1. Field of the Invention
The present invention relates to a session-based service and, more particularly, to a method and device for providing a session-based PT service.
2. Description of the Related Art
In general, a SIP (Session Initiation Protocol) is commonly used as a protocol for controlling a session. The SIP refers to a signaling protocol that defines a procedure for terminals, which want communication, to establish a session therebetween, or delete or change the established session. The SIP uses an URL (Uniform Resource Locator) similar to an e-mail address in order to distinguish each user, so it can provide a service without being dependent on an IP (Internet Protocol) address.
The SIP-based session service may be, for example, a PT (Push-To) service. The PT service is a service for providing high speed communication to users, for example, between two users (one-to-one) or between receiver groups (one-to-many). The PT service generally includes a PTT (Push-To-Talk) service for audio data transmission, a PoC (Push-to-talk over Cellular) service allowing audio data to be transmitted over a cellular communication network, a PTV (Push To View) service for video data transmission, and a PTD (Push To Data) for data transmission.
FIG. 1 is an exemplary view showing a flow of a PT service according to a related art.
As shown in FIG. 1, in the PT service, a user cannot transmit voice, image, media data or other data until he/she requests a permission to send media (namely, authority to send) from a PT server and receives the permission from the PT server. This will be described in detail as follows referring to steps 1-3 shown in FIG. 1.
Step 1: A PT client 10 (e.g., a mobile phone) requests a permission to send media data to a PT server 20 capable of providing a PT service. This can be achieved, e.g., by transmitting a media burst request message from the PT client 10 to the PT server 20.
Step 2: The PT server 20 determines whether to give (or grant) the permission to send media in response to the request. In this case, when the PT server 20 has already given the permission to send media to another PT client, the PT server 20 refuses (or rejects) to give the permission to send media to the PT client 10. However, if the PT sever 20 determines that the permission to send media can be given to the PT client 10 which has requested it, the PT server 20 gives the permission to send media to the PT client 10, e.g., by transmitting a media burst granted message to the PT client 10.
Step 3: Upon receiving the permission to send media, the PT client 10 transmits media data.
However, the related art session-based PT service has a problem that when the PT client 10 transmits data for along time, other PT clients need to wait for the corresponding long time. This problem becomes serious when a user of the PT client intentionally (or maliciously) keeps transmitting data. Then, the other PT clients participating in the same session cannot be given the permission to send media although he/she has data to send. Other limitations associated with the related art will be discussed later referring to FIGS. 2 and 3.