KR20040067273A - Method for providing ring back tone in wireless communication system - Google Patents

Abstract

PURPOSE: A method for providing a call connection tone when transferring a call in a mobile communication system is provided to continuously provide a call connection tone registered by a destination subscriber to an origination subscriber. CONSTITUTION: When an origination subscriber attempts a call to a destination subscriber, an origination MSC(Mobile Switching Center) transmits an IAM(Initial Address Message) to a destination MSC(20)(302). The destination MSC(20) transmits an ACM(Address Complete Message) to the origination MSC(10). When the destination subscriber has registered for the first call connection tone service, the destination MSC(20) transmits the IAM to the first call connection tone server(50)(306). The first call connection tone server(50) transmits the ACM to the destination MSC(20)(308). The first call connection tone server(50) transmits an ANM(Answer Message) to the destination MSC(20)(310). The destination MSC(20) determines that a speech path has not been established between the origination subscriber and the destination subscriber(312). The destination MSC(20) transmits a call transfer number request message(Transfer To Number Request Invoke) to an HLR(Home Location Register)(40)(314). The destination MSC(20) receives a response message(Transfer To Number Request R.R.) from the HLR(40)(316). The destination MSC(20) transmits the IAM to a call transfer destination MSC(30)(318). The call transfer destination MSC(30) transmits the ACM to the destination MSC(20)(320). The call transfer destination MSC(30) determines a destination response of a call transfer destination subscriber(322). The call transfer destination MSC(30) transmits the ANM to the destination MSC(20)(324). The destination MSC(20) transmits the ANM to the origination MSC(10)(326). The call transfer destination MSC(30) transmits a release message(REL) to the first call connection tone server(50)(328). The first call connection tone server(50) transmits a release complete message(RLC) to the call transfer destination MSC(30)(330).

Description

How to provide ring back tone when transferring call in mobile communication system {METHOD FOR PROVIDING RING BACK TONE IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method for providing a ring back tone in a mobile communication system, and more particularly, to a method for providing a ring back tone registered by the caller or the called party to a caller when a caller attempts a telephone call to a called party registered with a call transfer service. .

In general, a call forwarding service is a service that connects a call to another number previously designated by the called subscriber when the called subscriber does not want to receive a call or is not connected. This call transfer service corresponds to one of various additional services provided in a mobile communication system.

Next, the concept of a ring back tone is as follows. In general, when a caller attempts a phone call in a communication network such as a general telephone network or a mobile communication system, an exchange controlling the called party hears a ringback tone to the caller uniformly according to the International Telecommunications Union-Telecommunication Standardization Sector (ITU-T) standard. Giving way is adopted. That is, the ring back tone sounds the interruption period and the tone specified by the ITU-T standard when the caller connects to the called party in the communication network.

However, since the ring back tone providing method provides the same tone uniformly, the caller cannot determine whether or not a wrong connection is made until the called party answers, and furthermore, there is a problem in that it does not provide various ring back tone replacement services that match the characteristics of the user. there was. Accordingly, mobile network operators are currently providing various ring back tones to satisfy the needs of the subscribers.

Currently, the ring back tone to you (RING2YOU) service is uniformly provided to outgoing subscribers among the 2RING services provided by SKT and CRBT (Color Ring Back Tone) and Korea Telecom Freetel (KTF). It is a service that replaces ring back tone (second second, 440Hz + 480Hz, -15 ± 5 dbm) with "tones" of various colors desired by the called subscriber, for example, melody and natural sounds. Here, the ring back tone service (CBRT and RING2YOU service: hereinafter referred to as "first ring back tone service") registered by the called party is provided until the answering party answers at the time when the called party determines the idle state.

Among the 2RING services provided by the Korea Telecom Freetel, RING2ME (RING back tone To ME: hereinafter referred to as "second ring back tone service") is not a called subscriber but instead of the existing ring back tone, the calling subscriber has a variety of colors desired by his' Well it's a service that provides. The second ring back tone service may be said to be similar to the first ring back tone service in that it provides "tones" of various colors. However, the second ring back tone service differs from the first ring back tone service in which the function is registered to the called party in that the second ring back tone service is an intelligent network originating service in which the function is registered to the calling party. In the second ring back tone service, a called subscriber responds after a relay service switching point (Toll SSP) receives an additional information information return message from a service control point (SCP). Served up to the moment.

