WO2007091787A1

WO2007091787A1 - Method, system and mobile communication terminal for providing alternative multimedia ring back tone service

Info

Publication number: WO2007091787A1
Application number: PCT/KR2007/000308
Authority: WO
Inventors: Seongsoo Park; Donghahk Lee; Bumsoo Shin; Kimun Kim; Seongkeun Kim; Sehyun Oh; Bongju Kang; Joonggunn Park; Daesic Woo
Original assignee: SK Telecom Co Ltd
Current assignee: SK Telecom Co Ltd
Priority date: 2006-02-07
Filing date: 2007-01-19
Publication date: 2007-08-16
Anticipated expiration: 2008-08-07
Also published as: TWI369120B; TW200742397A

Abstract

Disclosed is a method, a system and a mobile communication terminal for providing a ringback tone alternative (hereinafter referred to as 'RBT-alternative') service, and more particularly to a method, a system and a mobile communication terminal for providing a RBT-alternative service by bit-streaming a specific preset tone as a replacement for a regular RBT in real time, in which, in order to adaptively apply various audio codecs associated with service types and thus provide a RBT-alternative having an improved quality, a signaling message controlling the mobile communication terminal to switch over its basic codec to an audio codec is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to reproduce a sound source by using the audio codec when the sound source using the audio codec is set as RBT- alternative, and a signaling message controlling the mobile communication terminal to switch over its basic codec to a voice codec again is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to perform voice communication by using the voice codec when the RBT-alternative service is terminated.

Description

METHOD, SYSTEM AND MOBILE COMMUNICATION TERMINAL FOR PROVIDING ALTERNATIVE MULTIMEDIA RING BACK TONE SERVICE

Technical Field

The present invention relates to a method, a system and a mobile communication terminal for providing a ringback tone alternative (hereinafter referred to as "RBT-alternative") service, and more particularly to a method, a system and a mobile communication terminal for providing a RBT- alternative service by bit-streaming a specific preset tone as a replacement for a regular RBT in real time, in which, in order to adaptively apply various audio codecs associated with service types and thus provide a RBT-alternative having ^■ an improved quality, a signaling message controlling the mobile communication terminal to switch over its basic codec to an audio codec is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to reproduce a sound source by using the audio codec when the sound source using the audio codec is set as RBT- alternative, and a signaling message controlling the mobile communication terminal to switch over its basic codec to a voice codec again is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to perform voice communication by using the voice codec when the RBT-alternative service is terminated.

Further, the present invention relates to a method, a system and a mobile communication terminal for providing an RBT- alternative service using an audio codec, in substitute for a common RBT-alternative service using a voice codec, by dividing a service section into audio and voice intervals, in which, in order to provide an calling mobile communication terminal with an additional voice service when a called mobile communication terminal does not respond to paging, a bypass mode for processing the audio codec is released, the calling mobile communication terminal is caused to set the voice codec as its basic codec, and then the additional voice service is provided to the calling mobile terminal.

Background Art

With the rapid development of computer, electronic and communication technologies, various wireless communication services are now provided over wireless communication networks. Among the services, a voice communication service is regarded as basic, which enables mobile communication subscribers to wirelessly perform mutual voice communication by using their own mobile communication terminals, regardless of time and place. Further, a wireless data service has recently emerged, which enables mobile communication subscribers on the move to carry out data communication over wireless communication networks with no spatial restrictions.

Therefore, mobile communication subscribers cannot only communicate with desired communication partners at any time and place by using the voice communication service, but also be provided with a variety of information necessary for their daily lives, such as news, weather, sports, stocks, exchange rates and traffic reports, in various forms including texts, voices and images, by using the wireless data service even on the move. In recent years, a so-called ringback tone (RBT) alternative service for giving a user of the calling mobile communication terminal (i.e., the calling party) various kinds of tunes or voices, which are specified as a call connection tone (i.e., ringback tone) by the called or calling party, has been developed and occupied the attention of mobile communication subscribers. This service is a service for providing an alterative tone specified by the called or calling party to the calling party' s mobile communication terminal, and makes it possible to use various kinds of tunes (e.g., latest Korean songs or foreign pop songs), birds singings, water sounds or even pre-recorded voices of the called or calling party, in substitute for conventional ringback tones, most of which are simple mechanical sounds (e.g., "ring-ring" sound) generated during call connection and heard by the calling party. By virtue of the RBT-alternative service, the calling party- can have the pleasure of hearing sounds from various sound sources, instead of hearing monotonous mechanical ringback tones.

In general, the RBT-alternative service is available to mobile communication terminals in a mobile communication network implemented by a mobile communication system, such as CDMA (Code Division Multiple Access) 2000 system or WCDMA (Wideband CDMA) system.

In providing such a RBT-alternative service, a mobile communication system usually uses a voice codec with a variable transfer rate, such as an EVRAC (Enhanced Variable Rate Codec) or an AMR (Adaptive Multiple Rate) codec, in order to improve the efficiency of voice communication and optimize the wireless channel. The voice codec is designed to maximize channel efficiency such that it can detect speech and silent intervals, create a suitable codebook and provide a voice service at a minimum bit transfer rate through mapping.

However, such a voice codec with a variable transfer rate, including the EVRC or AMR codec, applies the same logic even for a sound source having few silent intervals (e.g., music) and encodes the sound source by using a voice codebook provided therein. If a sound source, for example, music, is mapped onto a voice codebook and coded, the sound source is encoded pursuant to human voice patterns, which means that various patterns appearing in the music are ignored during the encoding process and consequently the resultant coding errors degrade the quality of music. In other words, the voice codec with a variable transfer rate is not suitable for encoding audio-type sound sources, such as music. In order to solve this problem of the voice codec with a variable transfer rate, an attempt has been proposed and widely adopted in the industry to correct a sound source. More specially, a content provider, who provides a sound source, extracts the sound source from high-quality music, for example, music with CD (Compact Disk) -level quality, modifies the sound source in such a manner as to be adapted to a voice codec such as EVRAC, and encodes the sound source with the voice codec, thereby minimizing damages to the sound source that may result from the voice codec. This approach relies on preprocessing under consideration of the characteristics of the EVRAC or manual works of sound technicians. Such preprocessing or manual works may supplement the quality of an EVRAC-based RBT-alternative service, comparable to the level of voice quality, but there is still a problem in that they have a limitation on improving the quality of the RBT-alternative service up to a high level.

Meanwhile, it is most efficient to use an audio codec for encoding a sound source and providing an alterative RBT. However, this requires several technical issues to be solved in advance.

Firstly, it must be possible to use an audio codec adapted to the voice channel of a mobile communication terminal. For example, a voice channel of 8kbps is used in the case of the CDMA 2000 system, and a voice channel of 12.3 kbps is used in the case of the GSM (Global System for Mobile Communications) . As such, the audio codec must be adapted to the transfer rate of the voice channel, so as to provide a RBT-alternative service with improved quality. Secondly, a service section needs to be divided into a RBT- alternative service interval and a voice communication interval. That is, an audio codec must be applied in the former interval and a voice codec must be applied in the latter interval so that a sound source transmitted to a mobile communication terminal can be decoded with a corresponding codec for playback.

Thirdly, it must be possible to fabricate and provide a sound source suitable for an audio codec applied in a mobile communication terminal and a mobile communication network.

In summary, in order to provide a high-quality RBT- alternative service, it is essential to divide a service section into the RBT-alternative service interval and the voice communication interval, and adaptively apply audio and voice codecs to those intervals, respectively, for application to a sound source. In other words, a codec to be provided to a mobile communication network and a mobile communication terminal must be adaptively selected and applied according to the service type, that is, according to the RBT-alternative service or the voice communication service. However, no technology has yet been developed to provide a RBT-alternative service in this way. Further, additional consideration must be given to a switchover of an audio codec and a voice codec when an additional voice service is to be provided because the called party does not answer a call.

Disclosure of the Invention Accordingly, the present invention has been made to solve at least the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method, a system and a mobile communication terminal for providing a RBT-alternative service by bit-streaming a specific preset tone as a replacement for a regular RBT in real time, in which, in order to adaptively apply various audio codecs associated with service types and thus provide a RBT-alternative having an improved quality, a signaling message controlling the mobile communication terminal to switch over its basic codec to an audio codec is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to reproduce a sound source by using the audio codec when the sound source using the audio codec is set as RBT-alternative, and a signaling message controlling the mobile communication terminal to switch over its basic codec to a voice codec again is transmitted to the mobile communication terminal to thereby enable the mobile communication terminal to perform voice communication by using the voice codec when the RBT-alternative service is terminated.

A further object of the present invention is to provide the present invention relates to a method, a system and a mobile communication terminal for providing an RBT-alternative service using an audio codec, in substitute for a common RBT-alternative service using a voice codec, by dividing a service section into audio and voice intervals, in which, in order to provide an calling mobile communication terminal with an additional voice service when a called mobile communication terminal does not respond to paging, a bypass mode for processing the audio codec is released, the calling mobile communication terminal is caused to set the voice codec as its basic codec, and then the additional voice service is provided to the calling mobile terminal.

In order to accomplish this object, in accordance with an aspect of the present invention, there is provided a method for providing a ringback tone alternative ("RBT-alternative", hereinafter) to a calling mobile communication terminal requesting communication with a called mobile communication terminal in a mobile communication network, the method comprising the steps of: (a) receiving a request for the communication from the calling mobile communication terminal, and establishing a communication path; (b) checking if the called mobile communication terminal is eligible to a RBT- alternative service; (c) checking a sound source of the RBT- alternative associated with the called mobile communication terminal when it is determined at step (a) that the called mobile communication terminal is eligible to the RBT- alternative service; (d) checking if the sound source is an audio codec sound source encoded with an audio codec; (e) controlling the calling mobile communication terminal to switch over a basic codec thereof to the audio codec when it is determined at step (d) that the sound source is the audio codec sound source; and (f) transmitting the audio codec sound source to the calling mobile communication terminal in a bypass mode without passing through a vocoder. In accordance with another aspect of the present invention, there is provided a system for providing a ringback tone alternative ("RBT-alternative", hereinafter) to a calling mobile communication terminal, which includes the calling mobile communication terminal requesting voice communication, a called mobile communication terminal receiving a request for the voice communication, and a sound source provider for providing a sound source of the RBT-alternative, the system comprising: a mobile communication network for establishing a communication path with the calling mobile communication terminal, checking if the called mobile communication terminal is eligible to a RBT-alternative service, analyzing the sound source of the RBT-alternative associated with the called mobile communication terminal to check if the sound source is an audio codec sound source encoded with an audio codec, controlling the calling mobile communication terminal to switch over a basic codec thereof to the audio codec, and transmitting the audio codec sound source to the calling mobile communication terminal when receiving the request for the voice communication from the calling mobile communication terminal.

In accordance with yet another aspect of the present invention, there is provided a mobile communication terminal for providing a ringback tone alternative ("RBT-alternative", hereinafter) , the mobile communication terminal being provided with a mobile communication service and a RBT- alternative service from a mobile communication network, and requesting voice communication with a called mobile communication terminal, which receives a request for the voice communication, the mobile communication terminal comprising: an antenna for receiving a signaling message as an RF signal from the mobile communication network and transferring a received signaling message; an RF signal processor unit for demodulating the RF signal and transferring a demodulated signal; a baseband converter unit for receiving the demodulated signal, converting the demodulated signal into a baseband signal, performing analog-to-digital conversion for the baseband signal, and transferring a converted digital signal; a digital signal processor unit for setting or switching over a basic codec to either a voice codec or an audio codec, the digital signal processor unit including at least one of the voice codec and the audio codec, each of which is implemented by software or hardware; a memory unit for storing a codec switch-over program by which one of the voice codec and the audio codec is set as the basic codec; and a controller unit for receiving the digital signal from the baseband converter unit, analyzing the signaling message, and controlling the digital signal processor unit to set one of the voice codec and the audio codec as the basic codec by executing the codec switch-over program when the basic codec is to be switched.

