher priority can be always secured. FIG. 1 is a system constitution diagram showing a mobile communication system in the prior art; FIG. 2 is a timing chart showing transmission timing of signals transmitted or received in the system of FIG. 1; FIG. 3 is a system constitution diagram showing another mobile communication system in the prior art; FIG. 4 is a system constitution diagram showing a mobile communication system in an embodiment of the invention; FIG. 5 is a sequence chart showing processing sequence of general communication in the system of FIG. 4; FIG. 6 is an explanation diagram showing format of signals transmitted or received in the processing of FIG. 5; FIG. 7 is a sequence chart showing processing sequence of other general call in the system of FIG. 4; FIG. 8 is an explanation diagram showing format of signals transmitted or received in the processing of FIG. 7; FIG. 9 is a sequence chart showing processing sequence of further general call in the system of FIG. 4; FIG. 10 is an explanation diagram showing format of signals transmitted or received in the processing of FIG. 9; FIG. 11 is a system constitution diagram showing a mobile communication system in another embodiment of the invention; An embodiment of the invention will be described referring to the accompanying drawings as follows. In FIG. 4, a mobile communication system in the embodiment comprises a switching station 1, base stations 2a - 2g, a wired network 3, communication zones 4a, 4d - 4g, and a service area 7. Parts in FIG. 4 designated by the same reference numerals as those in FIG. 1 are the same as or similar to the parts in the prior art, and the detailed description shall be omitted. Also mobile stations 6a - 6g corresponding to the mobile station 6 shown in FIG. 1 move in the service area 7. The mobile communication system in the embodiment is different from the system of the prior art in that one communication zone (for example, 4a) is constituted by a plurality of (for example, three) base stations (for example, 2a - 2c). In FIG. 4, regarding each of the communication zones 4d - 4g, one base station 6d - 6g only are shown for the simplification. Next, operation will be described. In this connection, FIG. 5 is a timing chart showing processing sequence of the general call, and FIG. 6 is an explanation diagram showing format of signals transmitted or received in this case. In FIG. 4, the base stations 2a - 2c combined in a group constitute the same communication zone 4a, and when the communication is performed between the mobile stations 6a - 6c within the communication zone 4a, the base stations 2a - 2c have the same base station identification code imaginarily, and the communication with the mobile stations 6a - 6c by Cn-ch (channels excluding Ce-ch among C channels) is performed by stations not performing the communication on the S-ch among the base stations 2a, 2b, and the base station 2c is allocated by the radio channel (hereinafter referred to as "Ce-ch") to be used only in the specific case among the C channel and is in the normally communication state. In this case, the base station 2a and the mobile station 6a perform the communication on the S-ch, and the Cn-ch is allocated to the base station 2b. Similar state applies also to other communication zones 4d - 4g. In this case, it is assumed that the mobile station 6c transmits the general call request signal 12a onto the Ce-ch by operation of the functional key installed on the mobile station 6c. The general call request signal 12a as shown in FIG. 6(a) includes the identification code (C) of the mobile station 6c, the base station identification code Ba of the base stations 2a - 2c, and the general call request code (A). The general call request signal 12a is received by the base station 2c, and the information of the signal shown in FIG. 6(b) is transmitted to the switching station 1, and further the switching station 1 receiving the information 14a transmits the general call command 14b also shown in FIG. 6(b) to each of the base stations 2a - 2g. The base station 2c receiving the general call command 14b transmits the general call request receiving signal 13a to the mobile station 6c. As shown in FIG. 6(c), the general call request signal 13a includes the general call request receiving code (E) and the base station identification code Ba. On the other hand, each of other base stations 2a, 2b, 2d - 2g transmits the general call signal 11a or 11b onto the channel S-ch or Cn-ch in use. The general call signal 11a is transmitted from the base stations 2a, 2e, 2g during communication by S-ch shown by double line in FIG. 5 onto the S-ch, and the general call signal 11b is transmitted from the base stations 2b, 2d, 2f not performing communication by S-ch shown by single line in FIG. 5 onto the Cn-ch. The general call signals 11a, 11b as shown in FIG. 6(d) include the base station identification code Bn (n: a, d, e, f or g) of each communication zone. Each of the mobile stations 6a, 6b, 6d - 6g receiving the general call signals 11a, 11b rumbles a buzzer provided therewith and informs a user of the general call. The buzzer keeps rumbling unless the user stops it. When the user knows the general call by the rumbling of the buzzer, he stops the buzzer and enters the general call. The communication after stopping the rumbling of the buzzer may be one-directional speech from one mobile station transmitting request of general call to other mobile station or teleconference communication between these mobile stations. In the above-mentioned embodiment, although the general call is performed for all mobile stations 6a - 6g within the service area 7, the mobile stations 6a - 6g may be divided into groups and the general call may be performed only for the specific group. FIG. 7 is a sequence chart showing