BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a message service of a mobile communication system, and more particularly to a service for transmitting a message free of charge.

2. Description of the Related Art

Nowadays, a message service in a mobile communication system is not just limited to a plain text message service such as a Short Message Service (SMS), and is being developed to a message service capable of transmitting much richer contents such as rich texts (e.g. XHTML), audio, images and videos. An example that provides this is a Multimedia Messaging Service (MMS), which is continuously being improved in various standardization bodies such as an Open

Mobile Alliance (OMA), a 3 ^rd Generation Partnership Project (3GPP) and 3GPP2.

As the type of information exchanged between users becomes richer, the amount of charge that users must bear may also increase, which may dissuade some users from using the service as freely as they would like. For example, in an MMS as standardized in a 3GPP (32.270), both the transmission of a multimedia message to an MMS server by an originating mobile communication terminal, i.e. an originating client, and the retrieval of the message by a recipient client from the MMS server are charged. The sender is expected to be charged for the amount of transmitted data and the recipient is expected to be charged for the amount of received data, so both parties must pay a price charges for the same transmitted data. For example, if multiple transmissions or receptions are necessary for the same message due to network problems, etc., and these repetitions of events are counted as separate events, the charged amount may considerably increase.

Another example where charges occur is when a mobile communication terminal B transmits a message, which is received from a mobile communication terminal A, to another mobile communication terminal C, in which case the mobile communication terminal B is the charged party. Even if the mobile

communication terminal B may think that the message could be highly valuable for a user of the mobile communication terminal C, but it does not want to pay the price for the transmission of the message and may finally decide not to transmit it. This may penalize not just a user of the mobile communication terminal C, who will not be able to receive potentially high- value content, but also a user of the mobile communication terminal A who may wish his message to be distributed to as many recipients as possible. A typical example is where an initial originating user is a service provider who wants to advertise his services (e.g. news service via MMS): the service provider would like his current subscribers to retransmit his content to other mobile communication terminal users, with the hope of attracting new users to his services. However, the charge that his current subscribers must bear to transmit his content may represent a barrier, and the service provider may also desire to bear the charge on their behalf.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the above- mentioned problems occurring in the prior art, and it is an object of the present invention to provide a method and a system for providing a free messaging service, in which an originating mobile communication terminal bears the charge when a receiving mobile communication terminal transmits a message, which is received from the originating mobile communication terminal, to another mobile communication terminal.

One of the desires of this invention is not just to limit the free-forward charging to an initial forward request, but to extend this possibility to any subsequent forward request as well. In other words, another object of the present invention is to provide a method and a system for providing a free messaging service, in which, even when a user does indirectly receives a message through transmission of an initial receiving mobile communication terminal instead of directly receiving the message from an initial originating mobile communication terminal, a mobile communication terminal of the user can transmit the message free of charge.

It is further another object of the present invention to provide a method and a system for providing a free messaging service, in which an initial originating user can set appropriate limits for a free messaging service.

It is still another object of the present invention to provide a method and a system for providing a free messaging service, in which an initial originating user can provide details relating to a free messaging service that the initial originating user will bear the charge for free messaging service. In accordance with one aspect of the present invention, there is provided a method for providing a free messaging service in a free messaging service system which includes a plurality of message service servers, a plurality of mobile communication terminals, a plurality of information service servers for providing various information through a message, an accounting server for processing charges incurred in relation to a messaging service, the method including the steps of: transmitting by the message service server the message to a free messaging service receiving terminal preset by a free messaging service request terminal according to a free messaging service request for a predetermined message; transmitting by the terminal having received the message a free transmission request for the message; and transmitting by the message service server the message to a receiving terminal set by the receiving terminal when the free transmission request is received, and imposing charges incurred by transmission of the message on the free messaging service request terminal.

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 block diagram illustrating the construction of a free messaging service system to which the present invention is applied;

FIG. 2 is a flow diagram illustrating an operation of a free messaging service system according to one embodiment of the present invention;

FIGs. 3 a and 3b are flow diagrams illustrating an operation of a message service server according to one embodiment of the present invention;

FIG. 4 is a flow diagram illustrating an operation of a mobile communication terminal according to one embodiment of the present invention

FIG. 5 is a ladder diagram illustrating message flow of a free messaging service system according to one embodiment of the present invention; FIG. 6 is a block diagram illustrating a charging particulars report process

- A -

of a free messaging service according to one embodiment of the present invention; and

FIG. 7 is a diagram illustrating the header of a free message according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will be described in detail herein below with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

FIG. 1 is a block diagram illustrating the construction of a free messaging service system to which the present invention is applied. Referring to FIG. 1 , the free messaging service system includes entities such as a plurality of message service servers 40, 50 and 60, a plurality of mobile communication terminals 10, 20 and 30, and an accounting server 70. In the present invention, the message service servers 40, 50 and 60 are provided, but the mobile communication terminals 10, 20 and 30 may also be connected to one message service server. The accounting server 70 is connected to the message service servers 40, 50 and 60, and the mobile communication terminals 10, 20 and 30 are connected to the message service servers 40, 50 and 60 through a mobile communication network 80, respectively. Herein, an accounting server may separately exist according to each message service server or one accounting server may also exist corresponding to multiple message service servers. According to one embodiment of the present invention, the first message service server 40 is connected to the first mobile communication terminal 10, the second message service server 50 is connected to the second mobile communication terminal 20, and the third message service server 60 is connected to the third mobile communication terminal 30. In the detailed description of the present invention, the fact that the certain message service server is connected to the certain mobile communication terminal through the mobile communication network 80 represents that the certain mobile communication terminal is located in a service area of the certain message service server. Further, the mobile communication terminal is not always necessary to be located near its own home message service

server, and may be connected to a home message service server through roaming.

The accounting server 70 receives all accounting information occurring according to a messaging service from the connected message service servers 40, 50 and 60, and imposes charges of a mobile communication terminal relating to the messaging service.

Each of the message service servers 40, 50 and 60 performs a messaging service operation for controlling message transmission/reception between random mobile communication terminals, and performs an operation based on a free messaging service according to the present invention. The free messaging service represents a messaging service in which an initial originating terminal bears the charge under the predetermined limitations, which occurs when a receiving terminal transmits a free massage received from the initial originating terminal to another mobile communication terminal. Herein, the retransmission of a free message by a request of a receiving terminal, which has received the free message according to the free messaging service, to another mobile communication terminal under non-occurrence conditions of the charge, i.e. the retransmission of the free message performed by receiving terminals receiving the free messaging service, will be referred to as a sub-messaging service. The free message represents a message transmitted through the free messaging service. The mobile communication terminals 10, 20 and 30 perform various communication services provided by a mobile communication system, and perform communication with the message service servers 40, 50 and 60 through the mobile communication network 80, respectively. Each of the mobile communication terminals 10, 20 and 30 has a construction similar to that of a general mobile communication terminal, and corresponds to a client which performs an operation based on the free messaging service according to the present invention.

In the present invention, the free messaging service system includes information service servers for providing various information such as news, weather and advertisements, and it is possible to request a free messaging service for messages transmitted from the information service servers. In such a case, each of the information service servers corresponds to a client of the free messaging service according to the present invention.