1 is a diagram illustrating a method of providing a conventional first ring back tone service.

Referring to FIG. 1, when a called subscriber registers a first ring back tone service and a call transfer service, a flow of signals between the called subscriber and the calling subscriber will be described.

First, when the calling subscriber attempts to make a phone call to the called subscriber, in step 102, an initial address message (IAM) is sent from the calling exchange 10 to which the calling subscriber belongs to the called exchange 20 to which the called subscriber belongs. Send a connection request. In step 104, the destination exchange 20 transmits an address complete message (ACM) to the source exchange 10 to confirm the connection between the source exchange 10 and the destination exchange 20.

When the called subscriber registers the first ring back tone service, the incoming exchange 20 transmits an initial address message (IAM) to the first ring back tone server 50 in step 106 so that the first ring back tone server 50 is received. Request a connection with). Then, in step 108, the first ring back tone server 50 transmits an address completion message (ACM) to the call forwarding exchange 20 to confirm the connection between the call forwarding switch 20 and the first ring back tone server 50. do. In step 110, the first ring back tone server 50 transmits an Answer Message (ANM) to the destination exchange 20. At this time, the calling party is provided with a first ring back tone registered by the called party.

After a predetermined time elapses after the first call connection tone is provided to the calling subscriber, the called exchange 20 determines that a call path between the calling subscriber and the called subscriber is not established (incoming call failure). The destination exchange 20 releases the provided first ring back tone and performs a registered call transfer service.

In step 114, the destination exchange 20 transmits a Release Message (REL) to the first ring back tone server 50 to request the cutting of the provided first ring back tone. Then, in step 116, the first ring back tone server 50 transmits a Release Complete Message (RLC) to the destination exchanger 20 to confirm the truncation of the first ring back tone.

In step 118, the destination exchange 20 transmits a call transfer number request message to a home location register (HLR) 40, and the call forwarding number preset by the called party. Ask. Thereafter, in step 120, the destination exchange 20 receives a response message (Transfer To Number Request R.R.) for the call transfer number request from the home location register 40.

In step 122, the destination exchange 20 sends a guide message indicating that the call is transferred to the calling subscriber. Thereafter, in step 124, the destination exchange 20 transmits an initial address message (IAM) to the call transfer destination exchange 30 set in advance, thereby connecting between the destination exchange 20 and the call transfer destination 30. Ask. Then, in step 126, the call transfer destination exchange 30 transmits an address completion message (ACM) to the destination exchange 20 to confirm the connection between the destination exchange 20 and the call transfer destination exchange 30. Thereafter, when the call forwarding subscriber of the call forwarding switching center 30 registers the first ring back tone, the call forwarding switching center 30 transmits an initial address message (step S128) to the first ring back tone server 50 in step 128. IAM) to make a connection request between the call transfer destination exchange 30 and the first ring back tone server 50. Then, in step 130, the first ring back tone server 50 transmits an address completion message (ACM) to the call forwarding destination exchange 30 so as to transfer the call forwarding destination 30 and the first ring back tone server 50. Check the connections between them. Thereafter, in step 132, the first ring back tone server 50 transmits a response message (ANM) to the call transfer destination exchange 30. At this time, the call subscriber is provided with a first ring back tone registered by the call transfer destination subscriber.

After a predetermined time elapses after the first ring back tone set by the call transfer destination subscriber is provided to the calling subscriber, the call transfer destination exchange 30 determines an incoming response of the call transfer destination subscriber in step 134. If there is an incoming response, in step 136, the call transfer destination exchange 30 transmits a response message (ANM) to the destination exchange 20. In step 138, the destination exchange 20 transmits a response message (ANM) to the originating exchange 10. In this way, after the response message (ANM) is transmitted from the call transfer destination exchange to the originating exchange, the first connection sound being provided must be cut so that the call transfer destination subscriber and the originating subscriber can make a call. Therefore, in step 140, the call transfer destination exchange 30 transmits a truncation message REL to the first RBT server 50 to request the truncation of the first RBT being provided. Then, in step 142, the first ring back tone server 50 transmits a truncation completion message (RLC) to the call forwarding exchanger 30 to confirm the truncation of the first ring back tone registered by the call forwarding subscriber. At this time, the originating exchange 10 and the call transfer destination exchange 30 are in a call state.