In accordance with still yet another aspect of the present invention, there is provided a method for providing a ringback tone alternative ("RBT-alternative", hereinafter) to a calling mobile communication terminal requesting communication with a called mobile communication terminal in a mobile communication network, the method comprising the steps of: (a) receiving a request for the communication from the calling mobile communication terminal, and paging the called mobile communication terminal; (b) checking if the called mobile communication terminal is eligible to a RBT- alternative service, controlling the calling mobile communication terminal to switch over a basic codec thereof to an audio codec, and transmitting an audio codec sound source encoded with the audio codec to the calling mobile communication terminal in a bypass mode; (c) checking if the called mobile communication terminal responds to the paging of step (a) ; (d) controlling the calling mobile communication terminal to switch over the basic codec thereof to a voice codec when a result of the checking at step (c) shows that the called mobile communication terminal does not respond to the paging; and (e) canceling the bypass mode, and transmitting a voice message for the additional voice service to the calling mobile communication terminal. In accordance with still yet another aspect of the present invention, there is provided A system for providing a ringback tone alternative (""RBT-alternative", hereinafter) to a calling mobile communication terminal, which includes the calling mobile communication terminal requesting voice communication, a called mobile communication terminal receiving a request for the voice communication, and a sound source provider for providing a sound source of the RBT- alternative, the system comprising: a mobile communication network for controlling the calling mobile communication terminal to switch over a basic codec thereof to an audio codec and transmitting a sound source encoded with the audio codec, as the sound source to the calling mobile communication terminal upon receiving the request for the voice communication from the calling mobile communication terminal, while controlling the calling mobile communication terminal to switch over the basic codec thereof to a voice codec and transmitting a voice message for a supplementary voice service to the calling mobile communication terminal if called mobile communication terminal do not respond to the request for the voice communication for a prescribed time interval after paging the called mobile communication terminal.

In accordance with still yet another aspect of the present invention, there is provided a mobile communication terminal capable of using a voice communication service, a supplementary voice service and a ringback tone alternative ("RBT-alternative", hereinafter) service, provided a mobile communication network, the mobile communication terminal requesting voice communication with a called mobile communication terminal which receives a request for the voice communication, by using the mobile communication network, the mobile communication terminal comprising: an antenna for receiving a signaling message as an RF signal from the mobile communication network and transferring the received signaling message; an RF signal processor unit for demodulating the RF signal and transferring the demodulated signal; a baseband converter unit for receiving the demodulated signal, converting the demodulated signal into a baseband signal, performing analog-to-digital conversion processing for the baseband signal, and transferring a converted digital signal; a digital signal processor unit for setting or switching over a basic codec to either a voice codec or an audio codec, the digital signal processor unit including at least one of the voice codec and the audio codec, each of which is implemented by software or hardware; a memory unit for storing a codec switch-over program by which one of the voice codec and the audio codec is set as the basic codec; and a controller unit for receiving the digital signal, analyzing the signaling message, controlling the digital signal processor unit to set either the voice codec or the audio codec as the basic codec by executing the codec switch-over program when the basic codec is to be switched over, and analyzing a data format of an audio codec sound source encoded with the audio codec or a voice message encoded with the voice codec and detecting a pattern thereof to set a codec corresponding to the detected pattern as the basic codec and reproduce the audio codec sound source or the voice message by using the basic codec when receiving the audio codec sound source or the voice message from the mobile communication network. Brief Description of the Drawings

The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a structural block diagram schematically showing a system for providing a RBT-alternative service by using a switch-over to an audio codec in accordance with a first preferred embodiment of the present invention; FIG. 2 is a structural block diagram schematically showing the internal construction of a mobile communication terminal for providing a RBT-alternative service by using a switch- over to an audio codec in accordance with the first embodiment of the present invention;

FIG. 3 is a flowchart for explaining a method of providing a RBT-alternative service by using a switch-over to an audio codec in accordance with the first embodiment of the present invention;

FIGS. 4a and 4b are illustrative views, each showing the first half and the second half of a detailed explanation on the method of providing a RBT-alternative service by using a switch-over to an audio codec in accordance with the first embodiment of the present invention;

FIG. 5 is a structural block diagram schematically showing a system for providing an additional voice service in a RBT- alternative service in accordance with a second preferred embodiment of the present invention;

FIG. 6 is a structural block diagram schematically showing a mobile communication terminal for providing an additional voice service in a RBT-alternative service in accordance with the second embodiment of the present invention; FIG. 7 is a flowchart showing the control of a receiver-side mobile communication exchange for explaining a method of providing an additional voice service in a RBT-alternative service in accordance with the second embodiment of the present invention; FIGS. 8a and 8b are illustrative view, each showing the first half and the second half of a detailed explanation on the method of providing an additional voice service in a RBT-alternative service in accordance with the second embodiment of the present invention; FIG. 9 is an illustrative view for explaining a signaling message in accordance with a preferred embodiment of the present invention; and

FIGS, 10a and 10b are illustrative views, each used for explaining the identification of a multiple audio codec in accordance with a preferred embodiment of the present invention.

Best Mode for Carrying Out the Invention

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and so repetition of the description on the same or similar components will be omitted. Further, a detailed description of known functions and configurations incorporated herein is omitted to avoid making the subject matter of the present invention unclear. It will be assumed in the following description of first and second preferred embodiments of the present invention that CDMA 2000 system is used as a mobile communication system for implementing a mobile communication network. However, this assumption is for the convenience of description only, and the technical idea of the present invention is applicable to other types of synchronous or asynchronous mobile communication systems without being limited to that assumption. That is, so long as, when a RBT-alternative as a substitute for a regular RBT is provided to a wireless terminal in a wireless network, the wireless network controls the wireless terminal to reproduce the sound source of a RBT-alternative after changing a codec for the sound source to a voice codec or an audio codec, and provides such a sound source, the wireless network may fall within the technical idea of the present invention.

Further, so long as, when a RBT-alternative as a substitute for a regular RBT is provided to a wireless terminal in a wireless network, the wireless network controls the wireless terminal to reproduce the sound source of a RBT-alternative after changing a codec for the sound source to a voice codec or an audio codec, provides such a sound source, and controls the called wireless terminal to switch over the voice or audio codec again if it does not answer an incoming call, the wireless network may fall within the technical idea of the present invention.

FIG. 1 is a structural block diagram schematically showing a system for providing a RBT-alternative service by using a switch-over to an audio codec according to a first preferred embodiment of the present invention.

The system for providing a RBT-alternative by using a switch-over to an audio codec according to the first embodiment of the present invention includes a calling mobile communication terminal 110, a called mobile communication terminal 112, a mobile communication network 120 and a sound source provider 190.

The calling mobile communication terminal 110 and the called mobile communication terminal 112 are mobile communication terminals performing voice communication with each other over the mobile communication network 120 or with common landline phones over a public switched telephone network

(not shown) . Here, examples of the mobile communication terminals include PDAs (Personal Digital Assistants) , cellular phones, PCS (Personal Communication Service) phones, handheld PCs, GSM (Global System for Mobile) phones, WCDMA

(Wideband CDMA) phones, CDMA-2000 phones, or MBS (Mobile

Broadband System) phones which are expected to be used in the 4^th generation system currently under consideration.

According to the first embodiment of the present invention, the calling mobile communication terminal 110 transmits a request for voice communication to the called mobile communication terminal 112 of the called party over the mobile communication network 120, according to the calling party's key operation. When the called party has joined a RBT-alternative service with regard to the called mobile communication terminal 112, the calling mobile communication terminal 110 receives a RBT-alternative from the mobile communication network 120 and outputs it to the calling • party.

More specially, let us suppose that the calling mobile communication terminal 110 transmits a request for voice communication to the called mobile communication terminal 112 over the mobile communication network 120 and then receives a RBT-alternative from the mobile communication network 120. When the sound source of the RBT-alternative is encoded with an audio codec, the calling mobile communication terminal 110 switches over its basic codec to the audio codec upon receiving a Data Burst Message (DBM) as a signaling message requesting such change from the mobile communication network 120. Then, the calling mobile communication terminal 110 decodes the sound source received from the mobile communication network 120 with the audio codec and reproduces it.

Upon receiving a data burst message as a signaling message requesting the calling mobile communication terminal 110 to switch over the basic codec to a voice codec from the mobile communication network 120, the calling mobile communication terminal 110 according to the first embodiment of the present invention carries out the switch-over and then voice communication by using the changed voice codec. The calling mobile communication terminal 110 will be described below in detail with reference to FIG. 2.

The called mobile communication terminal 112 according to the first embodiment of the present invention is adapted to receive a communication request from the calling mobile communication terminal 110 over the mobile communication network 120 and respond to a paging request from the mobile communication network 120.

The mobile communication network 120 according to the first embodiment of the present invention includes a caller-side wireless base station 130, a receiver-side wireless base station 132, an caller-side mobile communication exchange 140, a receiver-side mobile communication exchange 142, a Common Channel Signaling Network (hereinafter referred to as "CCSN") 150, an Home Location Register (hereinafter referred to as "HLR") 160, a gateway 170 and a sound source providing device 180, and provides the calling and called mobile communication terminals 110 and 112 with a voice communication service and a RBT-alternative service. Here, each of the calling and receiver-side wireless base stations 130 and 132 includes a Base station Transmission System (hereinafter referred to as "BTS") and a Base Station Controller (hereinafter referred to as "BSC") . According to the first embodiment of the present invention, upon receiving a speech call request from the calling mobile communication terminal 110, the caller-side wireless base station 130 establishes a speech path between the calling mobile communication terminal 110 and the caller-side mobile communication exchange 140. Further, upon receiving a bypass setup message, which is a transcoder control request message requesting a switchover to a bypass mode, from the caller-side mobile communication exchange 140, the wireless base station 130 switches to the bypass mode and relays an audio codec sound source, which is received from the caller- side mobile communication exchange 140, to the calling mobile communication terminal 110 in its entirety without passing through a vocoder.

Upon receiving a bypass release message, which is a transcoder control request message requesting bypass mode release, from the caller-side mobile communication exchange 140, the caller-side wireless base station 130 releases the bypass mode, vocodes a voice call for voice communication by using the vocoder, and then relays the vocoded voice call to the calling mobile communication terminal 110. The calling and receiver-side mobile communication exchanges 140, 142 are adapted to process basic and additional services, subscribers' originating and incoming calls, and location registration and handoff procedures, as well as interwork with other networks. Specially, each of the calling and receiver-side mobile communication exchanges 140, 142 uses the HLR 160 to detect information on the calling and called parties, who are mobile communication subscribers of the calling and called mobile communication terminals 110, 112, respectively, as well as location information and status information of the respective mobile communication terminals .

According to the first embodiment of the present invention, if the caller-side mobile communication exchange 140 receives a speech call request for voice communication from the calling mobile communication terminal 110, and a speech path between the caller-side mobile communication exchange 140 and the calling mobile communication terminal 110 is established, the caller-side mobile communication exchange 140 conducts ISUP call setup with the receiver-side mobile communication exchange 142. Further, if receiving information on an alterative RBT, information on a bypass mode and control information from the sound source providing device 180, the caller-side mobile communication exchange 140 checks if the RBT-alternative is a sound source encoded with an audio codec, that is, an audio codec sound source, and controls the caller-side wireless base station 130 to switch to the bypass mode. After the caller-side mobile communication exchange 140 controls the caller-side wireless base station 130 to switch to the bypass mode, it controls the calling mobile communication terminal 110 to switch over its basic codec to an audio codec by transmitting a signaling message to the calling mobile communication terminal 110 via the caller- side wireless base station 130, and transmits an audio codec sound source to the calling mobile communication terminal 110 if the audio codec sound source is transferred from the sound source providing device 180. If the receiver-side mobile communication exchange 142 notifies the caller-side mobile communication exchange 140 that the called mobile communication terminal 112 responds to paging, the caller-side mobile communication exchange 140 controls the caller-side wireless base station 130 to release the bypass mode, controls the calling mobile communication terminal 110 to switch over its basic codec to a voice codec, and transmits alert information, which notifies the calling mobile communication terminal 110 that the called mobile communication terminal 112 responds to paging, to the calling mobile communication terminal 110 so that the calling mobile communication terminal 110 carries out voice communication with the called mobile communication terminal 112. According to the first embodiment of the present invention, if the caller-side mobile communication exchange 140 notifies the receiver-side mobile communication exchange 142 that there is a voice communication request for the called mobile communication terminal 112, the receiver-side mobile communication exchange 142 conducts ISUP call setup with the caller-side mobile communication exchange 140, pages the called mobile communication terminal 112, uses the HLR 160 to check if the called mobile communication terminal 112 has joined a RBT-alternative service, and then conducts ISUP call setup with the sound source providing device 180 to transmit an audio codec sound source, which is received from the sound source providing device 180, to the caller-side mobile communication exchange 140. When the called mobile communication terminal 112 responds to the voice communication request, the receiver-side mobile communication exchange 142 notifies the caller-side mobile communication exchange 140 of this, relays the audio codec sound source transmitted from the sound source providing device 180 to caller-side mobile communication exchange 140, and relays voice communication between the calling mobile communication terminal 110 and the called mobile communication terminal 112.