Hereinafter, a process in which the free messaging service according to the present invention is provided by the free messaging service system having the

constraction as described above will be described with reference to FIG. 2. FIG. 2 is a flow diagram illustrating an operation of the free messaging service system according to one embodiment of the present invention. An entire operation process based on the free messaging service according to the present invention follows steps as shown in FIG. 2. However, detailed operation processes of a message service server and multiple mobile communication terminals, which constitute the free messaging service system according to various embodiments of the present invention, may be altered, and transmission of information which these entities exchange in order to share information necessary for performing operations may be selectively performed. Hereinafter, in a detailed description of FIG. 2, it is assumed that each element of the free messaging service system according to one embodiment of the present invention is stateless. That is, since both a mobile communication terminal and a message service server delete all information relating to the free messaging service after processing of a message, it is assumed that each entity transmits/receives all information relating to the free messaging service each time. Each step shown in FIG. 2 corresponds to each step shown in FIG. 1.

Referring to FIG. 2, in step a, one of the mobile communication terminals 10, 20 and 30 sets free forward limitation information on a random message, and requests a currently connected message service server to provide a free messaging service. Step a corresponds to step a. Submit shown in FIG. 1.

Hereinafter, one example in which the first mobile communication terminal 10 requests the free messaging service in step a according to the embodiment of the present invention will be described. That is, the first mobile communication terminal 10 is a free messaging service request client in one embodiment of the present invention, and thus corresponds to a client which bears all charges due to the use of the free messaging service. Further, the second mobile communication terminal 20 corresponds to a receiving terminal of the free messaging service by the first mobile communication terminal 10, and the third mobile communication terminal 30 corresponds to a receiving terminal of both the free messaging service and a free sub-messaging service by the second mobile communication terminal 20. In order to request the first message service server 40 to provide a free messaging service for a random message in step a, the first mobile communication terminal 10 inserts free forward limitation information and charging particulars-reporting information into the header of the random

message so as to create a free message, and transmits the free message to the first message service server 40.

The free forward limitation information represents information necessary for the free messaging service, and includes free forward messaging service indication information, forward charge bearer identification information, free forward sub-messaging information, limitation information on the allowed number of free forwards, information on the maximum size of a forwarded message, free forward message deadline information, and free forward message receiving terminal list information. Further, the free forward limitation information may become free forward limitation conditions if the situation requires.

The free forward messaging service indication information represents that the present message is an object of the free messaging service under the predetermined limitations. The forward charge bearer identification information is identification information of a client which bears the charge incurred by the free messaging service, and identification information of a client requesting an initial free messaging service. In one embodiment of the present invention, identification information of the first mobile communication terminal 10 corresponds to the forward charge bearer identification information. The forward charge bearer identification information must be maintained in the free messaging service system until the free messaging service is terminated.

The free forward sub-messaging information includes a message identifier (ID), and corresponds to information for identifying a request of a free sub-messaging service by a receiving client and a message transmitted free of charge. For example, ID information of a message recently received from an originating terminal is set as the free forward sub-messaging information.

The limitation information on the allowed number of free forwards corresponds to limitation setup information on the number of free forwards allowed to exempt the charge. The limitation information on the allowed number of free forwards includes the maximum number of free forwards and the maximum level of free forwards.

The maximum number of free forwards represents the maximum number of recipients to which a terminal can transmit, freely of charge, a message received through the free messaging service. This value decreases by the

number of receiving terminals each time when the free sub-messaging service is accepted, so it may also be interpreted as the remaining number of free forwards by a random receiving terminal.

The maximum level of free forwards indicates how many times a message can be subsequently transmitted from one receiving terminal to another mobile communication terminal. The maximum level of free forwards decreases by one when a random receiving terminal initially requests the free messaging service, so it may also be interpreted as the remaining number of levels of entire free forwards. The difference between the maximum number of free forwards and the maximum level of free forwards can be understood by the following examples. Suppose that a mobile communication terminal A transmits a message to a mobile communication terminal B through a free messaging service with the maximum number of free forwards set to 2 and the maximum level of free forwards set to 1. According to these limits, the mobile communication terminal B can transmit this message free of charge to two users at maximum, e.g. mobile communication terminals C and D. However, neither the mobile communication terminal C nor the mobile communication terminal D can transmit this message free of charge. This is because this message has already been transmitted once, so the maximum level of free forwards of 1 has been reached.

Suppose in another example that a mobile communication terminal A transmits a message to a mobile communication terminal B through a free messaging service with the maximum number of free forwards set to 1 and the maximum level of free forwards set to 2. In this case, the mobile communication terminal B can transmit this message free of charge only to a single mobile communication terminal, e.g. the mobile communication terminal C. This is because the maximum number of free forwards has been set to 1. On the other hand, the mobile communication terminal C can transmit this message to another mobile communication terminal. This is because this message has been transmitted only once and the maximum level of free forwards has been set to 2.

The information on a maximum size of a forwarded message represents information on the maximum size of a message which can be transmitted through the free messaging service, and the maximum size corresponds to a sum of a free message and additional data which can be added by the receiving terminal of the free message. The additional data have a size determined according to selection

of a free messaging service request terminal, and the receiving terminal can add a reason for transmitting a free message, etc., as the additional data. It is however necessary to limit the amount of the additional data to limit the resulting additional charges. The free forward message deadline information represents information on a deadline until which a message of a free messaging service can be transmitted free of charge. Sometimes, the content of a message may lose its importance or significance if it reaches a receiving terminal too late. For example, a news service provider would like his content to be distributed in a short period of time to give the maximum effect to potential future subscribers; it would give more effect to transmit some breaking news on the day the event happened rather than a week later. Accordingly, it is preferred to set a deadline of a free messaging service according to user selection.

The free forward message receiving terminal list information represents information on a list of recipients to which a free messaging service is provided, and includes information of multiple receiving terminals according to user selection. If a free messaging service request teπninal sets the list, a free message can be transmitted only to mobile communication terminals belonging to the list. For example, if a mobile communication teπninal A registers a mobile communication terminal C in the list and performs a free messaging service, a free message is received in a mobile communication terminal B and then the same message is also transmitted to the mobile communication terminal C according to the selection of the mobile communication terminal B. That is, the mobile communication terminal A leaves the choice, which regards transmission or non- transmission of the message to a certain receiving teπninal, to the mobile communication terminal B, and can encourage transmission of the message to the mobile communication terminal C by taking over the charge for the transmission of the message.

The charging particulars-reporting information is required when performing a charging particulars report for providing particulars about the charge actually occurring according to performance of the free messaging service to a free messaging service request terminal. The charging particulars report follows the accomplishment process of the free messaging service, and belongs to the free messaging service. In the free messaging service, since a mobile communication terminal requesting the free messaging service bears all charges,

the free messaging service request terminal needs to receive information on the charges of the free messaging service. Even if the free messaging service request terminal sets the free forward limitation conditions as described above when requesting the free messaging service, it is difficult to estimate the number of receiving terminals which actually use the opportunity of the free forward. Accordingly, actual charging particulars information based on the free messaging service is necessaiy.

The charging particulars-reporting information includes charging particulars report indication information and information on a time point at which the final charging particulars report is provided. The charging particulars report indication information represents that a free messaging service request terminal has requested a charging particulars report. The information on a time point represents information on a time point at which the final charging particulars, which have been collected for all charging particulars occurred during the free messaging service, are provided to a free messaging service request terminal. It is preferred to set the time point as a time point later than a transmission deadline of a free message preset in the free messaging service.