As shown in FIG. 1, when a call transfer occurs from an outgoing subscriber to a called party to a called party, a called party receives a first ring back tone registered by the called party and a first call registered by the called party. Connection sounds are provided sequentially. According to this method, when a call transfer occurs, the first ring back tone set by the called subscriber provided to the calling subscriber is cut off in the middle. In addition, after a predetermined time elapses, the first call connection tone set by the call transfer subscriber is provided to the calling subscriber. That is, the ring back tone set by the called subscriber is not continuously provided to the calling subscriber.

However, in contrast, the called subscriber or the first ring back tone operator may wish to continuously provide the first ring back tone registered by the called subscriber to the calling subscriber even when the call transfer occurs. However, there is a problem that the present method cannot satisfy these needs.

2 is a diagram illustrating a method of providing a conventional second ring back tone service.

Referring to FIG. 2, a flow of signals between an originating subscriber who registers a second ring back tone and a called party that registers call transfer service will be described.

First, when the calling subscriber attempts to make a phone call to the called subscriber, in step 202, an initial address message (IAM) from the calling switch 10 to which the calling subscriber belongs is relayed to a Toll Service Switching Point (Toll SSP) 60. Send a connection request. Then, in step 204, the relay service exchanger 60 transmits an information analysis request message to the service control point (SCP) 70. That is, the additional information set by the calling subscriber is requested. Then, in step 206, the service control system 70 notifies the relay service exchanger 60 that the originating subscriber has set up a second ring back tone service as an analyzed information R.R. In operation 208, the relay service exchanger 60 transmits an initial address message IAM to the second ring back tone server 80 to establish a connection between the relay service switch 60 and the second ring back tone server 80. request. Thereafter, in step 210, the second ring back tone server 80 transmits an address completion message (ACM) to the relay service exchanger 60, and thus, between the second ring back tone server 80 and the relay service switch 60. Check the connection. In operation 212, the relay service exchanger 60 transmits an address completion message (ACM) to the originating exchange 10 to confirm the connection between the relay service exchanger 60 and the originating exchange 10. In operation 214, the second ring back tone server 80 transmits an Answer Message (ANM) to the relay service exchanger 60. At this time, the call subscriber is provided with a second ring back tone set by the call subscriber.

Thereafter, in step 216, the relay service exchanger 60 transmits a location request request message (Location Request Invoke) of the called subscriber to which the calling subscriber tries to make a telephone call to the home location register 40. In step 218, the home location register 40 transmits a location request response message (location request R. R) of the called subscriber to the relay service exchange 60. In step 220, the relay service exchanger 60 sends an initial address message (IAM) to the destination exchanger 20 to which the called party belongs by using the location information of the called party received from the home location register 40. Send a connection request. Then, in step 222, the destination exchange 20 transmits an address completion message (ACM) to the relay service exchange 60 to confirm the connection between the relay service exchange 60 and the destination exchange 20.

After a predetermined time elapses after transmitting the second ring back tone to the calling subscriber, in step 224, the called exchange 20 determines that a call path between the calling subscriber and the called subscriber is not established (incoming call failure). Accordingly, in step 226, the destination exchange 20 transmits a call redirection request message to the relay service exchange 60. In step 228, the relay service exchanger 60 prepares for call transfer by transmitting a call redirection request response message (Redirection Request R.R) to the destination exchange 20. Thereafter, in step 230, the relay service exchanger 60 transmits a disconnect message REL to the second ring back tone server 80 and requests the cutting of the second ring back tone being transmitted. Then, in step 232, the second ring back tone server 80 transmits the truncation completion message RLC to the relay service exchanger 60 to cut the second ring back tone. In step 234, the relay service exchanger 60 transmits a call transfer request message to the home location register 40 to request a call transfer number preset by the called party. In step 236, the relay service exchange 60 receives the call transfer response message. Then, in step 238, the relay service exchange 60 sends a guide message indicating that the call is transferred to the calling subscriber through the originating exchange 10.

In step 240, the relay service exchanger 60 transmits an initial address message (IAM) to an exchange (call transfer destination exchange: 30) to which the call transfer subscriber belongs to the call transfer destination exchange 30 and the second ring back tone. Request the connection between the server 80. Then, in step 242, the call transfer destination exchange 30 transmits an address completion message (ACM) to the relay service exchange 60 to confirm the connection between the relay service exchange 60 and the call transfer destination 30. do.

