Abstract:
The present disclosure relates to technologies for a sensor network, machine-to-machine (M2M) communications, or machine type communications (MTC), and Internet of things (IoT), and may be utilized in intelligent services, based on the above technologies, such as a smart home, a smart building, smart cities, smart cars or connected cars, smart grids, healthcare, smart electronics, advanced medical services, public safety network communications through fusion and convergence with conventional IT technologies and various industries. Data transmission control between a group of uncoordinated electronic devices in a computer network including the use of transmission authorization request messages and transmission authorization grant messages.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/185,025, filed on Jun. 26, 2015, in the US Patent Office and Korean Patent Application No. 10-2015-0133879, filed on Sep. 22, 2015, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entireties by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a communication method between terminals and a terminal for performing communication, and a recording medium storing a program for executing the communication method between the terminals. 
         [0004]    2. Description of the Related Art 
         [0005]    The Internet is advancing from a connection network for humans, where a human creates and consumes information, to an Internet of things (IoT) network where distributed elements such as things exchange and process information. Internet of everything (IoE) technology, where big data processing technology and/or the like is combined with IoT technology through a connection with a cloud server, has been proposed. Technologies such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required for implementing IoT. Therefore, technology such as sensor network, machine to machine (M2M), and machine type communication (MTC) are being recently researched for a connection between things. 
         [0006]    An intelligent Internet technology (IT) service, which collects and analyzes data generated by things connected to each other to create a new value of human life, may be provided in an IoT environment. IoT may be applied to fields, such as smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart appliances, advanced medical service, disaster network communication, and/or the like, through mergence and combination of conventional information technology (IT) technology and various industries. 
       SUMMARY 
       [0007]    Provided is a communication method which, when communication is performed between a plurality of terminals, enables the terminals to distributively operate even without a terminal acting as a service. 
         [0008]    Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
         [0009]    According to an aspect of an embodiment, a communication method between terminals includes: receiving, by a terminal, media data of a first terminal having a transmission authority among other terminals included in a group including the terminal; transmitting a transmission authority request message to each of the other terminals of the group; receiving a transmission authority request acceptance message from the first terminal; and determining whether the media data of the first terminal is received, and transmitting media data of the terminal. 
         [0010]    The communication method may further include: retransmitting the transmission authority request message to the first terminal when the media data of the first terminal is not received for a certain time, wherein the transmitting of the media data of the terminal may include transmitting the media data of the terminal when the transmission authority request acceptance message is not re-received within a certain time after retransmitting the transmission authority request message. 
         [0011]    The communication method may further include determining whether a priority of the terminal is highest in priorities of one or more terminals which have requested the transmission authority from the first terminal, wherein the retransmitting of the transmission authority request message may include retransmitting the transmission authority request message when the priority of the terminal is highest and the media data of the first terminal is not received for a certain time. 
         [0012]    The transmission authority request acceptance message may include information about other terminals which have requested the transmission authority from the first terminal. 
         [0013]    The communication method may further include: updating transmission authority status information about the terminal, based on the information about other terminals which have requested the transmission authority from the first terminal. 
         [0014]    The transmitting of the media data may include, when a transmission release message is received from the first terminal, transmitting the media data to each of the other terminals of the group. 
         [0015]    The communication method may further include: receiving the transmission release message from the first terminal; and determining whether a priority of the terminal is highest in priorities of one or more terminals requesting the transmission authority, wherein the transmitting of the media data may include, when the priority of the terminal is highest, transmitting the media data to each of the other terminals of the group. 
         [0016]    According to an aspect of another embodiment, a communication method between terminals includes: transmitting, by a first terminal, media data to each of other terminals included in a group including the first terminal; receiving a transmission authority request message from at least one of the other terminals of the group; determining a transmission authority status of the at least one terminal, based on a priority of the at least one terminal; and transmitting a transmission authority request acceptance message, including information about the determined transmission authority status, to each of the other terminals of the group. 
         [0017]    The communication method may further include obtaining, by a terminal having a highest priority among the at least one terminal, a transmission authority when the transmission of the media data of the first terminal is completed. 
         [0018]    The communication method may further include obtaining, by a terminal having a highest priority among the at least one terminal, a transmission authority when the media data of the first terminal is not received for a certain time. 
         [0019]    According to an aspect of another embodiment, a terminal includes: a communicator configured to receive media data of a first terminal having a transmission authority among other terminals included in a group including a terminal, transmit a transmission authority request message to each of the other terminals of the group, and receive a transmission authority request acceptance message from the first terminal; and a controller configured to determine whether the media data of the first terminal is received, wherein the communicator transmits media data of the terminal, based on a result of the determination. 
         [0020]    When the media data of the first terminal is not received for a certain time, the communicator may retransmit the transmission authority request message to the first terminal, and when the transmission authority request acceptance message is not re-received within a certain time after retransmitting the transmission authority request message, the communicator may transmit the media data of the terminal. 
         [0021]    The controller may determine whether a priority of the terminal is highest in priorities of one or more terminals which have requested the transmission authority from the first terminal, and when the priority of the terminal is highest and the media data of the first terminal is not received for a certain time, the communicator may retransmit the transmission authority request message. 
         [0022]    The transmission authority request acceptance message may include information about other terminals which have requested the transmission authority from the first terminal. 
         [0023]    The controller may update transmission authority status information about the terminal, based on the information about other terminals which have requested the transmission authority from the first terminal. 
         [0024]    When a transmission release message is received from the first terminal, the communicator may transmit the media data to each of the other terminals of the group. 
         [0025]    The communicator may receive the transmission release message from the first terminal, and when a priority of the terminal is highest in priorities of one or more terminals requesting the transmission authority, the communicator may transmit the media data to each of the other terminals of the group. 
         [0026]    According to an aspect of another embodiment, a first terminal includes: a communicator configured to transmit media data to each of other terminals included in a group including the first terminal and receive a transmission authority request message from at least one of the other terminals of the group; and a controller configured to determine a transmission authority status of the at least one terminal, based on a priority of the at least one terminal, wherein the communicator transmits a transmission authority request acceptance message, including information about the determined transmission authority status, to each of the other terminals of the group. 
         [0027]    When the transmission of the media data of the first terminal is completed, a terminal having a highest priority among the at least one terminal may obtain a transmission authority. 
         [0028]    When the media data of the first terminal is not received for a certain time, a terminal having a highest priority among the at least one terminal may obtain a transmission authority. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
           [0030]      FIG. 1  is a diagram for describing a communication system according to an embodiment; 
           [0031]      FIG. 2  is a flowchart for describing a method of obtaining, by a first terminal of a plurality of terminals in a group, a transmission authority according to an embodiment; 
           [0032]      FIG. 3  is a flowchart for describing a method of determining, by one of a plurality of terminals in a group, a terminal having a transmission authority according to an embodiment; 
           [0033]      FIG. 4  is a flowchart for describing a method of obtaining, by a first terminal, a transmission authority when there is no terminal transmitting media data in a communication system, according to an embodiment; 
           [0034]      FIG. 5  is a flowchart for describing a method of determining a first terminal as a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system, according to an embodiment; 
           [0035]      FIG. 6  is a flowchart for describing a method of determining, by a terminal, a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system, according to an embodiment; 
           [0036]      FIG. 7  is a flowchart for describing a method of determining a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system, according to an embodiment; 
           [0037]      FIG. 8  is a flowchart for describing a method of obtaining, by a first terminal of a plurality of terminals in a group, a transmission authority according to another embodiment; 
           [0038]      FIG. 9  is a flowchart for describing a method of determining a terminal having a transmission authority among a plurality of terminals in a group in a communication system, according to another embodiment; 
           [0039]      FIG. 10  is a flowchart for describing a method of transmitting media data when a first terminal receives a transmission authority request message from another terminal included in a group in the middle of transmitting the media data, according to an embodiment; 
           [0040]      FIG. 11  is a flowchart for describing a method of transmitting media data when a transmission authority request message is transmitted from another terminal included in a group while a first terminal is transmitting the media data in a communication system, according to an embodiment; 
           [0041]      FIG. 12  is a flowchart for describing a method of transmitting media data when a plurality of terminals store queue information in a communication system, according to an embodiment; 
           [0042]      FIG. 13  is a flowchart for describing a method of transmitting media data when a first terminal receives a transmission authority request message from a higher-priority terminal in the middle of transmitting the media data in a communication system, according to an embodiment; 
           [0043]      FIG. 14  is a flowchart for describing a method of mediating in a transmission authority by using a media burst control protocol (MBCP) in a communication system, according to an embodiment; 
           [0044]      FIG. 15  is a flowchart for describing a method of mediating in a transmission authority by using an MBCP when a transmission authority request message is transmitted from a higher-priority terminal while a first terminal is transmitting media data in a communication system, according to an embodiment; 
           [0045]      FIG. 16  is a flowchart for describing a method of transmitting, by a terminal, media data according to whether the media data is received from a first terminal having a transmission authority in a group, according to an embodiment; 
           [0046]      FIG. 17  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal having the transmission authority is absent from a certain position in a communication system, according to an embodiment; 
           [0047]      FIG. 18  is a flowchart for describing a method of determining a transmission authority state of another terminal when a first terminal having a transmission authority receives from a transmission authority request message from the other terminal in the middle of transmitting media data, according to an embodiment; 
           [0048]      FIG. 19  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal is absent from a certain position in a communication system, according to an embodiment; 
           [0049]      FIG. 20  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal having the transmission authority is absent from a certain position in a communication system, according to an embodiment; 
           [0050]      FIG. 21  is a flowchart for describing a method of determining a terminal having a transmission authority according to priorities when a first terminal having the transmission authority is absent from a certain position in a communication system, according to an embodiment; 
           [0051]      FIG. 22  is a block diagram of a terminal according to an embodiment; and 
           [0052]      FIG. 23  is a block diagram of a first terminal according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0053]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
         [0054]    Terms used herein will be briefly described, and the inventive concept will be described in detail. 