The charging particulars report is requested together with the setup of the charging particulars-reporting information when the free messaging service is requested, and is performed according to an accomplishment process of the free messaging service. Hereinafter, for aiding the understanding of the present invention, an operation process of the free messaging service system according to the free messaging service will be first described, and then details of the charging particulars report according to the free messaging service will be described. The free forward limitation information and the charging particulars- reporting information as described above are included in a message provided through the free messaging service, i.e. information on the header of the free message, and the header including the free forward limitation information has a construction as shown in FIG. 7. FIG. 7 is a diagram illustrating the header of the free message according to one embodiment of the present invention. Referring to FIG. 7, the header field 500 includes a Fwd-Charging field 501, a Fwd-Charging-Party field 503, a Fwd-Charging-ID field 505, a Fwd-Charging- MaxNb field 507, a Fwd-Charging-MaxLvl field 509, a Fwd-Charging-MaxSize field 511, a Fwd-Charging-Deadline field 513, a Fwd-Charging-Recv field 515, a Fwd-Charging-Rep field 517, and a Fwd-Charging-Rep Data field 519.

The Fwd-Charging field 501 stores the free forward messaging service indication information, and the Fwd-Charging-Party field 503 stores the forward charge bearer identification information. The Fwd-Charging-ID field 505 stores ID information of a message recently received from an originating terminal, so stores free forward sub-messaging information. The originating terminal is a terminal which has recently requested a free sub-messaging service. The ID of the message received from the originating terminal is inserted into the Fwd- Charging-ID field 505, so that it is possible to request the free sub-messaging service and to provide information used for determining either a terminal capable of requesting the free sub-messaging service or a message. The Fwd-Charging- MaxNb field 507 stores the maximum number of free forwards, the Fwd- Charging-MaxLvl field 509 stores the maximum level of free forwards, and the Fwd-Charging-MaxSize field 511 stores the information on the maximum size of a forwarded message. The Fwd-Charging-Deadline field 513 stores the free forward message deadline information, and the Fwd-Charging-Recv field 515 stores the free forward message receiving terminal list information. The Fwd- Charging-Rep field 517 stores the charging particulars report indication information, and the Fwd-Charging-Rep Data field 519 stores the information on a time point at which the final charging particulars report is provided. Returning to FIG. 2, if the first mobile communication terminal 10 transmits a free messaging service request to the first message service server 40 in step a, the first message service server 40 refers to free forward limitation information included in a received free message, in step b. Then, the first message service server 40 transmits the free message and the free forward limitation information to the second message service server 50 which is a message service server connected to a receiving terminal. Step b corresponds to step b. Transfer shown in FIG. 1.

In step c, the second message service server 50 having received the free message informs the receiving terminal of the arrival of the free message, and transmits the free message. Herein, the second message service server 50 transmits the free forward limitation information together with a guidance message about the free message, thereby informing the receiving terminal that the free messaging service is possible. Then, if the receiving terminal requests transmission of the free message, the second message service server 50 transmits the free message to the receiving terminal. Step c corresponds to step

c. Notify/retrieve shown in FIG. 1.

In step d, the receiving terminal having received the free message transmits a free sub-messaging service request to the second message service server 50 in order to transmit the received free message to another terminal free of charge. Herein, the receiving terminal inserts the following information into the free sub-messaging service request. The following information includes the identification information of a party who bears the charge for the free sub- messaging service and the free forward sub-messaging information (i.e. Fwd- Charging-ID field 505) for identifying the free message with the acceptance of the free- forward by an initial originating terminal, i.e. the free forward limitation information equal to that included in step a. Further, the receiving terminal may set the address of a new receiving terminal which is to receive the free message, and add additional data according to user input to the free message.

Then, the second message service server 50 determines if the free forward sub-messaging information received from the receiving terminal coincides with the free forward sub-messaging information included in the free message before the free message is transmitted to the receiving terminal. The free forward sub- messaging information is indicated by the ID of the message recently received from the originating terminal, and each of the message service servers 40, 50 and 60 determines if a message ID received from a receiving terminal coincides with a message ID included in a free message before the free message is transmitted to the receiving terminal. Further, each of the message service servers 40, 50 and 60 checks another free forward limitation information, and grants a free sub- messaging service to the receiving terminal if conditions are satisfied. After the free sub-messaging service is granted, the free forward limitation information is partially altered. This may be performed by either each of the message service servers 40, 50 and 60 or the receiving terminal according to the embodiment of the present invention. First, the maximum number of free forwards decreases by the number of receiving terminals. This is because the free forward of a message from the receiving terminal to another terminal has been granted. The decrease in the maximum number of free forwards occurs whenever the free forward request for a message of the receiving terminal is granted, and the free forward request for a message is granted until the maximum number of free forwards becomes zero. Herein, both the message service server and the receiving terminal must know information on the maximum number of

free forwards altered as described above.

Step d corresponds to step d.Forward shown in FIG. 1. That is, in the embodiment of the present invention, the second mobile communication terminal 20 receives a free message. The second mobile communication terminal 20 designates the third mobile communication terminal 30 as a new receiving terminal, and transmits a free sub-messaging service request for the received free message to the second message service server 50. The second message service server 50 checks the free forward limitation information received from the second mobile communication terminal 20 together with the free sub-messaging service request, and grants the free sub-messaging service request.

In step e of FIG. 2, the second message service server 50 informs the accounting server 70 of occurrence of the free sub-messaging service, and transmits necessary accounting information to the accounting server 70. Herein, the second message service server 50 clearly informs the accounting server 70 that a charged terminal is the initial originating terminal, i.e. the first mobile communication terminal 10. Step e corresponds to step e. Charge shown in FIG. 1.

After the accounting information is completely transmitted to the accounting server 70, the free forward limitation information is modified according to the accomplishment of the free sub-messaging service, and the second message service server 50 transmits the free message and the modified free forward limitation information to a message service server to which the receiving terminal of the free message service is connected, in step f.

The free forward limitation information modified according to the accomplishment of the free sub-messaging service corresponds to the maximum level of free forwards and the sub-messaging service request information. The maximum level of free forwards decreases by one and reset. This resetting may also be performed by either the message service server or the receiving terminal according to the embodiment of the present invention. Since the maximum level of free forwards must decrease by one only when a certain receiving terminal initially requests the sub-messaging service, right management for this is necessary. Since the sub-messaging service request information is comprised of the message ID recently received from the originating terminal, the message service server sets a new ID in a message for which the receiving terminal has requested the sub-messaging service, and the ID of the message is converted as

the sub-messaging service request information.

The message service server inserts the free forward limitation information modified as described above into a free message, and transmits the free message to a message service server to which a receiving terminal according to the sub- messaging service, i.e. a sub-receiving terminal which is a new receiving terminal, is connected. Herein, the maximum number of free forwards included in the free forward limitation information is initialized as the initial maximum number of free forwards set by an initial originating terminal, i.e. a terminal requested the free messaging service, and is then transmitted. Step f corresponds to step f. Transfer shown in FIG. 1. The second message service server 50 modifies the free forward limitation information by the free sub-messaging service request of the second mobile communication terminal 20, inserts the modified free forward limitation information into a free message, and transmits the free message to the third message service server 60 to which the third mobile communication terminal 30 (the new receiving terminal) is connected.

In step g, the third message service server 60 having received the free message informs the receiving terminal of the free message, i.e. the third mobile communication terminal 30, of the arrival of the free message, and transmits the free message, similarly to step c. Herein, the free forward limitation information included in the free message corresponds to the free forward limitation information modified in step f. The sub-receiving terminal may perform the same operation as that of the receiving terminal in step d. However, if the maximum level of free forwards included in the modified free forward limitation information is zero, the sub-receiving terminal cannot receive the free messaging service any more, and cannot request the free sub-messaging service.