The CCSN 150 refers to a network which consists of signaling points and signaling links and provides a common channel signaling scheme standardized by ITU-T No. 7 scheme. As used herein, the common channel signaling scheme refers to a signaling scheme for separating the signaling information and network management information into voice and data and transmitting the separated voice and data over a separate channel, which is used in common for signal transmission. The HLR 160 is a database storing service profiles related to subscription information of mobile communication subscribers. Specially, the HLR 160 identifies the registration of respective mobile communication terminals, deletes the registration, and locates them. In addition, the HLR 160 stores the phone number of each mobile communication subscriber using each mobile communication terminal, MIN (Mobile Identification Number) , ESN (Electronic Serial Number) , information on the service type (e.g., whether or not a subscriber has joined a RBT- alternative service) , information necessary for routing to the sound source providing device 180, etc. The gateway 170 is a device for interconnecting a plurality of homogeneous or heterogeneous communication networks so as to exchange information among them. Specially, the gateway 170 interconnects a plurality of communication networks or devices, which are not compatible with one another because their protocols are different, and converts their protocols into those compatible with one another, thereby relaying information such that they exchange information with one another.

The sound source providing device 180 is an intelligent network IP for storing RBT-alternative sound sources. At a request for a RBT-alternative sound source, the sound source providing device 180 transmits a sound source authentication request to a sound source provider control server 194, and when the authentication has been successful, transmits the RBT-alternative sound source to the receiver-side mobile communication exchange 142. Further, if a web server 198 transfers a RBT-alternative sound to the sound source providing device 180, the sound source providing device 180 stores and manages it. According to the first embodiment of the present invention, the sound source providing device 180 conducts ISUP call setup with the receiver-side mobile communication exchange 142, checks a RBT-alternative sound source set for the called mobile communication terminal 112 to create information on a RBT-alternative, information on a bypass mode and control information, and then transmits the created information to the caller-side mobile communication exchange 140. Further, the sound source providing device 180 transmits an audio codec sound source to the receiver-side mobile communication exchange 142.

Specially, the sound source providing device 180 checks if the RBT-alternative sound source set for the called mobile communication terminal 112 is an audio codec sound source encoded with an audio codec, and when the RBT-alternative sound source is an audio codec sound source, creates information on a RBT-alternative, information on a bypass mode and control information. The sound source provider 190 includes the Internet 192, a sound source provider control server 194, a subscriber DB 196 and a web server 198. The sound source provider 190 creates or receives a RBT-alternative sound source, encodes it with an audio codec or a voice codec, and provides the sound source providing device 180 with it. The Internet 192 refers to a global open-type computer network architecture providing TCP/IP protocol and various services existing on its upper layers, in particular, HTTP

(Hypertext Transfer Protocol), Telnet, FTP (File Transfer

Protocol), DNS (Domain Name Server), SMTP (Simple Mail Transfer Protocol), SNTP (Simple Network Management Protocol) , NFS (Network File Service) and NIS (Network Information Service) .

The sound source provider control server 194 is adapted to control the provision of a RBT-alternative service. Specially, the sound source provider control server 194 authenticates sound sources by using information on the calling and called parties of the calling and called mobile communication terminals 110, 112, call request time, etc. The subscriber DB 196 is adapted to store and manage information on subscribers having joined a RBT-alternative service, and provides subscriber information necessary for the sound source provider control server 194 to authenticate sound sources. The web server 198 is connected to the sound source providing device 180 and the sound source provider control server 194 over the Internet 192. The web server 198 adds RBT-alternative to the sound source providing device 180, and provides a user terminal (e.g., computer) or a mobile communication terminal with a user interface through which the sound source provider control server 194 is caused to set and change information necessary to specify a sound source, i.e., information on the calling party, calling party group, calling time, etc, as well as a sound source code corresponding to that information. To this end, the web server 198 provides the user terminal or mobile communication terminal with a web page or WAP page. FIG. 2 is a structural block diagram schematically showing the internal construction of a mobile communication terminal for providing a RBT-alternative service by using a switchover to an audio codec according to the first embodiment of the present invention.

The mobile communication terminal for providing a RBT- alternative service by using a switch over to an audio codec according to the first embodiment of the present invention, which implements the calling mobile communication terminal 110 in FIG. 1, includes a memory unit 210, a controller unit 220, a DSP (Digital Signal processor) unit 230, a baseband converter unit 240, a speaker 250, an RF (Radio Frequency) signal processor unit 260 and an antenna 270. The mobile communication terminal decodes and reproduces an audio codec sound source by using an audio codec. Hereinafter, the mobile communication terminal is referred to as the calling mobile communication terminal 110 so as to standardize terms by those mentioned in FIG. 1.

The memory unit 210 stores a plurality of applications, which drive the calling mobile communication terminal 110, conduct voice and data communication and carry out various additional functions, protocol software processing messages transmitted to and received from the mobile communication network 120, etc. To this end, the memory unit 210 includes a non-volatile memory, i.e., an EEPROM (Electrically Erasable and Programmable Read Only Memory) capable of modifying contents in units of bytes, a flash memory capable of modifying contents in units of blocks, and a SDRAM (Synchronous Dynamic Random Access Memory) .

The memory unit 210 according to the first embodiment of the present invention stores a codec switch-over program from the mobile communication network 120. The codec switch-over program is software for interchanging a voice codec and an audio codec as a basic codec under the control of the mobile communication network 120, that is, under the control of the caller-side mobile communication exchange 140.

The controller unit 220 controls the overall operation of the calling mobile communication terminal 110. Further, the controller unit 220 executes various applications stored in the memory unit 210 so as to carry out functions for conducting voice and data communications, as well as additional functions.

Upon receiving a codec switch-over request from the mobile communication network 120, the controller unit 220 according to the first embodiment of the present invention executes the codec switch-over program to interchange a voice codec and an audio codec of the digital signal processor unit 230 as a basic codec. That is, the controller unit 220 analyzes a signaling message received from the mobile communication network 120 to check whether it has been requested to switch over the basic codec to the voice codec or the audio codec, and then controls the digital signal processor unit 230 to switch over the basic codec to the corresponding codec. The digital signal processor unit 230 encodes or decodes a voice signal, performs an equalizer function so as to remove multi-path noise, conducts sound data processing function, and so forth. Further, the digital signal processor unit 230 exchanges voice data with the baseband converter unit 240 and receives digital data from the baseband converter unit 240.

The digital signal processor unit 230 according to a preferred embodiment of the present invention is provided with software-implemented voice and audio codecs or hardware-implemented voice and audio codecs, so as to decode voice or a sound source with a codec that is basically set, i.e., a basic codec. In other words, the digital signal processor unit 230 is provided with both a voice codec and an audio codec and sets a specific codec of them as a basic codec. The digital signal processor unit 230 decodes voice or a sound source with the set basic codec and transfers the decoded voice or sound source.

Accordingly, the digital signal processor unit 230 according to the first embodiment of the present invention decodes voice with the voice codec and decodes a sound source with the audio codec, so that it can decode the voice or sound source into a high-quality voice or sound source, that is, a high-quality RBT-alternative.

The baseband converter unit 240 converts signals transmitted/received among the RF signal processor unit 260, the digital signal processor unit 230 and the speaker 250 into baseband signals, and conducts functions of digital-to- analog conversion processing, analog-to-digital conversion processing, etc. The speaker 250 outputs a voice signal, output from the baseband converter unit 240, as an audible sound. The RF signal processor unit 260 controls the power or gain of a transmission signal received from the baseband converter unit 240, demodulates and amplifies an RF signal received from the antenna 270, and modulates the transmission signal, received from the baseband converter unit 240, to transfer the modulated signal to the antenna 270. The antenna 270 transmits/receives an RF signal from/into air. FIG. 3 is a flowchart for explaining a method of providing a RBT-alternative service by using a switch-over to an audio codec according to the first embodiment of the present invention.

If the calling party inputs the phone number of the called mobile communication terminal 112 by operating keys of the calling mobile communication terminal 110 and selects a call button, in order to carry out voice communication with the called party, the calling mobile communication terminal 110 transmits a speech call request to the mobile communication network 120. In other words, the mobile communication network 120 receives a speech call request from the calling mobile communication terminal 110 and connects a speech path with the calling mobile communication terminal 110 (S310) . After the mobile communication network 120 connects the speech path with the calling mobile communication terminal 110, it checks service subscription information for the called mobile communication terminal 112 (S320) and checks if the called mobile communication terminal 112 has joined a RBT-alternative service (S330) . When a result of the checking in step S330 shows that the called mobile communication terminal 112 has not joined a RBT-alternative service, the mobile communication network 120 provides the calling mobile communication terminal 110 with a regular RBT according to a conventional procedure (S332) . The conventional procedure of providing a regular RBT is well known in the art, so a detailed description thereof will be omitted.

On the contrary, when a result of the checking in step S330 shows that the called mobile communication terminal 112 has joined a RBT-alternative service, the mobile communication network 120 checks the type of a RBT-alternative set for the called mobile communication terminal 112 (S340) and checks if the RBT-alternative set for the called mobile communication terminal 112 is an audio codec sound source encoded with an audio codec (S350) .

When a result of the checking in step S350 shows that the RBT-alternative is a regular RBT sound source encoded with not an audio codec but a voice codec, the mobile communication network 120 provides the calling mobile communication terminal 110 with the RBT-alternative service according to the conventional procedure (S352) . In contrast with this, when a result of the checking in step S350 shows that the RBT-alternative is not a regular RBT sound source encoded with a voice codec, but an audio codec sound source, the mobile communication network 120 controls a wireless base station, that is, the caller-side wireless base station 130, to switch to a bypass mode, and controls the calling mobile communication terminal 110 to switch over its basic codec to an audio codec by transmitting a predetermined signaling message to the calling mobile communication terminal 110 (S360) .

After the mobile communication network 120 controls the calling mobile communication terminal 110, it transmits the audio codec sound source to the calling mobile communication terminal 110 in the bypass mode without vocoding it in the caller-side wireless base station 130 (S370) . In step S360, the calling mobile communication terminal 110 decodes the received audio codec sound source by using the audio codec set as the basic codec, thereby reproducing a high-quality sound source as the RBT-alternative.

Meanwhile, after the mobile communication network 120 transmits the audio codec sound source to the calling mobile communication terminal 110 in step S370, it checks if the called mobile communication terminal 112 responds to paging (S380) .

When a result of the checking in step S380 shows that the calling mobile communication terminal 112 does not respond to paging, the mobile communication network 120 continues to transmit the audio codec sound source as real-time streaming data to the calling mobile communication terminal 110 until the called mobile communication terminal 112 responds to paging. On the contrary, when the called mobile communication terminal 112 responds to paging, the mobile communication network 120 controls the calling mobile communication terminal 110 to switch over the basic codec to a voice codec by transmitting a predetermined signaling message to the calling mobile communication terminal 110 (S390) .

After the mobile communication network 120 controls the calling mobile communication terminal 110, it transmits an alert message, which informs the calling mobile communication terminal 110 that the called mobile communication terminal 112 responds to paging, to the calling mobile communication terminal 110 so that the calling mobile communication terminal 110 can carry out voice communication with the called mobile communication terminal 112 (S392) .

At this point of time, since the calling mobile communication terminal 110 has switched over the basic codec to the voice codec, it can adaptively decode and reproduce voice received from the called mobile communication terminal 112.

FIGS. 4a and 4b are illustrative views, each showing the first half and the second half of a detailed explanation on the method of providing a RBT-alternative service by using a switch-over to an audio codec according to the first embodiment of the present invention.

Through FIG. 3, the method of providing a RBT-alternative service by using a switch-over to an audio codec according to the first embodiment of the present invention has been described with priority given to the calling mobile communication terminal 110 and the mobile communication network 120. Hereinafter, in order to describe the first embodiment of the present invention in more detail, a description will be given of interrelations among the respective constitutional elements within the mobile communication network 120, the calling mobile communication terminal 110 and the called mobile communication terminal 112, and their roles. In explaining FIGS. 4a and 4b, it should be appreciated that the following description will also be given based on the above-mentioned assumption that a mobile communication constituting the mobile communication network 120 is a CDMA 2000 system, for the convenience of explanation. Therefore, terms and functions as used in the following description may be somewhat different than those in other mobile communication systems.

