Abstract:
Disclosed is a terminal apparatus and a method for providing media transmission time information in a Push-to-talk over Cellular (PoC) system. The method includes receiving a media burst granted message in response to a media burst request message, and confirming media transmission time information in the received media burst granted message, and informing a user of the confirmed media transmission time information. By the method, it is possible to recognize media transmission time information included in a floor granted message transmitted from a PoC server and informing a user of the media transmission time information.

Description:
PRIORITY 
   This application claims priority under 35 U.S.C. §119(a) to an application entitled “Terminal Apparatus And Method For Providing Media Transmission Time Information In A PoC System And PoC System For The Same” a  filed in the Korean Industrial Property Office on Jan. 13, 2006 and assigned Serial No. 2006-4152, and filed May 12, 2006 and assigned Serial No. 2006-43144, respectively, the contents of both of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a Push-to-talk over Cellular (PoC) terminal, and more particularly to a method for informing a PoC user of remaining time information available for media transmission when a communication has been established according to a request for the communication. 
   2. Description of the Related Art 
   With the rapid development of mobile communications and the vast expansion of communication networks, cellular phones are now being used to provide a wider variety of extended services and applications. Cellular phone users are requiring a wider variety of services beyond the basic talk communication service, such as location, multimedia and Push-To-Talk (PTT) services. The current PTT service supports various additional functions, such as instant messenger and status display functions, as well as group and voice communication, which may also be provided by an existing radio transmitter or a Trunk Radio System (TRS). 
   Active research currently being conducted about establishment of a standard for a PoC service to be provided through a mobile communication network using the PTT concept. The PoC service is distinguished from the existing mobile communication services, in that a user belongs to multiple sessions and thus can continue communication while moving between sessions if necessary. The requirement that a user be capable of continuing communication while moving between sessions is clearly found in a requirement of the Open Mobile Alliance (OMA), which is a forum for specifying mobile communications services. 
     FIG. 1  illustrates a basic structure of a conventional PoC system. Referring to  FIG. 1 , the PoC client  10  corresponds to a service requester embedded in a mobile terminal, which is usually connected through an access network  20  to an Session Initiation Protocol (SIP) and Internet Protocol (IP) core network  30 , which is for supporting SIP/IP multimedia. 
   The PoC client  10  resides in a PoC client terminal in order to enable access to a PoC service. A main functions of the PoC client  10  are to generate a PoC session at the PoC client side, and participate in and terminate the session. Moreover, the PoC client  10  functions to make and transfer a talk burst, support an instant personal alert and perform authentication when accessing the PoC service. Hereinafter, unless otherwise stated, the PoC client  10  is assumed to be the same as a PoC service subscriber. 
   The SIP/IP core network  30  is connected to a PoC server  60 , a Group List and Management System (GLMS)  50  and a presence server  70 , in order to support a PoC service. 
   The GLMS  50  is a server that stores information of PoC service subscribers and transfers subscribers (e.g., subscriber ID, terminal number and group information) in cooperation with the PoC server  60 . 
   The presence server  70  stores status information, such as location and status (i.e., on-line or off-line) of a PoC service subscriber, which registers/maintains a current position of an on-line user and informs users of such registered/maintained information, thereby enabling instant communication between users. 
   The PoC server  60  serves as a Controlling PoC Function (CF) for maintaining and managing a PoC session, or a Participating PoC Function (PF) for participating in a PoC session for a one-to-one PoC call or a one-to-many PoC call (or group PoC call). 
   The PoC server is classified into a Controlling PoC Function (CF) of overseeing maintenance and management of a PoC session and a Participating PoC Function (PF) of overseeing maintenance and management between each PoC session, which will be explained with reference to the Tables 1 and 2 below. 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               Controlling PoC Function(CF) 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               Provides centralized PoC session handling 
             
             
                 
               Provides the centralized Media distribution 
             
             
                 
               Provides the centralized Talk Burst Arbitration functionality 
             
             
                 
               including talker identification 
             
             
                 
               Provides SIP session handling, such as SIP session origination, 
             
             
                 
               termination, etc. 
             
