Press-talk server, transcoder, and communication system
First Claim
1. A press-talk server in a communication system which achieves a half-duplex many-to-many call among a plurality of radio stations, the press-talk server which delivers voice information sent by a sending station as a radio station, which requests a talk burst, to a plurality of other radio stations through a gateway and a base station while passing or without passing through a transcoder, whereinif a packet is received, the press-talk server searches a press-talk table that stores call group identification information as an identifier of a press-talk call, received packet information indicating socket information of a packet to be receivable by a call of a call group, a coding system, and transmission packet information indicating socket information of a packet carrying voice information of a radio station, which is currently taking the talk burst, and checks whether an entry identical to the socket information of the received packet exists in the received packet information,if an entry exists, the press-talk server determines whether a source address of the received packet is an address of the gateway or an address of the transcoder,when the received packet is a packet from the gateway, for the call group identification information, the press-talk server refers to a talk burst table that stores socket information of a packet, and a talk burst request identifier for identifying a radio station, which is currently taking the talk burst,when the socket information of the received packet and the talk burst request identifier in the received packet are identical to the entries of the talk burst table, the press-talk server determines that the received packet is a packet which is to be delivered to other group members,the press-talk server refers to the press-talk table, according to transmission packet information corresponding to the received packet information of the received packet, copies the received packet if the transmission packet information has a plurality of socket information, and creates a transmission packet to the gateway and/or transcoder,when the created transmission packet is to be transmitted to the transcoder, the press-talk server refers to a sequence number table that stores a sequence number to be added to a packet when being transmitted to the transcoder in association with the call group identification information, inserts the sequence number into the transmission packet, and increments the sequence number of the sequence number table, andthe press-talk server sends the completed transmission packet.
1 Assignment
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Accused Products
Abstract
When half-duplex many-to-many communication is performed among a plurality of mobile stations having different codecs in a single group, transcoding is performed with a small number of codec circuits. A transcoder manages an SSRC of a received RTP packet, detaches voice information from a jitter buffer, which is identical to a latest SSRC, and inputs the detached voice information to a codec circuit. As the latest SSRC is switched, a voice sending station subject to transcode is switched, and mobile stations using the same codec share the codec circuit. Therefore, in a half-duplex many-to-many communication (group communication) system, called a professional mobile radio system, push-talk, or press-talk, it is not necessary to switch the transcoder until a radio station which takes a talk burst is changed during a single call (call session).
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Citations
17 Claims
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1. A press-talk server in a communication system which achieves a half-duplex many-to-many call among a plurality of radio stations, the press-talk server which delivers voice information sent by a sending station as a radio station, which requests a talk burst, to a plurality of other radio stations through a gateway and a base station while passing or without passing through a transcoder, wherein
if a packet is received, the press-talk server searches a press-talk table that stores call group identification information as an identifier of a press-talk call, received packet information indicating socket information of a packet to be receivable by a call of a call group, a coding system, and transmission packet information indicating socket information of a packet carrying voice information of a radio station, which is currently taking the talk burst, and checks whether an entry identical to the socket information of the received packet exists in the received packet information, if an entry exists, the press-talk server determines whether a source address of the received packet is an address of the gateway or an address of the transcoder, when the received packet is a packet from the gateway, for the call group identification information, the press-talk server refers to a talk burst table that stores socket information of a packet, and a talk burst request identifier for identifying a radio station, which is currently taking the talk burst, when the socket information of the received packet and the talk burst request identifier in the received packet are identical to the entries of the talk burst table, the press-talk server determines that the received packet is a packet which is to be delivered to other group members, the press-talk server refers to the press-talk table, according to transmission packet information corresponding to the received packet information of the received packet, copies the received packet if the transmission packet information has a plurality of socket information, and creates a transmission packet to the gateway and/or transcoder, when the created transmission packet is to be transmitted to the transcoder, the press-talk server refers to a sequence number table that stores a sequence number to be added to a packet when being transmitted to the transcoder in association with the call group identification information, inserts the sequence number into the transmission packet, and increments the sequence number of the sequence number table, and the press-talk server sends the completed transmission packet.
