KR20100077418A - Pr-sctp based real-time multimedia data transmission for qos enhancement - Google Patents

Abstract

PURPOSE: A PR-SCTP(Stream Control Transmission Protocol) based real-time multimedia data transmitting method for QoS improvement is provided to supply a real-time multimedia service by using only SCTP among transmission protocols, thereby saving resources of a server or a client. CONSTITUTION: If a client becomes a play state, a server calculates lifetime of each multimedia message according to a buffer state of the client and a network state(S204). The server performs reliable transmission during the calculated lifetime(S205). If the client becomes a buffering state, the server sets lifetime of all multimedia data by an unreliable transmission constant(S206). The server performs unreliable transmission(S207).

Description

PRC-SCPT based real-time multimedia data transmission method for service quality improvement {PR-SCPT based real-time multimedia data transmission for QoS enhancement}

The present invention relates to a technology for transmitting multimedia data in real time between a server and a client by using a Stream Control Transmission Protocol (SCTP), and more particularly, a PR-SCTP (Stream Control Transmission Protocol Partial Reliability Extension) that is an extension of SCTP. The present invention relates to a PR-SCTP-based real-time multimedia data transmission method that can improve the overall service quality by appropriately adjusting the lifetime of the PR-SCTP message in real-time multimedia data transmission using

Conventionally, a combination of TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) has been used as a transport layer protocol for a multimedia service using an IP packet network. More specifically, TCP is used to guarantee reliability as a channel for transmission control and UDP is used as a channel for real-time media delivery.

However, this approach is undesirable for both server and client in terms of resource utilization because the server and client must first use two protocols. Moreover, UDP, which is responsible for the transmission of multimedia data, only performs transmission to the destination, which may cause loss due to link failure or temporary network congestion, and may worsen the state of the network in a congested state.

Therefore, IETF is a new transport layer protocol standard, which is more effective for real-time multimedia transmission services such as IPTV than the conventional method, and the Stream Control Transmission Protocol Partial Reliability Extension, which is an extension specification of SCTP (Stream Control Transmission Protocol). ) Is proposed.

SCTP basically supports multistreaming to provide logical classification of application layer data in one session, and PR-SCTP extends SCTP, which only supported reliable transmission, to provide partial reliability only for a given time. Doing. With this PR-SCTP, retransmission is no longer performed after an appropriate time, and an error occurs by performing retransmission within the range that does not violate the requirements of the application while performing the best-effort transmission function such as UDP. Data can be recovered. From the point of view of the client application, it can be provided with a higher quality of service than when using UDP. In addition, with the recent rapid development of Ethernet technology, the improvement of service quality through real-time media data recovery using PR-SCTP is expected to be more significant.

Combining the multi-streaming function of SCTP and the real-time transmission function of PR-SCTP described above, it is possible to easily implement various two-way real-time multimedia service using only one SCTP protocol. The question of how to decide should be solved. Depending on how to determine the time to ensure the reliability of the real-time multimedia data, the quality of multimedia services based on the above-described SCTP and PR-SCTP can be significantly different.

The present invention has been proposed to solve the problem of determining the reliability guarantee in the transmission of multimedia data based on the conventional PR-SCTP, and in particular, improves the overall service quality by appropriately adjusting the life time of the multimedia data according to the state of the client. To provide a PR-SCTP-based real-time multimedia data transmission method for improving service quality that can be achieved.

As a means for solving the above problems, the present invention provides a method for transmitting multimedia data to a client in real time based on a PR-SCTP, wherein the server is a lifetime constant for real-time multimedia data transmission. A definition process of defining a reliable transmission constant for guaranteeing reliable transmission and an untrusted transmission constant for guaranteeing one transmission but not retransmission; An initial buffering transmission process in which, while the client is in the initial buffering state, the server sets the life time of all the multimedia data as a reliable transmission constant to perform a reliable transmission; When the client is in the playback state, the server calculates a life time of each multimedia message according to the buffer state and the network state of the client, and performs a transmission transmission for the reliable time for the calculated life time; And when the client is in the buffering state, sets the life time of all multimedia data to an untrusted transmission constant, and transmits all the multimedia data only once and does not perform retransmission. Provides a method for transmitting real-time multimedia data based on PR-SCTP.