             
                 
               Provides policy enforcement for participation in group sessions 
             
             
                 
               Provides the participants information Collects and provides 
             
             
                 
               centralized media quality information 
             
             
                 
               Provides centralized charging reports 
             
             
                 
               May provide transcoding between different codecs; Support Talk 
             
             
                 
               Burst Control Protocol Negotiation 
             
             
                 
                 
             
           
        
       
     
   
   As shown in Table 1, the CF maintains and manages an entire PoC session. The PoC server receives requests for a floor from PoC clients, arranges an order in which to give the clients the floor, and gives the clients the floor in that order. The PoC server also distributes a talk burst, for which an arbitrary PoC client makes a request, to all other PoC clients participating in a group PoC call, and provides information of the PoC clients participating in the group PoC call. 
   As shown in Table 2 below, the PF manages a PoC session between the CF and each PoC client. In particular, the PF relays the floor between the PoC client and the CF when the PoC client makes a request for the floor or when the CF gives the floor to the PoC client. In addition, the PF relays media between the CF and the PoC client, performs transcoding between different codecs, and filters one of two concurrent PoC sessions according to the choice of a PoC user when there is simultaneous talking in the two concurrent PoC sessions. 
   
     
       
             
           
             
           
         
             
               TABLE 2 
             
             
                 
             
             
               Participating PoC Function(PF) 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               Provides PoC session handling 
             
             
               May provide the Media relay function between PoC Client and 
             
             
               Controlling PoC server 
             
             
               May provide user media adaptation procedures 
             
             
               May provide the Talk Burst control message relay function between 
             
             
               PoC Client and Controlling PoC server Provides SIP session handling, 
             
             
               such as SIP session origination, termination, etc, on behalf of the 
             
             
               represented PoC Client. 
             
             
               Provides policy enforcement for incoming PoC session (e.g. access 
             
             
               control, incoming PoC session barring, availability status, etc) 
             
             
               May collect and provide media quality information; Provides the 
             
             
               participant charging reports 
             
             
               May provide filtering of the media streams in the case of simultaneous 
             
             
               sessions 
             
             
               May provide transcodmg between different codecs 
             
             
               May support Talk Burst Control Protocol Negotiation; Stores the 
             
             
               current Answer 
             
             
               Mode and Incoming PoC Session Barring preferences of the PoC Client 
             
             
                 
             
           
        
       
     
   