According to the above-described embodiment in which each elements of the free messaging service system is stateless, the entities of the free messaging service system, i.e. each mobile communication terminal and each message service server transmit/receive all free forward limitation information when transmitting/receiving a free message or performing operations relating to the transmission /reception of the free message. This is because the "stateless" means a state in which, after transmission of the free message, neither the mobile communication terminal nor the message service server need to remember any information element relating to the free messaging service.

However, in another embodiment of the present invention, transmission of the free forward limitation information may be selectively performed between entities. If each element of the free messaging service system is stateful, a message service server and a mobile communication terminal, which relate to the free messaging service, store information necessary for the free messaging service even after message transmission. Accordingly, the message service server inserts free forward limitation information required in each operation into a free message, etc., and transmits the free message.

As described above, the entities of the free messaging service system basically share the free forward limitation information required when performing the free messaging service, but free forward limitation information actually exchanged among the entities in order to share the free forward limitation information may be altered according to embodiments of the present invention.

In addition to the stateless and stateful states of each entity of the free messaging service system as described above, the type of free forward limitation information exchanged among the entities of the free messaging service system may be altered according to existence or absence of a default value.

When the free forward limitation information is not set according to user selection, the default value of the free forward limitation information is a basic value set as the free forward limitation information by the free messaging service system. The default value may also exist corresponding to all information included in the free forward limitation information or may also selectively exist.

When the element of the free forward limitation information having the default value as described above has not been specified by a user, or has been specified as equal to this default value by a mobile communication terminal or a message service server, if such a default value has been previously stored in subsequent mobile communication terminal or message service server, the mobile communication terminal and the message service server do not need to insert the free forward limitation information having the default value into a free message. Accordingly, the free forward limitation information exchanged among mobile communication terminals or message service servers is selectively transmitted.

The selective transmission of the free forward limitation information may also be performed according to free messaging service request states, in addition to the stateful state or the stateless state and existence or absence of a default value.

For example, when the address of a free messaging service request terminal is used as identification information of a charge bearer in a free messaging service, it is not necessary to specify the forward charge bearer identification information when the free messaging service request terminal initially transmits a free message. This is because the address of the free messaging service request terminal has already been specified elsewhere, e.g. in the "From field". However, this assumes that right mapping must be made by a certain message service server between information on the "From field" and the forward charge bearer identification information in order to correctly notify an accounting server of information on a mobile communication terminal taking over the charge. Further, omitting transmission of the forward charge bearer identification information must be limited to a case where the free messaging service request terminal transmits the free message to a message service center. In a case where a free message receiving terminal retransmits the free message, the forward charge bearer identification information should not be omitted because the information on the "From field" differs from the party to be charged.

Further, according to whether a sub-free forward service request is granted by a message service server or a receiving terminal, selective transmission of free forward limitation information may be variously performed, and the operation processes of a message service server and a mobile communication terminal may also change.

Hereinafter, the free forward limitation information selectively transmitted while the steps of FIG. 2 are performed according to the various embodiments as described above will be described. It should be noted that the default value is generally applicable to all the steps below unless specified otherwise, even if they are explicitly mentioned in some of them only.

Referring to FIGs. 1 and 2, in step a of requesting the free messaging service, the free messaging service request terminal transmits all forward limitation information to the message service server regardless of the stateless/stateful state. In order to perform the free messaging service, any information should not be omitted because all free forward limitation information is required. However, when default values exist for information included in the free forward limitation information and the default values have been known by the message service server, it is not necessary to transmit free forward limitation information not explicitly specified by the user of the free messaging service

request terminal or specified as equal to the default values. For example, if free forward message receiving terminal list information has not been specified and known default values are to be transmitted to anybody free of charge within the range of the other free forward limitation information, it is not necessary to transmit the free forward message receiving terminal list information to a message service server.

Next, similar remarks as in step a are applied to step b of transmitting the free message to the message service server, to which the receiving terminal is connected, according to the free messaging service requested in step a. All forward limitation information is transmitted to the message service server, to which the receiving terminal is connected, regardless of the stateless/stateful state of each entity, but forward limitation information having default values is not transmitted. For example, in a case where the first message service server 40 transmits a free message to the second message service server 50, if a default value for the free forward limitation information exists, the second message service server 50 stores the default value, and free forward limitation information corresponding to the default value has not been specified by a free messaging service request terminal or specified as equal to the default value, the first message service server 40 does not transmit the free forward limitation information corresponding to the default value to the second message service server 50. The selective transmission of the free forward limitation information according to existence or absence of the default value is similarly performed in steps c to g below.

In step c in which the message service server transmits the received free message to a receiving terminal, the type of transmitted/received free forward limitation information is altered according to whether the free sub-messaging service is granted by a message service server or a mobile communication terminal under the condition that entities of the free messaging service system are stateful. First, when the message service server determines whether to grant the free sub-messaging service, the maximum level of free forwards is not transmitted to the receiving terminal. This is because the maximum level of free forwards is necessary only when the message service server determines whether to grant the free sub-messaging service. However, it is necessary to transmit the free forward limitation information except for the maximum level of free forwards to the receiving terminal and to provide the user of the receiving

terminal with information on the free messaging service.

Further, when the mobile communication terminal determines whether to grant the free sub-messaging service, the message service server must transmit the free forward limitation information including the maximum level of free forwards to the receiving terminal.

Also in step d in which the free message receiving terminal requests the free sub-messaging service, if each entity is stateless, all free forward limitation information is transmitted/received. However, if each entity is stateful, the type of transmitted/received free forward limitation information is altered according to whether the free sub-messaging service is granted by a message service server or a mobile communication terminal.

In a state where all entities are stateful, when the message service server determines whether to grant the free sub-messaging service, if a receiving terminal transmits a sub-messaging service request to the message service server, all free forward limitation information is not specified. In this case, free forward limitation information, which must be uniquely provided to the message service server, is sub-messaging service infoπnation. The sub-messaging service information corresponds to ID information of a message recently received from an originating terminal, and the message service server determines whether to grant the free sub-messaging service by means of the sub-messaging service information.

In a state where all entities are stateful, when the mobile communication terminal determines whether to grant the free sub-messaging service, if the receiving terminal requests the free sub-messaging service, free forward limitation information, which is transmitted from the receiving terminal to the message service server, is free forward sub-messaging information.

When each entity is stateful, since the message service server stores the limitation information on the allowed number of free forwards, i.e. the maximum number of free forwards and the maximum level of free forwards, the mobile communication terminal do not transmit the maximum number of free forwards and the maximum level of free forwards to the message service server. Further, since both the maximum number of free forwards and the maximum level of free forwards decrease whenever the free sub-messaging service is granted, the message service server must manage the maximum number of free forwards and the maximum level of free forwards corresponding to each mobile

communication terminal which receives the free messaging service. The message service server decreases the maximum level of free forwards relating to a certain receiving terminal only when the certain receiving terminal initially requests the free sub-messaging service. When the same receiving terminal requests the free sub-messaging service secondarily and thirdly, the message service server does not decrease the maximum level of free forwards. Further, the decreased maximum level of free forwards is not restored. In the meantime, the message service server decreases the maximum number of free forwards by the number of sub-receiving terminals designated as recipients of the free sub- messaging service by the certain receiving terminal. However, since the maximum number of free forwards, which is included in the free message transmitted to another receiving terminal, is initialized and transmitted, the maximum number of free forwards of said another receiving terminal is reset.