The calling mobile communication terminal 110 requests a speech call by transmitting information on the called mobile communication terminal 112, that is, its phone number and the like, to the caller-side wireless base station 130

(S402) . After the caller-side wireless base station 130 receives the speech call from the calling mobile communication terminal 110, it requests the caller-side mobile communication exchange 140 to establish a speech path (S404), and the caller-side mobile communication exchange 140 requests the caller-side wireless base station 130 to allocate the speech path to the calling mobile communication terminal 110 (S406) . The caller-side wireless base station 130 connects the speech path with the calling mobile communication terminal 110 (S408) , the calling mobile communication terminal 110 acknowledges the connection of the speech path by notifying this to the caller-side wireless base station 130 (S410) , and the caller-side wireless base station 130 notifies the caller-side mobile communication exchange 140 that the allocation of the speech path to the calling mobile communication terminal 110 has been completed (S412) . Upon acknowledging the connection of the speech path through the caller-side wireless base station 130, the caller-side mobile communication exchange 140 uses the HLR 160 to identify the receiver-side mobile communication exchange 142, which is a mobile communication exchange controlling an area where the called mobile communication terminal 112 is located, and sets up an ISUP call with the receiver-side mobile communication exchange 142 (S414) .

After the receiver-side mobile communication exchange 142 sets up the ISUP call with the caller-side mobile communication exchange 140, it uses the receiver-side wireless base station 132 to page the called mobile communication terminal 112, that is, performs paging (S416) , and uses the HLR 160 to check if the called mobile communication terminal 112 has joined a RBT-alternative service (S418) .

When a result of the checking in step S418 shows that the called mobile communication terminal 112 has not joined a RBT-alternative service, the receiver-side mobile communication exchange 142 provides the calling mobile communication terminal 110 with a regular RBT via the caller-side mobile communication exchange 140 (S420) . On the contrary, when a result of the checking in step S418 shows that the called mobile communication terminal 112 has joined a RBT-alternative service, the receiver-side mobile communication exchange 142 sets up an ISUP call with the sound source providing device 180 (S422) .

After the sound source providing device 180 sets up the ISUP call with the receiver-side mobile communication exchange 142, it checks a RBT-alternative sound source set for the called mobile communication terminal 112, and transmits an ISUP_CPG message, which contains information on the RBT- alternative sound source, and also contains information on a bypass mode and control information when the RBT-alternative sound source is an audio codec sound source encoded with an audio codec, to the caller-side mobile communication exchange 140 (S424) .

Upon receiving the ISUP_CPG message from the receiver-side mobile communication exchange 142, the caller-side mobile communication exchange 140 analyzes the ISUP_CPG message to check if the RBT-alternative sound source is an audio codec sound source encoded with an audio codec (S426) . When a result of the checking in step S426 shows that the RBT-alternative sound source is not an audio codec sound source, the caller-side mobile communication exchange 140 provides a RBT-alternative service according to the conventional procedure (S428). In contrast with this, when a result of the checking in step S426 shows that the RBT- alternative sound source is an audio codec sound source, the caller-side mobile communication exchange 140 transmits a bypass setup message, which is a transcoder control request message requesting a switchover to the bypass mode, to the caller-side wireless base station 130. Upon receiving the transcoder control request message, the caller-side wireless base station 130 switches to the bypass mode where a vocoder does not operate, and then transmits a bypass setup acknowledge message, which is a transcoder control acknowledge message informing the completion of the switchover to the bypass mode, to the caller-side mobile communication exchange 140 (S430) .

After the caller-side mobile communication exchange 140 controls the caller-side wireless base station 130 as in step S430, it transmits a data burst message, the TI (Teleservice Identifier) of which is 61888, as a signaling message to the calling mobile communication terminal 110 so as to switch over the basic codec of the calling mobile communication terminal 110 to an audio codec (S432) . Upon receiving the data burst message, the TI of which is 61888, the calling mobile communication terminal 110 checks the TI value of the data burst message, i.e., 61888 to confirm that it has received a request for changing άts basic codec to an audio codec. Then, in response to the data burst message, the calling mobile communication terminal 110 transmits a data burst ACK message, the TI of which is 61889, as a signaling message to the caller-side mobile communication exchange 140 via the caller-side wireless base station 130 (S434) . The data burst ACK message cannot be reprocessed, and the caller-side mobile communication exchange 140 does not perform any other operation upon receiving this message.

After the calling mobile communication terminal 110 transmits the data burst ACK message, the TI of which is 61889, it switches over its basic codec to an audio codec ( S436 ) .

After the basic codec of the calling mobile communication terminal 110 is switched over to an audio codec, an audio codec sound source is transmitted to the calling mobile communication terminal 110. That is, the sound source providing device 180 transmits an audio codec sound source set as the RBT-alternative of the called mobile communication terminal 112 to the receiver-side mobile communication exchange 142, the receiver-side mobile communication exchange 142 relays the audio codec sound source to the caller-side mobile communication exchange 140, and the caller-side mobile communication exchange 140 transmits the audio codec sound source to the calling mobile communication terminal 110 via the caller-side wireless base station 130 (S438) .

Upon receiving the audio codec sound source, the calling mobile communication terminal 110 decodes the audio codec sound source with the audio codec set as the basic codec and reproduces it (S440) . With regard to this, it is preferred that the calling mobile communication terminal 110 retrieves bit streams of the audio codec sound source to select or switch over a codec to be applied. That is, in order to provide against a case where a codec switch-over is not normally done, which occurs when the data burst message received from the caller-side mobile communication exchange 140 to the calling mobile communication terminal 110 is erroneous or the specified codec is different from the codec provided therein due to other causes, the calling mobile communication terminal 110 itself preferably retrieves the received audio codec sound source to switch over its basic codec to an audio codec suitable to the audio codec sound source. In this way, the mobile communication network 120 can provide the calling mobile communication terminal 110 with an audio codec sound source encoded with an audio codec, and the calling mobile communication terminal 110 can reproduce the audio codec sound source by using the audio codec, so that the quality of a RBT-alternative service can be improved.

Meanwhile, while the caller-side mobile communication exchange 140 reproduces a RBT-alternative, the called mobile communication terminal 112 may respond to the communication request, that is, may respond to paging of the receiver-side mobile communication exchange 142. Then, the mobile communication network 120 is to allow voice communication between the calling mobile communication terminal 110 and the called mobile communication terminal 112. Reference will now be made to a way to control the calling mobile communication terminal 110, which has switched over its basic codec to an audio codec, to switch over its basic codec to a voice codec again, and thus to enable the calling mobile communication terminal 110 to conduct voice communication with the called mobile communication terminal 112 by using the voice codec.

Upon receiving a paging request from the receiver-side mobile communication exchange 142 in step S414, the called mobile communication terminal 112 informs the called party of the communication request through a bell sound or vibration, and the called party, who has confirmed this, expresses an intention of conducting called communication by operating the called mobile communication terminal 112 through a specific action, for example, by pressing a specific key or opening the folder of the called mobile communication terminal 112. Then, the called mobile communication terminal 112 responds to paging of the receiver-side mobile communication exchange 142 (S442) . Upon receiving a response to paging, the receiver-side mobile communication exchange 142 transmits an ISUP_ANM message notifying the response of the called mobile communication terminal 112 to the caller-side mobile communication exchange 140 (S444), and cancels the ISUP call with the sound source providing device 180 because it need not provide the calling mobile communication terminal 110 with a RBT-alternative, i.e., an audio codec, any longer (S446) .

Upon receiving the ISUP_ANM message in step S444, the caller-side mobile communication exchange 140 transmits a bypass release message, which is a transcoder control message requesting bypass mode release, to the calling mobile communication terminal 110 (S448) . The calling mobile communication terminal 110 releases the bypass mode, vocodes a subsequently transferred voice with a voice codec, and then transfers the vocoded voice to calling mobile communication terminal 110.

After the caller-side mobile communication exchange 140 requests the caller-side wireless base station 130 to release the bypass mode, it transmits a data burst message, the TI of which is 61890, as a signaling message to the calling mobile communication terminal 110 via the caller- side wireless base station 130 so as to switch over the basic codec of the calling mobile communication terminal 110 (S450) .

Upon receiving the data burst message, the calling mobile communication terminal 110 checks the TI value of the data burst message to confirm that it has received a request for changing its basic codec. Then, in response to the data burst message, the calling mobile communication terminal 110 transmits a data burst ACK message, the TI of which is 61891, as a signaling message to the caller-side mobile communication exchange 140 via the caller-side wireless base station 130 (S452) .

The caller-side mobile communication exchange 140 transmits alert information, which notifies the calling mobile communication terminal 110 that the called mobile communication terminal 112 responds to paging, to the calling mobile communication terminal 110 (S454) .

Upon receiving the alert information, the calling mobile communication terminal 110 switches over its basic codec to a voice codec (S456) , and conducts voice communication with the called mobile communication terminal 110 by using the vice codec (S458) . At this point of time, the caller-side wireless base station 130 vocodes voice with the switched- over voice codec and transfers the vocoded voice to the calling mobile communication terminal 110 in step S448. The calling mobile communication terminal 110 reproduces the transferred voice by using the voice codec. In this way, the calling mobile communication terminal 110 can decode and reproduce a RBT-alternative encoded with an audio codec, that is, an audio codec sound source, by using an audio codec, and can decode and reproduce voice by using a voice codec. Therefore, voice and audio are separately transferred and reproduced by using a voice codec and an audio codec, so that a high-quality RBT-alternative service can be provided. FIG. 5 is a structural block diagram schematically showing a system for providing an additional voice service in a RBT- alternative service according to a second preferred embodiment of the present invention. The system for providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention includes a calling mobile communication terminal 510, a called mobile communication terminal 512, a mobile communication network 520 and a sound source provider 590. The calling mobile communication terminal 510 and the called mobile communication terminal 512 are mobile communication terminals performing voice communication with each other over the mobile communication network 520 or with common landline phones over a public switched telephone network (not shown) . Here, examples of the mobile communication terminals include PDAs (Personal Digital Assistants), cellular phones, PCS (Personal Communication Service) phones, handheld PCs, GSM (Global System for Mobile) phones, WCDMA (Wideband CDMA) phones, CDMA-2000 phones, or MBS (Mobile Broadband System) phones which are expected to be used in the 4^th generation system currently under consideration. According to the second embodiment of the present invention, the calling mobile communication terminal 510 transmits a request for voice communication to the called mobile communication terminal 512 of the called party over the mobile communication network 520, according to the calling party's key operation. When the called party has joined a RBT-alternative service with regard to the called mobile communication terminal 512, the calling mobile communication terminal 510 receives a RBT-alternative from the mobile communication network 520 and outputs it to the calling party. More specially, let us suppose that the calling mobile communication terminal 510 transmits a request for voice communication to the called mobile communication terminal 512 over the mobile communication network 520 and then receives a RBT-alternative from the mobile communication network 520. When the sound source of the RBT-alternative is encoded with an audio codec, the calling mobile communication terminal 510 switches over its basic codec to the audio codec upon receiving a signaling message requesting such switch-over from the mobile communication network 520. Then, the calling mobile communication terminal 510 decodes the sound source received from the mobile communication network 520 with the audio codec and reproduces it.

Upon receiving a signaling message requesting the calling mobile communication terminal 510 to switch over the basic codec to a voice codec from the mobile communication network 520, the calling mobile communication terminal 110 according to the second embodiment of the present invention carries out the switch-over and is provided with an additional service using voice (e.g., voice mailbox service, voice mail service, etc.), that is, an additional voice service. When the calling mobile communication terminal 510 cannot receive the above-mentioned signaling message or when the signaling message is erroneous, the calling mobile communication terminal 510 self-analyzes the data format of a received sound source or message (voice message etc.) and detects its pattern so as to set a codec suitable to the corresponding sound source or message as its basic codec, and decode and reproduce the corresponding sound source or message by using the set basic codec. The calling mobile communication terminal 510 will be described below in detail with reference to FIG. 6.