   In the PoC service system as described above, the PoC user can input information on a group and its members to the GLMS  50  through his/her PoC terminal, and can learn information about PoC users whom he or she can call through an individual or group list transmitted from the GLMS  50 . Alternatively, the information on the group and its members may be input, corrected and managed in the GLMS  50  via a reliable communication network such as the Internet or Intranet. 
   In order to make use of the PoC service, the PoC user registers his/her PoC address with the SIP/IP core network  30 . The SIP/IP core network  30  stores PoC user information based on the request of the PoC user. Thus, when another PoC user tries to request a group PoC call, the PoC user registers his/her information in the SIP/IP core network  30  in advance as described above, and requests the group PoC call to his/her SIP/IP core network  30  by using group identification information transmitted from the GLMS  50 . At this time, the SIP/IP core network  30  performs address and domain location determination by using information of the call requesting PoC user and then transfers a PoC call request to a home PoC server with which the call requesting PoC user is registered. In regard to the PoC call request, the PoC server prepares for establishment of a PoC session, obtains each user&#39;s information from the GLMS  50 , and then transfers a PoC call request signal to a corresponding SIP/IP core network  30 . Here, in the case of a PoC call request to users within an Intradomain, the PoC server performs both the CF and PF. The PoC server, which manages a call-requested PoC user, requests a PoC call to the PoC user after the SIP/IP core network  30  performs the location determination procedure, by using information of the PoC user that is transmitted to the PoC server. 
   Hereinafter, a general procedure where a PoC user obtains a floor in a conventional PoC system having the construction described above will be discussed with reference to  FIG. 2 . 
   Within a PoC session where a PoC client A is connected to a PoC client B, when there is an input from a user in order to obtain a floor, the PoC client A makes a request for the floor by transmitting a message making a request for media transmission, a Media Burst Request message, to a PoC server A in step  200 . The PoC server A acts as the PF. After receiving Media Burst Request message, the PoC server A transmits the Media Burst Request message to a PoC server X in step  202 . The PoC server X acts as the CF. After receiving the message requesting the floor, the PoC server X transmits a message granting the floor, a Media Burst granted message, to the PoC client A through steps  204  and  206 . Further, the PoC server X transmits a message indicating that the PoC client A has been granted the floor, a Media Burst Taken message, to the PoC client B. At this time, the Media Burst Taken message includes an IDentifier (ID) of the PoC client A, that is, information by which the PoC client B having received the message can know the identity of the talker. In the PoC communication as described above, when the talker has been granted the right to transmit the media burst, the talker can transmit media only during a time interval set by a service provider. According to a standard arranged by the Open Mobile Alliance (OMA), a service provider can determine such a time interval. The reason why a client sets and operates an available time interval for media transmission as described above is to mediate between PoC participants in a PoC system, thereby preventing exclusive and continuous media transmission by one PoC session participant, which may disturb media transmission by another PoC session participant because the PoC service employs a half-duplex scheme. 
   Hereinafter, a signal flow between a PoC client and a PoC server when a PoC terminal apparatus transmits a media burst in a conventional PoC system will be discussed with reference to  FIG. 6 . Referring to  FIG. 6 , the PoC client makes a request for media transmission by transmitting a media burst request message for media transmission to a PoC server in step  601  as in steps  200  to  202  of  FIG. 2 . 
   Then, the PoC server having received the media burst request message transmits a media burst granted message to the PoC client who transmitted the media burst request message in step  602  as in steps  204  to  206  of  FIG. 2 . Thereafter, the PoC server operates a timer T 2  related to the media transmission time. When the time set in the timer T 2  has expired, the PoC server transmits a media burst revoke message to the PoC client in step  603 . The transmitted media burst revoke message corresponds to a message reporting that the transmission time has expired and it is impossible to continue transmitting media. After receiving the media burst revoke message, the PoC client stops encoding of the PoC user&#39;s voice, generates a media burst release message and transmits the generated media burst release message to the PoC server. 
   Thereafter, the PoC server operates another timer T 3  for allowing extra time for transmission of the media burst remaining in the PoC client buffer message and allows the PoC client to transmit the media burst stored in the buffer while the timer T 3  is operated. Further, when the PoC client has transmitted a media burst release message in step  604 , the PoC server transmits a media burst idle or media burst taken message (step  605 ) to all PoC clients participating in the PoC session, thereby reporting that the previous PoC client has completed the media transmission. The media burst includes voice in the OMA spec PoC v1 and includes media in the OMA spec PoC v2. In the following description, the media burst includes voice. Therefore, one of the media burst may be a talk burst. 
   In the process described above, the media burst granted message transmitted from the PoC server X (CF X) to the PoC client A includes a header having a media transmission time value, from which the PoC client A can recognize an allowed initial media transmission time value. However, although the PoC client is aware of the initial media transmission time value, when the PoC client has transmitted the media burst during a time interval, the PoC client cannot inform a PoC user of the remaining available time for media transmission because the PoC client does not have an interval function for measuring the transmission time. Therefore, the media transmission may be unexpectedly interrupted due to the expiration of the transmission time. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a terminal apparatus and method for recognizing media transmission time information included in a floor granted message transmitted from a PoC server and informing a user of the media transmission time information. 
   It is another object of the present invention to provide a terminal apparatus and method for recognizing media transmission time information included in a floor granted message transmitted from a PoC server and informing a user of a floor expiration time information before a floor time expires. 
   In order to accomplish these objects, there is provided a method for providing media transmission time information in a PoC system, the method including receiving a media burst granted message in response to a media burst request message, confirming media transmission time information in the received media burst granted message, and informing a user of the confirmed media transmission time information. 
