JPH1127725A - Exchanging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of an exchanging system by detecting failures of its own exchanging device and notifying it to a base station at the time of detecting the failure to switch the connection with an exchang device connected to a terminal through a line connection interface, thereby disconnecting an exchanging device which is related to a failure notification and connecting a terminal which is connect thereto to an exchange device that does not have a failure notification. SOLUTION: When a failure occurs in one exchange device #a, the faulty exchange device #a notifies the failure to a service control station 4 and a base station CS #1 via a common signal network. When there is such a notification, the stations 4 and CS #1 respectively recognize the failure of the exchange device #a and switch the transmission of all traffic via the exchange device #a to an exchange device #b. At this time, a controlling part 4a of the station 4 converts into the exchange device #b, what is related to the exchange device #a in positional information of each terminal PS that has been registered on a table on a file 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching system, and more particularly, to a switching system used in a mobile communication system such as a portable telephone system (PHS).

[0002]

2. Description of the Related Art In a public communication system, measures such as duplication of a device and a backup power supply have been taken for the purpose of strengthening fault tolerance of a network-side device (a transmission device such as an exchange). And such precautionary measures are required by law).

[0003] Also, between the network side device and the terminal,
Measures have been taken to improve the reliability of the entire system by taking measures such as duplicating the transmission path. Furthermore, PH
Terminal devices such as the wireless base station of S have been devised to secure communication by providing a backup power supply as a measure against power failure.

By the way, in a mobile communication system, a mobile station can move during a call and continue the call (handover) while switching a corresponding radio base station. In order to realize such services, protocols for realizing handover between the radio base station and the mobile station and between the radio base station and the exchange are prepared, and are standardized by respective standardization organizations.

[0005]

However, when a complex severe fault occurs in a network device (exchange, transmission equipment), the operation may be stopped even if the above measures are taken. As a result, the terminal connected to the device (in the case of the PHS, the radio base station and the mobile stations under the base station) cannot receive the predetermined service. For this reason, even if a serious failure occurs in a specific exchange (or a transmission path and a transmission device between the exchange and the radio base station) accommodating the radio base station and the exchange service cannot be continued, other services prepared in advance can be used. Service can be continued by connecting to an exchange.

In a mobile communication service using an existing public network such as a PHS, handover may not be possible even in an adjacent wireless area. In the current PHS service, such a service (handover) is provided only between radio base stations connected to the same switch (it may be a module of the switch, but hereinafter all are referred to as the switch). I have. This is because standardization has not been performed to realize handover between exchanges, and even if standardization has been performed,
This is because adding a function to an existing switching network imposes a very heavy burden. Therefore, it is expected that it is difficult to provide a handover between exchanges in the future in a system such as a PHS that pursues economic efficiency.

[0007] The present invention has been made in view of the above-described problems, and has as its object to provide an exchange system that can improve reliability. Another object of the present invention is to provide a switching system capable of realizing handover between exchanges.

[0008]

A switching system according to the present invention comprises a base station for performing wireless communication with a terminal, an exchange to which the base station is connected, and an exchange network to which the exchange is connected. An exchange system that provides a communication service to the exchange, wherein the exchange comprises: a failure detection unit that detects a failure of the own exchange; and a failure notification unit that notifies a base station when the failure detection unit detects a failure. Equipped, the base station,
A line connection interface for connecting to a plurality of exchanges, switching control means for switching the connection between the terminal and the exchange connected via the line connection interface, and when a failure is notified from the exchange, the failure notification Traffic control means for disconnecting the exchange and connecting a terminal connected to the exchange to an exchange having no failure notification.

Another switching system according to the present invention comprises:
A base station that performs wireless communication with the terminal;
An exchange system comprising: a first exchange connected to one base station; and a second exchange connected to at least one base station identical to the first exchange, and providing a communication service to a terminal. A base station connected to at least the first and second exchanges establishes a line connection interface for connecting to the plurality of exchanges, and a connection between the terminal and the exchange connected via the line connection interface. Switching control means for switching, and traffic relay means for controlling the switching control means and relaying traffic from one of the exchanges to another exchange are provided.

[0010]

FIG. 1 is a circuit diagram showing a configuration of a switching system according to a first embodiment of the present invention. This switching system includes terminals (PS) #w, #x, #y, #z,.
..Base stations (CS) 1a, 1b,...
, And exchanges 2a, 2b, 2c, 2d, 2e,... To which base stations 1a, 1b,.
It is provided with an exchange network 3 to which the exchanges 2a, 2b, 2c, 2d, 2e,... Are connected, and a service control station 4 for controlling communication.