The called mobile communication terminal 512 according to the second embodiment of the present invention is adapted to receive a communication request from the calling mobile communication terminal 510 over the mobile communication network 520 and receives a paging request from the mobile communication network 520. The mobile communication network 520 according to the second embodiment of the present invention includes a caller-side wireless base station 530, a receiver-side wireless base station 532, an caller-side mobile communication exchange 540, a receiver-side mobile communication exchange 542, a CCSN 550, an HLR 560, a gateway 570 and a sound source providing device 580, and provides the calling and called mobile communication terminals 510 and 512 with a voice communication service, a RBT-alternative service and an additional voice service. Here, each of the calling and receiver-side wireless base stations 530 and 532 includes a BTS and a BSC. According to the second embodiment of the present invention, upon receiving a speech call request from the calling mobile communication terminal 510, the caller-side wireless base station 530 establishes a speech path between the calling mobile communication terminal 510 and the caller-side mobile communication exchange 540. Further, upon receiving a bypass setup message, which is a transcoder control request message requesting a switchover to a bypass mode, from the caller-side mobile communication exchange 540, the wireless base station 530 switches to the bypass mode and relays an audio codec sound source, which is received from the caller- side mobile communication exchange 540, to the calling mobile communication terminal 110 in its entirety without passing through a vocoder.

Upon receiving a bypass release message, which is a transcoder control request message requesting bypass mode release, from the caller-side mobile communication exchange 540, the caller-side wireless base station 530 releases the bypass mode, vocodes a voice message for an additional voice service by using the vocoder, and then relays the vocoded voice message to the calling mobile communication terminal 510. The calling and receiver-side mobile communication exchanges 540, 542 are adapted to process basic and additional services, subscribers' originating and incoming calls, and location registration and handoff procedures, as well as interwork with other networks. Specially, each of the calling and receiver-side mobile communication exchanges 540, 542 uses the HLR 560 to detect information on the calling and called parties, who are mobile communication subscribers of the calling and called mobile communication terminals 510, 512, respectively, as well as location information and status information of the respective mobile communication terminals .

According to the second embodiment of the present invention, if the caller-side mobile communication exchange 540 receives a speech call request for voice communication from the calling mobile communication terminal 510, and a speech path between the caller-side mobile communication exchange 540 and the calling mobile communication terminal 510 is established, the caller-side mobile communication exchange 540 conducts ISUP call setup with the receiver-side mobile communication exchange 542. Further, upon receiving information on an alterative RBT, information on a bypass mode and control information from the sound source providing device 580, the caller-side mobile communication exchange 540 checks if the RBT-alternative is a sound source encoded with an audio codec, that is, an audio codec sound source, and controls the caller-side wireless base station 530 to switch to the bypass mode. After the caller-side mobile communication exchange 540 controls the caller-side wireless base station 530 to switch to the bypass mode, it controls the calling mobile communication terminal 510 to switch over its basic codec to an audio codec by transmitting a signaling message to the calling mobile communication terminal 510 via the caller- side wireless base station 530, and transmits an audio codec sound source to the calling mobile communication terminal 510 if the audio codec sound source is transferred from the sound source providing device 580. Upon receiving a setup request for an additional voice service from -the receiver-side mobile communication exchange 542, the caller-side mobile communication exchange 540 controls the caller-side wireless base station 530 to switch to the bypass mode, controls the calling mobile communication terminal 510 to switch over its basic codec to a vice codec, and provides a transferred voice message according to the additional voice service to the calling mobile communication terminal 510. According to the second embodiment of the present invention, if the caller-side mobile communication exchange 540 notifies the receiver-side mobile communication exchange 542 that there is a voice communication request for the called mobile communication terminal 512, the receiver-side mobile communication exchange 542 conducts ISUP call setup with the caller-side mobile communication exchange 540, pages the called mobile communication terminal 512, uses the HLR 560 to check if the called mobile communication terminal 512 has joined a RBT-alternative service, and then conducts ISUP call setup with the sound source providing device 580 to transmit an audio codec sound source, which is received from the sound source providing device 580, to the caller-side mobile communication exchange 540.

The receiver-side mobile communication exchange 542 checks if the called mobile communication terminal 512 responds to paging. If there has been no response from the called mobile communication terminal 512 and a preset timer has expired, the receiver-side mobile communication exchange 542 confirms that an additional voice service is to be provided by using the HLR 560, release the ISUP call set up with the sound source providing device 580, and then transmits a setup request for the additional voice service to the caller-side mobile communication exchange 540. The receiver-side mobile communication exchange 542 uses the HLR 580 to acquire the type of a guidance message and information for routing to a voice message server 582, sets up an ISUP call with the voice message server 582, and transfers a voice message, which is received from the voice message server 582, to the caller-side mobile communication exchange 540.

The CCSN 550 refers to a network which consists of signaling points and signaling links and provides a common channel signaling scheme standardized by ITU-T No. 7 scheme. As used herein, the common channel signaling scheme refers to a signaling scheme for separating the signaling information and network management information into voice and data and transmitting the separated voice and data over a separate channel, which is used in common for signal transmission. The HLR 560 is a database storing service profiles related to subscription information of mobile communication subscribers. Specially, the HLR 560 identifies the registration of respective mobile communication terminals, deletes the registration, and locates them. In addition, the HLR 560 stores the phone number of each mobile communication subscriber using each mobile communication terminal, MIN (Mobile Identification Number) , ESN (Electronic Serial Number) , information on the service type (e.g., whether or not a subscriber has joined a RBT- alternative service, whether or not a subscriber has joined an additional voice service, etc.), and information necessary for routing to the sound source providing device 580 and the voice message server 582. The gateway 570 is a device for interconnecting a plurality of homogeneous or heterogeneous communication networks so as to exchange information among them. Specially, the gateway 570 interconnects a plurality of communication networks or devices, which are not compatible with one another because their protocols are different, and converts their protocols into those compatible with one another, thereby relaying information such that they exchange information with one another.

The sound source providing device 580 is an intelligent network IP for storing RBT-alternative sound sources. At a request for a RBT-alternative sound source, the sound source providing device 580 transmits a sound source authentication request to a sound source provider control server 594, and when the authentication has been successful, transmits the RBT-alternative sound source to the receiver-side mobile communication exchange 542. Further, if a web server 598 transfers a RBT-alternative sound to the sound source providing device 580, the sound source providing device 580 stores and manages it. According to the second embodiment of the present invention, the sound source providing device 580 conducts ISUP call setup with the receiver-side mobile communication exchange 542, checks a RBT-alternative sound source set for the called mobile communication terminal 512 to create information on a RBT-alternative, information on a bypass mode and control information, and then transmits the created information to the caller-side mobile communication exchange 540. Further, the sound source providing device 580 transmits an audio codec sound source to the receiver-side mobile communication exchange 542.

Specially, the sound source providing device 580 checks if the RBT-alternative sound source set for the called mobile communication terminal 512 is an audio codec sound source encoded with an audio codec, and when the RBT-alternative sound source is an audio codec sound source, creates information on a RBT-alternative, information on a bypass mode and control information. The voice message server 582 stores and transmits voice messages for an additional voice service including a voice message service, a voice mail service, etc.

The sound source provider 590 includes the Internet 592, a sound source provider control server 594, a subscriber DB 596 and a web server 598. The sound source provider 590 creates or receives a RBT-alternative sound source, encodes it with an audio codec or a voice codec, and provides the sound source providing device 580 with it.

The Internet 592 refers to a global open-type computer network architecture providing TCP/IP protocol and various services existing on its upper layers, in particular, HTTP (Hypertext Transfer Protocol), Telnet, FTP (File Transfer Protocol) , DNS (Domain Name Server) , SMTP (Simple Mail Transfer Protocol), SNTP (Simple Network Management Protocol) , NFS (Network File Service) and NIS (Network Information Service) .

The sound source provider control server 594 is adapted to control the provision of a RBT-alternative service. Specially, the sound source provider control server 594 authenticates sound sources by using information on the calling and called parties of the calling and called mobile communication terminals 510, 512, call request time, etc. The subscriber DB 596 is adapted to store and manage information on subscribers having joined a RBT-alternative service, and provides subscriber information necessary for the sound source provider control server 594 to authenticate sound sources.

The web server 598 is connected to the sound source providing device 580 and the sound source provider control server 594 over the Internet 592. The web server 598 adds RBT-alternatives to the sound source providing device 580, and provides a user terminal (e.g., computer) or a mobile communication terminal with a user interface through which the sound source provider control server 594 is caused to set and change information necessary to specify a sound source, i.e., information on the calling party, calling party group, calling time, etc, as well as a sound source code corresponding to that information. To this end, the web server 598 provides the user terminal or mobile communication terminal with a web page or WAP page. FIG. 6 is a structural block diagram schematically showing a mobile communication terminal for providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention.

The mobile communication terminal for providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention, which implements the calling mobile communication terminal 510 in FIG. 5, includes a memory unit 610, a controller unit 620, a DSP (Digital Signal processor) unit 630, a baseband converter unit 640, a speaker 650, an RF (Radio Frequency) signal processor unit 660 and an antenna 670. The mobile communication terminal decodes and reproduces an audio codec sound source by using an audio codec. Hereinafter, the mobile communication terminal is referred to as the calling mobile communication terminal 510 so as to standardize terms by those mentioned in FIG. 5. The memory unit 610 stores a plurality of applications, which drive the calling mobile communication terminal 510, conduct voice and data communication and carry out various additional functions, protocol software processing messages transmitted to and received from the mobile communication network 520, etc. To this end, the memory unit 610 includes a non-volatile memory, i.e., an EEPROM (Electrically Erasable and Programmable Read Only Memory) capable of modifying contents in units of bytes, a flash memory capable of modifying contents in units of blocks, and a SDRAM (Synchronous Dynamic Random Access Memory) .

The memory unit 610 according to the second embodiment of the present invention stores a codec switch-over program from the mobile communication network 520. The codec switch-over program is software for interchanging a voice codec and an audio codec as a basic codec under the control of the mobile communication network 520, that is, under the control of the caller-side mobile communication exchange 140. The controller unit 620 controls the overall operation of the calling mobile communication terminal 510. Further, the controller unit 620 executes various applications stored in the memory unit 610 so as to carry out functions for conducting voice and data communications, as well as additional functions. Upon receiving a codec switch-over request from the mobile communication network 520, the controller unit 620 according to the second embodiment of the present invention executes the codec switch-over program to interchange a voice codec and an audio codec of the digital signal processor unit 630 as a basic codec. That is, the controller unit 620 analyzes a signaling message received from the mobile communication network 520 to check whether it has been requested to switch over the basic codec to the voice codec or the audio codec, and then controls the digital signal processor unit 630 to switch over the basic codec to the corresponding codec.

Upon receiving a voice message or a sound source from the mobile communication network 520, the controller unit 620 according to the second embodiment of the present invention analyzes the data format of the received voice message or sound source and detects its pattern to discover the type of an encoding codec of the voice message or sound source, thereby decoding the voice message or sound source with a codec suitable to that type and reproducing it. In other words, when the calling mobile communication terminal 510 cannot receive a signaling message from the mobile communication network 520 or a received signaling message is erroneous, the calling mobile communication terminal 510 analyzes the data format of a received voice message or sound source and detects its pattern to determine the type of a codec suitable to the corresponding format. Based on this, the calling mobile communication terminal 510 can decode the received voice message by using a voice codec and then output it, and can decodes the received audio codec sound source, which is a RBT-alternative sound source encoded with an audio codec, by using an audio codec and then output it. Further, in the case of an audio codec sound source, the calling mobile communication terminal 510 can the audio codec sound source with a specified audio codec by identifying codec identification information of bit streaming data.

The digital signal processor unit 630 encodes or decodes a voice signal, performs an equalizer function so as to remove multi-path noise, conducts sound data processing function, and so forth. Further, the digital signal processor unit 630 exchanges voice data with the baseband converter unit 640 and receives digital data from the baseband converter unit 640. The digital signal processor unit 630 according to a preferred embodiment of the present invention is provided with software-implemented voice and audio codecs or hardware-implemented voice and audio codecs, so as to decode voice or a sound source with a codec that is basically set, i.e., a basic codec. In other words, the digital signal processor unit 630 is provided with both a voice codec and an audio codec and sets a specific codec of them as a basic codec. The digital signal processor unit 630 decodes voice or a sound source with the set basic codec and transfers the decoded voice or sound source. Accordingly, the digital signal processor unit 630 according to the second embodiment of the present invention decodes voice with the voice codec and decodes a sound source with the audio codec, so that it can decode the voice or sound source into a high-quality voice or sound source, that is, a high-quality RBT-alternative.