         [0055]    Terms used in the inventive concept have been selected as general terms which are widely used at present, in consideration of the functions of the inventive concept, but may be altered according to the intent of an operator of ordinary skill in the art, conventional practice, or introduction of new technology. Also, if there is a term which is arbitrarily selected by the applicant in a specific case, in which case a meaning of the term will be described in detail in a corresponding description portion of the inventive concept. Therefore, the terms should be defined on the basis of the entire content of this specification instead of a simple name of each of the terms. 
         [0056]    In this disclosure below, when it is described that one comprises (or includes or In this disclosure below, when it is described that one comprises (or includes or has) some elements, it should be understood that it may comprise (or include or has) only those elements, or it may comprise (or include or have) other elements as well as those elements if there is no specific limitation. Moreover, each of terms such as “ . . . unit”, “ . . . apparatus” and “module” described in specification denotes an element for performing at least one function or operation, and may be implemented in hardware, software or the combination of hardware and software. 
         [0057]    Hereinafter, exemplary embodiments will be described in detail to be easily embodied by those of ordinary skill in the art with reference to the accompanying drawings. The inventive concept may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. In the accompanying drawings, a portion irrelevant to a description of the inventive concept will be omitted for clarity. Moreover, like reference numerals refer to like elements throughout. 
         [0058]      FIG. 1  is a diagram for describing a communication system  100  according to an embodiment. 
         [0059]    The communication system  100  according to an embodiment may include a plurality of terminals  110 ,  120 ,  130  and  140 . 
         [0060]    The communication system  100  of  FIG. 1  is illustrated as including only elements associated with the present embodiment. Therefore, it may be understood by one of ordinary skill in the art that the communication system  100  may further include general-use elements in addition to the elements of  FIG. 1 . For example, the communication system  100  of  FIG. 1  may further include other terminals in addition to the plurality of terminals  110 ,  120 ,  130  and  140 . In the communication system  100 , a session for transmitting or receiving data may be set between the plurality of terminals  110 ,  120 ,  130  and  140 . Here, the plurality of terminals  110 ,  120 ,  130  and  140  may be terminals included in one group of at least one group which is previously provided in the communication system  100 . 
         [0061]    Referring to  FIG. 1 , when the plurality of terminals  110 ,  120 ,  130  and  140  included in a group are located within different communication ranges, the plurality of terminals  110 ,  120 ,  130  and  140  may directly transmit or receive data. For example, each of the terminals  110 ,  120 ,  130  and  140  of the group may transmit or receive media data and control data such as a transmission authority request message, a transmission authority acceptance message, a transmission release message, and a transmission authority request acceptance message according to a multicast method. However, this is merely an embodiment, and a communication method between the terminals  110 ,  120 ,  130  and  140  of the group is not limited to the multicast method. 
         [0062]    Even when there is no server which is previously provided, the communication system  100  according to an embodiment may process a transmission authority request of at least one terminal of the group. For example, at least one terminal desiring to transmit media data among the plurality of terminals  110 ,  120 ,  130  and  140  may request a transmission authority from other terminals of the group and may receive a response to the request to obtain the transmission authority. 
         [0063]    Moreover, in a state where there is no server which is previously provided, when a plurality of terminals request a transmission authority and thus a competition condition is provided, the communication system  100  according to an embodiment may determine a terminal having the transmission authority. For example, when two or more terminals request the transmission authority, the communication system  100  according to an embodiment may determine a terminal having the transmission authority, based on a predetermined priority or a random value which is generated in each of the terminals of the group. 
         [0064]    According to another embodiment, when there is a terminal which is transmitting media data, the communication system  100  may process a transmission authority request received from another terminal. For example, when one of the terminals  110 ,  120 ,  130  and  140  of the group receives a transmission authority request from another terminal in the middle of transmitting media data, the transmission of the media data may be completed, and then, a transmission authority may be delegated to the other terminal. As another example, a terminal which is transmitting media data may compare priorities or random values of other terminals which has transmitted a transmission authority request message, and may delegate a transmission authority to a corresponding terminal, based on a result of the comparison. 
         [0065]    In the communication system  100  according to an embodiment, when a terminal having a transmission authority is absent from a certain position, other terminals included in a group may recognize an absence state of the terminal having the transmission authority and may quickly delegate the transmission authority to another terminal. Here, a case where the terminal having the transmission authority is absent from a certain position may include a case where a battery has been discharged, a case of deviating from direct communication coverage, and/or the like. However, this is merely an embodiment, and a case where a terminal is absent from a certain position is not limited thereto. 
         [0066]      FIG. 2  is a flowchart for describing a method of obtaining, by a first terminal  110  of a plurality of terminals  110 ,  120 ,  130  and  140  in a group, a transmission authority according to an embodiment. 
         [0067]    In operation S 210 , the first terminal  110  may transmit a transmission authority request message to each of the other terminals  120 ,  130  and  140  of the group including the first terminal  110 . 
         [0068]    Each of the terminals  110 ,  120 ,  130  and  140  of the group according to an embodiment may request a transmission authority, for transmitting media data to the other terminals. For example, the first terminal  110  may transmit a transmission authority request message to each of the other terminals  120 ,  130  and  140  of the group, for transmitting the media data of the first terminal  110 . 
         [0069]    Moreover, the first terminal  110  according to an embodiment may monitor whether there is another terminal requesting the transmission authority, for a certain time before transmitting the transmission authority request message. When the transmission authority request message is not received from the other terminal for the certain time as a result of the monitoring, the first terminal  110  may transmit the transmission authority request message of the first terminal  110  to each of the other terminals  120 ,  130  and  140  of the group. 
         [0070]    In operation S 220 , when a standby time which is randomly determined in each of the other terminals  120 ,  130  and  140  of the group elapses, the first terminal  110  may receive a transmission authority acceptance message from at least one of the other terminals  120 ,  130  and  140  of the group. 
         [0071]    When there is no terminal requesting the transmission authority among the other terminals  120 ,  130  and  140  of the group, the first terminal  110  according to an embodiment may receive the transmission authority acceptance message from at least one of the other terminals  120 ,  130  and  140  of the group. 
         [0072]    According to another embodiment, when there is another terminal requesting the transmission authority in addition to the first terminal  110 , the first terminal  110  may receive the transmission authority acceptance message according to a competition condition. For example, when the transmission authority request message is transmitted from another terminal before or after a certain time from a time when the first terminal  110  transmits the transmission authority request message, the first terminal  110  may not receive the transmission authority request message from the other terminal during a monitoring period, and thus, a competition may occur between the first terminal  110  and other terminals. A case where a competition occurs will be described below in detail with reference to  FIG. 5 . 
         [0073]    Moreover, another terminal (for example,  130 ) of the group receiving the transmission authority request message from the first terminal  110  may monitor whether another transmission authority request message is received for a certain time from a time when the transmission authority request message is received. Here, the certain time may be, for example, 1 round trip time (1RTT). When the other transmission authority request message is not received, the transmission authority acceptance message may be transmitted to the first terminal  110 . 
         [0074]    Moreover, when the other transmission authority request message is not received for a certain time, each of the other terminals  120 ,  130  and  140  of the group may transmit the transmission authority acceptance message after a standby time which is randomly determined in each terminal elapses. Also, in order to prevent a network resource from being wasted, when a terminal (for example,  120 ) receives the transmission authority acceptance message including the same information from another terminal (for example,  130 ), the terminal (for example,  120 ) may not transmit the transmission authority acceptance message. Here, for example, when a standby time of the other terminal (for example,  130 ) elapses first and thus the transmission authority acceptance message has been already transmitted, the terminal (for example,  120 ) may not transmit the transmission authority acceptance message. 
         [0075]    For example, among second to fourth terminals  120 ,  130  and  140 , the third terminal  130  where a randomly determined standby time elapses first may transmit the transmission authority acceptance message, indicating that a transmission authority of the first terminal  110  is accepted, to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140  when the transmission authority acceptance message is not received from the other terminals  120  and  140 . 
         [0076]    In operation S 230 , the first terminal  110  may transmit the media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0077]    When the transmission authority acceptance message is received from one terminal, where the standby time elapses first, among the other terminals  120 ,  130  and  140  of the group, the first terminal  110  according to an embodiment may transmit the media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0078]      FIG. 3  is a flowchart for describing a method of determining, by one of a plurality of terminals  110 ,  120 ,  130  and  140  in a group, a terminal having a transmission authority according to an embodiment. 
         [0079]    In operation S 310 , a terminal (for example,  120 ) may receive a transmission authority request message from a first terminal  110  of other terminals included in the group including the terminal (for example,  120 ). 