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4. A transcoder in the communication system which achieves a half-duplex many-to-many call among a plurality of radio stations, by a press-talk server which delivers voice information sent by a sending station as a radio station, which requests a talk burst, to a plurality of other radio stations through a gateway and a base station while passing or without passing through the transcoder, wherein:
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on the basis of a packet received from the press-talk server, the transcoder refers to a jitter buffer that stores, with respect to call group identification information, a port number of the press-talk server, a received sequence number, and a talk burst request identifier for identifying a radio station, which is expected to currently have a talk burst, (a) when the port number of the press-talk server and the talk burst request identifier stored in the jitter buffer are not identical to a port number of the press-talk server and a talk burst request identifier of the received packet, (i) if the received sequence number of the jitter buffer is more up-to-date than the sequence number of the received packet, the transcoder determines that, after a radio station which has taken the talk burst is switched, an old packet before being switched is received, and discards the packet, and (ii) if the received sequence number of the jitter buffer is 0 or null, the transcoder determines that the received packet is an initial packet after press-talk call setup, or if the sequence number of the received packet is more up-to-date than the received sequence number of the jitter buffer, the transcoder determines that the received packet is an initial packet after the ratio station which has taken the talk burst is switched, the transcoder copies the value of the sequence number of the received packet to the received sequence number of the jitter buffer, and copies the talk burst request identifier of the received packet to the talk burst request identifier of the jitter buffer, thereby newly construct a buffer of the jitter buffer, and (b) when the port number of the press-talk server and the talk burst request identifier stored in the jitter buffer are identical to the port number of the press-talk server and the talk burst request identifier in the received packet, the transcoder compares the sequence number of the received packet and the received sequence number of the jitter buffer, if the sequence number of the received packet is larger, sets the value of the sequence number of the received packet in the received sequence number of the jitter buffer, inserts the received packet in an input wait queue of an input buffer to a coding conversion unit so as to be arranged in ascending order of a timestamp from the head of the queue, and converts the received packet from a first coding system to a second coding system by the coding conversion unit. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A communication system which achieves a half-duplex many-to-many call among a plurality of radio stations, by a press-talk server that delivers voice information sent by a sending station as a radio station, which requests a talk burst, to a plurality of other radio stations through a gateway and a base station while passing or without passing through a transcoder, wherein
if a packet is received, the press-talk server searches a press-talk table that stores call group identification information as an identifier of a press-talk call, received packet information indicating socket information of a packet to be receivable by a call of a call group, a coding system, and transmission packet information indicating socket information of a packet carrying voice information of a radio station, which is currently taking the talk burst, and checks whether an entry identical to the socket information of the received packet exists in the received packet information, if an entry exists, the press-talk server determines whether a source address of the received packet is an address of the gateway or an address of the transcoder, when the received packet is a packet from the gateway, for the call group identification information, the press-talk server refers to a talk burst table that stores socket information of a packet, and a talk burst request identifier for identifying a radio station, which is currently taking the talk burst, when the socket information of the received packet and the talk burst request identifier in the received packet are identical to the entries of the talk burst table, the press-talk server determines that the received packet is a packet which is to be delivered to other group members, the press-talk server refers to the press-talk table, according to transmission packet information corresponding to the received packet information of the received packet, copies the received packet if the transmission packet information has a plurality of socket information, and creates a transmission packet to the gateway and/or transcoder, when the created transmission packet is to be transmitted to the transcoder, the press-talk server refers to a sequence number table that stores a sequence number to be added to a packet when being transmitted to the transcoder in association with the call group identification information, inserts the sequence number into the transmission packet, and increments the sequence number of the sequence number table, and the press-talk server sends the completed transmission packet, and wherein on the basis of a packet received from the press-talk server, the transcoder refers to a jitter buffer that stores, with respect to call group identification information, a port number of the press-talk server, a received sequence number, and a talk burst request identifier for identifying a radio station, which is expected to currently have a talk burst, (a) when the port number of the press-talk server and the talk burst request identifier stored in the jitter buffer are not identical to a port number of the press-talk server and a talk burst request identifier of the received packet, (i) if the received sequence number of the jitter buffer is more up-to-date than the sequence number of the received packet, the transcoder determines that, after a radio station which has taken the talk burst is switched, an old packet before being switched is received, and discards the packet, and (ii) if the received sequence number of the jitter buffer is 0 or null, the transcoder determines that the received packet is an initial packet after press-talk call setup, or if the sequence number of the received packet is more up-to-date than the received sequence number of the jitter buffer, the transcoder determines that the received packet is an initial packet after the ratio station which has taken the talk burst is switched, the transcoder copies the value of the sequence number of the received packet to the received sequence number of the jitter buffer, and copies the talk burst request identifier of the received packet to the talk burst request identifier of the jitter buffer, thereby newly construct a buffer of the jitter buffer, and (b) when the port number of the press-talk server and the talk burst request identifier stored in the jitter buffer are identical to the port number of the press-talk server and the talk burst request identifier in the received packet, the transcoder compares the sequence number of the received packet and the received sequence number of the jitter buffer, if the sequence number of the received packet is larger, sets the value of the sequence number of the received packet in the received sequence number of the jitter buffer, inserts the received packet in an input wait queue of an input buffer to a coding conversion unit so as to be arranged in ascending order of a timestamp from the head of the queue, and converts the received packet from a first coding system to a second coding system by the coding conversion unit.
Specification