The baseband converter unit 640 converts signals transmitted/received among the RF signal processor unit 660, the digital signal processor unit 630 and the speaker 650 into baseband signals, and conducts functions of digital-to- analog conversion processing, analog-to-digital conversion processing, etc.

The speaker 650 outputs a voice signal, output from the baseband converter unit 640, as an audible sound. The RF signal processor unit 660 controls the power or gain of a transmission signal received from the baseband converter unit 640, demodulates and amplifies an RF signal received from the antenna 670, and modulates the transmission signal, received from the baseband converter unit 640, to transfer the modulated signal to the antenna 670. The antenna 670 transmits/receives an RF signal from/into air. FIG. 7 is a flowchart showing the control of a terminating mobile switching center for explaining a method of providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention. If the calling party inputs the phone number of the called mobile communication terminal 512 by operating keys of the calling mobile communication terminal 510 and selects a call button, in order to carry out voice communication with the called party, the calling mobile communication terminal 510 transmits a speech call request to the mobile communication network 520. In other words, the mobile communication network 520 receives a speech call request from the calling mobile communication terminal 510 and connects a speech path with the calling mobile communication terminal 510. After the mobile communication network 520 connects the speech path with the calling mobile communication terminal 510, it checks service subscription information for the called mobile communication terminal 512 and checks if the called mobile communication terminal 512 has joined a RBT- alternative service.

When the called mobile communication terminal 512 has not joined a RBT-alternative service, the mobile communication network 520 provides the calling mobile communication terminal 510 with a regular RBT according to a conventional procedure. The conventional procedure of providing a regular RBT is well known in the art, so a detailed description thereof will be omitted. On the contrary, when the called mobile communication terminal 512 has joined a RBT-alternative service, the mobile communication network 520 checks the type of a RBT-alternative set for the called mobile communication terminal 512 and checks if the RBT- alternative set for the called mobile communication terminal 512 is an audio codec sound source encoded with an audio codec.

When the RBT-alternative is a regular RBT sound source encoded with a voice codec, the mobile communication network 520 provides the calling mobile communication terminal 510 with the RBT-alternative service according to the conventional procedure.

In contrast with this, when the RBT-alternative is not a regular RBT sound source encoded with a voice codec, but an audio codec sound source, the mobile communication network 520 controls a wireless base station, that is, the caller- side wireless base station 530, to switch to a bypass mode, and controls the calling mobile communication terminal 510 to switch over its basic codec to an audio codec by transmitting a predetermined signaling message to the calling mobile communication terminal 510.

After the mobile communication network 520 controls the calling mobile communication terminal 510, it transmits the audio codec sound source to the calling mobile communication terminal 510 in the bypass mode without vocoding it in the caller-side wireless base station 530. The calling mobile communication terminal 510 decodes the received audio codec sound source by using the audio codec set as the basic codec, thereby reproducing a high-quality sound source as the RBT- alternative. In this way, the mobile communication network 520 provides the calling mobile communication terminal 510 with the audio codec sound source as a RBT-alternative sound source (S710) . As described above, when the mobile communication network 520 provides the calling mobile communication terminal 510 with a RBT-alternative, it provides an alternative multimedia service in such a manner that, if a sound source set for the called mobile communication terminal 512 is an audio codec sound source, it controls the calling mobile communication terminal 510 to switch over its basic codec to an audio codec, and transmits the audio codec sound source to the calling mobile communication terminal 510 in a bypass mode without vocoding the audio codec sound source. In the course of this, when the calling mobile communication terminal 510 and the called mobile communication terminal 512 cannot conduct voice communication with each other, for example, when the called mobile communication terminal 512 does not respond to paging, an additional voice service is to be provided to the calling mobile communication terminal 510. Hereinafter, a way to treat such a case will be described in detail.

The mobile communication network 520 pages the called mobile communication terminal 512 while providing an audio codec sound source as in step S710, and checks if the called mobile communication terminal 510 responds to paging (S720) . When a result of the checking in step S720 shows that the called mobile communication terminal 512 responds to paging, the mobile communication network 520 release the bypass mode set up for the caller-side wireless base station 530 (S722), controls the calling mobile communication terminal 510 to set a voice codec as its basic codec (S724), and then interconnects the calling mobile communication terminal 510 and the called mobile communication terminal 512 so as to conduct voice communication with each other. On the contrary, when a result of the checking in step S720 shows that the called mobile communication terminal 512 does not respond to paging, the mobile communication network 520 uses the HLR 560 to perceive that an additional voice service as the next processing procedure is to be provided to the calling mobile communication terminal 510, releases the bypass mode set up for the caller-side wireless base station 530 (S740) , controls the calling mobile communication terminal 510 to set a voice codec as its basic codec (S750) , and then transmits a voice message for the additional voice service to the calling mobile communication terminal 510 (S760) . The subsequent procedure of providing the additional voice service follows a conventional procedure, so a detailed description thereof will be omitted. In other words, after the mobile communication network 520 provides the RBT-alternative service by setting up the bypass mode and controlling the calling mobile communication terminal 510 to set an audio codec as its basic codec, it releases the set bypass mode and controls the calling mobile communication terminal 510 to set a voice codec as its basic codec even when the called mobile communication terminal 510 does not respond to paging, thereby enabling an additional voice service to be normally provided to the calling mobile communication terminal 510.

FIGS. 8a and 8b are illustrative view, each showing the first half and the second half of a detailed explanation on the method of providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention.

Through FIG. 7, the method of providing an additional voice service in a RBT-alternative service according to the second embodiment of the present invention has been described with priority given to the calling mobile communication terminal 510 and the mobile communication network 520. Hereinafter, in order to describe the second embodiment of the present invention in more detail, a description will be given of interrelations among the respective constitutional elements within the mobile communication network 520, the calling mobile communication terminal 510 and the called mobile communication terminal 512, and their roles. In explaining FIGS. 8a and 8b, it should be appreciated that the following description will also be given based on the above-mentioned assumption that a mobile communication constituting the mobile communication network 120 is a CDMA 2000 system, for the convenience of explanation. Therefore, terms and functions as used in the following description may be somewhat different than those in other mobile communication systems.

The calling mobile communication terminal 510 requests a speech call by transmitting information on the called mobile communication terminal 512, that is, its phone number and the like, to the caller-side wireless base station 530

(S802) . After the caller-side wireless base station 530 receives the speech call from the calling mobile communication terminal 510, it requests the caller-side mobile communication exchange 540 to establish a speech path (S804), and the caller-side mobile communication exchange 540 requests the caller-side wireless base station 530 to allocate the speech path to the calling mobile communication terminal 510 (S806) . The caller-side wireless base station 530 connects the speech path with the calling mobile communication terminal 510 (S808), the calling mobile communication terminal 510 acknowledges the connection of the speech path by notifying this to the caller-side wireless base station 530 (S810) , and the caller-side wireless base station 530 notifies the caller-side mobile communication exchange 540 that the allocation of the speech path to the calling mobile communication terminal 510 has been completed (S812) . Upon acknowledging the connection of the speech path through the caller-side wireless base station 530, the caller-side mobile communication exchange 540 uses the HLR 560 to identify the receiver-side mobile communication exchange 542, which is a mobile communication exchange controlling an area where the called mobile communication terminal 512 is located, and sets up an ISUP call with the receiver-side mobile communication exchange 542 (S814) .

After the receiver-side mobile communication exchange 542 sets up the ISUP call with the caller-side mobile communication exchange 540, it uses the receiver-side wireless base station 532 to page the called mobile communication terminal 512, that is, performs paging (S816) , and uses the HLR 560 to check if the called mobile communication terminal 512 has joined a RBT-alternative service (S818) .

When a result of the checking in step S818 shows that the called mobile communication terminal 512 has not joined a RBT-alternative service, the receiver-side mobile communication exchange 542 provides the calling mobile communication terminal 510 with a regular RBT via the caller-side mobile communication exchange 540 (S820) . On the contrary, when a result of the checking in step S518 shows that the called mobile communication terminal 512 has joined a RBT-alternative service, the receiver-side mobile communication exchange 542 sets up an ISUP call with the sound source providing device 580 (S822) .

After the sound source providing device 580 sets up the ISUP call with the receiver-side mobile communication exchange 542, it checks a RBT-alternative sound source set for the called mobile communication terminal 512, and transmits an ISUP_CPG message, which contains information on the RBT- alternative sound source, and also contains information on a bypass mode and control information when the RBT-alternative sound source is an audio codec sound source encoded with an audio codec, to the caller-side mobile communication exchange 540 (S824) .

Upon receiving the ISUP_CPG message from the receiver-side mobile communication exchange 542, the caller-side mobile communication exchange 540 analyzes the ISUP_CPG message to check if the RBT-alternative sound source is an audio codec sound source encoded with an audio codec (S826) . When a result of the checking in step S826 shows that the RBT-alternative sound source is not an audio codec sound source, the caller-side mobile communication exchange 540 provides a RBT-alternative service according to the conventional procedure (S828) . In contrast with this, when a result of the checking in step S826 shows that the RBT- alternative sound source is an audio codec sound source, the caller-side mobile communication exchange 540 transmits a bypass setup message, which is a transcoder control request message requesting a switchover to the bypass mode, to the caller-side wireless base station 530. Upon receiving the transcoder control request message, the caller-side wireless base station 530 switches to the bypass mode where a vocoder does not operate, and then transmits a bypass setup acknowledge message, which is a transcoder control acknowledge message informing the completion of the switchover to the bypass mode, to the caller-side mobile communication exchange 540 (S830) .

After the caller-side mobile communication exchange 540 controls the caller-side wireless base station 530 as in step S830, it transmits a data burst message, the TI (Teleservice Identifier) of which is 61888, as a signaling message to the calling mobile communication terminal 510 so as to switch over the basic codec of the calling mobile communication terminal 510 to an audio codec (S832) . Upon receiving the data burst message, the TI of which has a peculiar value (e.g., 61888), the calling mobile communication terminal 510 checks the TI value of the data burst message, i.e., 61888 to confirm that it has received a request for changing its basic codec to an audio codec. Then, in response to the data burst message, the calling mobile communication terminal 510 transmits a data burst ACK message, the TI of which has a peculiar value (e.g., 61889), as a signaling message to the caller-side mobile communication exchange 540 via the caller-side wireless base station 530 (S834) . The data burst ACK message cannot be reprocessed, and the caller-side mobile communication exchange 140 does not perform any other operation upon receiving this message. After the calling mobile communication terminal 510 transmits the data burst ACK message, the TI of which is 61889, it switches over its basic codec to an audio codec (S836) .

After the basic codec of the calling mobile communication terminal 510 is switched over to an audio codec, an audio codec sound source is transmitted to the calling mobile communication terminal 510. That is, the sound source providing device 580 transmits an audio codec sound source set as the RBT-alternative of the called mobile communication terminal 512 to the receiver-side mobile communication exchange 542, the receiver-side mobile communication exchange 542 relays the audio codec sound source to the caller-side mobile communication exchange 540, and the caller-side mobile communication exchange 540 transmits the audio codec sound source to the calling mobile communication terminal 510 via the caller-side wireless base station 530 in a bypass mode without performing vocoding (S838) .

Upon receiving the audio codec sound source, the calling mobile communication terminal 510 decodes the audio codec sound source with the audio codec set as the basic codec and reproduces it (S840) . With regard to this, it is preferred that the calling mobile communication terminal 510 retrieves bit streams of the audio codec sound source to select or switch over a codec to be applied. That is, in order to provide against a case where a codec switch-over is not normally done, which occurs when the data burst message received from the caller-side mobile communication exchange 540 to the calling mobile communication terminal 510 is erroneous or the specified codec is different from the codec provided therein due to other causes, it is preferred that the calling mobile communication terminal 510 identifies the audio codec sound source by analyzing the data format of the received audio codec sound source and detecting its pattern, and personally switch over its basic codec to a suitable audio codec by using specified codec identification information.