         [0080]    In operation S 320 , the terminal (for example,  120 ) may transmit a transmission authority acceptance message for the first terminal  110  to each of the other terminals of the group, based on whether the transmission authority acceptance message is received from another terminal of the group. 
         [0081]    The terminal (for example,  120 ) according to an embodiment may monitor whether a transmission authority request message of another terminal (for example,  130 ) is received for a certain time after a time when the transmission authority request message is received from the first terminal  110 . For example, the terminal (for example,  120 ) may monitor whether the transmission authority request message of the other terminal (for example,  130 ) is received for 1RTT after the time when the transmission authority request message is received from the first terminal  110 . 
         [0082]    If the transmission authority request message of the other terminal (for example,  130 ) is not received for the certain time after the time when the transmission authority request message is received from the first terminal  110 , the terminal (for example,  120 ) according to an embodiment may determine the first terminal  110  as a terminal having a transmission authority. 
         [0083]    According to another embodiment, if the transmission authority request message of the other terminal (for example,  130 ) is received for the certain time after the time when the transmission authority request message is received from the first terminal  110 , the terminal (for example,  120 ) may compare priorities or random values of other terminals transmitting a transmission authority request message according to a competition condition to determine a terminal having a transmission authority. This will be described below in detail with reference to  FIG. 5 . 
         [0084]    The terminal (for example,  120 ) according to an embodiment may randomly generate a value of a standby time for transmitting a transmission authority acceptance message. The terminal (for example,  120 ) may transmit the transmission authority acceptance message to the other terminals  110 ,  130  and  140  of the group when a standby time, which is started after a certain time elapses from a time when the transmission authority request message is received from the first terminal  110 , elapses. 
         [0085]    Moreover, when the transmission authority acceptance message for the first terminal  110  is received from another terminal before the standby time elapses, the terminal (for example,  120 ) according to an embodiment may not transmit the transmission authority acceptance message so as to prevent a network resource from being unnecessarily used. 
         [0086]    When information included in the transmission authority acceptance message received from the other terminal differs from information included in the transmission authority acceptance message of the terminal (for example,  120 ), the terminal (for example,  120 ) may transmit the transmission authority acceptance message. For example, when a plurality of terminals (for example,  110  and  130 ) in the group request the transmission authority, a terminal having the transmission authority determined by the terminal (for example,  120 ) may differ from a terminal having the transmission authority determined by another terminal (for example,  140 ). In this case, due to a network state, the transmission authority request messages of some terminals may be deleted. 
         [0087]    In operation S 330 , the terminal (for example,  120 ) may receive media data from the first terminal  110 . The terminal (for example,  120 ) according to an embodiment may receive the media data from the first terminal  110  which has obtained the transmission authority. 
         [0088]      FIG. 4  is a flowchart for describing a method of obtaining, by a first terminal  110 , a transmission authority when there is no terminal transmitting media data in a communication system  100 , according to an embodiment. 
         [0089]    In operation S 410 , the first terminal  110  may transmit a transmission authority request message to each of other terminals  120 ,  130  and  140  included in a group when data is not received from another terminal for a certain time. 
         [0090]    In operation S 420 , a third terminal  130  may transmit a transmission authority acceptance message for the first terminal  110  to the first terminal  110 , a second terminal  120 , and a fourth terminal  140 . 
         [0091]    According to an embodiment, each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140  which have received the transmission authority request message of the first terminal  110  may determine a terminal having a transmission authority. In  FIG. 4 , it is assumed that another transmission authority request message is not received for a certain time after a time when the transmission authority request message of the first terminal  110  is received by each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140 . 
         [0092]    According to an embodiment, each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140  may randomly generate a value of a standby time. Each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140  may monitor whether a transmission authority acceptance message for the first terminal  110  is received for the standby time. 
         [0093]    According to an embodiment, when the transmission authority acceptance message is not received from the second terminal  120  and the fourth terminal  140  for the standby time, the third terminal  130  where the standby time elapses first may be selected as a respondent. The third terminal  130  may transmit the transmission authority acceptance message for the first terminal  110  to the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0094]    In operation S 430 , when the transmission authority acceptance message is received from the third terminal  130 , the first terminal  110  may transmit media data to each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140 . 
         [0095]      FIG. 5  is a flowchart for describing a method of determining a first terminal  110  as a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system  100 , according to an embodiment. 
         [0096]    In operation S 510 , the first terminal  110  may transmit a transmission authority request message to each of other terminals  120 ,  130  and  140  included in a group including the first terminal  110 . 
         [0097]    Moreover, operation S 510  may correspond to the above-described operation S 210 . 
         [0098]    In operation S 520 , the first terminal  110  may receive the transmission authority request message from another terminal (for example,  140 ) of the group for a certain time after transmitting the transmission authority request message. 
         [0099]    For example, the first terminal  110  may receive the transmission authority request message from a fourth terminal  140  for 1RTT after transmitting the transmission authority request message. 
         [0100]    In operation S 530 , the first terminal  110  may obtain a transmission authority, based on a comparison result which is obtained by comparing at least ones of priorities and random values of the first terminal  110  and the other terminal (for example,  140 ). 
         [0101]    In the communication system  100  according to an embodiment, when the transmission authority request message is generated from a plurality of terminals  110  and  140 , a terminal having the transmission authority may be determined based on at least ones of priorities and random values of the plurality of terminals  110  and  140 . 
         [0102]    For example, the first terminal  110  may have a highest priority of priorities of the terminals included in the group. Here, the priorities may be previously set between the terminals of the group. Therefore, the first terminal  110  of the first terminal  110  and a fourth terminal  140  may be determined as a terminal having a transmission authority. 
         [0103]    According to another embodiment, a random value generated from the first terminal  110  may be added into the transmission authority request message of the first terminal  110 , and a random value generated from the fourth terminal  140  may be added into the transmission authority request message of the fourth terminal  140 . When the random value of the first terminal  110  is greater than that of the fourth terminal  140 , the first terminal  110  may be determined as a terminal having a transmission authority. However, this is merely an embodiment, and a terminal having a smaller random value may be determined as a terminal having a transmission authority according to a setting. 
         [0104]    In operation S 540 , the first terminal  110  may transmit media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0105]    Moreover, operation S 540  may correspond to the above-described operation S 230 . 
         [0106]      FIG. 6  is a flowchart for describing a method of determining, by a terminal (for example  120 ), a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system  100 , according to an embodiment. 
         [0107]    In operation S 610 , a terminal (for example,  120 ) may receive a transmission authority request message from each of a plurality of terminals  110  and  140  included in a group. 
         [0108]    For example, the terminal (for example,  120 ) may receive the transmission authority request message of a fourth terminal  140  within a certain time from a time when the transmission authority request message of a first terminal  110  is received. However, this is merely an embodiment, and the terminal (for example,  120 ) may receive the transmission authority request message of the first terminal  110  within a certain time from a time when the transmission authority request message of the fourth terminal  140  is received. 
         [0109]    In operation S 620 , the terminal (for example,  120 ) may compare at least ones of priorities and random values of the plurality of terminals  110  and  140  requesting a transmission authority. The terminal (for example,  120 ) according to an embodiment may compare priorities of the first and fourth terminals  110  and  140  which have requested the transmission authority. According to another embodiment, when priorities of the first and fourth terminals  110  and  140  are equal, the terminal (for example,  120 ) may compare random values which are respectively generated from the first and fourth terminals  110  and  140 . According to another embodiment, when there is no predetermined priority between a plurality of terminals  110 ,  120 ,  130  and  140  included in the group, the terminal (for example,  120 ) may compare the random values which are respectively generated from the first and fourth terminals  110  and  140 . 
         [0110]    In operation S 630 , the terminal (for example,  120 ) may determine a terminal having the transmission authority, based on a result of the comparison. 
         [0111]    The terminal (for example,  120 ) according to an embodiment may compare the priorities of the first and fourth terminals  110  and  140  requesting the transmission authority to determine a terminal having the transmission authority. The terminal (for example,  120 ) may determine the first terminal  110  having a higher priority as a terminal having the transmission authority. 
         [0112]    When the priorities of the first and fourth terminals  110  and  140  are equal, the terminal (for example,  120 ) according to an embodiment may compare the random values respectively generated from the first and fourth terminals  110  and  140  to determine a terminal having the transmission authority. The terminal (for example,  120 ) may determine the first terminal  110  having a greater random value as the terminal having the transmission authority. However, a terminal having a smaller random value may be determined as the terminal having the transmission authority according to a setting. 
         [0113]    According to another embodiment, when there is no predetermined priority between the plurality of terminals  110 ,  120 ,  130  and  140  included in the group, the terminal (for example,  120 ) may determine the first terminal  110 , having a greater random value among the first and fourth terminals  110  and  140 , as the terminal having the transmission authority. However, a terminal having a smaller random value may be determined as the terminal having the transmission authority according to a setting. 
         [0114]    In operation S 640 , the terminal (for example,  120 ) may transmit a transmission authority acceptance message for the first terminal  110  to each of the other terminals of the group, based on whether the transmission authority acceptance message is received from another terminal of the group. 
         [0115]    Moreover, operation S 640  may correspond to operation S 320  described above with reference to  FIG. 3 . 
         [0116]    In operation S 650 , the terminal (for example,  120 ) may receive media data from the determined terminal. 
