WO2000010339A2

WO2000010339A2 - Method and system for maximising the capacity of a telecommunication system

Info

Publication number: WO2000010339A2
Application number: PCT/FI1999/000662
Authority: WO
Inventors: Heimo PENTIKÄINEN; Janne Kuvaja
Original assignee: Nokia Networks Oy
Priority date: 1998-08-17
Filing date: 1999-08-09
Publication date: 2000-02-24
Also published as: FI981767A; AU5291999A; FI981767A0; WO2000010339A3

Abstract

The invention relates to a method and a system for maximising the available capacity of a telecommunication system, said telecommunication system comprising a local exchange (LE), an access node (AN) connected to the local exchange, a wireless communication system (WLL) connected to the access node, a telecommunication terminal (MS) connected to the access node (AN) via the wireless communication system. In the method, a message indicating activation of call transfer is sent from the access node (AN) to the local exchange (LE) after the access node (AN) has received from the telecommunication terminal (MS) a message indicating that the terminal has been turned off. In the system of the invention, the access node (AN) comprises means (4) for sending to the local exchange (LE) a message indicating activation of call transfer after the access node (AN) has received from the telecommunication terminal (MS) a message indicating that the terminal (MS) is in the off state.

Description

METHOD AND SYSTEM FOR MAXIMISING THE CAPACITY OF A TELECOMMUNICATION SYSTEM

FIELD OF THE INVENTION The present invention relates to telecommunication systems, especially WLL systems.

BACKGROUND OF THE INVENTION

'WLL system' (WLL, Wireless Local Loop) re- fers to a system in which a subscriber is connected to a telephone network via a wireless communication system. The wireless communication system can be implemented by applying mobile communication technology, e.g. GSM technology (GSM, Global System for Mobile Communications) . A subscriber connection is achieved by using a special telecommunication terminal. In the WLL system, the telecommunication terminal is connected via a radio link to an access node. Between the terminal and the access node there is a base station, by means of which call signals received by radio from the terminal to the base station are transmitted via the access node further to the public telephone network and vice versa. The access node is connected to the telephone exchange e.g. using the V5.1 or V5.2 protocol.

Open interfaces (V5.1 and V5.2) between an access node and a telephone exchange are defined in the ETSI (European Telecommunications and Standards Institute) standards of the ETS 300 324 and ETS 300 347 series. V5 interfaces enable subscribers belonging to a physically separate access network, either wired or wireless, to be connected a using a standard telephone exchange interface .

In prior-art telephone systems, in a situa- tion where a subscriber cannot be reached, a call can be transferred to another subscriber line. Call transfer is effected e.g. upon the lapse of a specified length of time, in which case the caller has been trying to reach the subscriber at the number in question. The subscriber him/herself can also define a setting to effect immediate call transfer when a call is being connected.

In a WLL system, a local exchange in a telephone network is connected to an access node in the WLL system. A seen by the telephone network local exchange, a WLL subscriber is a wired network subscriber. If the subscriber activates call transfer before closing the WLL terminal, then the call transfer function will reroute the call directly from the local exchange to the other subscription. Otherwise, the local exchange will try to connect the call through the access node to the terminal. When the call is directed from the local exchange to a WLL subscription with the terminal turned off, the access node will try to set up a connection over the wireless communication system. This means wasting wireless network capacity while the terminal is off. In other words, it is useless to try to set up a call to a terminal in the off state. In another solution, data indicating that the terminal has been switched off is stored in the access node. When the local exchange tries to set up a call to a WLL subscription shut off, the access node will cancel the call setup, in which case call transfer by the local exchange is not possible.

The object of the present invention is to solve the problems described above. A specific object of the present invention is to disclose a new type of method and system for maximising the capacity of a WLL system and reducing the workload of the radio network. BRIEF DESCRIPTION OF THE INVENTION

The invention concerns a method for maximising the available capacity of a telecommunication system. The telecommunication system comprises a local exchange, an access node connected to the local exchange, a wireless communication system connected to the access node and a telecommunication terminal, which is connected to the access node via the wireless communication system. In the method of the invention, a message indicating activation of call transfer is sent from the access node to the local exchange when the connection between the terminal and the wireless communication system is interrupted. Call transfer also takes place after the access node has received from the terminal a message indicating that the terminal has been turned off. In a preferred embodiment of the invention, the method also functions conversely; in this case, the access node sends to the local exchange a message indicating deactivation of call transfer when a connection between the WLL system and the terminal is established or after the access node has received from the terminal a message indicating that the terminal has been turned on. Call transfer is preferably directed to an answering service in the local exchange.