After a predetermined time elapses after the second call connection tone is sent to the calling subscriber, the call transfer destination exchange 30 determines the incoming response of the call transfer recipient in step 244. If there is the incoming response, in step 246, the call transfer destination exchange 30 transmits a response message (ANM) to the relay service exchange 60. In step 248, the relay service exchanger 60 transmits a response message (ANM) to the originating exchange 10. At this time, the originating exchange 10 and the call transfer destination exchange 30 are in a call state.

As shown in FIG. 2, when a call transfer occurs from an outgoing subscriber to a called party to a called party, a second call ring tone selected by the calling party is stopped. According to this method, when a call transfer occurs, the first ring back tone set by the called subscriber provided to the calling subscriber is cut off in the middle. In addition, when the call transfer subscriber is a first ring back tone service subscriber, a call ring tone set by the call transfer subscriber is provided to the calling subscriber.

However, in contrast, the calling subscriber or the second ring back tone operator may wish to continuously provide the second ring back tone registered by the calling subscriber even if the call transfer occurs. However, there is a problem that these needs cannot be met if the conventional method is followed.

Accordingly, an object of the present invention is to provide a method in which a ring back tone registered by a called subscriber in a mobile communication system is continuously provided to the calling subscriber.

Another object of the present invention is to provide a method in which a ring back tone registered by a calling subscriber in a mobile communication system is continuously provided to the calling subscriber.

Still another object of the present invention is to set the ring back tone even when a call attempted by an originating subscriber is diverted to a third party other than the called subscriber when the called party registers the ring back tone service and the call transfer service in the mobile communication system. The present invention provides a method that is continuously provided to the calling subscriber.

It is still another object of the present invention to set up a call forwarding service when a calling party registers a ring back tone service in a mobile communication system and sets up a call forwarding service. Even when the call subscriber is registered to provide a method for continuously providing the ring back tone to the calling subscriber.

1 is a diagram illustrating a method for providing a conventional first ring back tone service;

2 is a diagram illustrating a method of providing a conventional second ring back tone service;

3 is a diagram illustrating a method for continuously providing a ring back tone selected by a called subscriber in a mobile communication service according to the present invention;

4 is a diagram illustrating a method for continuously providing a ring back tone selected by a calling subscriber in a mobile communication service according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention is a method in which the registered ring back tone is continuously provided to the caller when the ring back tone service is registered by the calling party or the called party in the mobile communication system.

3 is a diagram illustrating a method for continuously providing a ring back tone selected by a called subscriber in a mobile communication service according to the present invention.

Referring to FIG. 3, when a called party registers a first ring back tone service and a call transfer service, a flow of signals between the called party and the calling party will be described.

First, when the calling subscriber tries to make a phone call to the called subscriber, in step 302, an initial address message (IAM) is sent from the calling exchange 10 to which the calling subscriber belongs to the called exchange 20 to which the called subscriber belongs. Send a connection request. In step 304, the destination exchange 20 transmits an address complete message (ACM) to the source exchange 10 to confirm the connection between the source exchange 10 and the destination exchange 20.

When the called subscriber registers the first ring back tone service, the called exchange 20 transmits an initial address message (IAM) to the first ring back tone server 50 in step 306 to the first ring back tone server 50. Request a connection with). Then, in step 308, the first ring back tone server 50 transmits an address completion message (ACM) to the call forwarding exchange 20 to confirm the connection between the call forwarding switch 20 and the first ring back tone server 50. do. Thereafter, in step 310, the first ring back tone server 50 transmits an Answer Message (ANM) to the destination exchange 20. At this time, the calling party is provided with a first ring back tone registered by the called party.

After a predetermined time elapses after the first call connection tone is provided to the calling subscriber, the called exchange 20 determines that a call path between the calling subscriber and the called subscriber is not established (incoming call failure). However, unlike the conventional case, when the incoming call fails, the incoming exchange 20 performs a call transfer service registered in advance without releasing the first ring back tone to the first ring back tone server 50. Therefore, at this time, the first ring back tone is continuously provided to the calling subscriber.