Then, in step e of transmitting accounting information of the free sub- messaging service to the accounting server 70, the message service server must rightly provide the accounting server 70 with all information necessary for the charge about a transmission request, and transmits forward charge bearer identification information.

In step f of transmitting the free message to the free message sub- receiving terminal according to the free sub-messaging service, free forward limitation information is transmitted/received similarly to step b. For example, if a default value exists in given free forward limitation information, the third message service server 60 stores the default value, and the free forward limitation information having the default value has not been specified by the second mobile communication terminal 20 or specified as equal to the default value, the second message service server 50 does not need to transmit the free forward limitation information having the default value to the third message service server 60. However, the maximum level of free forwards decreasing whenever the free sub- messaging service is requested must be necessarily transmitted. Further, since the maximum number of free forwards is initialized according to the setup of a new receiving terminal, when a default value for the maximum number of free forwards exists and the initialized value is equal to the default value, the maximum number of free forwards may not be transmitted.

In step g in which the message service server transmits the received free message to the sub-receiving terminal, the free forward limitation information is

transmitted/received similarly to step c.

The above description relates to the free forward limitation information transmitted/received by each entity when the free messaging service is provided according to the stateless state or the stateful state of each entity of the free messaging service system, existence or absence of the default value, and the granter of the free sub-messaging service.

Hereinafter, operation processes of the message service server and the mobile communication terminal according to the stateless state or the stateful state of each entity, and the granter of the free sub-messaging service will be described with reference to FIGs. 3 a, 3b, 4a and 4b. FIGs. 3 a and 3b are flow diagrams illustrating an operation of the message service server according to one embodiment of the present invention. FIGs. 4a and 4b are flow diagrams illustrating an operation of the mobile communication terminal according to one embodiment of the present invention. First, the operation process of the message service server will be described with reference to FIGs. 3a and 3b. FIGs. 3a and 3b illustrate the operation process of the message service server when each entity of the free messaging service system is stateful and the free sub-messaging service is granted by the message service server. Referring to FIG. 3 a, in step 101, the message service server receives a free message. In step 103, the message service server checks free forward limitation information included in the free message. In step 105, the message service server determines if a free message receiving terminal exists in a service area of the message service server. If the receiving terminal exists in the service area, step 107 is performed. However, if the receiving terminal does not exist in the service area, step 133 is performed. In step 133, the message service server transmits the free message to a corresponding message service server to which the receiving terminal is connected.

In step 107, the message service server determines if the maximum level of free forwards included in the free forward limitation information is zero. As a result of the determination, if the maximum level of free forwards is zero, step 111 is performed. However, if the maximum level of free forwards is not zero, step 109 is performed. The fact that the maximum level of free forwards is zero represents that the receiving terminal can receive the free message, but it has no authority to transmit the free message to another terminal free of charge.

Accordingly, in step 111, the message service server transmits only a guidance message about the free message to the receiving terminal. Then, step 115 is performed.

When the maximum level of free forwards of the free message is not zero, the message service server performs operations corresponding to steps 109 and 113. In step 109, the message service server sets the current maximum number of free forwards of the free message receiving terminal to be the initial maximum number of free forwards, and stores the set maximum number of free forwards. In step 113, the message service server transmits a guidance message about the free message, which includes the free forward limitation information with the initial maximum number of free forwards, to the receiving terminal. Herein, the maximum level of free forwards may be excluded from the free forward limitation information. The free forward limitation information provides the receiving terminal with information representing that the receiving terminal receives the free messaging service and has authority to request the free sub- messaging service. The guidance message reports existence of a free message to be received. The maximum number of free forwards represents the number of times by which the receiving terminal can transmit the free message to another terminal free of charge. The receiving terminal receives the free forward limitation information and the guidance message, so that the user of the receiving terminal can become aware of reception of the free messaging service. Further, the user of the receiving terminal checks the maximum number of free forwards, thereby becoming aware of the number of times by which a message can be transmitted free of charge. If the receiving terminal receives the guidance message, the receiving terminal transmits a response message to the message service server in response to the guidance message, and requests transmission of a free message according to user input.

In step 115, the message service server receives the response message and the free message transmission request from the receiving terminal. In step 117, the message service server transmits the free message to the receiving terminal. Then, step 119 of FIG. 3 is performed.

After receiving the free message from the message service server, the receiving terminal requests the free sub-messaging service in which the receiving terminal can transmit the received free message to another terminal free of charge

according to user demand. Herein, the receiving terminal transmits free forward sub-messaging information of the received free forward limitation information together with the free sub-messaging service request, and can omit transmission of another free forward limitation information. Further, the receiving terminal transmits both the address of a mobile communication terminal (i.e. new receiving terminal), which receives the free sub-messaging service, and additional data according to user input.

In step 119, the message service server receives the free sub-messaging service request from the receiving terminal, i.e. the free sub-messaging service request terminal. In step 121, the message service server compares message ID information, which is included in the received free forward sub-messaging information, with the message ID of a recent originating terminal included in stored free forward limitation information. If the two message IDs coincide with each other, step 123 is performed. Otherwise, step 139 is performed. In step 123, the message service server determines if the requested free sub-messaging service satisfies free forward limitation conditions. In other words, the message service server determines if the size of the additional data received in step 119 satisfies the maximum size of a forwarded message, the address of the new receiving terminal received in step 119 is included in the free forward message receiving terminal list, the number of receiving terminals does not exceed the current maximum number of free forwards, and the current time point satisfies the free forward message deadline. If the free sub-messaging service satisfies all conditions, step 125 is performed. Otherwise, step 139 is performed. In step 139, the message service server transmits a message representing that the free messaging service is impossible and terminates the operation process because the message ID received from the receiving terminal does not coincide with the stored message ID of the recent originating terminal, and the requested free sub- messaging service does not satisfy the free forward limitation conditions.

In step 125, the message service server decreases the current maximum number of free forwards for the receiving terminal by the number of free message sub-receiving terminals for resetting. In step 127, the message service server transmits charge information incurred according to the free sub-messaging service request to the accounting server 70. In step 129, the message service server sets a new ID in the received sub-free message, and transmits a free sub-messaging service request response message including the new message ID and the reset

maximum number of free forwards, thereby granting the free sub-messaging service of the receiving terminal. The receiving terminal receives the free sub- messaging service request response message, and can become aware of the remaining number of transmissions of a free message through the reset maximum number of free forwards.

In step 131, the message service server determines if the free sub- messaging service for the same free message had been previously requested by the terminal requested the free sub-messaging in step 119. If the free sub- messaging service for the same free message had been previously performed by the terminal, step 135 is performed. Otherwise, step 133 is performed. In step 133, the message service server decreases the maximum level of free forwards by one for resetting. This is because the maximum level of free forwards of a free message decreases by one whenever the free sub-messaging service is initially performed by a certain mobile communication terminal. In step 135, the message service server initializes the maximum number of free forwards, sets the address of a sub-free message receiving terminal, and modifies the free forward limitation information. In step 137, the message service server transmits the free message, the new set message ID, and the modified free forward limitation information to a message server to which the sub-free message receiving terminal is connected. Then, step 119 is performed.