         [0117]    For example, when the first terminal  110  is determined as the terminal having the transmission authority, the terminal (for example,  120 ) may receive the media data from the first terminal  110 . 
         [0118]      FIG. 7  is a flowchart for describing a method of determining a terminal having a transmission authority when a competition for the transmission authority occurs in a communication system  100 , according to an embodiment. 
         [0119]    In operation S 710 , when data is not received from another terminal for a certain time, a first terminal  110  may transmit a transmission authority request message to each of a plurality of terminals  120 ,  130  and  140  included in a group. 
         [0120]    In operation S 720 , when data is not received from another terminal for a certain time, a fourth terminal  140  may transmit the transmission authority request message to each of the plurality of terminals  110 ,  120  and  130  included in the group. 
         [0121]    Moreover, the fourth terminal  140  cannot receive, for a certain time, the transmission authority request message of the first terminal  110  which is transmitted in operation S 710 , based on a distance to the first terminal  110  and a network state between the first and fourth terminals  110  and  140 . 
         [0122]    In operation S 730 , a third terminal  130  may transmit a transmission authority acceptance message for the first terminal  110  to the first terminal  110 , a second terminal  120 , and the fourth terminal  140 . 
         [0123]    The second and third terminals  120  and  130  according to an embodiment may receive the transmission authority request message of the fourth terminal  140  within a certain time from a time when the transmission authority request message of the first terminal  110  is received. Also, the first terminal  110  may receive the transmission authority request message of the fourth terminal  140  within a certain time from a time when the transmission authority request message of the first terminal  110  is transmitted. 
         [0124]    Each of the terminals  110 ,  120 ,  130  and  140  of the group may determine a terminal having a transmission authority, based on at least ones of priorities and random values of the terminals  110  and  140  requesting the transmission authority. 
         [0125]    For example, the third terminal  130  may determine the first terminal  110 , having a higher priority among the first and fourth terminals  110  and  140 , as the terminal having the transmission authority. As another example, when priorities of the first and fourth terminals  110  and  140  are equal, the third terminal  130  may compare random values respectively generated from the first and fourth terminals  110  and  140  to determine the first terminal  110  having a greater random value as the terminal having the transmission authority. 
         [0126]    According to another embodiment, when there is no predetermined priority between the plurality of terminals  110 ,  120 ,  130  and  140  included in the group, the third terminal  130  may compare the random values respectively generated from the first and fourth terminals  110  and  140  to determine the first terminal  110  having a greater random value as the terminal having the transmission authority. 
         [0127]    Moreover, each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140  may compare at least ones of the priorities and random values of the first and fourth terminals  110  and  140  requesting the transmission authority to determine the terminal having the transmission authority. 
         [0128]    According to an embodiment, each of the first to fourth terminals  110 ,  120 ,  130  and  140  may randomly generate a value of a standby time. Each of the first to fourth terminals  110 ,  120 ,  130  and  140  may monitor whether a transmission authority acceptance message for the first terminal  110  is received for the standby time. 
         [0129]    According to an embodiment, when the transmission authority acceptance message is not received from the first terminal  110 , the second terminal  120 , and the fourth terminal  140  for the standby time, the third terminal  130  where the standby time elapses first may be selected as a respondent. The third terminal  130  may transmit the transmission authority acceptance message for the first terminal  110  to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0130]    In operation S 740 , when the transmission authority acceptance message is received from the third terminal  130 , the first terminal  110  may transmit media data to each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140 . 
         [0131]      FIG. 8  is a flowchart for describing a method of obtaining, by a first terminal  110  of a plurality of terminals  110 ,  120 ,  130  and  140  in a group, a transmission authority according to another embodiment. 
         [0132]    In operation S 810 , the first terminal  110  may transmit a transmission authority request message to each of the other terminals  120 ,  130  and  140  of the group including the first terminal  110 . 
         [0133]    The first terminal  110  according to an embodiment may monitor whether there is another terminal requesting a transmission authority for a certain time before transmitting the transmission authority request message. When the transmission authority request message is not received from the other terminal for the certain time as a result of the monitoring, the first terminal  110  may transmit the transmission authority request message of the first terminal  110  to each of the other terminals  120 ,  130  and  140  of the group. 
         [0134]    In operation S 820 , the first terminal  110  may transmit media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0135]    The first terminal  110  according to an embodiment may transmit the media data after transmitting the transmission authority request message to each of the other terminals  120 ,  130  and  140  of the group. After transmitting the transmission authority request message, the first terminal  110  may transmit the media data without waiting for reception of a transmission authority acceptance message from the other terminals  120 ,  130  and  140  of the group. 
         [0136]    In operation S 830 , the first terminal  110  may determine whether the transmission authority acceptance message is received from at least one of the other terminals  120 ,  130  and  140  of the group within a certain time. 
         [0137]    In operation S 840 , when the transmission authority acceptance message is received from at least one of the other terminals  120 ,  130  and  140  of the group within the certain time, the first terminal  110  may continuously transmit the media data. 
         [0138]    In operation S 850 , when the transmission authority acceptance message is not received from at least one of the other terminals  120 ,  130  and  140  of the group within the certain time, the first terminal  110  may stop transmission of the media data. 
         [0139]      FIG. 9  is a flowchart for describing a method of determining a terminal having a transmission authority among a plurality of terminals  110 ,  120 ,  130  and  140  in a group in a communication system  100 , according to another embodiment. 
         [0140]    In operation S 910 , when data is not received from another terminal for a certain time, a first terminal  110  may transmit a transmission authority request message to each of the other terminals  120 ,  130  and  140  of the group. 
         [0141]    In operation S 920 , the first terminal  110  may transmit media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0142]    After transmitting the transmission authority request message, the first terminal  110  may transmit the media data without waiting for reception of a transmission authority acceptance message from the other terminals  120 ,  130  and  140  of the group. 
         [0143]    In operation S 930 , a third first terminal  110  may transmit a transmission authority acceptance message for the first terminal  110  to each of the first terminal  110 , a second terminal  120 , and a fourth terminal  140 . Here, the third terminal  130  may be a terminal where a standby time determined based on a randomly generated value elapses first, and when the transmission authority acceptance message is not received from the second terminal  120  and the fourth terminal  140  for the standby time, the third terminal  130  may be selected as a respondent. The third terminal  130  may transmit the transmission authority acceptance message for the first terminal  110  to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0144]    Moreover, when the transmission authority acceptance message is received from the third terminal  130  within a certain time, the first terminal  110  according to an embodiment may continuously transmit the media data. 
         [0145]      FIG. 10  is a flowchart for describing a method of transmitting media data when a first terminal  110  receives a transmission authority request message from another terminal included in a group in the middle of transmitting the media data, according to an embodiment. 
         [0146]    In operation S 1010 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of the group. 
         [0147]    The first terminal  110  obtaining a transmission authority may transmit the media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0148]    In operation S 1020 , the first terminal  110  may receive a transmission authority request message from another terminal (for example,  120 ) of the group in the middle of transmitting the media data. 
         [0149]    For example, the first terminal  110  may receive the transmission authority request message from a second terminal  120  in the middle of transmitting the media data. 
         [0150]    In operation S 1030 , the first terminal  110  may transmit a transmission authority rejection message to the other terminal (for example,  120 ) of the group. 
         [0151]    When the transmission authority request message is received from another terminal of the group before the transmission of the media data is completed, the first terminal  110  may transmit the transmission authority rejection message to the other terminal (for example,  120 ) of the group. For example, when the first terminal  110  receives the transmission authority request message from the second terminal  120  in the middle of transmitting the media data, the first terminal  110  may transmit the transmission authority rejection message to the second terminal  120 . Here, the first terminal  110  having a transmission authority may act as an arbitrary transmission authority mediator. 
         [0152]    In operation S 1040 , when the transmission of the media data is completed, the first terminal  110  may transmit a transmission release message to each of the other terminals  120 ,  130  and  140  of the group. 
         [0153]    In  FIG. 10 , each of the terminals  110 ,  120 ,  130  and  140  of the group may not store queue information about the transmission authority request message of another terminal which is generated while the first terminal  110  is transmitting the media data. 
         [0154]    Therefore, another terminal (for example,  120 ) of the group which has requested a transmission authority while the first terminal  110  is transmitting the media data may again transmit the transmission authority request message to obtain the transmission authority after the transmission of the media data from the first terminal  110  is completed. 
         [0155]      FIG. 11  is a flowchart for describing a method of transmitting media data when a transmission authority request message is transmitted from another terminal included in a group while a first terminal  110  is transmitting the media data in a communication system  100 , according to an embodiment. 
         [0156]    In operation S 1110 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of the group. 
         [0157]    The first terminal  110  obtaining a transmission authority may transmit the media data to each of the other terminals  120 ,  130  and  140  of the group. 
         [0158]    In operation S 1120 , a second terminal  120  may transmit a transmission authority request message to each of the first terminal  110 , a third terminal  130 , and a fourth terminal  140  while the first terminal  110  is transmitting the media data. 
         [0159]    In operation S 1130 , the first terminal  110  may transmit a transmission authority rejection message to each of the other terminals  120 ,  130  and  140  of the group. 
         [0160]    In operation S 1140 , the first terminal  110  may end the transmission of the media data. 
         [0161]    In operation S 1150 , the first terminal  110  may transmit a transmission release message to each of the other terminals  120 ,  130  and  140  of the group. 