the processing sequence of the general call in such embodiment, and FIG. 8 is an explanation diagram showing format of signals transmitted or received then. In this case, for example, the mobile stations 6a, 6c, 6e, 6g are made the first group, and the mobile stations 6b, 6d, 6f are made the second group, and each group is supplied with mobile station group identification code FN1 or FN2 peculiar thereto respectively. Each of the mobile stations 6a - 6g stores the mobile station group identification code FN1 or FN2 of the group to which each station belongs. In the mobile station 6c, the general call request signal 12b with the mobile station group identification code FN1 shown in FIG. 8(a) added thereto is transmitted onto the Ce-ch by operation of a functional key provided on the mobile station 6c and subsequently by operation of a mobile station group identification code transmission key. The general call request signal 12b is received by the base station 2c and the information 14c of the signal is transmitted to the switching station 1, which transmits the general call command 14d to each of the base stations 2a - 2g. The mobile station group identification code FN1 is added also to the information 14c and the general call command 14d as shown in FIG. 8(b). On receiving the general call command 14d, the base station 2c transmits the general call request receiving signal 13b with the mobile station group identification code FN1 added thereto as shown in FIG. 8(c) to the mobile station 6c. On the other hand, other base stations 2a, 2b, 2d - 2g transmit the general call signal 11c or 11d with the mobile station group identification code FN1 added thereto as shown in FIG. 8(d) onto the channel S-ch or Cn-ch in use. Each of the mobile stations 6a, 6b, 6d - 6g receiving the general call signals 11c, 11d rumbles a buzzer and informs a user of the general call, only when the mobile station group identification code FN1 on the general call signals 11c, 11d is coincident with the mobile station group identification code FN1 or FN2 stored in each mobile station. Consequently, the buzzer rumbles in the mobile stations 6a, 6e, 6g included in the same group as that of the mobile station 6c. In the above-mentioned embodiment, although the mobile station group identification code FN1 or FN2 is stored in each of the mobile stations 6a - 6g, the switching station 1 may have the mobile station group identification code FN1 or FN2 and the information of the mobile stations included in the group and the communication to each mobile station of the group may be performed by processing of the switching station 1. The embodiment has been described where the mobile stations 6a - 6g are divided into groups. However, in the mobile communication system according to the invention, the communication zones 4a, 4d - 4g may be divided into groups and the general call may be performed only to the specific group. FIG. 9 is a sequence chart showing processing sequence of the general call in such embodiment, and FIG. 10 is an explanation diagram showing format of signals transmitted or received then. In this case, for example, the communication zones 4a, 4d are made the first group and the communication zones 4e - 4g are made the second group, and each group is allocated with the base station group identification code HN1 or HN2 peculiar thereto respectively. Each of the base stations 2a - 2g within the communication zones 4a, 4d - 4g stores the base station group identification code HN1 or HN2 of the group to which the communication zones 4a, 4d - 4g belong. In the mobile station 6c, the general call request signal 12c with the base station group identification code HN1 shown in FIG. 10(a) added thereto is transmitted onto the Ce-ch by operation of a functional key provided on the mobile station 6c and subsequently by operation of a mobile station group identification code transmission key. The general call request signal 12c is received by the base station 2c and the information 14e of the signal is transmitted to the switching station 1, which transmits the general call command 14f to each of the base stations 2a - 2g. The base station group identification code HN1 is added to the information 14e and the general call command 14f as shown in FIG. 10(b). On receiving the general call command 14f, the base station 2c transmits the general call request receiving signal 13c with the base station group identification code HN1 added thereto as shown in FIG. 10(c) to the mobile station 6c. On the other hand, other base stations 2a, 2b, 2d - 2g transmit the general call signals 11a, 11b shown in FIG. 10(d), only when the base station group identification code HN1 on the general call command 14f is coincident with the base station identification information HN1 or HN2 stored in each base station. Consequently, the general call signals 11a, 11b are transmitted from the base stations 2a, 2b, 2d having the identification information HN1. Each of the mobile stations 6a - 6d moving in the communication zones 4a, 4b receiving the general call signals 11a, 11b rumbles a buzzer and informs a user of the general call. Also in this case, the switching station 1 may have the base station group identification code HN1 or HN2 and the information of the base stations included in the group, and the general call command 14f may be transmitted to each of the base stations of the group by processing of the switching station 1 and the general call may be applied to the communication zone. Further, the communication zone of the destination station may be assigned not only from the base station previously set but also from the mobile station at the start state of the general call. In each embodiment as above described, although the user is informed of the general call by the rumbling of the buzzer, the