Thereafter, in step 314, the called exchange 20 transmits a call transfer number request message to a home location register (HLR) 40 to transfer a call previously set by the called subscriber. Ask for a number. In step 316, the destination exchange 20 receives a Transfer To Number Request R.R. message from the home location register 40.

In step 318, the destination exchanger 20 transmits an initial address message (IAM) to a preset call transfer destination exchange 30 to request a connection between the destination exchange 20 and the call transfer destination exchange 30. do. At this time, the initial address message (IAM) in step 318 includes information (first call connection tone override information) that does not establish a call with the first call connection tone server even if the call transfer destination subscriber is registered in the first call connection tone service. Included. Thereafter, in step 320, the call transfer destination exchange 30 transmits an address completion message (ACM) to the destination exchange 20 to confirm the connection between the destination exchange 20 and the call transfer destination exchange 30. .

After a predetermined time elapses after the incoming exchange 20 and the call transfer destination exchange 30 are connected, the call transfer destination exchange 30 determines an incoming response of the call transfer destination subscriber in step 322. If there is an incoming response, the call transfer destination exchange 30 transmits a response message (ANM) to the destination exchange 20 in step 324. In step 326, the destination exchanger 20 transmits a response message (ANM) to the originating exchange 10. In this way, after the response message (ANM) is transmitted from the call transfer destination exchange to the originating exchange, the first call connection tone being provided must be cut so that the call transfer destination subscriber and the originating subscriber can make a call. Therefore, in step 328, the call transfer destination exchange 30 transmits a truncation message REL to the first RBT server 50 to request the truncation of the first RBT being provided. Then, in step 330, the first ring back tone server 50 transmits a truncation completion message (RLC) to the call forwarding exchanger 30 to confirm the truncation of the first ring back tone registered by the call forwarding subscriber. At this time, the originating exchange 10 and the call transfer destination exchange 30 are in a call state.

As described above, according to the method illustrated in FIG. 3, when a call transfer occurs from the calling party to the called party, the called party to the called party, the calling party may be continuously provided with the ring back tone registered by the called party.

4 is a diagram illustrating a method for continuously providing a ring back tone selected by a calling subscriber in a mobile communication service according to the present invention.

Referring to FIG. 4, the flow of signals between an originating subscriber who registers a second ring back tone and a called subscriber who registers a call transfer service will be described.

First, when the calling subscriber attempts to make a phone call to the called subscriber, a toll service switching point (Toll SSP) 60 for switching an intelligent network service call at the calling switch 10 to which the calling subscriber belongs in step 402. Sends an initial address message (IAM) to make a connection request. Then, in step 404, the relay service exchanger 60 transmits an analyzed information invoke message to a service control system (SCP) 70 having an intelligent network service database. That is, the additional information registered by the calling subscriber is requested. In step 406, the service control system 70 notifies the relay service exchanger 60 that the originating subscriber has registered the second ring back tone service as an analyzed information R.R. In step 408, the relay service exchanger 60 transmits an initial address message (IAM) to the second ring back tone server 80 to establish a connection between the relay service switch 60 and the second ring back tone server 80. request. Thereafter, in step 410, the second ring back tone server 80 transmits an address completion message (ACM) to the relay service exchanger 60, and thus, between the second ring back tone server 80 and the relay service switch 60. Check the connection. In step 412, the relay service exchanger 60 transmits an address completion message (ACM) to the originating exchange 10 to confirm the connection between the relay service exchanger 60 and the originating exchange 10. In operation 414, the second ring back tone server 80 transmits an Answer Message (ANM) to the relay service exchanger 60. At this time, the call subscriber is provided with a second ring back tone set by the call subscriber.

Thereafter, in step 416, the relay service exchanger 60 transmits a location information request message of a called subscriber to which the calling subscriber tries to make a phone call to the home location register 40. In step 418, the home location register 40 transmits a location request response message (location request R. R) of the called subscriber to the relay service exchanger 60. In step 420, the relay service exchanger 60 sends an initial address message (IAM) to the destination exchanger 20 to which the called party belongs by using the location information of the called subscriber received from the home location register 40. Send a connection request. Thereafter, in step 422, the destination exchanger 20 transmits an address completion message (ACM) to the relay service exchanger 60 to confirm the connection between the relay service exchanger 60 and the destination exchanger 20.