         [0162]    Moreover, the first terminal  110  may not store queue information about the transmission authority request message of the second terminal  120  which is received in the middle transmitting the media data. Therefore, after the transmission of the media data from the first terminal  110  ends, there may not be a terminal transmitting the media data in the group. A terminal desiring to obtain the transmission authority may transmit the transmission authority request message to other terminals, thereby obtaining the transmission authority. 
         [0163]      FIG. 12  is a flowchart for describing a method of transmitting media data when a plurality of terminals store queue information in a communication system  100 , according to an embodiment. 
         [0164]    In operation S 1210 , a first terminal  110  may transmit media data. 
         [0165]    In operation S 1220 , a second terminal  120  may transmit a transmission authority request message to the first terminal  110 , the second terminal  120 , a third terminal  130 , and a fourth terminal  140  while the first terminal  110  is transmitting the media data. 
         [0166]    In operation S 1230 , the first terminal  110  may store information about the second terminal  120 . 
         [0167]    In the transmission system  100  according to an embodiment, the first terminal  110  having a transmission authority may act as an arbitrary transmission authority mediator and may store the transmission authority request message received from another terminal (for example,  120 ) of the group. 
         [0168]    For example, when the first terminal  110  receives the transmission authority request message from the second terminal  120  in the middle of transmitting the media data, the first terminal  110  may store queue information about the transmission authority request message of the second terminal  120 . The queue information about the transmission authority request message of the second terminal  120  may include information about at least one of an identification value of the second terminal  120 , a priority of the second terminal  120  in a queue, and a transmission authority status of the second terminal  120 . 
         [0169]    In operation S 1240 , the first terminal  110  may transmit a transmission authority request acceptance message for the second terminal  120  to each of the other terminals  120 ,  130  and  140  of the group. Here, the transmission authority request acceptance message may be a message indicating that the transmission authority request message of the second terminal  120  has been received. 
         [0170]    The transmission authority request acceptance message may include information about at least one of the identification value of the second terminal  120 , the priority of the second terminal  120  in the queue, and a time when the transmission authority request message of the second terminal  120  is received. By receiving the transmission authority request acceptance message, the second terminal  120  may check that the transmission authority request message of the second terminal  120  is received by the first terminal  110  having a transmission authority. 
         [0171]    When the media data is received from the first terminal  110  but the transmission authority request message is not received, the second terminal  120  according to an embodiment may monitor whether the transmission authority request acceptance message is received for a certain time. Here, the certain time may be, for example, 1RTT. When the transmission authority request acceptance message is not received for the certain time, the second terminal  120  may retransmit the transmission authority request message. 
         [0172]    In operation S 1250 , the first terminal  110  may end the transmission of the media data. 
         [0173]    In operation S 1260 , the first terminal  110  may transmit a transmission authority acceptance message to each of the other terminals  120 ,  130  and  140  of the group. 
         [0174]    When the transmission of the media data ends, the first terminal  110  according to an embodiment may determine a terminal having a transmission authority, based on at least one of a time when the transmission authority request message is received from another terminal which is waiting for transmission authority acceptance, a priority, and a random value, which are stored in a queue. 
         [0175]    For example, the first terminal  110  may determine the second terminal  120 , which is stored as having a first priority in the queue, as the terminal having the transmission authority. The first terminal  110  may transmit the transmission authority acceptance message for the second terminal  120 , indicating that the second terminal  120  obtains the transmission authority, to each of the other terminals  120 ,  130  and  140  of the group. 
         [0176]    Here, the transmission authority acceptance message may include information about another terminal which is waiting for the transmission authority. For example, when the third terminal  130  in addition to the second terminal  120  is stored as having a second priority for standby, the transmission authority acceptance message for the second terminal  120  may include a transmission authority status and an identification value of the third terminal  130 . When the second terminal  120  obtains the transmission authority, the third terminal  130  having a second priority for standby may be updated to a first priority for standby. 
         [0177]    In operation S 1270 , the second terminal  120  may transmit the media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0178]    When the second terminal  120  according to an embodiment receives the transmission authority request message from another terminal (for example,  140 ) in the middle of transmitting the media data, the second terminal  120  may store queue information about the received transmission authority request message. As another example, when queue information detected from the transmission authority acceptance message received from the first terminal  110  is already stored, the second terminal  120  may add newly obtained queue information into the already stored queue information and store the newly obtained queue information. 
         [0179]      FIG. 13  is a flowchart for describing a method of transmitting media data when a first terminal  110  receives a transmission authority request message from a higher-priority terminal in the middle of transmitting the media data in a communication system  100 , according to an embodiment. 
         [0180]    In operation S 1310 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of a group. 
         [0181]    In operation S 1320 , a third terminal  130  may transmit a transmission authority request message to each of the first terminal  110 , a second terminal  120 , and a fourth terminal  140  while the first terminal  110  is transmitting the media data. 
         [0182]    In operation S 1330 , when the first terminal  110  receives the transmission authority request message from the third terminal  130  (a higher-priority terminal) in the middle of transmitting the media data, the first terminal  110  may relinquish a transmission authority. Also, information about a priority of the third terminal  130  may be added into the transmission authority request message of the third terminal  130 . 
         [0183]    In operation S 1340 , the first terminal  110  may transmit a transmission authority acceptance message for the third terminal  130  to each of the other terminals  120  and  140  of the group. 
         [0184]    In operation S 1350 , when the transmission authority acceptance message is received, the third terminal  130  may transmit the media data to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0185]      FIG. 14  is a flowchart for describing a method of mediating in a transmission authority by using a media burst control protocol (MBCP) in a communication system  100 , according to an embodiment. 
         [0186]    In operation S 1410 , a first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of a group. 
         [0187]    In operation S 1420 , a second terminal  120  may transmit a transmission authority request message to each of the first terminal  110 , a third terminal  130 , and a fourth terminal  140  in the middle of receiving the media data from the first terminal  110 . 
         [0188]    In operation S 1430 , the first terminal  110  may transmit a transmission authority request acceptance message for the second terminal  120  to each of the other terminals  130  and  140  of the group. 
         [0189]    In the transmission system  100  according to an embodiment, the first terminal  110  having a transmission authority may act as an arbitrary transmission authority mediator and may store the transmission authority request message received from another terminal (for example,  120 ) of the group. 
         [0190]    For example, the first terminal  110  may store queue information about the transmission authority request message of the second terminal  120 . The queue information about the transmission authority request message of the second terminal  120  may include information about at least one of an identification value of the second terminal  120 , a priority of the second terminal  120  in a queue, and a transmission authority status of the second terminal  120 . 
         [0191]    Moreover, the first terminal  110  according to an embodiment may transmit a transmission authority request acceptance message for the second terminal  120  to each of the other terminals  120 ,  130  and  140  of the group. Here, the transmission authority request acceptance message may be a message indicating that the transmission authority request message of the second terminal  120  has been received. 
         [0192]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification value of the second terminal  120 , the priority of the second terminal  120  in the queue, and a time when the transmission authority request message of the second terminal  120  is received. By receiving the transmission authority request acceptance message, the second terminal  120  may check that the transmission authority request message of the second terminal  120  is received by the first terminal  110  having a transmission authority. 
         [0193]    When the media data is received from the first terminal  110  but the transmission authority request message is not received, the second terminal  120  according to an embodiment may monitor whether the transmission authority request acceptance message is received for a certain time. When the transmission authority request acceptance message is not received for the certain time, the second terminal  120  may retransmit the transmission authority request message. 
         [0194]    In operation S 1440 , the third terminal  130  may transmit the transmission authority request message to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140  while the first terminal is transmitting the media data. 
         [0195]    In operation S 1450 , the first terminal  110  may transmit the transmission authority request acceptance message for the third terminal  130  to each of the other terminals  120 ,  130  and  140  of the group. 
         [0196]    The first terminal  110  may store queue information about the transmission authority request message of the third terminal  130 . The queue information about the transmission authority request message of the third terminal  130  may include information about at least one of an identification value of the third terminal  130 , a priority of the third terminal  130  in the queue, and a transmission authority status of the third terminal  130 . 
         [0197]    Moreover, the first terminal  110  according to an embodiment may transmit the transmission authority request acceptance message for the third terminal  130  to each of the other terminals  120 ,  130  and  140  of the group. Here, the transmission authority request acceptance message may be a message indicating that the transmission authority request message of the third terminal  130  has been received. 
         [0198]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification value of the third terminal  130 , the priority of the third terminal  130  in the queue, and a time when the transmission authority request message of the third terminal  130  is received. By receiving the transmission authority request acceptance message, the third terminal  130  may check that the transmission authority request message of the third terminal  130  is received by the first terminal  110  having the transmission authority. 
         [0199]    According to an embodiment, when the transmission authority request message of the third terminal  130  is received later than the transmission authority request message of the second terminal  120 , the first terminal  110  may determine a standby priority of the second terminal  120  as a first priority and may determine a standby priority of the third terminal  130  as a second priority. However, this is merely an embodiment, the standby priority of the second terminal  120  may be determined based on at least one of the priority and random value of the second terminal  120 , and the standby priority of the third terminal  130  may be determined based on at least one of the priority and random value of the third terminal  130 . 