The operation process as illustrated in FIGs. 3 a and 3b corresponds to an operation process when the message service server determines the accomplishment or non-accomplishment of the free sub-messaging service and grants the free sub-messaging service. If a mobile communication terminal in a stateful state determines the accomplishment or non-accomplishment of the free sub-messaging service and grants the free sub-messaging service, the maximum level of free forwards excluded from the free forward limitation information in step 113 of FIG. 3 a is included in the free forward limitation information and transmitted. The receiving terminal (i.e. mobile communication terminal) having received the maximum level of free forwards determines if it can receive the free sub-messaging service according to the maximum level of free forwards and the maximum number of free forwards. If the free sub-messaging service request is possible, the free sub-messaging service request is transmitted to the message service server according to user requirement. The maximum level of free forwards and the maximum number of free forwards may also be decreased

by the message service server or the mobile communication terminal according to the process as illustrated in FIGs. 3 a and 3b because each entity is stateful.

Hereinafter, an operation process of a mobile communication terminal when each entity of the free messaging service system is stateless and the mobile communication terminal determines the accomplishment or non- accomplishment of a free sub-messaging service and grants the free sub-messaging service according to another embodiment of the present invention will be described with reference to FIGs. 4a and 4b.

Referring to FIGs. 4a and 4b, in step 201, the mobile communication terminal receives a free message. In step 203, the mobile communication terminal checks free forward limitation information. In step 205, the mobile communication terminal determines if the maximum level of free forwards is not zero. If the maximum level of free forwards is not zero, step 207 is performed. Otherwise, the operation process is terminated. In step 207, the mobile communication terminal informs a user that a free messaging service is possible. In step 209, the mobile communication terminal determines if a free messaging service request is input from the user. If the free messaging service request is input, step 211 is performed. In step 211, the mobile communication terminal receives the address of a free message receiving terminal and additional data from the user. In step 213, the mobile communication terminal determines if the data received in step 211 satisfy free forward limitation conditions. If the data satisfy the free forward limitation conditions, step 215 is performed. Otherwise, step 227 of FIG. 4b is performed. That is, the mobile communication terminal checks the size of the additional data received in step 211 and determines if the size of the additional data satisfies the maximum size of a forwarded message. Further, the mobile communication terminal determines if the address of the receiving terminal received in step 211 is included in a free forward message receiving terminal list, the input number of receiving terminals does not exceed the current maximum number of free forwards, and the current time point satisfies the free forward message deadline. If all conditions are satisfied, step 215 is performed. Otherwise, step 227 is performed. Herein, some of the free forward limitation conditions such as the free forward message deadline may also be checked before informing the user that the free messaging service is possible in step 207. In step 215, the mobile communication terminal decreases the maximum

level of free forwards by one for setup, and decreases the maximum number of free forwards by the input number of free message receiving terminals for storage. In step 217, the mobile communication terminal transmits a free message including free forward limitation information to a message service server. Herein, the free forward limitation information includes the free sub-messaging service request, the input address of the free message receiving terminal, the reset maximum level of free forwards, and the initialized maximum number of free forwards.

After receiving the free sub-messaging service request and the free message, the message service server transmits a free sub-messaging service request response message to the mobile communication terminal.

In step 219, the mobile communication terminal receives the free sub- messaging service request response message from the message service server.

In step 221 of FIG. 4b, the mobile communication terminal determines if the free messaging service request is input from the user again. If the free messaging service request is input from the user again, step 223 is performed. In step 223, the mobile communication terminal determines if the current maximum number of free forwards is not zero. If the maximum number of free forwards is not zero, step 225 is performed. Otherwise, step 227 is performed. In step 225, the mobile communication terminal receives the address of a free message receiving terminal and additional data from the user. If the input data satisfy the free forward limitation conditions, the mobile communication terminal decreases the maximum number of free forwards by the input number of free message receiving terminals for storage. Then, step 217 is performed, and steps 217, 219, 221, 223, 225 and 227 are performed. In step 227, the mobile communication terminal reports the impossibility of the free messaging service and terminates the operation process.

As described above, when the mobile communication terminal in a stateless state determines the accomplishment or non-accomplishment of the free sub-messaging service and grants the free sub-messaging service, the mobile communication terminal counts both the maximum level of free forwards and the maximum number of free forwards, modifies the free forward limitation information by means of result values of the counting, and transmits the modified free forward limitation information to the message service server. However, when the message service server in a stateless state determines the

accomplishment or non-accomplishment of the free sub-messaging service and grants the free sub-messaging service, the message service server counts both the maximum level of free forwards and the maximum number of free forwards as illustrated in FIG. 4. Further, it is possible to perform the counting of both the maximum level of free forwards and the maximum number of free forwards separately from the determination of whether to grant the free sub-messaging service. That is, the message service server may perform the counting and the mobile communication terminal may perform the determination, and vice versa.

Hereinafter, a mutual operation among entities according to a free messaging service based on one embodiment of the present invention will be described with reference to FIGs. 1 and 5. FIG. 5 is a ladder diagram illustrating the message flow of the free messaging service system according to one embodiment of the present invention. In the embodiment of the present invention, each entity has no default value, the granter of the free messaging service is a message service server, and each entity is stateful. FIG. 6 illustrates one example in which receiving terminals receiving the free messaging service are connected to different message service servers, respectively. However, the present invention can also be applied to a case in which a plural of receiving terminals are connected to the same server. For aiding the understanding of the present invention, the following description will be given an assumption that the maximum number of free forwards is 1 and the maximum level of free forwards is 2.

Referring to FIG. 5, in step 301 (Ml_submit.REQ), the first mobile communication terminal 10 transmits a free messaging service request to the first message service server 40. As described above, a client requesting the free messaging service may also be an information server of a service provider. In this case, a message M7_submit.REQ is used. The originating terminal, i.e. the first mobile communication terminal 10 or the information server, transmits a free message including free forward limitation information. The free forward limitation information is included in the header information of the free message as illustrated in FIG. 7. Further, the free forward limitation information is comprised of the free forward messaging service indication information (Fwd- Charging), the forward charge bearer identification information (Fwd-Charging- Party), the maximum number (Fwd-Charging-MaxNb) of free forwards, the maximum level (Fwd-Charging-MaxLvl) of free forwards, the information on the

maximum size (Fwd-Charging-MaxSize) of a forwarded message, the free forward message deadline information (Fwd-Charging-Deadline), and the free forward message receiving terminal list information (Fwd-Charging-Recv).

Each piece of information is set to have the following content according to one embodiment of the present invention. The free forward messaging service indication information (Fwd- Charging) indicates that the first mobile communication terminal 10 is a terminal requesting the free messaging service, and the forward charge bearer identification information (Fwd-Charging-Party) includes identification information of the first mobile communication terminal 10. The maximum number (Fwd-Charging-MaxNb) of free forwards is I ₅ the maximum level (Fwd-Charging-MaxLvl) of free forwards is 2, and the information on the maximum size (Fwd-Charging-MaxSize) of a forwarded message includes a size obtained by combining the original size of a free message with the size of additional data granted by the first mobile communication terminal 10. The free forward message deadline information (Fwd-Charging- Deadline) includes free messaging service validity period set by the first mobile communication terminal 10, and the free forward message receiving terminal list information (Fwd-Charging-Recv) includes information on the third mobile communication terminal 30. Further, the free sub-messaging service information (Fwd-Charging-ID) is not set.