After a predetermined time elapses after transmitting the second ring back tone to the calling subscriber, in step 424, the called exchange 20 determines that a call path between the calling subscriber and the called subscriber is not established (incoming call failure). Accordingly, in step 426, the destination exchange 20 transmits a Redirection Request Invoke to the relay service exchange 60. In step 428, the relay service exchanger 60 prepares for call transfer by transmitting a call redirection request response message (Redirection Request R.R) to the destination exchange 20. Unlike the related art, however, the relay service exchanger 60 transmits the second call ring tone server 80 to the second ring back tone server 80 even after transmitting the redirection request RR to the destination exchanger 20. Do not release ring tone. In addition, the relay service exchanger 60 performs a call transfer service that is registered in advance. Accordingly, the second ring back tone is continuously provided to the calling subscriber at this time.

In step 430, the relay service exchanger 60 transmits a call transfer request message to the home location register 40 to request a call transfer number preset by the called party. In step 432, the relay service exchange 60 receives the call transfer response message.

In step 434, the relay service exchanger 60 transmits an initial address message (IAM) to an exchange (call transfer destination exchange: 30) to which the call transfer subscriber belongs to the call transfer destination exchange 30 and the second ring back tone. Request the connection between the server 80. At this time, the initial address message (IAM) in step 434 includes information (first call ring tone override information) not to set up a call with the first ring back tone server even if the call transfer destination subscriber is registered in the first call ring tone service. Included. Then, in step 436, the call transfer destination exchange 30 transmits an address completion message (ACM) to the relay service exchange 60 to confirm the connection between the relay service exchange 60 and the call transfer destination 30. do.

After a predetermined time elapses after transmitting the second ring back tone to the calling subscriber, in step 438, the call forwarding destination exchange 30 determines an incoming response of the call forwarding called party. If there is an incoming response, in step 440, the call transfer destination exchange 30 transmits a response message (ANM) to the relay service exchange 60. In step 442, the relay service exchanger 60 transmits a response message (ANM) to the originating exchange 10. In this way, after the response message (ANM) is transmitted from the call transfer destination exchange to the originating exchange, the second call connection tone being provided must be cut so that the call transfer destination subscriber and the originating subscriber can make a call. Therefore, in step 444, the relay service exchanger 60 transmits a disconnect message REL to the second ring back tone server 80 to request the cutting of the provided second ring back tone. Then, in step 446, the second ring back tone server 80 transmits a truncation completion message (RLC) to the relay service switch 60 to confirm the truncation of the second ring back tone registered by the calling subscriber. At this time, the originating exchange 10 and the call transfer destination exchange 30 are in a call state.

As described above, according to the method illustrated in FIG. 4, when a call transfer occurs from an originating subscriber to a called party to a third called party, the calling party may be provided with a second ring back tone selected by the calling party. .

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention has an advantage in that the calling subscriber or the called subscriber can continuously receive the ring back tone registered by the calling subscriber or the called subscriber in the mobile communication system. Furthermore, the operator of the ring back tone operator can satisfy the needs of the advertiser even more because the commercials can be continuously sent out in case of providing a discount to the calling party or the called party according to the business policy. have. In addition, since the call setup procedure between the call transfer destination exchange and the RBT server is not required, the present invention has an advantage of preventing waste of circuits and resources.

Claims (2)

In a mobile communication system comprising a home location register having call transfer information and a ring back tone server that provides a preset ring back tone for each mobile terminal, comprising: Providing a ring back tone set to the called terminal to the calling terminal; When the call transfer request, the destination exchange to obtain the call transfer information from the home location register, The destination exchange includes performing a call transfer according to the call transfer information and providing override information to the call transfer destination exchange to provide the provided ring back tone until the call is connected. How to provide a ring back tone when transferring a call. A home location register having call switching information, a ring back tone server providing preset ring back tones for each mobile terminal, a relay service exchange for switching intelligent network service calls, and a service control system having an intelligent network service database; In the mobile communication system, a method for providing a ring back tone when transferring a call, Providing a ring back tone set to the calling terminal to the calling terminal; When the call transfer request is made, the relay service exchanger obtaining additional information from the service control system, and obtaining call transfer information from the home location register; In the mobile communication system, the relay service exchange includes performing a call transfer according to the call transfer information and providing override information to the call transfer destination exchange to provide the provided ring back tone until the call is connected. To provide ring back tone when transferring a call.