         [0200]    When the media data is received from the first terminal  110  but the transmission authority request message is not received, the second terminal  120  according to an embodiment may monitor whether the transmission authority request acceptance message is received for a certain time. When the transmission authority request acceptance message is not received for the certain time, the second terminal  120  may retransmit the transmission authority request message. 
         [0201]    In operation S 1460 , the first terminal  110  may end the transmission of the media data. 
         [0202]    In operation S 1470 , the first terminal  110  may transmit a transmission authority acceptance message for the second terminal  120  having a first priority for standby. 
         [0203]    When the transmission of the media data ends, the first terminal  110  according to an embodiment may determine a terminal having a transmission authority, based on at least one of a time when the transmission authority request message is received from another terminal which is waiting for transmission authority acceptance, a priority, and a random value, which are stored in the queue. 
         [0204]    For example, the first terminal  110  may determine the second terminal  120 , which is stored as having a first priority in the queue, as the terminal having the transmission authority. The transmission authority acceptance message for the second terminal  120  may include information about an identification value and a transmission authority status of the second terminal  120  for informing that the transmission authority of the second terminal  120  is accepted. Also, the transmission authority acceptance message for the second terminal  120  may include information about the third terminal  130  which is waiting for the transmission authority. When the transmission authority of the second terminal  120  is accepted, the third terminal  130  having a second priority for standby may be updated to a first priority for standby. 
         [0205]    In operation S 1480 , the second terminal  120  may transmit the media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0206]    When the second terminal  120  according to an embodiment receives the transmission authority acceptance message from the first terminal  110 , the second terminal  120  may transmit the media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0207]    Moreover, the second terminal  120  may store transmission authority status information about the third terminal  130  included in the received transmission authority acceptance message. The second terminal  120  may manage the transmission authority status information about the third terminal  130  until the transmission of the media data ends. 
         [0208]      FIG. 15  is a flowchart for describing a method of mediating in a transmission authority by using an MBCP when a transmission authority request message is transmitted from a higher-priority terminal while a first terminal  120  is transmitting media data in a communication system  100 , according to an embodiment. 
         [0209]    In operation S 1510 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of a group. 
         [0210]    In operation S 1520 , a second terminal  120  may transmit a transmission authority request message to each of the first terminal  110 , a third terminal  130 , and a fourth terminal  140  in the middle of receiving the media data from the first terminal  110 . 
         [0211]    In operation S 1530 , the first terminal  110  may transmit a transmission authority request acceptance message for the second terminal  120  to each of the other terminals  130  and  140  of the group. 
         [0212]    Moreover, operation S 530  may correspond to operation S 1430  described above with reference to  FIG. 14 . 
         [0213]    In operation S 1540 , the third terminal  130  may transmit a transmission authority request message to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140  while the first terminal  110  is transmitting the media data. 
         [0214]    In operation S 1550 , when the first terminal  110  receives the transmission authority request message from the third terminal  130  (a higher-priority terminal) in the middle of transmitting the media data, the first terminal  110  may relinquish a transmission authority. Also, information about a priority of the third terminal  130  may be added into the transmission authority request message of the third terminal  130 . 
         [0215]    In operation S 1560 , the first terminal  110  may transmit a transmission authority acceptance message for the third terminal  130  to each of the other terminals  120  and  140  of the group. 
         [0216]    When the transmission of the media data ends, the first terminal  110  according to an embodiment may determine a terminal having a transmission authority, based on at least one of a time when the transmission authority request message is received from another terminal which is waiting for transmission authority acceptance, a priority, and a random value, which are stored in a queue. 
         [0217]    For example, the first terminal  110  may determine the second terminal  120 , which is stored as having a first priority in the queue, as the terminal having the transmission authority. The transmission authority acceptance message for the second terminal  120  may include information about an identification value and a transmission authority status of the second terminal  120  for informing that the transmission authority of the second terminal  120  is accepted. Also, the transmission authority acceptance message for the second terminal  120  may include information about the third terminal  130  which is waiting for the transmission authority. When the transmission authority of the second terminal  120  is accepted, the third terminal  130  having a second priority for standby may be updated to a first priority for standby. 
         [0218]    In operation S 1570 , the second terminal  120  may transmit the media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0219]    When the second terminal  120  according to an embodiment receives the transmission authority acceptance message from the first terminal  110 , the second terminal  120  may transmit the media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0220]    Moreover, the second terminal  120  may store transmission authority status information about the third terminal  130  included in the received transmission authority acceptance message. The second terminal  120  may manage the transmission authority status information about the third terminal  130  until the transmission of the media data ends. 
         [0221]      FIG. 16  is a flowchart for describing a method of transmitting, by a terminal (for example,  120 ), media data according to whether the media data is received from a first terminal  110  having a transmission authority in a group, according to an embodiment. 
         [0222]    In operation S 1610 , the terminal (for example,  120 ) may receive media data from the first terminal  110  having the transmission authority among other terminals  110 ,  130  and  140  of the group. 
         [0223]    In operation S 1620 , the terminal (for example,  120 ) may transmit a transmission authority request message to each of the other terminals  110 ,  130  and  140  of the group. 
         [0224]    The terminal (for example,  120 ) according to an embodiment may transmit the transmission authority request message to each of the other terminals  110 ,  130  and  140  of the group in the middle of receiving the media data from the first terminal  110 . 
         [0225]    In operation S 1630 , the terminal (for example,  120 ) may receive a transmission authority request acceptance message from the first terminal  110 . 
         [0226]    By receiving the transmission authority request acceptance message from the first terminal  110 , the terminal (for example,  120 ) may check that the transmission authority request message of the terminal (for example,  120 ) is received by the first terminal  110 . Also, the transmission authority request acceptance message may include information about at least one of an identification value of the terminal (for example,  120 ), a priority of the terminal (for example,  120 ) in a queue, and a time when the transmission authority request message of the terminal (for example,  120 ) is received. 
         [0227]    Moreover, when another terminal (for example,  140 ) in addition to the terminal (for example,  120 ) transmits the transmission authority request message to the first terminal  110 , information about the other terminal (for example,  140 ) may be added into the transmission authority request acceptance message. 
         [0228]    In operation S 1640 , the terminal (for example,  120 ) may determine whether the media data is received from the first terminal  110  and may transmit the media data of the terminal (for example,  120 ), based on a result of the determination. 
         [0229]    By receiving a transmission release message from the first terminal  110 , the terminal (for example,  120 ) according to an embodiment may check that the transmission of the media data from the first terminal  110  ends. 
         [0230]    Moreover, the terminal (for example,  120 ) may determine a terminal having a transmission authority, based on information about a transmission authority of the terminal (for example,  120 ) included in the received transmission release message. For example, when a priority of the terminal (for example,  120 ) is the highest among priorities of terminals that have requested the transmission authority from the first terminal  120 , the transmission authority of the terminal (for example,  120 ) may be accepted. Therefore, the terminal (for example,  120 ) may transmit the media data of the terminal (for example,  120 ) to each of the other terminals  110 ,  130  and  140  of the group. 
         [0231]    According to another embodiment, when the media data is not received from the first terminal  110  for a certain time, the terminal (for example,  120 ) may determine that the first terminal  110  is in an absent state. When it is determined that the first terminal  110  is in the absent state, the terminal (for example,  120 ) may transmit the media data of the terminal (for example,  120 ) to each of the other terminals  110 ,  130  and  140  of the group, based on the transmission authority status information about the terminal (for example,  120 ) obtained from the transmission authority request acceptance message. 
         [0232]    Moreover, when the media data is not received from the first terminal  110  for a certain time, the terminal (for example,  120 ) may retransmit the transmission authority request message to each of the other terminals  110 ,  130  and  140  of the group, for determining whether the first terminal  110  is in the absent state. When the transmission authority request acceptance message is not retransmitted for a certain time from a time when the transmission authority request message is transmitted, the terminal (for example,  120 ) may determine that the first terminal  110  is in the absent state. 
         [0233]    However, this is merely an embodiment, and a method of determining, by the terminal (for example,  120 ), whether the first terminal  110  having a transmission authority is in an absent state is not limited thereto. 
         [0234]      FIG. 17  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal  110  having the transmission authority is absent from a certain position in a communication system  100 , according to an embodiment. 
         [0235]    In operation S 1710 , the first terminal  110  may transmit media data to each of a second terminal  120 , a third terminal  130 , and a fourth terminal  140 . 
         [0236]    In operation S 1720 , the second terminal  120  may transmit a transmission authority request message to each of other terminals  110 ,  130  and  140  of the group in the middle of receiving the media data from the first terminal  110 . 
         [0237]    In operation S 1730 , the first terminal  110  may store information about the second terminal  120 , based on the transmitted transmission authority request message. Here, the information about the second terminal  120  may include, for example, information about at least one of an identification value of the second terminal  120 , a priority of the second terminal  120  in a queue, and a time when the transmission authority request message of the second terminal  120  is received. 
         [0238]    In operation S 1740 , the first terminal  110  may transmit a transmission authority request acceptance message for the second terminal  120  to each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140 . 
         [0239]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification value of the second terminal  120 , the priority of the second terminal  120  in the queue, and the time when the transmission authority request message of the second terminal  120  is received. By receiving the transmission authority request acceptance message, the second terminal  120  may check that the transmission authority request message of the second terminal  120  is received by the first terminal  110  having a transmission authority. 
