KR100748990B1 - Ssrc conflict control method in poc service - Google Patents

Abstract

An SSRC(Synchronization Source) collision control method in the PoC(Push to talk over Cellular) service is provided to be capable of newly generating/using an SSRC even though SSRC collision occurs in the PoC service, thus a call can be consecutively made without terminating an RTP(Real time Transport Protocol) session. When an RTP packet is received(S400), a client analyzes header of the received RTP packet(S405). The client decides whether an SSRC of the received packet is the same as a self SSRC(S410). If so, the client generates a new SSRC(S415). The client transmits the newly generated SSRC to a server(S420). However, if the SSRC is not identical to the self SSRC, a process for controlling SSRC collision is terminated.

Description

SSRC Conflict control method in POC service

1 is a diagram referred to for schematically explaining a PoC service,

2 is a view showing an example of a PoC system applied to the SSRC collision control method according to the present invention,

3 is a message sequence chart provided in the description of the SSRC collision control method according to an embodiment of the present invention;

4 is a flowchart provided to explain the client-side operation method in the SSRC collision control method according to the present invention, and

5 is a flowchart provided to explain the server-side operation in the SSRC collision control method according to the present invention.

Explanation of symbols on the main parts of the drawings

200: PoC Client A 210: PoC Server A

230: PoC server X 240: PoC server B

250: PoC Client B

The present invention relates to an SSRC collision control method, and more particularly, to an SSRC collision control method and system for controlling SSRC collision in a Push to talk over Celluar (PoC) service.

PoC service is a kind of half duplex instant call service like radio service. The PoC service enables one-way voice communication using a circuit or packet service of an existing wireless network, and uses a technology such as Session Initiation Protocol (SIP) or Ad-hoc.

1 is a diagram referred to schematically describe a PoC service. Referring to FIG. 1, there are first to fifth PoC clients 10, 20, 30, 40, and 50 that are terminals connected to a wireless network 130 and that can use PoC services. The first and second PoC clients 10, 20 are in the area of the first base station 100, the third PoC client 30 is in the area of the second base station 110, and the fourth and fifth PoC clients ( 40 and 50 reside within the area of the third base station 120. In this configuration, the first PoC client 10 delivers data for the voice call to the second to fourth PoC clients 20, 30, 40, and 50, so that one-to-many calls are unidirectional. Is done.

In the PoC service, data for a voice call is delivered through a Real-Time Packet. In this case, the header of the RTP packet includes a synchronization source identifier (SSRC) to distinguish the terminal transmitting the packet, and the SSRC is randomly generated by each PoC client. Therefore, when generating the same SSRC in different PoC clients, SSRC collision may occur.

However, SSRC conflict resolution in PoC service is to apply the RTP SSRC conflict resolution method specified in RFC 3550. However, if this is applied as it is, the received RTP packet may be discarded without being reproduced, thereby causing a disconnection of the voice call. That is, according to the RFC 3550 protocol, when the originator detects an SSRC collision, it should send an RTCP BYE to terminate the RTP session. However, due to the nature of PoC service capable of unidirectional group call, it is not desirable to unilaterally terminate the RTP session at the calling party. In addition, if an SSRC collision occurs but the RTP session is not terminated, the calling party recognizes that the received RTP packet is sent by the sender and discards the received RTP packet without reproducing it. Even when the receiving side detects the SSRC collision, since the RTP packet having the same SSRC is discarded, voices transmitted by PoC clients using the same SSRC cannot be heard among PoC clients participating in the group call.

Therefore, when SSRC collision occurs in the PoC service, there is a need for a method that can solve the RTP session without disconnecting to suit the PoC service.

Accordingly, an object of the present invention is to provide an SSRC collision control method for controlling an SSRC collision without terminating an RTP session when an SSRC collision occurs in a PoC service.

SSRC collision control method according to the present invention for achieving the above object, Comparing the first SSRC included in the received packet and the second SSRC which is its synchronization source identifier, the first SSRC and the second SSRC In the same case, changing the synchronization originator identifier to a new third SSRC, and generating and transmitting a packet including the third SSRC.

In addition, SSRC collision control method according to the present invention for achieving the above object, Comparing the first SSRC included in the packet received from the client and the second SSRC included in the information of the client, the first SSRC and Changing the second SSRC included in the client information to the first SSRC when the second SSRC is not the same.

In order to achieve the above object, the present invention provides a computer-readable recording medium recording a program for executing the method on a computer.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

The SSRC collision control method according to the present invention is basically applied to PoC service, but is not necessarily limited thereto, and may be applied to other communication service environments that satisfy the conditions according to the present invention. In addition, the SSRC collision control method according to the present invention, when detecting the SSRC collision during PoC service, uses a method of creating and using a new SSRC without termination of the RTP session.

2 is a view showing an example of a PoC system applied to the SSRC collision control method according to the present invention. Referring to FIG. 2, in a plurality of network environments in which network A, network B, and network X exist, in network A, PoC client A 200 participates in a PoC service through PoC server A 210 (Participation). In network B, PoC client B 250 participates in PoC service through PoC server B 240. PoC server A 210 and PoC server 240 are connected to PoC server X 230 in network X, and PoC server X 250 controls the entire PoC service. In FIG. 2, for convenience of description, there is one PoC client in each of network A and network B, but there may be more PoC clients participating in the PoC service. It is also possible to configure one PoC server to perform both participation and full control.