In a preferred embodiment of the invention, data indicating the state of the terminal is stored in the access node by using an IMSI attach/detach procedure between the access node and the terminal as de- scribed e.g. in the ETS 300 530 standard series. When power is switched on to the terminal, the terminal starts an IMSI attach function, which in practice corresponds to the terminal location updating procedure defined in the standard. The data indicating that the terminal is in a state of readiness is generally stored in binary form in the access node. The IMSI detach function is executed when power is switched off from the terminal. In this case, too, state information is stored in the access node. In the access node, the state of the terminal is indicated by the access port status data. In a preferred embodiment, a subscriber- specific number to which call transfer is to be directed is defined in the access node. Thus, it will be possible e.g. to define for each subscriber a different call transfer sequence, a string for controlling the functions of the local exchange. In an embodiment of the invention, the message regarding activation or deactivation of call transfer is transmitted from the access node to the local exchange using the Digit - signal information element of a SIGNAL message. The SIGNAL message is described e.g. in the standard ETS 300 324-1: 1994, pages 53-56.

In an embodiment of the method, the wireless communication system used is based on a digital mobile communication system, such as e.g. the GSM system. The invention also relates to a system for maximising the available capacity in a telecommunication system, said telecommunication system being a system as described above. In the system of the invention, the access node comprises means for sending a message indicating activation of call transfer to the local exchange when a connection between the terminal and the wireless communication system is interrupted or after the access node has received a message from the terminal indicating that the terminal has been turned off. In an embodiment, the access node comprises means for sending the local exchange a message indicating deactivation of call transfer when a connection between the terminal and the wireless communication system is established or after the access node has received from the terminal a message indicating that the terminal has been turned on. The access node preferably comprises means for directing call transfer to an answering service in the local exchange.

In an embodiment, the access node comprises means for storing data indicating the state of the terminal using an IMSI attach/detach procedure between the access node and the terminal. The access node preferably comprises means for determining a subscriber-specific number to which call transfer is to be directed. In an embodiment, the access node comprises means for sending a message announcing activation or deactivation of call transfer to the local exchange using the Digit-signal information element of the SIGNAL message. In an embodiment of the system, the wireless communication system used is based on a digital mobile communication system, e.g. the GSM system.

As compared with prior art, the invention allows several advantages to be achieved. The invention allows call transfer in conjunction with a WLL system without using the resources of the radio network. The invention reduces the exchange of messages between different network components, thus increasing the available capacity. Moreover, the invention adds a new kind of intelligent function to the access node, a function that allows the local exchange to perceive call transfer as an action identical with call transfer performed by the user of the terminal .

LIST OF ILLUSTRATIONS

In the following, the invention will be described by the aid of a few examples of its embodiments with reference to the attached drawing, wherein

Fig. 1 is a diagram illustrating a system ac- cording to the invention; and

Fig. 2a and 2b present a signalling arrangement according to the invention. DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 presents the components of a system according to the invention. In the wireless mobile communication system, a telecommunication terminal MS is connected via a wireless communication system to an access node AN, which is e.g. a DAXnode 5000 WLL manufactured by Nokia. The wireless communication system comprises at least one base station BS; the example presented in the figure comprises two base stations BSl and BS2 , forming cell areas 1 and 2. The access node AN controls the operation of the base stations BS . The cell areas 1 and 2 together form a mobility area 3, which is an operating area defined for the telecommunication terminal MS. The access node AN is connected via a V5 interface to a local exchange LE; therefore, as seen by the local exchange LE, the WLL system telecommunication terminal MS is a normal wired network subscriber.

The access node AN comprises means 4 for sending to the local exchange LE a message indicating activation of call transfer when the access node AN has received from the terminal MS a message announcing that the terminal has detached itself from the radio network. Correspondingly, the access node AN comprises means 5 for deactivating call transfer from the local exchange when a message indicating that the terminal is on has been received from the terminal. Activation of call transfer is effected e.g. by having the access node send on the calling subscriber's behalf the string *21*XXXXX#, where XXXXX is an example telephone number to which the call is to be transferred, to the local exchange.

Using means 6, the access node AN directs the call transfer in the local exchange LE to an answering service. In this case, in a possible embodiment, the access node AN sends to the local exchange LE the string *14# to activate the answering service. The access node comprises means 8 for determining the number to which the call transfer is to be directed. As there are several different ways to implement activa- tion/deactivation . of a call transfer and answering service, it is possible to define several different subscriber-specific activation sequences in the access node. This can be accomplished e.g. using the MML language (MML, Man-Machine Language) , by means of which it is possible to manipulate e.g. the parameter file (PRFILE) of the access node.

Using means 9, the access node AN can send the local exchange LE information regarding control of call transfer, e.g. the string *14#. In this case, the information is carried one character at a time in the Digit-signal information element of a SIGNAL message.