In this switching system, a service providing area is divided into small areas (wireless zones), and base stations 1a, 1b,... Are arranged for each wireless zone. One base station 1a, 1b, ... is a plurality of exchanges (2a, 2b),
(2c, 2d, 2e),... Are connected to the switching network 3.

The switching network 3 is a digital switching network such as an ISDN, and a digital switching network 3a for transmitting data of a speech channel (corresponding to a B channel in the case of ISDN).
And a common line signal network 3b for transmitting data of the control channel.
(Corresponding to the D channel in the case of ISDN).
Hereinafter, the case of ISDN will be described.

The service control station (SCP) 4 includes a control unit 4a for controlling the switching of the communication channel setting (including the path) and a database or a file device for storing the settings of the communication channel and the like. Hereinafter, it is simply referred to as a file.) 4b.

The service control station 4 is connected to each terminal #w, #
Control of registration of the positions of x, #y, #z,... (which base station is in the coverage area), and control of handover (described later) for switching a communication channel with movement of the terminal are executed. These controls are performed by the common channel signal network 3b (D channel).
This is done by information transmitted and received via Further, the service control station 4 also performs a route switching control (described later) for controlling an incoming call from the faulty exchange to the substitute exchange.

Each of the base stations 1a, 1b,... Has a radio section 12 for transmitting and receiving radio signals via an antenna 11, a time division frame configuration, and a time slot of a radio channel, as shown in FIG. A TDMA / TDD unit 13 for allocating a communication channel and a control channel, a switching control unit 14 for switching a line and the like, and a plurality of line termination units (DSUs, line connection interfaces) 15a, 1
5b,..., A control unit 16 for controlling the entire base station
And The control unit 16 controls each DSU 15a, 15
b, a plurality of exchanges 2a, 2
, a handover control unit (traffic relay means) 16b for controlling handover between exchanges
And

Each of the exchanges 2a, 2b,... Has an input processing unit 21 to which an input line is connected, as shown in FIG.
An output processing unit 22 to which an output line is connected, and an input processing unit 21 a switching control unit 23 for selecting an output destination of the line.
And a control unit 24 for controlling the operation of the entire exchange. The control unit 24 also performs control for realizing handover between exchanges.

The exchanges 2a, 2b,...
Monitors the failure of its own device, and when a failure occurs, notifies the service control station 4 and the base stations 1a, 1b,... Via the common channel signaling network 3b (D channel).

Hereinafter, the operation of the switching system configured as described above will be described.

A. Route switching control system control station 4
4 shows the communication settings shown in FIG. 4 (table indicating correspondence between communication channels of individual base stations and exchanges), and the correspondence between individual terminals (PS) and location information (exchanges, base stations). The table (FIG. 5) is stored in the file 4b.

As shown in FIG. 4, a base station connected to a plurality of exchanges, for example, base station CS # 1 is associated with a plurality of exchanges #a and #b. Hereinafter, such a correspondence relationship is referred to as double attribution.

(1) Normal Operation The base station CS # 1 and the system control station 4 are connected to each of the exchanges #a,
It monitors whether #b is operating normally. FIG.
When both exchanges #a and #b are functioning normally, as shown in (1), the system control station 4 switches the terminals (PS) #x, #y and #z under the base station CS # 1 to the exchange # a and #b are distributed and registered. At this time, the control unit 4a of the system control station 4 stores a table as shown in FIG.
b, and the subsequent PS # x, #y with respect to CS # 1.
Is performed via the exchange #a, and communication with the PS # z is performed via the exchange #b. As a result, traffic from CS # 1 is switched to switch #a,
#B and transmitted. Therefore, traffic concentration can be avoided.

(2) Operation when a failure occurs As shown in FIG. 7, when a failure occurs in one of the exchanges #a (including the transmission line connected to the exchange #a), the exchange #a in which the failure has occurred Indicates that a failure has occurred in the common signaling network 3.
b (D channel), system control station 4, base station C
Notify S # 1. When such a notification is received, the system control station 4 and the base station CS # 1 each recognize the failure of the exchange #a and switch the traffic transmission via all the exchanges #a to via the exchange #b.

At this time, the control unit 4a of the system control station 4
As shown in FIG. 8, among the location information of each terminal (PS) registered in the table on the file 4b, the exchange #
The one related to a is converted to the exchange #b. Subsequent control (terminating control) on the terminals (terminals PS # x and PS # y in the case of FIG. 8) changed to the exchange #b is performed via the exchange #b.