   In accordance with the present invention, there is provided a PoC terminal apparatus for providing media transmission time information in a PoC system, the PoC terminal apparatus including a key input unit for outputting specific key input data according to input of each key, a display unit for displaying received media data and data output through the key input unit, and a control unit for receiving a media burst granted message in response to a media burst request message, confirming media transmission time information in the received media burst granted message, and informing a user of the confirmed media transmission time information. 
   In accordance with the present invention, there is provided a PoC system including a PoC server for transmitting a media burst granted message including a media transmission time value to a PoC client having transmitted a media burst request message to the PoC server, and transmitting a message for informing termination of media transmission of a previous PoC client to all PoC clients participating in a PoC session when the PoC server has received a media burst release message, and a PoC client for transmitting a media burst request message to the PoC server when there is an input for making a request for a media burst, confirming a media transmission time value included in the media burst granted message and transmitting media during the confirmed media transmission time when it has received the media burst granted message, and transmitting a media burst release message to the PoC server when the media transmission time value has expired. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  illustrates a basic structure of a conventional PoC system; 
       FIG. 2  illustrates a conventional procedure by which a PoC user obtains a floor; 
       FIG. 3  illustrates an internal structure of a PoC terminal apparatus that provides media transmission time information received from the PoC server according to the present invention; 
       FIG. 4  illustrates a process in which a PoC terminal apparatus informs users of media transmission time information received from a PoC server according to the present invention; 
       FIGS. 5A and 5B  illustrate examples of screens for informing a user of media transmission time information received by a PoC terminal from a PoC server according to the present invention; 
       FIG. 6  is a signal flow diagram of signals between a PoC client and a PoC server when a PoC terminal apparatus transmits a media burst in a conventional PoC system; and 
       FIG. 7  is a signal flow diagram of signals between a PoC client and a PoC server when a PoC terminal apparatus transmits a media burst in a PoC system according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted for the sake of clarity and conciseness. 
   The present invention discloses a scheme for informing a PoC user of remaining time information available for a floor included in a Media burst granted message received from a PoC server by a PoC terminal apparatus equipped with a timer, so that the PoC user can confirm the remaining time during which he/she can speak. Further, the present invention discloses a scheme for informing a PoC user of time available for media transmission when a PoC terminal apparatus transmits media in a PoC communication service. 
   Hereinafter, an internal structure and operation of a PoC terminal apparatus for informing a PoC user of time information available for media transmission according to the present invention will be described with reference to  FIG. 3 . 
   The PoC terminal apparatus  300  interfaces with the user and includes a key input unit  304  for outputting specific key input data corresponding to each of the keys provided at the PoC terminal apparatus  300 . Further, the PoC terminal apparatus  300  includes a data transceiver unit  305  for transmission/reception of packet data with the PoC server. Moreover, the PoC terminal apparatus  300  includes a display unit  303  for displaying media data received through the data transceiver unit  305  and data output through the key input unit  304 , and a control unit  301  for controlling the data transmission/reception of the PoC terminal apparatus  300  and the display by the display unit  303 . The control unit  301  controls reception of a media burst granted message in response to the media burst request message, confirmation of transmission time information within the received media burst granted message, and reporting of the confirmed transmission time information to the user. In informing a user of the confirmed media transmission time information, two embodiments of the present invention can be described as follows. According to the first embodiment, the control unit  301  operates a timer  306  such that confirmed media transmission time information is set as an initial value and the confirmed initial value is then down-counted. For example, the initial transmission time value may be set as 30 seconds and may be then down-counted per second in the manner of “29 seconds, 28 seconds, . . . ” Otherwise, the initial value may be set as “0 seconds” and be then up-counted to a value as high as a transmission time informing value. Then, when there remains a time value as much as the transmission time informing value, this value may be reported to the user. For example, when the transmission time informing value has been set as five seconds and the transmission time value is confirmed to be 30 seconds, the initial timer value is set as “0” seconds and is then up-counted per second to 5 seconds in the manner of “0 seconds, 1 second, 2 seconds, . . . ” When 25 seconds has elapsed, that is, there remains five seconds corresponding to the transmission time informing value, the user is informed that five seconds remains as time available for the media transmission. Further, the up-counted time value from the “0” seconds to the transmission time value may be continuously displayed on a screen regardless of transmission time informing value. This is another way to implement. 
   Thereafter, when the timer value of the timer  306  becomes equal to the media transmission time informing value, the media transmission time informing value for informing the remaining time available for the media transmission is displayed on a screen under the control of the control unit  301 . According to the second embodiment, under the control of the control unit  301 , confirmed media transmission time information is set as an initial value, a timer is then operated to down-count the confirmed initial value, and the timer value down-counted from the initial value is displayed on a screen. Further, the PoC terminal apparatus  300  includes a memory  307  for storing information in relation to general functions of the terminal, data related to provision of the PoC service, a user account for identification of a terminal, information set by a user or provided by a server, and a time value for reporting media transmission expiration time by the user. Further, the PoC terminal apparatus  300  includes the timer  306  controlled by the control unit  301 . The timer  306  counts a remaining time value available for the media transmission by a driving control signal from the control unit  301 . 
   Hereinafter, a process in which the PoC terminal apparatus  300  confirms the media transmission time information included in the Media Burst granted message received from the PoC server and informs a user of the Media transmission expiration time information before the media transmission expiration time set in advance, will be described with reference to  FIGS. 3 and 4 . 