visual display using a light emission diode, a liquid crystal indicator or the like is possible, and in transmission of the general call request signal, the specific S-ch may be used in place of the Ce-ch. In any case, similar effects to the above-mentioned embodiments can be obtained. According to the invention as above described, a plurality of base stations are arranged in one communication zone, and one of the base stations is made the normally receiving state and the radio channel to be used only in the specific case is allocated to the base station and used for the communication of the emergency signal such as general call request, thereby the mobile communication system can be obtained in that the emergency signal does not collide with a signal for ordinary speech control and the general call of high accuracy can be performed. FIG. 11 is a system constitution diagram showing a mobile communication system in another embodiment of the invention. In FIG. 11, the mobile communication system comprises a switching station 1, a wired network 3, communication zones 4a - 4j, a crossover zone 5, and a mobile station 6. Parts in FIG. 11 designated by the same reference numerals as those in FIG. 1 are the same as or similar to the parts in the prior art, and the detailed description shall be omitted. Numerals 27a - 27j designate base station groups each comprising plural base stations or single base station, and the communication zones 4a - 4j are constituted by these base station groups 27a - 27j. In the embodiments as above described, although the communication destination of the mobile station is the telephone terminal, it may be other terminal connected through the mobile station or public network, or the direction of transmission and reception of the connection confirmation signal and the connection confirmation response signal may be made the reverse direction.

Claims: A mobile communication system comprising: a switching station (1); a plurality of base stations (2a - 2g) connected to said switching station (1); and a plurality of mobile stations (6a - 6g) moving in a service area (7) formed by combination of communication zones (4a - 4g) constituted by said base stations (2a - 2g); wherein each base station (2a - 2g) and each mobile station (6a - 6g) having a speech radio channel for speech and a control radio channel for communication of control signals, said speech radio channel and said control radio channel being constituted by an upward channel from the mobile station to the base station and a downward channel from the base station to the mobile station, respectively, each communication zone (4a - 4g) contains a plurality of base stations (2a - 2g), and said switching station (1) being adapted to transmit a general call command (14b) to said base stations (2a - 2g) in accordance with information included in a general call request signal (12a - 12c), characterized in that a radio channel for building up a communication line on receipt of respective general call request signal (12a - 12c) from a mobile station (6c) is dedicated to one base station (2c) for each communication zone (4a - 4g) normally residing in a receiving state, said base station (2c) on receipt of said general call request signal (12a - 12c) from the requesting mobile station (6c) within said communication zone (4a - 4g) at the upward channel of said radio channel being adapted to transmit the general call request signal (12a - 12c) to said switching station (1), and said base stations (2a, 2b, 2d - 2g) on receipt of said command (14b) from said switching station (1) being adapted to transmit a general call signal (11a; 11b) to said mobile stations (6a, 6b, 6d-6g) on the speech radio channel or the control radio channel in use. A mobile communication system as set forth in claim 1, wherein the mobile station (6a - 6g) to request the general call is adapted to transmit a base station identification code allocated to the communication zone (4a - 4g) in which said mobile station (6a - 6g) exists at present together with a general call request code, and each base station (2a - 2g) within the service area (7) is adapted to transmit the base station identification code allocated to the communication zone (4a - 4g) constituted by the base station (2a - 2g) together with the communication zone (4a - 4g). A mobile communication system as set forth in claim 1, wherein all mobile stations (6a - 6g) within the service area (7) are previously divided into groups, a group identifiction code is allocated to each group, the mobile station (6a - 6g) to request the general call is adapted to transmit a group identification code of the group as the object of the general call together with a general call request code, and each base station (2a - 2g) within the service area (7) is adapted to transmit the group identification code of the group as the object of the general call together with the general call request code. A mobile communication system as set forth in claim 1, wherein a mobile station (6a - 6g) to request the general call is adapted to transmit a base station group identification code indicating the communication zone (4a - 4g) as the object of the general call together with a general call request code, and only each base station (2a - 2g) within the base station group (27a - 27j) corresponding to the base station group identification code among the base stations (2a - 2g) within the service area (7) is adapted to transmit the general call signal.

Inventors: FUJYU MITSUO, MONMA TAKESHI, OZU YASUSHI, FUJYU, MITSUO, MONMA, TAKESHI, OZU, YASUSHI, FUJYU, MITSUO, C/O MITSUBISHI DENKI K. K., MONMA, TAKESHI, C/O MITSUBISHI DENKI K. K., OZU, YASUSHI, C/O MITSUBISHI DENKI K. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1991
Main classification: H04Q7
IPC codes: H04W36