In step 303 (Ml/7_submit.REQ), the first message service server 40 having received the free messaging service request sets a new ID in the message received from the first mobile communication terminal 10, and grants the free messaging service request. Herein, the first message service server 40 analyzes the header information of the received free message and becomes aware of the fact that a receiving terminal corresponds to the second mobile communication terminal 20. Since the second mobile communication terminal 20 has not been connected to the first message service server 40, the second mobile communication terminal 20 transmits the free message to the second message service server 50 to which the second mobile communication terminal 20 is connected, thereby requesting the free messaging service in step 305 (MM4_forward.REQ). Herein, the second mobile communication terminal 20 also transmits the message ID set in step 303. If the free message is received in step 305, step 307 (MM4_forward.RES) is performed. That is, the second message service server 50 transmits a response message to the first message

service server 40 in response to the free messaging service request. In step 309 (MMl_notification.REQ), the second message service server 50 notifies the second mobile communication terminal 20 of the existence of the free message to be received. Further, the second message service server 50 transmits the free forward limitation information, which has excluded the maximum level of free forwards and has been set by the first mobile communication terminal 10, thereby reporting the availability of a free sub-messaging service capable of transmitting the free message to another terminal according to limitation conditions free of charge. The second message service server 50 transmits the message ID received from the first message service server 40 in step 305.

In step 309, the second mobile communication terminal 20 receives information on the free message from the second message service server 50. In step 311(MMl_notification.RES), the second mobile communication terminal 20 transmits a response message to the second message service server 50. If a free message transmission request is received from the user of the second mobile communication terminal 20, the second mobile communication terminal 20 transmits the free message transmission request to the second message service server 50 in step 313 (MMl_retrieve.REQ).

After receiving the free message transmission request from the second mobile communication terminal 20, the second message service server 50 transmits a free message to the second mobile communication terminal 20 in step 315 (MMl_retrieve.RES). Herein, the free message includes all free forward limitation information except for the maximum level of free forwards. Further, the second message service server 50 also transmits both the message ID received from the first message service server 40 in step 305 and a guidance message about the free messaging service.

After receiving the free message transmitted from the second message service server 50 in step 315, the second mobile communication terminal 20 transmits a response message to the second message service server 50 in response to the free message in step 317 (MMl_acknowledge.REQ), thereby informing the second message service server 50 that the free message has been successfully received. Then, if a free sub-messaging service request is received from a user, the second mobile communication terminal 20 requests a free sub-messaging service in step 319 (MMl_submit.REQ). Herein, the second mobile communication terminal 20 also transmits the free forward sub-messaging

information received in step 315. That is, the message ID received from the second message service server 50 in step 315 is included in the free forward sub- messaging information. Further, the second mobile communication terminal 20 appends additional data in consideration of a message size, which has been set in the information on the maximum size of a forwarded message, according to use input, and transmits the address of a receiving terminal (i.e. the third mobile communication terminal 30) intended for reception of the free sub-messaging service.

After receiving the free sub-messaging service request transmitted from the second mobile communication terminal 20 in step 319, the second message service server 50 compares the free forward sub-messaging information, which is included in the free forward limitation information received in step 305, with the free sub-messaging service request information received in step 319, in step 321 (Authorization & limit control). If the free forward sub-messaging information coincides with the free sub-messaging service request information, the second message service server 50 checks both a terminal and a message for which the free sub-messaging service has been granted. Further, the second message service server 50 determines if the free forward limitation information set by the first mobile communication terminal 10 is satisfied. If the free forward limitation information is satisfied, the second message service server 50 can grant the free sub-messaging service. The free sub-messaging service may not be allowed in the following cases: when the maximum level of free forwards and the maximum number of free forwards become zero, respectively; when an entire size of a given message exceeds the maximum size of a forwarded message; when the free forward message deadline has passed; and when a receiving terminal not included in the free message receiving terminal list is designated.

If the free sub-messaging service is granted, the second message service server 50 decreases the maximum number of free forwards for the second mobile communication terminal 20 by the number of free sub-messaging service receiving terminals so as to set it to zero for storage. In step 323 (Charging data.TRA), the second message service server 50 notifies the accounting server 70 of the occurrence of the free sub-messaging service, and transmits all information necessary for right charges based on the occurrence of the free sub- messaging service. Further, the second message service server 50 transmits identification information of a mobile communication terminal to be charged in

order to report that the mobile communication terminal to be charged is the first mobile communication terminal 10. In step 325 (MMl_submit.RES), the second message service server 50 sets a new ID in the message received from the second mobile communication terminal 20, and notifies that the free sub- messaging request has been granted. Further, the second message service server 50 reports the exemption of charges according to free message transmission, and transmits the maximum number of free forwards updated in step 321. In step 327 (MM4_forward.REQ), the second message service server 50 determines if the third mobile communication terminal 30 exists in a messaging service area in order to perform the free sub-messaging service. If the third mobile communication terminal 30 does not exist in the messaging service area, the second message service server 50 transmits the free message including modified free forward limitation information to a message service server (i.e. the third message service server 60) to which the third mobile communication terminal 30 is connected, thereby requesting the free messaging service. The maximum level of free forwards decreases by one and is transmitted after being reset to 1 , and the message ID set in step 325 is also transmitted. The maximum number of free forwards) is set to 1, which is the initial setup value, and is transmitted. This is because the maximum number of free forwards corresponds to the maximum number of transmissions of a free message, which is set for each terminal capable of requesting the free sub-messaging service.

After receiving the free message transmitted in step 327, the third message service server 60 transmits a response for the free messaging service request to the second message service server 50 in step 329 (MM4_forward.RES). In step 331(MMl_notification.REQ), the third message service server 60 notifies the third mobile communication terminal 30 of the existence of a free message to be received. Herein, the third message service server 60 checks the received maximum level of free forwards. If the maximum level of free forwards is zero, the third message service server 60 has only to notify the receiving terminal of the existence of a free message to be received without transmission of free forward limitation information because the free messaging service cannot be performed any more. Since the maximum level of free forwards transmitted in step 327 is 1, the third message service server 60 transmits the free forward limitation information, which excludes the maximum level of free forwards and having been set by the first mobile communication terminal 10, thereby reporting the

availability of the free sub-messaging service capable of transmitting the free message to another terminal free of charge according to limitation conditions.

After receiving information on the free message transmitted from the third message service server 60 in step 331, the third mobile communication terminal 30 transmits a response message to the third message service server 60 in step 333(MMl_notification.RES).

Then, if a free sub-messaging service request is received from a user, the third mobile communication terminal 30 transmits the free sub-messaging service request to the third message service server 60 in step 335 (MMl_forward.REQ). That is, if the third mobile communication terminal 30 has not received a free message, but has received information on the free message, the third mobile communication terminal 30 can request the free sub-messaging service. The third mobile communication terminal 30 also transmits the free forward sub- messaging information received in step 331 according to the free sub-messaging service request. Further, the third mobile communication terminal 30 also transmits the address of a receiving terminal intended for reception of the free sub-messaging service.