         [0240]    In operation S 1750 , the third terminal  130  may transmit media data to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0241]    In operation S 1760 , the first terminal  110  may store information about the third terminal  130 , based on the transmission authority request message received from the third terminal  130 . Here, the information about the third terminal  130  may include, for example, information about at least one of an identification value of the third terminal  130 , a priority of the third terminal  130  in a queue, and a time when the transmission authority request message of the third terminal  130  is received. 
         [0242]    Herein, it may be assumed that the priority of the second terminal  120  is higher than that of the third terminal  130 . Therefore, a standby priority of the second terminal  120  being a first priority and a standby priority of the third terminal  130  being a second priority may be stored in the queue of the first terminal  110 . 
         [0243]    In operation S 1770 , the first terminal  110  may transmit the transmission authority request acceptance message to each of the second terminal  120 , the third terminal  130 , and the fourth terminal  140 . 
         [0244]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification values of the second and third terminals  120  and  130 , the priorities of the second and third terminals  120  and  130  in the queue, the time when the transmission authority request message of the second terminal  120  is received, and the time when the transmission authority request message of the third terminal  130  is received. By receiving the transmission authority request acceptance message, the third terminal  130  may check that the transmission authority request message of the third terminal  130  is received by the first terminal  110  having the transmission authority. 
         [0245]    In operation S 1780 , when the media data is not received from the first terminal  110  for a certain time, the second terminal  120  may transmit the media data of the second terminal  120 . 
         [0246]    Despite that a message indicating the end of transmission is not received from the first terminal  110 , when the media data is not received from the first terminal  110 , the second terminal  120  according to an embodiment may determine that the first terminal  110  is in an absent state. 
         [0247]    Moreover, the second terminal  120  may retransmit the transmission authority request message for checking whether the first terminal  110  is in the absent state. When the transmission authority request acceptance message is not received for a certain time from a time when the transmission authority request message is retransmitted, the second terminal  120  may determine that the first terminal  110  is in the absent state. 
         [0248]    Moreover, the second terminal  120  may be a terminal having a first priority for standby. When it is determined that the first terminal  110  is in the absent state, the second terminal  120  may obtain the transmission authority. 
         [0249]      FIG. 18  is a flowchart for describing a method of determining a transmission authority state of another terminal when a first terminal  110  having a transmission authority receives from a transmission authority request message from the other terminal in the middle of transmitting media data, according to an embodiment. 
         [0250]    In operation S 1810 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  included in a group including the first terminal  110 . 
         [0251]    In operation S 1820 , the first terminal  110  may receive a transmission authority request message from at least one of the other terminals  120 ,  130  and  140  of the group. 
         [0252]    In operation S 1830 , the first terminal  110  may determine a transmission authority status of the at least one terminal, based on a priority of the at least one terminal. Here, the transmission authority status of the at least one terminal may indicate a standby priority for obtaining a transmission authority. 
         [0253]    The standby priority may be determined based on a random value generated from the at least one terminal, in addition to a predetermined priority of the at least one terminal. As another example, the standby priority may be determined based on a time when the transmission authority request message of the at least one terminal is received by the first terminal  110 . 
         [0254]    In operation S 1840 , the first terminal  110  may transmit a transmission authority request acceptance message, including information about the determined transmission authority status, to each of the other terminals  120 ,  130  and  140  of the group. 
         [0255]      FIG. 19  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal  110  is absent from a certain position in a communication system  100 , according to an embodiment. 
         [0256]    In operation S 1910 , a terminal (for example,  120 ) may transmit a transmission authority request message to each of other terminals  110 ,  130  and  140  included in a group. 
         [0257]    In operation S 1920 , the terminal (for example,  120 ) may receive a transmission authority request acceptance message from the first terminal  110  having a transmission authority. 
         [0258]    In operation S 1930 , the terminal (for example,  120 ) may determine whether first media data is received for a first time. 
         [0259]    In operation S 1940 , the terminal (for example,  120 ) may retransmit the transmission authority request message to each of the other terminals  110 ,  130  and  140  included in the group. 
         [0260]    In operation S 1950 , the terminal (for example,  120 ) may determine whether the transmission authority request acceptance message is re-received for a second time. 
         [0261]    In operation S 1960 , the terminal (for example,  120 ) may determine whether there is a terminal having a higher priority among one or more terminals which have requested the transmission authority from the first terminal  110 . 
         [0262]    In operation S 1970 , the terminal (for example,  120 ) may transmit media data. 
         [0263]    In operation S 1980 , the terminal (for example,  120 ) may receive the media data from the terminal having a higher priority among the one or more terminals which have requested the transmission authority from the first terminal  110 . 
         [0264]    In operation S 1990 , the terminal (for example,  120 ) may receive the media data from the first terminal  110  until transmission by the first terminal  110  ends. 
         [0265]      FIG. 20  is a flowchart for describing a method of determining a terminal having a transmission authority when a first terminal  110  having the transmission authority is absent from a certain position in a communication system  100 , according to an embodiment. 
         [0266]    In operation S 2010 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of a group. 
         [0267]    In operation S 2020 , the second terminal  120  may transmit a transmission authority request message to each of the first terminal  110 , a third terminal  130 , and a fourth terminal  140 . 
         [0268]    In operation S 2030 , the first terminal  110  may transmit a transmission authority request acceptance message, corresponding to the transmission authority request message of the second terminal  120 , to each of the other terminals  120 ,  130  and  140  of the group. 
         [0269]    The transmission authority request acceptance message according to an embodiment may include information about at least one of an identification value of the second terminal  120 , a priority of the second terminal  120  in a queue, and a time when the transmission authority request message of the second terminal  120  is received. 
         [0270]    In operation S 2040 , the third terminal  130  may transmit the transmission authority request message to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0271]    In operation S 2050 , the first terminal  110  may transmit the transmission authority request acceptance message, corresponding to the transmission authority request message of the third terminal  130 , to each of the other terminals  120 ,  130  and  140  of the group. 
         [0272]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification values of the second and third terminals  120  and  130 , the priorities of the second and third terminals  120  and  130  in the queue, the time when the transmission authority request message of the second terminal  120  is received, and the time when the transmission authority request message of the third terminal  130  is received. 
         [0273]    In the embodiment of  FIG. 20 , a standby priority of the second terminal  120  transmitting the transmission authority request message which is first received by the first terminal  110  may be determined as a first priority. Therefore, a standby priority of the third terminal  130  may be determined as a second priority. 
         [0274]    In operation S 2060 , when the media data is not received from the first terminal  110  for a certain time, the second terminal  120  may transmit the media data of the second terminal  120 . 
         [0275]    The second terminal  120  according to an embodiment may check standby priority information about the second terminal  120 , based on the transmission authority request acceptance message received from the first terminal  110 . When it is determined that the second terminal  120  is a terminal having a standby priority which is a first priority, the second terminal  120  may transmit media data to each of the first terminal  110 , the third terminal  130 , and the fourth terminal  140 . 
         [0276]    The second terminal  120  may update a standby priority of the third terminal  130  to a first priority. 
         [0277]      FIG. 21  is a flowchart for describing a method of determining a terminal having a transmission authority according to priorities when a first terminal  110  having the transmission authority is absent from a certain position in a communication system  100 , according to an embodiment. 
         [0278]    In operation S 2110 , the first terminal  110  may transmit media data to each of other terminals  120 ,  130  and  140  of a group. 
         [0279]    In operation S 2120 , the second terminal  120  may transmit a transmission authority request message to each of the first terminal  110 , a third terminal  130 , and a fourth terminal  140 . 
         [0280]    In operation S 2130 , the first terminal  110  may transmit a transmission authority request acceptance message, corresponding to the transmission authority request message of the second terminal  120 , to each of the other terminals  120 ,  130  and  140  of the group. 
         [0281]    The transmission authority request acceptance message according to an embodiment may include information about at least one of an identification value of the second terminal  120 , a priority of the second terminal  120  in a queue, and a time when the transmission authority request message of the second terminal  120  is received. 
         [0282]    In operation S 2140 , the third terminal  130  may transmit the transmission authority request message to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0283]    In operation S 2150 , the first terminal  110  may transmit the transmission authority request acceptance message, corresponding to the transmission authority request message of the third terminal  130 , to each of the other terminals  120 ,  130  and  140  of the group. 
         [0284]    The transmission authority request acceptance message according to an embodiment may include information about at least one of the identification values of the second and third terminals  120  and  130 , the priorities of the second and third terminals  120  and  130  in the queue, the time when the transmission authority request message of the second terminal  120  is received, and the time when the transmission authority request message of the third terminal  130  is received. 
         [0285]    In the embodiment of  FIG. 21 , it may be assumed that a priority of the third terminal  130  is higher than that of the second terminal  120 . Therefore, a standby priority of the third terminal  130  may be determined as a first priority. On the other hand, a standby priority of the second terminal  120  may be determined as a second priority. 
         [0286]    In operation S 2160 , when the media data is not received from the first terminal  110  for a certain time, the third terminal  130  may transmit the media data of the third terminal  130 . 
         [0287]    The third terminal  130  according to an embodiment may check standby priority information about the third terminal  130 , based on the transmission authority request acceptance message received from the first terminal  110 . When it is determined that the third terminal  130  is a terminal having a standby priority which is a first priority, the third terminal  130  may transmit media data to each of the first terminal  110 , the second terminal  120 , and the fourth terminal  140 . 