In this way, the mobile communication network 520 can provide the calling mobile communication terminal 510 with an audio codec sound source encoded with an audio codec, and the calling mobile communication terminal 510 can reproduce the audio codec sound source by using the audio codec, so that the quality of a RBT-alternative service can be improved. Meanwhile, while the caller-side mobile communication exchange 540 reproduces a RBT-alternative, the receiver-side mobile communication exchange 542 checks if the called mobile communication terminal 512 responds to the communication request (S842) When a result of the checking in step S842 shows that the called mobile communication terminal 512 responds to paging, voice communication between the called mobile communication terminal 512 and the calling mobile communication terminal 510 is connected (S844). In order to connect this voice communication, the receiver-side mobile communication exchange 542 transmits an ISUP response message to the caller-side mobile communication exchange 540. The calling mobile communication terminal 540 requests the caller-side wireless base station 530 to release the bypass mode, controls the calling mobile communication terminal 510 to set its basic codec to as a voice codec, and then connects the voice communication, thereby enabling the calling mobile communication terminal 540 to conduct the voice communication by using the voice codec. In contrast with this, when a result of the checking in step S842 shows that the called mobile communication terminal 512 does not respond to paging, that is, does not answer the phone, the receiver-side mobile communication exchange 542 checks if a preset timer has expired (S846) . When the preset timer has not expired, the receiver-side mobile communication exchange 542 continues to check if the called mobile communication terminal 512 responds to paging. When the preset timer has expired, the receiver-side mobile communication exchange 542 inquires the HLR 560 about the next procedure, receives a request for providing an additional voice service from the HLR 560, and requests the caller-side mobile communication exchange 540 to process the additional voice service by transmitting an ISUP response message to the caller-side mobile communication exchange 540

(S848) .

After the receiver-side mobile communication exchange 542 requests the calling mobile communication terminal 510 to process the additional voice service, it release the ISUP call with the sound source providing device 580 so as to stop providing the RBT-alternative service (S850) , and sets up an ISUP call with the voice message server 582 so as to provide the additional voice service (S852) . Meanwhile, upon receiving the ISUP response message, that is, a request for processing the additional voice service from the receiver-side mobile communication exchange 542 in step S848, the caller-side mobile communication exchange 540 controls the caller-side wireless base station 530 to release the bypass mode by transmitting a transcoder control message to the caller-side wireless base station 530 (S854), and requests the calling mobile communication terminal 510 to switch over its basic codec to a voice codec by transmitting a data burst message, the TI of which has a peculiar value (e.g., 61890), as a signaling message to the calling mobile communication terminal 510 (S856) . Upon receiving the signaling message, the calling mobile communication terminal 510 checks the received data burst message to perceive that it has received a request for changing its basic codec, transmits an acknowledge message for the received data burst message, that is, a data burst message, the TI of which has a peculiar value (e.g., 61891), as a signaling message to the caller-side mobile communication exchange 540 (S858), and then switches over its basic codec to a voice codec (S860) .

Subsequently, the voice message server 582 transmits a voice message for the additional voice service to the calling mobile communication terminal 510 via the receiver-side mobile communication exchange 542, the caller-side mobile communication exchange 540 and the caller-side wireless base station 530, and the calling mobile communication terminal 510 decodes the voice message by using the voice codec and outputs it. With regard to this, the caller-side wireless base station 530 vocodes the voice message in a state where the bypass mode is released, and transmits the vocoded voice message to the calling mobile communication terminal 510. Further, it is also preferred that the calling mobile communication terminal 510 identifies the voice message by analyzing the data format of the received voice message and detecting its pattern, and then decodes it by using the voice codec, thereby providing against a case where the signaling message is not received, a case where the signaling message is erroneous, a case where the type of a codec specified in the signaling message is not suitable, and so forth. FIG. 9 is an illustrative view for explaining a signaling message according to a preferred embodiment of the present invention. 9A of FIG. 9 shows the message format of a data burst message. The caller-side mobile communication exchange 140, 540 controls the calling mobile communication terminal 110, 510 to switch over its basic codec by transmitting a data burst message, the TI value of which specifies a codec, as a signaling message to the calling mobile communication terminal 110, 510. Such a data burst message is configured as presented in FIG. 9A.

As illustrated in the drawing, the message format of the data burst message includes a TI field, an MIN (Mobile Identification Number) field and a used codec information field. The TI field has a value predefined between the caller-side mobile communication exchange 140, 540 and the calling mobile communication terminal 110, 510, and informs the calling mobile communication terminal 110, 510 of the start and end of a RBT-alternative service interval. The value of the TI field may vary if necessary. That is, although four values of 61888, 61889, 61890 and 61891 are used as the TI value of the data burst message in FIGS. 4 and 8, these are merely illustrative values and may vary if necessary.

The MIN field represents the MIN of the calling mobile communication terminal 110, 510 or the called mobile communication terminal 112, 512. The last field of the data burst message, that is, the used codec information field, represents information on the type of a codec to be applied by the calling mobile communication terminal 110, 510. In other words, this field represents information on the type of a codec to be set as a basic codec from among various codecs included in the calling mobile communication terminal 110, 510. The types of codecs and their field values will be described with reference to FIG. 9B. The used codec information field is not necessarily required to specify a used codec in the data burst message. That is, used codec information may be represented by the TI value of the TI field. When Ti values are differently set according to codec information, and the calling mobile communication terminal 110, 510 and the caller-side mobile communication exchange 140, 540 have prearranged to use them, an used codec may be specified only by the TI field while the used codec information field is reserved.

9B of FIG. 9 shows the types of codec applicable according to values of the used codec information field. The calling mobile communication terminal 110, 510 checks the field value of the used codec information field to identify an used codec corresponding thereto, and then sets the identified used codec as its basic codec. FIGS. 10a and 10b are illustrative views, each used for explaining the identification of a multiple audio codec according to a preferred embodiment of the present invention. As described in steps S440 and S840 of FIGS. 4 and 8, the calling mobile communication terminal 110, 510 preferably analyzes a received RBT-alternative sound source, that is, an audio codec sound source in a bit stream, to select or switch over to an audio codec suitable for decoding the audio codec sound source. Accordingly, in order to enable the calling mobile communication terminal 510 to personally select or switch over to a suitable audio codec by analyzing an audio codec sound source, corresponding information must be specified in the audio codec sound source. That is, when the sound source providing device 580 creates a sound source encoded with an audio codec, i.e., an audio codec sound source, it must encode information on an audio codec suitable for the audio codec sound source together.

1OA of FIG. 10a shows the data format of a sound source encoded with a common audio codec, that is, a common audio codec sound source. The common audio codec sound source has a total length of 171 bits, and includes an audio data bit stream field of 168 bits (21 bytes) and a dummy of 3 bits. 1OB of FIG. 10a shows the data format of an audio codec sound source according to a preferred embodiment of the present invention. In the present invention, in order to indicate information on an audio codec suitable for the audio codec sound source, information on an audio codec, that is, audio codec identification information, is specified in the dummy field of 3 bits, which is not used in the above-mentioned data field of a common audio codec sound source.

FIG. 10b illustratively shows the audio codec identification information. Since the dummy field consists of 3 bits, total eight pieces of audio codec identification information can be specified.

The calling mobile communication terminal 110, 510 checks the dummy field to identify an audio codec suitable for a corresponding audio codec sound source, and accordingly selects or switches over to the suitable audio codec. Therefore, even when a data burst message created in the calling mobile communication terminal 110, 510 is erroneous or a suitable audio codec is not specified for other reasons, the calling mobile communication terminal 110, 510 can personally select a suitable audio codec and switch over its basic codec to the selected suitable audio codec. Although only the audio codec identification information for identifying an audio codec has been described herein, voice codec identification information for identifying a voice codec may also be specified by using the dummy field, as described through FIG. 9.

Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Industrial Applicability

According to the present invention as described above, in providing a RBT-alternative service, a high-quality RBT service can be provided by separately applying an audio codec and a voice codec.

Further, a RBT-alternative service can be stably provided by transmitting a signaling message from a mobile communication network to a mobile communication terminal to thereby control the mobile communication terminal such that it can apply various audio codecs.

Further, even when a signaling message is erroneous or a suitable audio codec is not specified for other reasons, a mobile communication terminal can personally select or switch over to a suitable audio codec, so that a stable service can be provided.

Further, when the called party does not respond to paging and thus an additional voice service, such as a voice mailbox service, is to be provided to the calling party, a stable additional voice service can be provided with a high- quality RBT-alternative service by controlling a mobile communication terminal to switch over from an audio codec to a voice codec and reproduce a voice message by using the voice codec.

Claims

1. A method for providing a ringback tone alternative ("RBT- alternative", hereinafter) to a calling mobile communication terminal requesting communication with a called mobile communication terminal in a mobile communication network, the method comprising the steps of:

(a) receiving a request for the communication from the calling mobile communication terminal, and establishing a communication path;

(b) checking if the called mobile communication terminal is eligible to a RBT-alternative service;

(c) checking a sound source of the RBT-alternative associated with the called mobile communication terminal when it is determined at step (a) that the called mobile communication terminal is eligible to the RBT-alternative service;

(d) checking if the sound source is an audio codec sound source encoded with an audio codec; (e) controlling the calling mobile communication terminal to switch over a basic codec thereof to the audio codec when it is determined at step (d) that the sound source is the audio codec sound source; and (f) transmitting the audio codec sound source to the calling mobile communication terminal in a bypass mode without passing through a vocoder.

2. The method as claimed in claim 1, further comprising, after step (c) , step (cl) of transmitting a ringback tone to the calling mobile communication terminal when a result of the checking at step (b) shows that the called mobile communication terminal is not subscribed to the RBT- alternative service.

3. The method as claimed in claim 1, further comprising, after step (e) , step (el) of transmitting a sound source encoded with a voice codec to the calling mobile communication terminal when a result of the checking at step (d) shows that the sound source is not the audio codec sound source but the sound source encoded with the voice codec.

4. The method as claimed in claim 1, further comprising, after step (f) , the steps of: (g) paging the called mobile communication terminal;

(h) receiving a response to the paging at step (g) from the called mobile communication terminal;

(i) controlling the calling mobile communication terminal to switch over the basic codec thereof to a voice codec; and (j) controlling the calling and called mobile communication terminals to conduct the communication with each other.

5. The method as claimed in claim 1, wherein, in step (e) , the mobile communication network controls ^'the calling mobile communication terminal to change the basic codec thereof by transmitting a signaling message to the calling mobile communication terminal.

6. The method as claimed in claim 5, wherein the signaling message includes a data burst message when the mobile communication network employs a synchronous scheme.

7. The method as claimed in claim 6, wherein the data burst message has a TI (Teleservice Identifier) field specifying a

TI value which represents a start and an end of an interval of the RBT-alternative service, a MIN (Mobile Identification Number) field representing an MIN of at least one of the calling and called mobile communication terminals, and a used codec information field representing a type of a codec to be used as the basic codec.

8. The method as claimed in claim 6, wherein the data burst message includes a TI (Teleservice Identifier) field and an MIN (Mobile Identification Number) field, and the TI field specifies a plurality of values, each representing a start and an end of an interval of the RBT-alternative service, and indicates types of codecs to be used as the basic codec, corresponding to the plurality of values.

9. The method as claimed in claim 1, further comprising, after step (f), the steps of:

(k) checking if the audio codec, with which the audio codec sound source is encoded, is of the same type as the audio codec set as the basic codec by comparing the two audio codecs with each other in the calling mobile communication; and

(1) setting the audio codec, with which the audio codec sound source is encoded, as the basic codec by analyzing data of the audio codec sound source, and reproduce the audio codec sound source in the calling mobile communication terminal when a result of the checking in step (k) shows that the two audio codecs are not of the same type.

10. A system for providing a ringback tone alternative ("RBT-alternative", hereinafter) to a calling mobile communication terminal, which includes the calling mobile communication terminal requesting voice communication, a called mobile communication terminal receiving a request for the voice communication, and a sound source provider for providing a sound source of the RBT-alternative, the system comprising: a mobile communication network for establishing a communication path with the calling mobile communication terminal, checking if the called mobile communication terminal is eligible to a RBT-alternative service, analyzing the sound source of the RBT-alternative associated with the called mobile communication terminal to check if the sound source is an audio codec sound source encoded with an audio codec, controlling the calling mobile communication terminal to switch over a basic codec thereof to the audio codec, and transmitting the audio codec sound source to the calling mobile communication terminal when receiving the request for the voice communication from the calling mobile communication terminal.

11. The system as claimed in claim 10, wherein the mobile communication network pages the called mobile communication terminal, and controls the calling mobile communication terminal to switch over the basic codec thereof to a voice codec when the called mobile communication terminal responds to the paging.