After receiving the free sub-messaging service request transmitted from the third mobile communication terminal 30 in step 335, the third message service server 60 compares the free forward sub-messaging information included in the free forward limitation information transmitted in step 327 with the free forward sub-messaging information transmitted in step 335, in step 337 (authorization & limit control). If the two pieces of free forward sub-messaging information coincide with each other, the third message service server 60 determines that the third mobile communication terminal 30 is a terminal for which the free sub- messaging service is granted. Further, the third message service server 60 determines if the free forward limitation information set by the first mobile communication terminal 10 is satisfied. If the free forward limitation information is satisfied, the third message service server 60 can grant the free sub-messaging service. If the free sub-messaging service is granted, the third message service server 60 decreases the maximum number of free forwards for the third mobile communication terminal 30 by one, and stores the decreased maximum number of free forwards. In step 339 (Charging data.TRA), the third message service server 60 notifies the accounting server 70 of the occurrence of the free sub-messaging service, and transmits all information necessary for right

charges based on the occurrence of the free sub-messaging service. Further, the third message service server 60 transmits identification information of a mobile communication terminal to be charged in order to report that the mobile communication terminal to be charged is the first mobile communication terminal 10. In step 341 (MMl_forward.RES), the third message service server 60 notifies that the free sub-messaging request has been granted. Further, the third message service server 60 reports the exemption of the charges according to free message transmission, and transmits the maximum number of free forwards updated in step 337. Hereinafter, a report about charging particulars incurred by the free messaging service performed according to the afore-described process will be described.

The charging particulars report represents that particulars about charges actually incurred during the free messaging service according to the present invention are provided to a free messaging service request terminal. The charging particulars provided through the charging particulars report include the effective number of requests for the free sub-messaging service granted according to the embodiment of the present invention, the amount of data to be finally charged, a list of mobile communication terminals requested the free sub- messaging service, and the amount of data transmitted free of charge by each free sub-messaging service request terminal. According to the embodiment of the present invention, the charging particulars may also be unconditionally transmitted to the free sub-messaging service request terminal, or may also be transmitted to the free sub-messaging service request terminal only when there exists permission from users of each free sub-messaging service request terminal.

The charging particulars report is requested when a certain mobile communication terminal requests the free messaging service. If the charging particulars report is requested, the message service server reports that the charging particulars report has been requested when informing a receiving terminal of the arrival of a free message. The receiving terminal determines whether to grant the charging particulars report according to user selection, and transmits results of the determination to the message service server when free message transmission is requested. If the receiving terminal grants the charging particulars report, the message service server collects charging particulars incurred by the receiving terminal up to a time point at which the preset final

charging particulars report is provided, and transmits the collected charging particulars to the free messaging service requesting terminal.

Hereinafter, the charging particulars report process according to the accomplishment of the free messaging service as described above will be described with reference to FIG. 6. FIG. 6 is a block diagram illustrating the charging particulars report process of the free messaging service according to one embodiment of the present invention. That is, FIG. 6 illustrates the process in which the charging particulars are reported according to the free messaging service process illustrated in FIG. 1, and illustrates the charging particulars report process under an assumption that all charging particulars are transmitted only when permission from a mobile communication terminal exist.

Referring to FIGs. 1 and 6, in step 401, the mobile communication terminal 10 transmits not only a free messaging service request but also a report request for charging particulars incurred during the free messaging service to the first message service server 40. When requesting the charging particulars report, the mobile communication terminal 10 sets and transmits the final charging particulars report time point. Such a request for the charging particulars report is accomplished by setting the charging particulars report indication information in the field Fwd-Charging-Rep 517 of the free message as illustrated in FIG.7, setting information on a time point, at which the final charging particulars report is provided, in the field Fwd-Charging-Rep Date 519, and transmitting the free message to the message service server. The charging particulars report indication information and the information on the time point may also be set by either the user of the mobile communication terminal 10 or a default value as in the case of the free forward limitation information. Herein, if the charging particulars report indication information is not set, the charging particulars report is not requested.

After receiving the free messaging service request and the charging particulars report request, the first message service server 40 transmits the free message to the second message service server 50, to which the free message receiving terminal is connected, in step 403 (report request), thereby informing the second message service server 50 that the charging particulars report has been requested.

After receiving the free message, the second message service server 50 transmits charging particulars-reporting information to the second mobile

communication terminal 20 together with free forward limitation information in order to report the arrival of the free message in step 405 (report ok?), thereby reporting that the charging particulars report has been requested by the mobile communication terminal 10 which is the free messaging service request terminal. In step 407 (ok/Not ok), the second mobile communication terminal 20 determines whether to grant the charging particulars report according to user selection in response to the charging particulars report request, and transmits results of the determination to the second message service server 50 when free message transmission is requested. The second message service server 50 determines whether to report particulars incurred by the second mobile communication terminal 20 according to the received results. If the second mobile communication terminal 20 has granted the charging particulars report, the second message service server 50 sets a charging report time point of the second mobile communication terminal 20 according to the information on the time point, at which the final charging particulars report is provided, included in the charging particulars-reporting information, and collects charging particulars incurred by the second mobile communication terminal 20 up to the set charging report time point. Further, the second message service server 50 stores that a terminal receiving the charging particulars report is the mobile communication terminal 10.

Then, if the free sub-messaging service is requested by the second mobile communication terminal 20, the second message service server 50 transmits a free message to the third message service server 60, to which the third mobile communication terminal 30 (receiving terminal according to the free sub- messaging service) is connected, after a series of operation processes in step 409 (report request). Herein, the second message service server 50 also transmits the charging particulars report request.

After receiving the free message transmitted in step 409, the third message service server 60 transmits the charging particulars-reporting information to the third mobile communication terminal 30 together with the free forward limitation information in step 411 as in the case of step 405, thereby reporting that the charging particulars report has been requested by the mobile communication terminal 10 which is the free messaging service request terminal.

In step 413 (ok/Not ok), the third mobile communication terminal 30 determines whether to grant the charging particulars report according to user

selection in response to the charging particulars report request, and transmits results of the determination to the third message service server 60 when free message transmission is requested. The third message service server 60 determines whether to report particulars incurred by the third mobile communication terminal 30 according to the received results. If the third mobile communication terminal 30 has granted the charging particulars report, the third message service server 60 sets a charging report time point of the third mobile communication terminal 30 according to the information on the time point, at which the final charging particulars report is provided, included in the charging particulars-reporting information, and collects charging particulars incurred by the third mobile communication terminal 30 up to the set charging report time point. Further, the third message service server 60 stores that a terminal receiving the charging particulars report is the mobile communication terminal 10.

Then, if a current time point corresponds to the time point at which the final charging particulars report is provided, the second message service server 50 and the third message service server 60 transmit the charging particulars, which has been collected in relation to the second mobile communication terminal 20 and the third mobile communication terminal 30, to the first message service server 40 to which the mobile communication terminal 10 is connected, in step 415 (report server). According to another embodiment of the present invention, the message service servers 50 and 60 may also transmit the collected charging particulars at a given time offset before the time point at which the final charging particulars report is provided.

In step 417 (report global), the first message service server 40 transmits the received charging particulars to the mobile communication terminal 10.

According to the present invention as described above, charges incurred when a mobile communication terminal transmits a received free massage to another mobile communication terminal is charged by the initial originating terminal of the free massage, and the mobile communication terminal that bears the charges sets predetermined free forward limitation conditions, so that the amount and features of free forwards allowed can be controlled and charging particulars resulting from free forward of the massage can be reported. Accordingly, message originator and recipient can have many more messaging opportunities: the originator such as a service provider can have an opportunity for encouraging its own content to be distributed to a greater extent and

potentially attracting new customers; and the recipient can transmit the message free of charge.

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, including the full scope of equivalents thereof. For example, in the above description, a mobile communication terminal requests a free messaging service. However, in another embodiment of the present invention, information service servers, which provide various information such as news, weather and advertisements, requests the free messaging service, so that the free messaging service can be provided for an information message.