         [0288]    The third terminal  130  may update a standby priority of the third terminal  130  to a first priority. 
         [0289]      FIG. 22  is a block diagram of a terminal  2200  according to an embodiment. 
         [0290]    Referring to  FIG. 22 , the terminal  2200  according to an embodiment may include a communicator  2210 , a controller  2220 , and a memory  2230 . 
         [0291]    The terminal  2200  of  FIG. 22  is illustrated as including only elements associated with the present embodiment. Therefore, it may be understood by one of ordinary skill in the art that the terminal  2200  may further include general-use elements in addition to the elements of  FIG. 22 . 
         [0292]    The communicator  2210  may receive a transmission authority request message from a first terminal of a plurality of terminals included in a group including the terminal  2200 . The communicator  2210  may transmit a transmission authority acceptance message for the first terminal to each of the other terminals of the group and may receive media data from the first terminal, based on a result of determination by the controller  2220 . 
         [0293]    When the transmission authority acceptance message for the first terminal is not received from the other terminals of the group, the communicator  2210  according to an embodiment may transmit the transmission authority acceptance message. 
         [0294]    Moreover, the communicator  2210  according to an embodiment may transmit the transmission authority acceptance message to the first terminal having a priority higher than that of a second terminal. According to another embodiment, the communicator  2210  may transmit the transmission authority acceptance message to the first terminal having a random value greater than that of the second terminal. 
         [0295]    The communicator  2210  may transmit the transmission authority request message to each of the other terminals of the group in the middle of receiving the media data from the first terminal having a transmission authority among the other terminals of the group including the terminal  2200 . Also, the communicator  2210  may receive a transmission authority request acceptance message from the first terminal. 
         [0296]    Moreover, the communicator  2210  may transmit the media data, based on a result obtained by determining whether the media data of the first terminal is received. 
         [0297]    According to an embodiment, when the media data of the first terminal is not received for a certain time, the communicator  2210  may retransmit the transmission authority request message to the first terminal. When the transmission authority request acceptance message is retransmitted within a certain time after retransmitting the transmission authority request message, the communicator  2210  may transmit the media data. 
         [0298]    A priority of the terminal  2200  may be the highest in priorities of one or more terminals which have requested a transmission authority from the first terminal, and when the media data of the first terminal is not received for a certain time, the communicator  2210  according to an embodiment may retransmit the transmission authority request message. 
         [0299]    When a transmission release message is received from the first terminal, the communicator  2210  according to an embodiment may transmit the media data to each of the other terminals. Also, the communicator  2210  may receive the transmission release message from the first terminal, and when the priority of the terminal  2200  is the highest in priorities of the one or more terminals which have requested the transmission authority, the communicator  2210  may transmit the media data to each of the other terminals. 
         [0300]    The controller  2220  may implement a proposed function, operation, and/or method. The above-described operation of the terminal  2200  may be implemented by the controller  2220 . 
         [0301]    The controller  2220  may determine whether the transmission authority acceptance message is received from another terminal of the group. 
         [0302]    The controller  2220  according to an embodiment may monitor whether the transmission authority request message of another terminal is received for a certain time from a time when the transmission authority request message of the first terminal is received. Also, when the transmission authority request message of the other terminal is not received, the controller  2220  may determine the first terminal as a terminal having the transmission authority. 
         [0303]    Moreover, when the transmission authority request message is received from a second terminal of the other terminals of the group, the controller  2220  may compare a priority of the first terminal with a priority of the second terminal to determine a terminal having the transmission authority. 
         [0304]    Moreover, when the transmission authority request message is received from the second terminal of the other terminals of the group, the controller  2220  may compare random values respectively generated from the first and second terminals to determine the terminal having the transmission authority. 
         [0305]    The controller  2220  according to an embodiment may determine whether the media data of the first terminal is received. Also, the controller  2220  may determine whether the priority of the terminal  2200  is the highest in priorities of the one or more terminals which have requested the transmission authority from the first terminal. The controller  2220  may update transmission authority status information about the terminal  2200 , based on information about the one or more terminals which have requested the transmission authority from the first terminal. 
         [0306]    The memory  2230  may be connected to the controller  2220  and may store a protocol or a parameter for an operation. For example, the memory  2230  may store at least one of queue information and transmission authority status information about terminals requesting the transmission authority. 
         [0307]      FIG. 23  is a block diagram of a first terminal  2300  according to an embodiment. 
         [0308]    Referring to  FIG. 23 , the first terminal  2300  according to an embodiment may include a communicator  2310 , a controller  2320 , and a memory  2330 . 
         [0309]    The first terminal  2300  of  FIG. 23  is illustrated as including only elements associated with the present embodiment. Therefore, it may be understood by one of ordinary skill in the art that the first terminal  2300  may further include general-use elements in addition to the elements of  FIG. 23 . 
         [0310]    The communicator  2310  may transmit a transmission authority request message to each of other terminals included in a group including the first terminal  2300 . When a standby time which is randomly determined in each of the other terminals of the group elapses, the communicator  2310  may receive a transmission authority acceptance message from at least one of the other terminals of the group. 
         [0311]    The communicator  2310  according to an embodiment may receive the transmission authority request message of another terminal of the group within a certain time after the transmission authority request message is received. 
         [0312]    Moreover, the communicator  2310  may receive the transmission authority request message from another terminal of the group in the middle of transmitting media data, and when the transmission of the media data ends, the communicator  2310  may transmit a transmission release message to each of the other terminals of the group. 
         [0313]    The communicator  2310  according to an embodiment may transmit a transmission authority acceptance message to another terminal and may receive media data of the other terminal from the other terminal. 
         [0314]    Moreover, the communicator  2310  may transmit a transmission authority request acceptance message, including information about a transmission authority status determined for at least one terminal which has requested a transmission authority from the first terminal  2300 , to each of the other terminals of the group. 
         [0315]    The controller  2320  may implement a proposed function, operation, and/or method. The above-described operation of the first terminal  2300  may be implemented by the controller  2320 . 
         [0316]    The controller  2320  may determine whether the transmission authority acceptance message is received from at least one of the other terminals of the group. 
         [0317]    Moreover, the controller  2320  may receive the transmission authority request message from another terminal of the group in the middle of transmitting media data, and when a priority of the other terminal is higher than that of the first terminal  2300 , the controller  2320  may stop the transmission of the media data. 
         [0318]    The controller  2320  according to an embodiment may determine a transmission authority status of at least one terminal, based on a priority of the at least one terminal. 
         [0319]    The memory  2330  may be connected to the controller  2320  and may store a protocol or a parameter for an operation. For example, the memory  2330  may store at least one of queue information and transmission authority status information about terminals requesting the transmission authority. 
         [0320]    An apparatus according to the inventive concept may include a processor, a memory storing and executing program data, a permanent storage such as a disk drive, a communication port for communication with an external device, a user interface device such as a touch panel, keys or buttons, and the like. Methods embodied as a software module or an algorithm may be stored on a computer-readable recording medium as computer readable codes or program commands executable by the processor. Examples of the computer-readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.), optical recording media (e.g., CD-ROMs, or DVDs), and the like. The computer-readable recording medium may also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. The medium may be read by a computer, stored in a memory, and executed by the processor. 
         [0321]    All the documents including the public laid open documents, patent applications, patent documents, and the like cited in the inventive concept may be merged into the inventive concept in the same manner as that indicated by individually or specifically merging the respective cited documents or as that indicated by merging them overall in the inventive concept. 
         [0322]    To aid in understanding the inventive concept, reference numerals are used in the exemplary embodiments shown in the drawings, and specific terms are used to explain the exemplary embodiments of the inventive concept; however, they are not intended to limit the inventive concept and may represent all the components that could be considered by those of ordinary skill in the art. 
         [0323]    The inventive concept may be embodied as functional blocks and various processing operations. The functional blocks may be implemented with various hardware and/or software configurations executing specific functions. For example, the inventive concept employs integrated circuit configurations such as a memory, processing, logic, a look-up table and the like capable of executing various functions upon control of microprocessors or other control devices. In a similar manner to that in which the elements of the inventive concept may be executed with software programming or software elements, the inventive concept may be implemented with a scripting language or a programming language such as C, C++, Java, assembler, and the like, including various algorithms implemented by a combination of data structures, processes, processes, routines or other programming configurations. The functional aspects may be implemented by algorithms executed in one or more processors. Also, the inventive concept may employ conversional arts to establish an electronic environment, process signals and/or process data. The terms “mechanism”, “element”, “means” and “configuration” may be widely used and are not limited to mechanical and physical configurations. Such terms may have the meaning of a series of routines of software in association with a processor or the like. 
         [0324]    Specific executions described herein are merely examples and do not limit the scope of the inventive concept in any way. For simplicity of description, other functional aspects of conventional electronic configurations, control systems, software and the systems may be omitted. Furthermore, line connections or connection members between elements depicted in the drawings represent functional connections and/or physical or circuit connections by way of example, and in actual applications, they may be replaced or embodied as various additional functional connection, physical connection or circuit connections. Also, the described elements may not be inevitably required elements for the application of the inventive concept unless they are specifically mentioned as being “essential” or “critical.” 
         [0325]    It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
         [0326]    While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.