When CS # 1 detects a failure in exchange #a, CS # 1 transmits the terminal PS # assigned to exchange #a.
The subsequent position control (call control) from x, PS # y is performed via the normally operating exchange #b.

By performing the switching control as described above, even if a serious failure occurs in the exchange #a (including the transmission line connected to the exchange #a), the switching is performed via the failed exchange #a. The communication that has been performed can be performed via the exchange #b. Therefore, even if a failure occurs in any of the exchanges connected to the base station, if at least one exchange connected to the base station is functioning normally, the terminal under the base station continues to operate. Service can be provided. Therefore, the reliability of the entire system can be improved without improving the reliability of individual exchanges, transmission paths, and the like.

B. Control of Handover In this switching system, as shown in FIG. 1, a plurality of exchanges are connected to one base station, and handover between the exchanges is performed through the base stations connected to the plurality of exchanges. It can be realized.

(1) Normal handover Conventionally, a base station CS # 1 connected to the same exchange shown in FIG. 9 (which is different from FIG. 1 but is assumed to be exchange #a).
And handover was possible between CS # 2 and CS # 2. For example, when the terminal PS in FIG. 9 moves from the wireless zone A to the wireless zone B during communication via the base station CS # 1, the base station C
Communication via S # 1 becomes difficult. In this case, the terminal PS
Has detected that it has entered the coverage area of the base station CS # 2, gives up communication with the base station CS # 1, transmits a call setup message accompanied by a request for handover to the base station CS # 2, Requests handover to exchange #a.

The exchange #a confirms the validity of the handover request, the state of the call, etc., and resets the communication path.
The communication channel with the terminal PS is switched from the base station CS # 1 to the base station CS # 2. As a result, the terminal PS can continuously perform communication. In this case, exchange #a performs control (path switching) for handover, but the protocol for this handover is not unified between exchanges having different specifications. Therefore, conventionally, only a handover between base stations connected to an exchange having the same specification could be performed.

(2) Handover between exchanges In this exchange system, a base station is connected to a plurality of exchanges as shown in FIG. The connection in FIG. 10 is different from that in FIG. 1, but will be described below with reference to FIG. Base station CS # 2 is connected to exchange #a and exchange #b. The exchanges #a and #b each have a base station CS #
1. The base station CS # 3 is connected. For this reason, even between base stations that are not connected to the same exchange, there are cases where they are indirectly connected via a certain base station (base station # 2 in FIG. 10). Communication can be maintained between such base stations (base station # 1 and base station # 3 in FIG. 10).

In this switching system, handover between a plurality of exchanges is realized as follows in addition to the above-described normal handover.

For example, if the terminal PS in FIG.
If the mobile station moves from the wireless zone A to the wireless zone B during communication via the first base station 1, communication via the base station CS # 1 becomes difficult.
In this case, since the terminal PS has detected that it has entered the coverage of the base station CS # 2, it gives up the communication with the base station CS # 1, and as shown in FIG.
2 transmits a call setup message accompanied by a request for handover, and requests the exchange #a for handover.

After confirming the validity of the handover request, the state of the call, and the like, the exchange #a re-establishes the communication path as shown in FIG. 11B and establishes the communication channel with the terminal PS. Switching from station CS # 1 to base station CS # 2.
Up to this point, it is the same as the above-described conventional handover.

Further, when the terminal PS moves from the wireless zone B to the wireless zone C during communication via the base station CS # 2, communication via the base station CS # 2 becomes difficult. Terminal P
Since S has detected that it has entered the coverage area of base station CS # 3, it gives up communication with base station CS # 2 and returns to FIG.
As shown in FIG. 1 (c), a call setup message accompanied by a request for handover to the base station CS # 3 is transmitted, and a handover is requested to the exchange #b.

The exchange #b, which has received such a handover request, does not control the call (secure a communication channel, etc.) for the relevant PS at present, so that the exchange #b belongs to the double.
It is determined that the request is a handover request from S. Therefore,
As shown in FIG. 11D, the exchange #b makes a simultaneous incoming call (call setup) to the base station (CS # 2 in this case) which is connected to the own exchange and is in the dual belonging state. . The base station in the double belonging state is detected by making an inquiry to the service control station 4 described above.

In the case of CS # 2 receiving the simultaneous call, the corresponding terminal P
If S is communicating, it is recognized as a handover between exchanges, and unlike a normal incoming call procedure, processing for the subordinate terminal PS is not performed, and as shown in FIG. To set a handover path and return a response (call setting acceptance) to exchange #b. The setting of the handover path is performed by controlling the switching control unit 14 by the handover control unit 16b in the control unit 16 in FIG. Further, such a handover is performed in the exchange #
b and base stations CS # 2 and CS # 3,
The exchange #a does not know that a handover has occurred on the communication channel of the terminal PS, and continues to recognize that it is within the coverage of the base station CS # 2.