The access node also comprises means 7, e.g. an IMSI DETACH flag, which is used to store terminal state information. The location updating procedure between the telecommunication terminal MS and the ac- cess node AN contains four procedures, which supply the register program block of the access node AN with information regarding the location and accessibility of the subscriber. These procedures are normally location updating, periodic location updating, IMSI attach and IMSI detach. When the telecommunication terminal MS is switched off, it sends IMSI DETACH information to the access node AN to tell the access node that it is not accessible. The register program block of the access node sets the IMSI DETACH flag to show that no calls terminating at the subscription in question can be connected. All calls addressed to that subscription will be rejected and no search by radio will be performed. In an embodiment, the IMSI DETACH flag is set if the terminal does not respond within a period specified for the wireless communication system. The IMSI DETACH flag is calculated by using the IMSI attach procedure or periodic location updating, where the terminal MS performs location updating in the network when the terminal MS is on.

Fig. 2a presents an example signalling arrangement in a situation where call transfer is deac- tivated. The actions carried out first are CHANNEL REQUEST, allocation, CHANNEL ACTIVATION and IMMEDIATE ASSIGN. After this, the terminal MS sends an IMSI ATTACH code in a location update frame (SABM, LOCATION UPDATE REQUEST) . The IMSI attach information is sent to the register program block, which checks the subscriber data and whether the subscriber is within the allowed mobility area. If the necessary parts of the link are in order, then the access node AN will send to the local exchange LE a message as described above concerning cancellation of call transfer. The access node AN then returns to the terminal MS a message indicating that the location update procedure has been successful .

Fig. 2b presents a signalling arrangement corresponding to a case of activation of the call transfer function. The signalling is mainly similar to that presented in the above, except that the terminal MS sends an IMSI DETACH code in the location update frame . The invention is not restricted to the examples of its embodiments described above, but many variations are possible within the scope of the inventive idea defined in the claims.

Claims

1. Method for maximising the available capacity of a telecommunication system, said telecommunication comprising a local exchange (LE) , an access node (AN) connected to the local exchange, a wireless communication system (WLL) connected to the access node and a telecommunication terminal (MS) connected to the access node (AN) via the wireless communication system, charact eri s ed in that a message indi- eating activation of call transfer is sent from the access node (AN) to the local exchange (LE) when a connection between the telecommunication terminal (MS) and the wireless communication system (WLL) is interrupted.

2. Method as defined in claim 1, char ac t eri s ed in that a message indicating deactivation of call transfer is sent from the access node (AN) to the local exchange (LE) when a connection between the terminal (MS) and the wireless communication system (WLL) is established.

3. Method as defined in claim 1 or 2, cha rac t e ri s ed in that call transfer is directed to an answering service in the local exchange (LE) .

4. Method as defined in any one of claims 1 -

3, charact eri sed in that information regarding the state of the telecommunication terminal (MS) is stored in the access node (AN) using an IMSI attach/detach procedure between the access node (AN) and the telecommunication terminal (MS) .

5. Method as defined in any one of claims 1 -

4, charact eri s ed in that a subscriber- specific number to which call transfer is to be directed is defined in the access node (AN) .

6. Method as defined in any one of claims 1 -

5, charac t eri sed in that the message indicating activation/deactivation of call transfer is transmitted from the access node (AN) to ^" the local exchange (LE) in the Digit-signal information element of a SIGNAL message.

7. Method as defined in any one of claims 1 - ╬▓, charac t eri s ed in that the wireless communication system is based on a digital mobile communication system.

8. System for maximising the available capacity of a telecommunication system, said telecommunica- tion system comprising a local exchange (LE) , an access node (AN) connected to the local exchange, a wireless communication system (WLL) connected to the access node, a telecommunication terminal (MS) connected to the access node (AN) via the wireless commu- nication system, charac t eri sed in that the access node (AN) comprises means (4) for sending to the local exchange (LE) a message indicating activation of call transfer when a connection between the telecommunication terminal (MS) and the wireless com- munication system (WLL) is interrupted.

9. System as defined in claim 8, char ac t eri sed in that the access node (AN) comprises means (5) for sending to the local exchange (LE) a message indicating deactivation of call transfer when a connection between the telecommunication terminal (MS) and the wireless communication system (WLL) is established.

10. System as defined in claim 8 or 9, characteri sed in that the access node (AN) comprises means (6) for directing call transfer to an answering service in the local exchange (LE) .

11. System as defined in any one of claims 8 - 10, charac t er i s ed in that the access node (AN) comprises means (7) for storing data indicating the state of the telecommunication terminal (MS) using an IMSI attach/detach procedure between the access node (AN) and the telecommunication terminal (MS) .

12. System as defined in any one of claims 8

- 11, charac t e ri s ed in that the access node (AN) comprises means (8) for defining a subscriber- specific number to which call transfer is to be di- rected.

13. System as defined in any one of claims 8

- 12, charac t er i s ed in that the access node (AN) comprises means (9) for sending to the local exchange (LE) a message indicating activation or deacti- vation of call transfer using the Digit-signal information element of a SIGNAL message.

14. System as defined in any one of claims 8

- 13, charac t eri s ed in that the wireless communication system is based on a digital mobile com- munication system.