   First, the PoC user stores a time value for informing expiration of the media transmission time in advance in the memory  307  through the key input unit  304 . For example, if the media transmission time value included in the floor granted message received from the PoC server is 30 seconds and the media transmission expiration informing time value is five seconds, the PoC terminal apparatus  300  sets the timer value as 30 seconds from the time point at which the apparatus  300  has received the floor granted message and operates the timer to be down-counted, and informs the user, when there remains five seconds, that the floor will soon expire. 
   After the time value for informing the expiration of the media transmission is set as described above, the control unit  301  maintains PoC Session connection state in step  400  and, the control unit  301  determines in step  402  whether there is an input for making a request for media transmission. When there is no input in order to make a request for media transmission, the process returns to step  400 . However, when there is an input for making a request for media transmission, the control unit  301  transmits, in step  404 , a media burst request message through the PF to the PoC server that acts as the CF. Then, in step  406 , the control unit  301  determines whether a media burst granted message is received from the PoC server, and proceeds to step  408  when the media burst granted message is received. 
   In step  408 , the control unit  301  confirms the media transmission time value within the media burst granted message and operates the timer  306  by setting the media transmission time value as an initial value. Thereafter, in step  410 , the control unit  301  determines whether the timer value is equal to the media transmission time informing value during the operation of the timer  306 . For example, when the confirmed media transmission time value is 30 seconds and the transmission time informing value is five seconds, that is, when it has been set to alarm five seconds before the media transmission time expires, the control unit  301  counts the timer value from an initial value of 30 seconds at a time point of receiving a media burst granted message, and determines whether the timer value reaches five seconds. 
   As a result of the determination in step  410 , when the timer value is equal to the media transmission time informing value, the control unit  301  informs the user of remaining time information available for the media transmission. That is, the control unit  301  outputs to the PoC user an alarm that the remaining media transmission time is as much as the time value set in advance. In order to report the remaining time information available for the media transmission to the user, various methods can be used, such as vibration, flashing light or screen display of remaining time. Further, for example, by displaying a warning message for the termination of the media transmission as shown in  FIG. 5B , it is possible to report to the user that the time given to the user for the media transmission will soon expire. 
   As described above with reference to  FIGS. 3 and 4 , when a time value reaches a media transmission informing time value set in advance from an initial value, it is possible to inform a user of the remaining time for the media transmission. 
   According to another embodiment of the present invention, the control unit  301  confirms the media transmission time value within the media burst granted message and operates the timer  306  with the media transmission time value as an initial value while displaying the down-counted media transmission time value as shown in  FIG. 5A . From the screen on which the media transmission time value is down-counted, the PoC user always can confirm his/her available media transmission time. 
   Hereinafter, a signal flow between a PoC client and a PoC server when a PoC client having the construction as shown in  FIG. 3  transmits a media burst will be discussed with reference to  FIG. 7 . According to the present invention, a right to transmit media, i.e., the media burst, includes a right to transmit voice, that is, a floor or a talk burst. 
   Referring to  FIG. 7 , the PoC client makes a request for media transmission by sending a media burst request message to a PoC server in step  700 . Then, in step  701 , the PoC server having received the media burst request message sends a media burst granted message to the PoC client having sent the media burst request message. 
   After receiving the media burst granted message, the PoC client confirms the media transmission time value in the media burst granted message and operates the timer  306  with the media transmission time value as an initial value. When the timer value becomes equal to a media transmission time informing value during operation of the timer  306 , the PoC client informs the user of remaining time information available for the media transmission. Further, when the time for the media transmission set in the timer expires, the PoC client stops encoding of the PoC user&#39;s voice, generates a media burst release message and sends the generated media burst release message to the PoC server. In this manner, the PoC client informs termination of the media transmission by sending the media burst release message to the PoC server. After receiving the media burst release message, the PoC server sends a media burst idle or media burst taken message to all PoC clients participating in the PoC session, thereby reporting that the previous PoC client has completed the media transmission. 
   According to the present invention as described above, a PoC user can recognize remaining time available for media transmission and thus can control his/her media transmission. For example, a PoC user can recognize the remaining seconds while he/she speaks, and thus can easily close out the transmission before getting penalty, which prohibits to send Media Bursts during pre-determined time. Further, a user can schedule the media transmission according to the remaining time available for the media transmission. Moreover, according to the present invention, the PoC server sends a media burst granted message including a media transmission time value to the PoC client having sent a media burst request message, and the PoC client operates a media transmission timer with an initial media transmission time value and sends a media burst release message when the time set in the timer expires. Therefore, according to the present invention, it is unnecessary to operate the conventional timer for counting the media transmission time in the PoC Server (That is T 2  timer as specified in OMA PoC UserPlane Document) and the extra conventional timer in PoC Server (which is T 3  ‘grace timer’ as specified in OMA PoC UserPlane Document) for providing extra time for transmission of the media stored in the buffer within the PoC client. Moreover, the PoC server does not have to deliberately transmit a media burst revoke message for informing that it is impossible to continue transmitting the media due to expiration of the media transmission time. Therefore, the present invention can increase the efficiency of air and network resources. Further, according to the present invention, instead of transmitting the media burst revoke message, the PoC server receives the media burst release message from the PoC client at that time. Therefore, it is possible to reduce the time for mediation of the media transmission by the PoC server as much as the time value for allowing extra time for transmission of the media stored in the buffer within the PoC client. 
   While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.