12. The system as claimed in claim 10, wherein the mobile communication network comprises: a sound source providing device for storing and transferring the sound source, and creating and transferring an ISUP_CPG message containing information on the RBT-alternative, information on a bypass mode and control information when the sound source is the audio codec sound source; a caller-side wireless base station for receiving a communication call request from the calling mobile communication terminal, transferring the communication request, receiving a request for a switchover to a bypass mode, and transmitting the audio codec sound source to the calling mobile communication terminal in the bypass mode; a caller-side mobile communication exchange for receiving the communication request transferred from the caller-side wireless base station, checking if the sound source is the audio codec sound source by analyzing the ISUP_CPG message received from the sound source providing device, controlling the caller-side wireless base station to switch over to the bypass mode, controlling the calling mobile communication terminal to switch over the basic codec thereof to the audio codec, and transmitting the audio codec sound source to the calling mobile communication terminal via the caller-side wireless base station if the audio codec sound source is transferred; and a receiver-side mobile communication exchange for establishing an ISUP call with the caller-side mobile communication exchange, establishing an ISUP call with the sound source providing device, and relaying the audio codec sound source, received from the sound source providing device, to the calling mobile communication terminal.

13. The system as claimed in claim 12, wherein the receiver- side mobile communication exchange pages the called mobile communication terminal after establishing the ISUP call with the caller-side mobile communication exchange, and when the called mobile communication terminal responds to the paging, releases the ISUP call with the sound source providing device and notifies the caller-side mobile communication exchange that the called mobile communication terminal has responded to the paging.

14. The system as claimed in claim 13, wherein the caller- side mobile communication exchange controls the caller-side wireless base station to release the bypass mode, and controls the calling mobile communication terminal to switch over the basic codec thereof to a voice codec.

15. The system as claimed in claim 12 or 14, wherein the caller-side mobile communication exchange controls the calling mobile communication terminal to change the basic codec thereof by transmitting a signaling message to the calling mobile communication terminal.

16. The system as claimed in claim 15, wherein the signaling message includes a data burst message when the mobile communication network employs a synchronous scheme.

17. The system as claimed in claim 16, wherein the data burst message includes a TI (Teleservice Identifier) field specifying a TI value which represents a start and an end of an interval of the alternative ringback tone service, an MIN (Mobile Identification Number) field representing an MIN of at least one of the calling and called mobile communication terminals, and a used codec information field representing a type of a codec to be used as the basic codec.

18. The system as claimed in claim 16, wherein the data burst message includes a TI (Teleservice Identifier) field and an MIN (Mobile Identification Number) field, and the TI field specifies a plurality of values, each representing a start and an end of an interval of the alternative ringback tone service, and indicates a type of codecs to be applied as the basic codec, corresponding to the plurality of values.

19. The system as claimed in claim 12, wherein the caller- side mobile communication exchange controls the caller-side wireless base station to set the bypass mode by transmitting a bypass setup message to the caller-side wireless base station, the bypass setup message having a transcoder control message controlling the caller-side wireless base station to set the bypass mode.

20. The system as claimed in claim 14, wherein the caller- side mobile communication exchange controls the caller-side wireless base station to cancel the bypass mode by transmitting a bypass cancel message to the caller-side wireless base station, the bypass release message having a transcoder control message controlling the caller-side wireless base station to cancel the bypass mode.

21. A mobile communication terminal for providing a ringback tone alternative ("RBT-alternative", hereinafter), the mobile communication terminal being provided with a mobile communication service and a RBT-alternative service from a mobile communication network, and requesting voice communication with a called mobile communication terminal, which receives a request for the voice communication, the mobile communication terminal comprising: an antenna for receiving a signaling message as an RF signal from the mobile communication network and transferring a received signaling message; an RF signal processor unit for demodulating the RF signal and transferring a demodulated signal; a baseband converter unit for receiving the demodulated signal, converting the demodulated signal into a baseband signal, performing analog-to-digital conversion for the baseband signal, and transferring a converted digital signal; a digital signal processor unit for setting or switching over a basic codec to either a voice codec or an audio codec, the digital signal processor unit including at least one of the voice codec and the audio codec, each of which is implemented by software or hardware; a memory unit for storing a codec switch-over program by which one of the voice codec and the audio codec is set as the basic codec; and a controller unit for receiving the digital signal from the baseband converter unit, analyzing the signaling message, and controlling the digital signal processor unit to set one of the voice codec and the audio codec as the basic codec by executing the codec switch-over program when the basic codec is to be switched.

22. The mobile communication terminal as claimed in claim 21, further comprising a speaker for outputting voice or a sound source decoded with one of the voice codec and the audio codec.

23. The mobile communication terminal as claimed in claim 21, wherein, when the controller unit receives an audio codec sound source encoded with the audio codec from the mobile communication network, the controller unit analyzes the audio codec sound source to check if an audio codec specified in the audio codec sound source coincides with an audio codec specified in the signaling message, and sets the audio codec specified in the audio codec sound source as the basic codec when the two audio codecs do not coincide with each other.

24. A method for providing a ringback tone alternative ("RBT- alternative", hereinafter) to a calling mobile communication terminal requesting communication with a called mobile communication terminal in a mobile communication network, the method comprising the steps of:

(a) receiving a request for the communication from the calling mobile communication terminal, and paging the called mobile communication terminal;

(b) checking if the called mobile communication terminal is eligible to a RBT-alternative service, controlling the calling mobile communication terminal to switch over a basic codec thereof to an audio codec, and transmitting an audio codec sound source encoded with the audio codec to the calling mobile communication terminal in a bypass mode;

(c) checking if the called mobile communication terminal responds to the paging of step (a) ;

(d) controlling the calling mobile communication terminal to switch over the basic codec thereof to a voice codec when a result of the checking at step (c) shows that the called mobile communication terminal does not respond to the paging; and

(e) canceling the bypass mode, and transmitting a voice message for the additional voice service to the calling mobile communication terminal.

25. The method as claimed in claim 24, further comprising, after step (c) , step (cl) of checking if a preset timer has expires .

26. The method as claimed in claim 24, further comprising, after step (d) , the steps of: (dl) controlling the calling mobile communication terminal to switch over the basic codec thereof to the voice codec when a result of the checking at step (c) shows that the called mobile communication terminal responds to the paging; and (d2) connecting the communication between the calling mobile communication terminal and the called mobile communication terminal .

27. The method as claimed in claim 24, wherein, at steps (b) and (e) , the mobile communication network controls the calling mobile communication terminal to change the basic codec thereof by transmitting a signaling message to the calling mobile communication terminal.

28. The method as claimed in claim 27, wherein the signaling message includes a data burst message when the mobile communication network employs a synchronous scheme.

29. The method as claimed in claim 24, further comprising, after step (b) , the steps of:

(bl) checking if the audio codec, with which the audio codec sound source is encoded, coincides with the audio codec set as the basic codec by analyzing the audio codec sound source and comparing the two audio codecs with each other in the calling mobile communication; and

(b2) setting the audio codec, with which the audio codec sound source is encoded, as the basic codec, and reproducing the audio codec sound source in the calling mobile communication terminal when a result of the checking at step

(bl) shows that the two audio codecs do not coincide with each other.

30. The method as claimed in claim 24, further comprising, after step (e) , step (el) of analyzing a data format of the voice message, detecting a pattern thereof, and reproducing the voice message by using the voice codec, set as the basic codec, in the calling mobile communication terminal upon learning that the voice message is encoded with the voice codec.

31. A system for providing a ringback tone alternative (""RBT-alternative", hereinafter) to a calling mobile communication terminal, which includes the calling mobile communication terminal requesting voice communication, a called mobile communication terminal receiving a request for the voice communication, and a sound source provider for providing a sound source of the RBT-alternative, the system comprising: a mobile communication network for controlling the calling mobile communication terminal to switch over a basic codec thereof to an audio codec and transmitting a sound source encoded with the audio codec, as the sound source to the calling mobile communication terminal upon receiving the request for the voice communication from the calling mobile communication terminal, while controlling the calling mobile communication terminal to switch over the basic codec thereof to a voice codec and transmitting a voice message for a supplementary voice service to the calling mobile communication terminal if called mobile communication terminal do not respond to the request for the voice communication for a prescribed time interval after paging the called mobile communication terminal.

32. The system as claimed in claim 31, wherein, if the called mobile communication terminal responds to the paging, the mobile communication network controls the calling mobile communication terminal to switch over the basic codec thereof to the voj.ce codec, and establishes a voice communication path between the calling mobile communication terminal and the called mobile communication terminal.

33. The system as claimed in claim 31, wherein the mobile communication network includes: a sound source providing device for storing and transferring the sound source, and creating and transferring an ISUP_CPG message containing information on the RBT-alternative, information on a bypass mode and control information when the sound source is the audio codec sound source; a voice message server for storing and transferring the voice message for the supplementary voice service; a caller-side wireless base station for transmitting the audio codec sound source to the calling mobile communication terminal in the bypass mode when receiving a request for a switchover to the bypass mode, and vocoding and transferring the voice message upon receiving a request for canceling the bypass mode; a caller-side mobile communication exchange for controlling the caller-side wireless base station to switch to the bypass mode, controlling the calling mobile communication terminal to switch over the basic codec thereof to the audio codec and then transmitting the audio codec sound source, transferred from the sound source providing device, to the calling mobile communication terminal via the caller-side wireless base station when receiving the ISUP_CPG message from the sound source providing device, and for requesting the caller-side wireless base station to cancel the bypass mode, controlling the calling mobile communication terminal to switch over the basic codec thereof to the voice codec and then transferring the voice message to the calling mobile communication terminal via the caller-side wireless base station upon receiving a request for processing the voice message; and a receiver-side mobile communication exchange for establishing an ISUP call with the caller-side mobile communication exchange, establishing an ISUP call with the sound source providing device, relaying the audio codec sound source, received from the sound source providing device, to the calling mobile communication terminal, and requesting the caller-side wireless base station to process the voice message if called mobile communication terminal do not respond to the request for the voice communication for a prescribed time interval after paging the called mobile communication terminal.

34. The system as claimed in claim 33, wherein the caller- side mobile communication exchange controls the calling mobile communication terminal to change the basic codec thereof by transmitting a signaling message to the calling mobile communication terminal.

35. The system as claimed in claim 34, wherein the signaling message has a data burst message when the mobile communication network employs a synchronous scheme.

36. The system as claimed in claim 33, wherein the caller- side mobile communication exchange controls the caller-side wireless base station to set up the bypass mode by transmitting a bypass setup message to the caller-side wireless base station, the bypass setup message having a transcoder control message controlling the caller-side wireless base station to set up the bypass mode.

37. The system as claimed in claim 33, wherein the caller- side mobile communication exchange controls the caller-side wireless base station to release the bypass mode by transmitting a bypass release message to the caller-side wireless base station, the bypass release message having a transcoder control message controlling the caller-side wireless base station to release the bypass mode.

38. A mobile communication terminal capable of using a voice communication service, a supplementary voice service and a ringback tone alternative ("RBT-alternative", hereinafter) service, provided a mobile communication network, the mobile communication terminal requesting voice communication with a called mobile communication terminal which receives a request for the voice communication, by using the mobile communication network, the mobile communication terminal comprising: an antenna for receiving a signaling message as an RF signal from the mobile communication network and transferring the received signaling message; an RF signal processor unit for demodulating the RF signal and transferring the demodulated signal; a baseband converter unit for receiving the demodulated signal, converting the demodulated signal into a baseband signal, performing analog-to-digital conversion processing for the baseband signal, and transferring a converted digital signal; a digital signal processor unit for setting or switching over a basic codec to either a voice codec or an audio codec, the digital signal processor unit including at least one of the voice codec and the audio codec, each of which is implemented by software or hardware; a memory unit for storing a codec switch-over program by which one of the voice codec and the audio codec is set as the basic codec; and a controller unit for receiving the digital signal, analyzing the signaling message, controlling the digital signal processor unit to set either the voice codec or the audio codec as the basic codec by executing the codec switch-over program when the basic codec is to be switched over, and analyzing a data format of an audio codec sound source encoded with the audio codec or a voice message encoded with the voice codec and detecting a pattern thereof to set a codec corresponding to the detected pattern as the basic codec and reproduce the audio codec sound source or the voice message by using the basic codec when receiving the audio codec sound source or the voice message from the mobile communication network.