In the real-time multimedia data transmission method, the initial buffering transmission process, the step of initializing by setting a buffer state variable indicating the playback buffer state of the client; If there is a multimedia service request from the client, setting the client state variable to an initial buffering state; Updating the buffer state variable with a current state value; Setting a life time as a reliable transmission constant to transmit the multimedia message; Checking whether the buffer state variable is equal to or greater than an upper limit; And repeating the step of updating the buffer state variable to a current state value if the buffer state variable is not greater than or equal to an upper limit value, and changing the client state variable to a replay state if the buffer state variable is greater than or equal to an upper limit value. Is done.

In the real-time multimedia data transmission method, the playback transmission process, comprising the steps of setting a buffer state variable representing the playback buffer state of the client and a network state variable representing the network delay state, and updating to a current state value; Calculating a life time of the multimedia message to be transmitted so as to be proportional to the value of the buffer state variable and inversely proportional to the value of the network state variable; Transmitting a multimedia message while ensuring reliability during the calculated lifetime; Checking whether the buffer status variable is zero; And repeating the step of updating the buffer state variable and the network state variable to the current state value if the buffer state variable is not 0, and changing the value of the client state variable to the buffering state if the buffer state variable is O. It comprises a step.

In the real-time multimedia data transmission method, the buffering playback process, the step of setting a buffer state variable indicating the playback buffer status of the client, updating the current status value; Transmitting a multimedia message by setting a life time as an untrusted transmission constant; Checking whether the buffer state variable is equal to or greater than an upper limit; And repeating the step of updating the buffer state variable to a current state value if the buffer state variable is not greater than or equal to an upper limit value, and changing the client state variable to a replay state if the buffer state variable is greater than or equal to an upper limit value. Is done.

In addition, in the real-time multimedia data transmission method, the upper limit value is set to the maximum value of the playback buffer existing in the client, the buffer state variable and the network state variable, the buffer status information and RTT (Round Trip Time) periodically from the client ) May be transmitted and updated with the recently received buffer status information and the RTT value.

In addition, in the real-time multimedia data transmission method, the reproduction transmission process, before checking whether the buffer state variable is 0, calculates the reproduction time at the client for the transmitted multimedia message, the buffer state by the reproduction time Increasing the value of the variable, or checking whether there is a multimedia message for which retransmission is abandoned among the transmitted multimedia messages, and reducing the buffer state variable by the playing time at the client for the multimedia message for which the retransmission was abandoned. It may include.

(여기서, B는 버퍼 상태 변수의 현재 값이고, S는 이전 메시지와의 전송 간격이고, RTT는 네트워크 상태 변수의 값이고, α는 라이프타임의 상한을 설정하기 위한 가중치로서 0보다 크고 1보다 작은 값이다) 에 의하여 라이프타임(Lifetime)을 산출할 수 있다. 상기에서, 클라이언트로부터 버퍼 상태 변수가 보고되지 않는 경우, 상기 RTT값을 0로 하여 라이프타임을 산출한다.In the real-time multimedia data transmission method, the step of calculating the life time,

(Where B is the current value of the buffer state variable, S is the transmission interval with the previous message, RTT is the value of the network state variable, and α is a weight for setting an upper limit of the lifetime as a weight greater than 0 and less than 1 Value), the Lifetime can be calculated. In the above, when the buffer status variable is not reported from the client, the life time is calculated by setting the RTT value to zero.

In addition, in the real-time multimedia data transmission method, the step of transmitting the multimedia message of the initial buffering process comprises the step of processing the data chunk in accordance with the SCTP basic standard.

The transmitting of the multimedia message in the reproduction transmission process may include: dividing the multimedia message to be transmitted into data chunks, assigning a transmission sequence number (TSN) to each of the divided data chunks, and then performing a data chunk processing method of the PR-SCTP extension standard. Processing according to; And checking whether the life time has expired, and if the life time expires, designating the data chunk as an abandonment chunk, and processing according to the abandonment chunk processing scheme of the PR-SCTP extension standard.

The transmitting of the multimedia message in the buffering transmission process may include: splitting the multimedia message and assigning a transmission sequence number (TSN) to each divided data chunk when the life time is set to an unreliable constant; Transmitting the partitioned data chunk to a client; Designating the transmitted data chunk as a discard chunk; And processing the abandonment chunk according to the abandonment chunk processing scheme of the PR-SCTP extension standard.

According to the above-mentioned problem solving means, the present invention provides a real-time multimedia service using only SCTP in the transport layer protocol, thereby reducing the resource savings of both the server and the client as compared to the case of performing a combination of TCP and UDP In addition, by using the reliability providing function of the SCTP and the partial reliability providing function of the PR-SCTP, the life time can be set appropriately according to the state of the client, thereby providing the most optimal service quality.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in describing in detail the operating principle of the preferred embodiment of the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In addition, the same reference numerals are used for parts having similar functions and functions throughout the drawings.

The present invention utilizes SCTP and PR-SCTP to improve service quality of real-time multimedia services. More specifically, the present invention, in order to real-time multimedia services using SCTP and PR-SCTP, first, in addition to the full reliability transmission, partial reliability transmission of the existing SCTP and PR-SCTP, untrusted transmission function has been added. Secondly, by using full reliability transmission, partial reliability transmission and unreliable transmission selectively according to the client's status, the service quality of real-time multimedia service is improved by providing services that meet the requirements of each client's status. I want to.

Prior to describing the detailed configuration and operation of the present invention, the state of the client serving as the reference for setting the lifetime of the present invention will be described.

1 is a state transition diagram of a client in a real-time multimedia service.

In the real-time multimedia service based on PR-SCTP according to the present invention, the reliability providing time of all the multimedia data is determined at the server, and the server determines the reliability providing time based on the current state of the client. In providing a real-time multimedia service, the client operates in one of four states shown in FIG.

Referring to FIG. 1, the client operating state has four states of Stopped, Initial Buffering, Playing, and Buffering. Here, the stopped state refers to a state before the multimedia service is provided or after the multimedia service is terminated by the user's request. According to the service request of the user, the client enters the initial buffering state from the stopped state.

The initial buffering state is a state in which initial multimedia data for multimedia playback is transmitted to the client side, and all the multimedia data transmitted in this state is only stored in the client's playback buffer, so the user does not feel that the service has started yet. Therefore, in the initial buffering state, reliability of all multimedia data transmissions must be provided for safe service start.

When the play buffer is first filled by the multimedia data transmitted from the server, the client transitions from the initial buffering state to the play state.

The playback state is a step of playing multimedia data stored in the playback buffer and receiving the multimedia data from the server while the user is provided with the service, and storing the multimedia data in the playback buffer. When the playback starts, the client should inform the server that the playback has started. do. In the playback state, it should be possible to recover packets lost by temporary link failure or congestion without depleting the client's playback buffer.

In the reproduction state as described above, when the reproduction buffer is exhausted due to network congestion or the like, the user waits without receiving a service, which is called a buffering state.

The most important issue in the buffering state is the urgent recovery of services, which is more important than the quality of multimedia. Therefore, all the multimedia data needs to be delivered quickly in the buffered state.

Next, a description will be given of a multimedia data transmission method according to the present invention for providing an optimal quality of service by differently setting a life time which is a reliability providing time according to the state of the client described above.

2 is a flowchart showing the overall flow of the PR-SCTP-based real-time multimedia data transmission method for improving the service quality according to the present invention, referring to this, the real-time multimedia data transmission method according to the present invention, the definition process and the initial buffering A transmission process, a reproduction transmission process, and a buffering transmission process.

In the defining process, that is, step S201, a new untrusted transmission constant (SCTP_LIFETIME_UNRELIABLE) is defined in addition to the reliable transmission constant (SCTP_LIFETIME_RELIABLE) specified in the existing SCTP standard. The reliable transmission constant (SCTP_LIFETIME_RELIABLE), which is given in the SCTP standard, means that complete reliable transmission of multimedia data is performed. In other words, this means that retransmission and error recovery are performed so that all multimedia data is completely transmitted to the client. On the contrary, the untrusted transmission constant (SCTP_LIFETIME_UNRELIABLE) is a new concept proposed for fast service recovery in the buffering state in the present invention and is defined as "not providing reliability but transmitting at least once." Reducing the lifetime value in the existing partial trust transmissions can have a similar effect as unreliable transmissions, but it may happen that the lifespan expires before being sent and abandons the transmission itself. have. Therefore, in the unreliable transmission according to the present invention, one transmission is necessarily performed, but reliability thereof is not provided.

In the initial buffering process, when the start of the multimedia service is requested from the client side (S202), that is, when the client transitions from the stopped state to the initial buffering state, the server sends a lifetime value to all multimedia messages to be transmitted to the client. The reliable transmission constant is set to perform reliable transmission on the multimedia message (S203). In other words. Data transmission is performed to ensure retransmission and error recovery until the multimedia message is completely transmitted to the client side.

Subsequently, in the reproduction transmission process, when the multimedia data is transmitted to the client side by the initial buffering process, and the client transitions to the reproduction state (S204), the server sends each multimedia message according to the state of the client reproduction buffer and the delay state of the network. The lifetime value of S is calculated, and partial trust transmission is performed to ensure the reliability of the multimedia message only during the calculated lifetime (S205).

In the buffering transmission process, when the client playback buffer is exhausted due to network congestion, that is, when the client state transitions to the buffering state (S206), the life time of all multimedia messages is set to the untrusted transmission constant, Although performing transmission, unreliable transmission that does not guarantee reliability is performed (S208). The untrusted transmission is repeated until the state of the client transitions to the playback state (S208).

When the server transitions from the buffering state to the playback state, the server performs the above-described reproduction transmission process again.

Hereinafter, each process will be described in more detail with reference to the accompanying drawings.

3 is a flowchart illustrating a detailed operation of an initial buffering transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving service quality according to the present invention.

Referring to FIG. 3, the initial buffering transmission process is performed as follows.

In the present invention, the server sets and initializes the buffer state variable B indicating the client playback buffer and the network state variable RTT indicating the network delay state in order to check the buffer state and the network delay state of the current client ( S301). The initial values of the buffer state variable B and the network state variable RTT may be different according to the actual network situation and the operator's policy. Therefore, the buffer state variable B and the network state variable RTT are defined as BUF_INITIAL and RTT_INITIAL, respectively. The default value is 0 and the unit is millisecond (ms). Can be.

In addition, the server defines a client state variable Client.State to record the state of the client, and sets this value to the initial buffering state (INITIAL_BUFFERING) immediately after the service starts (S302).

As described above, when all necessary variables are initialized in the server, multimedia data is transmitted according to a client's request. In this case, the server first updates the buffer state variable B and the network state variable RTT with the current state values. (S303). The update of the buffer state variable B and the network state variable RTT may be performed by periodically receiving buffer state information and network state information, more specifically, a round trip time (RTT) value from a client, and the buffer as a recently received value. By setting the state variable B and the network state variable RTT. Since the network state variable RTT is unnecessary during the initial buffering transmission process, the definition and update of the network state variable may be omitted.

The server sets a lifetime of each multimedia message to a reliable transmission constant (SCTP_LIFETIME_RELIABLE) defined in the definition process (S304), and each multimedia message (SCTP message) whose lifetime is set to the reliable transmission constant. In step S305, reliable transmission is performed.

Whenever the multimedia message is transmitted, the server checks whether the value of the buffer state variable B is equal to or greater than the upper limit value B. Maximum (S306), and if not equal to or greater than the upper limit value, the above-described steps (S303 to S305). By repeating, reliable transmission of multimedia data is continued. On the contrary, if the value of the buffer state variable B is equal to or greater than the upper limit value, the client state variable Client.state is changed to the playing state PLAYING. Here, the upper limit value (B.Maximum) is the maximum value of the client's playback buffer and is expressed in milliseconds (ms).

Once the play buffer is full, the client starts playing the multimedia and reports the situation to the server side, and then the server performs the play transmission process described above.

4 is a flowchart illustrating a detailed operation of a reproduction transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving service quality according to the present invention.

In the present invention, the purpose of the reproduction transmission process is to improve the quality of service of the real-time multimedia data transmission, for the purpose of the present invention assumes the following.

First, the PR-SCTP application transmits the size of the multimedia message to the transport layer at a size less than 1 x MTU (Maximum Transfer Unit) so that packet fragmentation does not occur in the transport layer. Second, it is assumed that transmission intervals between messages occurring at the protocol level (eg, transmission intervals due to delayed SACKs) can be ignored. Third, the client immediately reports its current status to the server at regular intervals or status changes.

Referring to FIG. 4, in the reproduction transmission process, the server updates the buffer state variable B and the network state variable RTT with the current state values in order to check the buffer state and the network delay state of the client (S401). As described above, the unit of the buffer state variable B is milliseconds (ms), and the value of the variable B is modified to a value reported from the client at a predetermined period (B. Interval). When the multimedia message is transmitted between the periods B. Interval, the server predicts and updates the buffer status. This will be described later. In addition, the value of the network state variable RTT is also updated to a value reported from the client at a predetermined period (RTT.Interval).

Subsequently, the server calculates each life time for the multimedia message to be transmitted. First, a transmission interval S with the previous message is measured (S402), and a lifetime is calculated according to Equation 1 below. It calculates (S403).

In Equation 1, B is a value of the buffer state variable, S is a transmission interval with a previous message, RTT is a value of the network state variable, and α is a weight to set an appropriate upper limit according to a service policy. Is arbitrarily set among values greater than 0 and less than 1. In the above, the value of the buffer state variable and the value of the network state variable are updated by being periodically reported from the client. In this case, when the buffer state variable is not reported from the client, the lifetime is determined by setting RTT to 0 in Equation 1 above. To calculate.

When the life time is calculated as described above, the server transmits a multimedia message (SCTP) while ensuring reliability only during the calculated life time (S404). That is, the multimedia message is guaranteed to be retransmitted only for the calculated lifetime. This means that the current multimedia message should be delivered to the client within the set lifetime. For the PR-SCTP, the error occurring during this time does not affect the playback even if recovery is performed. Therefore, in the regeneration state, the loss due to network congestion or link error is recovered within the range that does not affect the regeneration of the client, and as a result, the quality of service may be improved compared to the application using UDP.

After the multimedia message is transmitted as described above, the buffer state variable B is modified in consideration of the playing time of the currently transmitted multimedia message. To this end, how much of the multimedia message currently transmitted can be played. The reproduction time D indicated is calculated (S405). The playing time D may be obtained by dividing the length L of the multimedia message by the playing speed R at the client. In this case, since the length L unit of the multimedia message is a byte and the unit R is bps, in order to match the unit (ms) of the buffer state variable B, 1000 and 8 are further multiplied. Thereafter, the value of the buffer state variable B is increased by the calculated reproduction time D (S406).

In addition, the present invention, in order to predict a change in the buffer state due to a message that has not been transmitted, confirms whether there is data designated as an abandon chunk through the SCTP notification procedure (S407), and as a result of the confirmation, the abandon chunk exists. In operation S408, the playback time D _N of the abandoned chunk is reduced from the value of the buffer state variable. The playback time of the abandoned chunk is made in the same manner as the playback time D in step S405 above. Here, the abandoned chunks mean a situation in which there is a retransmission request due to the loss of the data chunks, but the corresponding data chunks are not retransmitted due to the expiration of the life time. The playback time of the multimedia message is not reflected in the buffer status variable B.

The above-described steps S401 to S408 are repeated until the buffer is exhausted due to network congestion, that is, until the value of the buffer state variable B becomes 0, and the buffer state variable B becomes 0, the client state variable. Change (Client.state) to the buffering state (Buffering), so that the buffering transfer process is performed.

5 is a flowchart illustrating a detailed flow of a buffering transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving service quality according to the present invention.

The buffering transmission process aims at fast delivery of all multimedia messages as in UDP.

Accordingly, the server first updates the buffer state variable B and the network state variable RTT with the current state values (S501). Here, since the network state variable is not used in the buffering transmission process, the update of the network state variable RTT may be omitted.

The server sets a life time to an untrusted transmission constant (SCTP_LIFETIME_UNRELIABLE) (S502), and performs untrusted transmission of a multimedia message (SCTP message) (S503).

After the transmission of every multimedia message, it is checked whether the buffer state variable is equal to or greater than the upper limit value B. Maximum (S504), and if the buffer state variable B is not equal to or greater than the upper limit value, the process is repeated from the step S501, and the buffer state is If the variable B is greater than or equal to the upper limit value, the client state variable (Client.state) is changed to a playing state (PLAYING) to perform a play transmission process (S505).

As described above, the buffering state is a state in which a playback is performed in a client due to an unexpected network situation, but a multimedia message cannot be transmitted, and thus the playing buffer is depleted, and the user is not waiting for service. Therefore, the present invention transmits all messages in real time so that the user can receive the service as quickly as possible in the buffering state.

Next, FIG. 6 is a flowchart illustrating a detailed process of transmitting a multimedia message in a transport layer by a method of transmitting real-time multimedia data based on PR-SCTP according to the present invention.

Referring to FIG. 6, when receiving a multimedia message to be transmitted from an application layer, the transport layer examines a lifetime value set in the multimedia message (S601 to S603) and performs a message transmission according to each lifetime value. do.

That is, when the lifetime is the reliable transmission constant (SCTP_LIFETIME_RELIABLE) (S603), the transport layer processes the multimedia message according to the data chunk processing procedure defined in the SCTP basic standard (S604). More specifically, the data chunk divided into MTU sizes and assigned a transmission sequence number (TSN) is transmitted to the client, and the data chunk is retransmitted until the data chunk is normally transmitted to the client.

If the lifetime is an untrusted transmission constant (SCTP_LIFETIME_UNRELIABLE) (S602), the partitioning operation is first performed according to the size of the maximum transfer unit (MTU), and a TSN (transmission sequence number) is assigned to each divided data chunk. After that, the transmitted data chunk is transmitted to the client (S605 and S606).

After the data chunk is transmitted, the transmitted data chunk is designated as an abandoned chunk (S607).

The abandonment chunk is processed according to the abandonment chunk processing rule of the PR-SCTP (S608).

Finally, if the lifetime is neither a reliable transmission constant nor an unreliable transmission constant, i.e. a general constant value, the server recognizes the lifetime as a millisecond (ms), and extends the multimedia message as a PR-SCTP extension. Partial reliable transmission is performed according to the standard (S609). In the step S609, it is checked whether the lifetime expires before data chunk transmission. If the lifetime expires, the data chunk is designated as an abandoned chunk, and abandoned chunk processing of the PR-SCTP extension standard is performed. Process according to the procedure (S608).

That is, in step S608, when a retransmission request for abandoned chunk is received from the client, the FORWARD_TSN chunk is transmitted to the client, and the retransmission request of the data chunk is withdrawn.

As described above, in the present invention, in addition to reliable transmission and partial transmission, the present invention performs untrusted transmission that transmits once but does not guarantee reliability.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art.

1 is a diagram illustrating a client state transition in performing a real-time multimedia service.

2 is a flow chart showing the overall flow of the PR-SCTP-based real-time multimedia data transmission method for improving the service quality according to the present invention.

3 is a flowchart illustrating a detailed flow of an initial buffering transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving service quality according to the present invention.

4 is a flowchart illustrating a detailed flow of a reproduction transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving service quality according to the present invention.

5 is a flowchart illustrating a detailed flow of a buffering transmission process in the PR-SCTP-based real-time multimedia data transmission method for improving the service quality according to the present invention.

6 is a flowchart illustrating a process of transmitting a multimedia message in a transport layer in a method of transmitting real-time multimedia data based on PR-SCTP for improving service quality according to the present invention.

Claims (13)

In the method for transmitting the multimedia data to the client in real time based on the PR-SCTP, As a lifetime constant for real-time multimedia data transmission, the server defines a reliable transmission constant, which means that it guarantees reliable transmission of all data, and an untrusted transmission constant, which guarantees one transmission but does not retransmit. Justice process; An initial buffering transmission process in which, while the client is in the initial buffering state, the server sets the life time of all the multimedia data as a reliable transmission constant to perform a reliable transmission; When the client is in the playback state, the server calculates a life time of each multimedia message according to the buffer state and the network state of the client, and performs a transmission transmission for the reliable time for the calculated life time; And When the client is in the buffering state, the life time of all multimedia data is set to an untrusted transmission constant, so that all multimedia data is transmitted only once and retransmission is not performed. -SCTP based real time multimedia data transmission method. The method of claim 1, wherein the initial buffering transmission process is performed. Setting and initializing a buffer state variable indicating a play buffer state of the client; If there is a multimedia service request from the client, setting the client state variable to an initial buffering state; Updating the buffer state variable with a current state value; Setting a life time as a reliable transmission constant to transmit the multimedia message; Checking whether the buffer state variable is equal to or greater than an upper limit; And If the buffer state variable is not greater than or equal to an upper limit value, repeating the step of updating the buffer state variable to a current state value, and if the buffer state variable is greater than or equal to an upper limit value, changing the client state variable to a play state. PR-SCTP-based real-time multimedia data transmission method for improving the quality of service. The method of claim 1, wherein the reproduction transmission process is performed by: Setting a buffer state variable indicating a playback buffer state of the client and a network state variable indicating a network delay state and updating the current state value; Calculating a life time of the multimedia message to be transmitted so as to be proportional to the value of the buffer state variable and inversely proportional to the value of the network state variable; Transmitting a multimedia message while ensuring reliability during the calculated lifetime; Checking whether the buffer status variable is zero; And If the buffer state variable is not 0, repeating the step of updating the buffer state variable and the network state variable to the current state value, and if the buffer state variable is O, changing the value of the client state variable to the buffering state. PR-SCTP-based real-time multimedia data transmission method for improving the service quality comprising a. The method of claim 1, wherein the buffering reproduction process, Setting a buffer state variable indicative of the playback buffer state of the client, and updating the current state value; Transmitting a multimedia message by setting a life time as an untrusted transmission constant; Checking whether the buffer state variable is equal to or greater than an upper limit; And If the buffer state variable is not greater than or equal to an upper limit value, repeating the step of updating the buffer state variable to a current state value, and if the buffer state variable is greater than or equal to an upper limit value, changing the client state variable to a play state. PR-SCTP-based real-time multimedia data transmission method for improving the quality of service. The method according to claim 2 or 4, The upper limit value is a PR-SCTP-based real-time multimedia data transmission method for improving the service quality, characterized in that the maximum value of the playback buffer existing in the client. The method according to claim 2 or 4, The updating of the buffer state variable to the current state value may include receiving buffer state information periodically from a client and setting the buffer state variable to the most recently received buffer state information. PR-SCTP-based Real-time Multimedia Data Transmission Method for Computers. The method of claim 3, wherein the reproduction transmission process is performed by: Before checking whether the buffer status variable is 0, calculating a playing time at the client for the transmitted multimedia message, and increasing the value of the buffer status variable by the playing time. PR-SCTP based real time multimedia data transmission method for improvement. The method of claim 3, wherein the reproduction transmission process is performed by: Before checking whether the buffer status variable is 0, whether there is a multimedia message for which retransmission is abandoned among the transmitted multimedia messages, reducing the buffer status variable by the playing time at the client for the multimedia message for which the retransmission is abandoned. PR-SCTP-based real-time multimedia data transmission method for improving the quality of service, characterized in that it further comprises a step. The method of claim 3, wherein updating to the current state value Receiving buffer status information and round trip time (RTT) periodically from a client, and setting the buffer status variable and network status variable with the most recent buffer status information and RTT value. PR-SCTP based real time multimedia data transmission method. The method of claim 3, wherein the calculating of the life time comprises:

(Where B is the current value of the buffer state variable, S is the interval between transmissions with the previous message, RTT is the value of the network state variable, and α is a weight for setting the upper limit of the lifetime, greater than 0 and greater than 1). Small value) PR-SCTP-based real-time multimedia data transmission method for improving the service quality, characterized in that the step of calculating the Lifetime (Lifetime) by. The method of claim 2, wherein the transmitting of the multimedia message comprises PR-SCTP-based real-time multimedia data transmission method for improving the quality of service, characterized in that it comprises the step of processing the data chunk according to the SCTP basic standard. The method of claim 3, wherein transmitting the multimedia message Dividing a multimedia message to be transmitted into data chunks, assigning a transmission sequence number (TSN) to each divided data chunk, and processing the data chunk according to the PR-SCTP extension standard; Checking whether the lifetime has expired, and if the lifetime expires, designating the data chunk as an abandonment chunk, and processing according to the abandonment chunk processing scheme of the PR-SCTP extension standard. PR-SCTP based real time multimedia data transmission method. The method of claim 4, wherein the transmitting of the multimedia message comprises If the lifetime is set to an untrusted constant, performing segmentation of the multimedia message and transmission sequence number (TSN) allocation for each segmented data chunk; Transmitting the partitioned data chunk to a client; Designating the transmitted data chunk as a discard chunk; And PR-SCTP-based real-time multimedia data transmission method for improving the quality of service, characterized in that it comprises the step of processing the abandonment chunk in accordance with the abandonment chunk processing scheme of the PR-SCTP extension standard.

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