In this configuration, the RTP packet transmitted by the PoC client A 210 for the voice call is transmitted to the PoC server X 230 through the PoC server A 210, and the PoC server X 230 receives the received RTP packet. Forwarding The RTP packet forwarded at PoC server X 230 is delivered to PoC client B 250 via PoC server B 240. Similarly, the PoC client B 250 transmits an RTP packet through the Poc server B 240 and receives the forwarded RTP packet from the PoC server A 230 through the PoC server A 210. 200).

3 is a message sequence chart provided to explain an SSRC collision control method in a PoC service according to an embodiment of the present invention. Referring to FIG. 3, the PoC service is started, and the RTP packet generated by the PoC client A 200 for the voice call is transmitted to the PoC server A 210, the PoC server X 230, and the PoC server B 240. The Poc is transmitted to the client B 250 through S300 to S306. If necessary, the status of the PoC client B 250 may be reported using the RTCP PP packet (S308, S310).

During the delivery of the RTP packet, if SSRC collision occurs because the SSRC included in the RTP packet received from the PoC client B 250 and the SSRC are the same (S312), the PoC client B 250 generates a new SSRC by itself. The RTCP transmits an RTCP RR (Receiver Report) packet including the newly generated SSRC to the server side (S314 and S316).

The PoC server X 230 compares the SSRC included in the received RTCP RR packet with the session information for the stored PoC client B 250 and updates the session information of the PoC client B 250 when it is determined that the SSRC has been changed. (update), and the received RTCP RR packet is transmitted to the PoC client A (200) (S318, S320). Subsequently, even when generating and transmitting a TBCP message, the updated PoC client session information is used.

When the RTP message is transmitted again from the PoC client 200 (S322 to S328), since the SSRC of the PoC client B 250 is newly changed, a voice call is made without SSRC collision. Then, when the PoC button is released by the PoC client A 200 (S330), these items are transmitted to the Poc server X 230 (S322 and S334). The PoC server X 230 transmits a TBCP Release to the PoC Client A 200 (S340 and S342), and transmits a TBCP Release message to the PoC Client B 250 (S336 and S338). The desired PoC client is able to deliver the voice.

Accordingly, the PoC client B 250 may press the PoC button for using the PoC service (S300), transmit a TBCP Req message to the PoC server X 230, and request data transmission for a voice call (S346). , S348). In this case, even when SSRC collision occurs, continuous communication is possible without interruption of the call.

4 is a flowchart provided to explain a client-side operation method in the SSRC collision control method according to an embodiment of the present invention. Referring to FIG. 4, when the client receives the RTP packet transmitted from the server (S400), the header of the received RTP packet is analyzed (S405). Since the SSRC is included in the received RTP packet, the SSRC of the received packet can be known by header analysis of such an RTP packet.

Next, it is determined whether the SSRC of the received packet and its SSRC are the same (S410). Since the client stores session member information including itself, it can be known whether the SSRC of the received packet is the same as its SSRC.

As a result of the comparison in step S410, if the SSRC and the SSRC of the received packet is not the same, the process for SSRC collision control is terminated. However, if the SSRC of the received packet is the same as its SSRC, a new SSRC is generated (S415), and the newly generated SSRC is transmitted to the server (S420). The newly created SSRC can be transmitted using an RTCP RR or SR (Sender Report) packet, and then the newly created SSRC is used as its synchronization source identifier.

5 is a flowchart provided to explain a server-side operation method in the SSRC collision control method according to an embodiment of the present invention. Referring to FIG. 5, when a PoC server receives an RTCP RR packet from a client side (S500), SSRC is compared with an SSCR value in an RTCP RR packet and a PoC client SSRC based on an IP and a port number. It is determined whether is changed (S505). If an RTCP SR packet is received instead of an RTCP RR packet, the same process is applied.

As a result of the comparison of step S505, if the SSRC has not been changed, the process for SSRC collision control is terminated. However, if the SSRC of the client has been changed, update to the changed SSRC and store the client session information (S510). The received RTCP RR packet is forwarded to other clients (S515).

Thereafter, even when generating and transmitting a TBCP message, the TBCP message is transmitted using the updated client session information. By such a process, when SSRC collision occurs in the PoC service, the call can be continued without ending the RTP session.

On the other hand, the present invention can also be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

As described above, according to the present invention, even when an SSRC collision occurs in the PoC service, by creating and using a new SSRC, the call is continuously made without ending the RTP session. Therefore, continuous calls can be made without interruption of the call, and it is possible to prevent a phenomenon in which voices of other clients cannot be heard due to SSRC collision during PoC service.

Claims (10)

Comparing the first SSRC included in the received packet with a second SSRC which is its synchronization source identifier; Changing its synchronization source identifier to a new third SSRC when the first SSRC and the second SSRC are the same; And Generating and transmitting a packet including the third SSRC; and SSRC collision control method comprising the. The method of claim 1, And the received packet is an RTP packet transmitted from a PoC server side. The method of claim 2, The packet including the third SSRC is transmitted to the PoC client using any one of the RTCP RR packet and the RTCP SR packet. The method of claim 3, And receiving the packet including the third SSRC, and changing information of the PoC client. Comparing the first SSRC included in the packet received by the client with the second SSRC included in the information of the client; And changing the second SSRC included in the client information to the first SSRC when the first SSRC and the second SSRC are not identical to each other. The method of claim 4, wherein SS forwarding the received packet to another client; SSRC collision control method further comprising. The method of claim 4, wherein And the received packet is one of an RTCP RR packet and an RTCP SR packet. The method of claim 4, wherein And generating and transmitting a TBCP message by using the changed client information. Claim 9 was abandoned upon payment of a set-up fee. Claim 10 was abandoned upon payment of a setup registration fee. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 5 to 8.

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