When the exchange #b receives the response, FIG.
As shown in FIG. 11 (f), the handover is notified (responded) to the base station CS # 3 and, as shown in FIG. A PS disconnection request (PS disconnection) is performed.

Base station CS # 2 receives P
When a request for S disconnection is received from the exchange #b, the call disconnection by handover is performed on the terminal PS while maintaining the bus setting (for the communication channel) between the exchanges #a and #b. As a result, the call between base station CS # 2 and terminal PS is physically disconnected, but simulated by base station CS # 2.
Since the call to the terminal PS is maintained via # 3, the base station CS # 2 behaves in the same way as when a call to the terminal PS exists for the exchange #a. Therefore, it appears as if the original call is continuing from exchange #a.

As described above, in this switching system, a handover between the plurality of exchanges (#a, #b) is realized via the base station (CS # 2) connected to the plurality of exchanges. Can be. Therefore, even when a small-capacity exchange having a small number of base stations that can be connected is used, the possible range of the handover can be increased.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the technical idea of the present invention.

[0040]

In the switching system according to the present invention, even when a failure occurs in any of the switches connected to the terminal, the traffic control means connects the switch connected to the terminal via the line interface. Since the switch to the switch having no failure notification among the plurality of switches is switched, the reliability of the entire switching system can be improved without improving the reliability of individual components such as the switch.

Further, in the switching system according to the present invention, the relay means of the base station can relay traffic from one of the exchanges connected to the base station to another exchange. Handover can be realized. Therefore, even when a small-capacity exchange having a small number of base stations that can be connected is used, the possible range of the handover can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a base station included in the switching system.

FIG. 3 is a block diagram showing a configuration of an exchange constituting the exchange system.

FIG. 4 is a diagram showing a table showing communication settings used in a service control station constituting the switching system.

FIG. 5 is a diagram showing a table indicating the correspondence between individual terminals and position information used in a service control station constituting the switching system.

FIG. 6 is a diagram illustrating route switching control in the switching system.

FIG. 7 is a diagram showing a table indicating the correspondence between individual terminals and position information used in a service control station constituting the switching system.

FIG. 8 is a diagram illustrating route switching control in the switching system.

FIG. 9 is a diagram illustrating a concept of a handover operation in the switching system.

FIG. 10 is a diagram illustrating a concept of a handover operation between exchanges in an exchange system.

FIG. 11 is a diagram showing a handover operation between exchanges in the exchange system.

[Explanation of symbols]

1a, 1b base station, 2a-2e exchange, 3 switching network, 4 service control station, 14 switching control unit, 15
a, 15b DSU, 16a Traffic control unit, 1
6b Handover control unit, 24 control unit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Koshiba 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Yoshiaki Minagawa 1-7-112 Toranomon, Minato-ku, Tokyo Inside Electric Industry Co., Ltd.

Claims (4)

[Claims] An exchange system for providing a communication service to a terminal, comprising: a base station for performing wireless communication with the terminal, an exchange to which the base station is connected, and an exchange network to which the exchange is connected. The exchange, the failure detection means for detecting a failure of its own exchange, failure detection means for notifying the base station when a failure is detected by the failure detection means, the base station, A line connection interface for connecting to a plurality of exchanges, switching control means for switching a connection between the terminal and an exchange connected via the line connection interface, and when a failure is notified from the exchange, the failure Traffic control means for disconnecting the exchange associated with the notification, and connecting the terminal connected to the exchange to an exchange having no failure notification. Exchange system. 2. The traffic control means of the base station,
2. The switching system according to claim 1, wherein the terminals connected to the base station are set so as to be connected in a distributed manner to the exchange having no failure notification. 3. A base station for performing wireless communication with a terminal, a first exchange connected to at least two base stations, and a first exchange connected to at least one base station identical to the first exchange. A switching system for providing a communication service to a terminal, wherein at least a base station connected to the first and second switches is connected to a plurality of switches. A connection interface, switching control means for switching the connection between the terminal and the exchange connected via the line connection interface, and controlling the switching control means to relay traffic from one of the exchanges to another exchange An exchange system comprising a traffic relay unit. 4. The terminal includes relay request means for transmitting a relay request to an exchange to which the terminal is not directly connected, and the traffic control means relays traffic in response to a relay request from the terminal. 4. The switching system according to claim 3, wherein: