JP6579627B2 - VoIP-TA, business phone and clock synchronization method - Google Patents

Description

  The present invention is a VoIP-TA (TA: terminal adapter) that performs conversion between a BRI (Basic Rate Interface) -based signal and a VoIP (Voice over Internet Protocol) -based signal compliant with ISDN (Integrated Service Digital Network) standards. The present invention relates to a business phone and a clock synchronization method in the VoIP-TA.

  In the market, as shown in FIG. 5, there is a business phone main unit that provides a telephone function using an ISDN line. Further, there are many business phone main apparatuses that can accommodate many ISDN lines and handle many telephone lines. FIG. 5 is a schematic diagram showing a connection configuration example when a business phone performs communication using an ISDN line in the current technology related to the present invention. As shown in FIG. 5, a plurality of ISDN lines are connected to the business phone main apparatus 2A. Then, when each of the plurality of key telephones accommodated in the business phone main apparatus 2A uses a telephone line, the clock synchronization is performed by the BRI signal generated in each of the plurality of BRI units 20A mounted in the business phone main apparatus 2A. In the taken state, each corresponding ISDN line is synchronized and connected to the ISDN access line network 4. The BRI signal is a signal defined as an ISDN standard, and forms a BRI interface in an ISDN line that assumes clock synchronization.

  However, recently, the transition from ISDN lines to IP (Internet Protocol) lines has progressed, and telephone function services have been provided by VoIP (Voice over Internet Protocol) technology. In order to connect the business phone main apparatus to the IP line (that is, the VoIP access line), a VoIP-TA (VoIP terminal adapter) for converting between the IP signal and the BRI signal as shown in FIG. It is necessary to connect to the main unit. FIG. 6 is a schematic diagram showing a connection configuration example when a business phone communicates using a VoIP line in the current technology related to the present invention. As shown in FIG. 6, when each of the plurality of key telephones uses a telephone line, the BRI signal from each of the plurality of BRI units 20A mounted on the business phone main unit 2A is in an ISDN line in a state of clock synchronization. Is then output to the VoIP-TA1A, re-generated as an IP signal (VoIP signal) in the VoIP-TA1A, and output to the VoIP access line network 3 via the VoIP access line.

  In the case of the ISDN line shown in FIG. 5, clock synchronization among all ISDN access lines is established on the ISDN access line network 4. However, in the case of the VoIP access line via the VoIP-TA1A of FIG. 6, since the clock synchronization between the VoIP access lines is not taken, the timings are independent from each other by the free-running clock of each VoIP-TA1A. Will work. As a result, the BRI signal output from the VoIP-TA 1A operating with the self-running clock to the ISDN line for the business phone main apparatus 2A is in a state where the clock synchronization between the ISDN lines is not taken. End up. Therefore, when each VoIP-TA 1A operating with a free-running clock is accommodated in the same business phone main apparatus 2A, the BRI interface, that is, the ISDN line of each VoIP-TA 1A is in a state where clock synchronization is not taken. Therefore, the operation timing of the BRI interface in each BRI unit 20A of the business phone main apparatus 2A is shifted, and the synchronization of the BRI interface is lost, resulting in a communication failure.

  In order to solve such a communication failure, as shown in FIG. 7, each VoIP-TA 1A is synchronized with each other, and the VoIP-TA BRI interfaces are synchronized with each other. It is necessary to be in a state where In order to achieve such clock synchronization, in the current technology, each VoIP-TA1A is synchronized with CLK (Clock) synchronization as described in Japanese Patent Laid-Open No. 2007-281730 “VoIP system” and the like. In general, a configuration is employed in which a port is provided and a cable connection is performed for clock synchronization between each VoIP-TA1A. FIG. 7 is a schematic diagram showing a connection configuration example different from FIG. 6 in the case where a business phone communicates using a VoIP line in the current technology related to the present invention, and the CLK synchronization port is connected to each VoIP- The case where it has in TA1A is shown. In FIG. 7, as shown by a broken line with an arrow between each VoIP-TA1A, by using the CLK (clock) synchronization port 16A provided in each VoIP-TA1A, the free-running of the leftmost VoIP-TA1A The case where the frequency of the clock in other VoIP-TA1A is adjusted so that the clock in other VoIP-TA1A may be synchronized with a clock is shown.

  FIG. 8 is a block diagram illustrating an example of the internal configuration of the VoIP-TA 1A illustrated in FIG. 7, and illustrates a configuration example of the VoIP-TA to which the current technology related to the present invention is applied. As shown in FIG. 8, the VoIP-TA1A has a CLK synchronization port 16A for adjusting the oscillation frequency of the PLL 15A that outputs its own clock in each VoIP-TA1A in order to synchronize the clock between each VoIP-TA1A. Are provided, and each VoIP-TA1A is connected by a cable.

  However, the provision of the CLK synchronization port 16A in each VoIP-TA 1A causes problems such as the labor of connection work, the cost of the connection cable, and the increase in the apparatus cost due to the provision of the CLK synchronization port 16A.

JP 2007-281730 A

  As described above, in the current technology related to the present invention such as Patent Document 1, each VoIP-TA is provided with a CLK synchronization port in order to achieve clock synchronization between the VoIP-TAs. As a result, problems such as the labor of connection work, the cost of connection cables, and the increase in device cost due to the provision of ports have arisen.

(Object of the present invention)
The present invention has been made in view of such a problem, and enables each VoIP-TA to synchronize clocks between VoIP-TAs without providing a CLK synchronization port in each VoIP-TA. It is an object of the present invention to provide a VoIP-TA, a business phone, and a clock synchronization method that do not cause a failure in BRI communication with a phone main device.

  In order to solve the above-described problems, the VoIP-TA, business phone, and clock synchronization method according to the present invention mainly adopt the following characteristic configuration.

(1) VoIP-TA according to the present invention is
VoIP-TA (TA: terminal adapter) that performs conversion between a BRI (Basic Rate Interface) -based signal compliant with ISDN (Integrated Service Digital Network) standard and a VoIP (Voice over Internet Protocol) -based signal,
A synchronization type setting means having a function of setting in advance a synchronization type indicating whether or not the VoIP-TA is a target to be synchronized with its own clock;
When the synchronization type is a slave VoIP-TA to be synchronized with the built-in own clock, the synchronization type is specified in advance as a device having a reference clock serving as a reference when performing clock synchronization of the own clock. Pseudo VoIP session management means having a function of setting a pseudo VoIP session for clock synchronization with the master VoIP-TA using connection destination information indicating the master VoIP-TA,
Based on the monitoring result of the VoIP-based communication status with the master VoIP-TA in the pseudo VoIP session set by the pseudo VoIP session management means, the own clock is used as the reference clock of the master VoIP-TA. It is characterized by synchronizing.

(2) The business phone according to the present invention is
The BRI-based signal and VoIP (Voice over Internet Protocol) are connected to each of a plurality of ISDN lines that communicate in a clock-synchronized state using a BRI (Basic Rate Interface) -based signal compliant with the ISDN (Integrated Service Digital Network) standard. A business phone that connects a VoIP-TA that performs conversion to and from a base signal and performs VoIP communication using a plurality of VoIP access lines,
Any one of the plurality of VoIP-TAs is set as a master VloIP-TA specified in advance as a device having a reference clock that serves as a reference when performing clock synchronization between the VoIP-TAs, and the remaining other VoIP-TAs The VoIP-TA is a slave VoIP-TA that is to be synchronized so that its own clock incorporated in each VoIP-TA matches the reference clock of the master VoIP-TA, and the master VoIP-TA and the slave VoIP-TA By setting a pseudo VoIP session for clock synchronization between each TA, the own clock of each slave VoIP-TA is synchronized with the reference clock of the master VoIP-TA. .

(3) A clock synchronization method according to the present invention includes:
To synchronize a clock built in VoIP-TA that performs conversion between a BRI (Basic Rate Interface) -based signal compliant with ISDN (Integrated Service Digital Network) standard and a VoIP (Voice over Internet Protocol) -based signal A clock synchronization method,
A synchronization type setting step having a function of setting in advance a synchronization type indicating whether or not the VoIP-TA is a target for synchronization of the built-in own clock;
When the synchronization type is a slave VoIP-TA to be synchronized with the built-in own clock, the synchronization type is specified in advance as a device having a reference clock serving as a reference when performing clock synchronization of the own clock. A pseudo VoIP session management step having a function of setting a pseudo VoIP session for clock synchronization with the master VoIP-TA using connection destination information indicating the master VoIP-TA,
Based on the monitoring result of the VoIP-based communication status with the master VoIP-TA in the pseudo VoIP session set in the pseudo VoIP session management step, the own clock is used as the reference clock of the master VoIP-TA. It is characterized by synchronizing.

  According to the VoIP-TA, business phone, and clock synchronization method of the present invention, the following effects can be obtained.

  When a plurality of VoIP-TAs are accommodated in the main device of the same business phone, each VoIP-TA does not have a CLK (clock) synchronization port which is essential in the current technology related to the present invention. Thus, clock synchronization between each VoIP-TA can be surely taken, and loss of synchronization of the BRI interface due to clock deviation between each VoIP-TA can be reliably avoided. The reason is that a device having a reference clock for clock synchronization, that is, one VoIP-TA specified in advance as a master VoIP-TA and a slave VoIP-TA that is a target of clock synchronization of the built-in own clock Is set as a pseudo VoIP session for clock synchronization with another VoIP-TA, and a reference clock provided in the master VoIP-TA with its own clock built in each slave VoIP-TA on an IP basis The clock synchronization processing to synchronize with each other is performed.

  Thus, in the present invention, not only the VoIP-TA device cost increases due to the provision of the CLK synchronization port, but also the connection work of each VoIP-TA associated with the provision of the CLK synchronization port and the increase in the cost of the connection cable. The problems to be solved in the current technology related to the invention can be solved.

It is a schematic diagram which shows an example of a connection structure in case the business phone based on this invention communicates using a VoIP line. It is a block block diagram which shows an example of the internal structure of VoIP-TA which concerns on this invention. 3 is a flowchart for explaining an example of the operation of VoIP-TA shown in FIG. 2 as an embodiment of the present invention. It is a schematic diagram which shows an example of the synchronous setting Web screen displayed on a PC for maintenance / management. It is a schematic diagram which shows the example of a connection structure in case the business phone communicates using an ISDN line | wire in the present technique relevant to this invention. It is a schematic diagram which shows the example of a connection structure in case the business phone communicates using a VoIP line in the present technique relevant to this invention. It is a schematic diagram which shows the example of a connection structure different from FIG. 6 in case the business phone communicates using a VoIP line in the present technique relevant to this invention. It is a block block diagram which shows an example of an internal structure of VoIP-TA shown in FIG.

  Hereinafter, preferred embodiments of a VoIP-TA, a business phone, and a clock synchronization method according to the present invention will be described with reference to the accompanying drawings. In addition, it is needless to say that the drawing reference numerals attached to the following drawings are added for convenience to each element as an example for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiment. Yes.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The present invention relates to a case where a plurality of VoIP-TAs are connected to a business phone main apparatus in order for a business phone to use a VoIP line, and clock synchronization between each VoIP-TA connected to the same business phone main apparatus is performed on an IP basis. By taking this, the main feature is that it is not necessary to provide each VoIP-TA with a CLK (clock) synchronization port, which is essential in the current technology related to the present invention. Thus, it is possible to reduce the cost of VoIP-TA equipment and labor of installation work.

  More specifically, the main feature of the present invention is that clock synchronization between VoIP and TA is achieved using a procedure as described below.

  (1) First, when the power of each of the plurality of VoIP-TAs connected to the main device of the business phone is turned on, the clock synchronization of each VoIP-TA among the plurality of VoIP-TAs is performed. One VoIP-TA having a reference clock that serves as a reference for this is specified as a synchronization destination VoIP-TA (that is, master VoIP-TA), and the remaining VoIP-TA is incorporated with its own clock in each of the synchronization destination VoIP -Determined as a synchronized VoIP-TA (ie, slave VoIP-TA) to be synchronized with the TA reference clock.

  (2) For each identified synchronization destination VoIP-TA, an IP-based pseudo VoIP session for clock synchronization is set from each synchronization VoIP-TA.

  (3) During the implementation of VoIP communication between the synchronized VoIP-TA and each synchronized VoIP-TA in the set pseudo VoIP session, each synchronized VoIP-TA has a jitter buffer provided for absorbing jitter. Monitor the amount of accumulated packets. If there is a clock deviation between each synchronized VoIP-TA and the synchronized VoIP-TA, if the VoIP communication is continued, the buffer overrun of each synchronized VoIP-TA's jitter buffer or A buffer underrun occurs.

  (4) Among the synchronized VoIP-TAs, when a buffer overrun occurs in the jitter buffer of any synchronized VoIP-TA or when the increase rate of the accumulated packet amount exceeds a predetermined speed range Is the case where the own clock incorporated in the synchronized VoIP-TA is slower than the reference clock of the opposite VoIP-TA (synchronization destination VoIP-TA) in the pseudo VoIP session. Make corrections to make your own clock faster.

  (5) Among the synchronized VoIP-TAs, when a buffer underrun occurs in the jitter buffer of any synchronized VoIP-TA or when the rate of decrease of the accumulated packet amount exceeds a predetermined rate range Is the case where the own clock incorporated in the synchronized VoIP-TA is faster than the reference clock of the opposite VoIP-TA (synchronization destination VoIP-TA) in the pseudo VoIP session. Compensate to slow down the clock.

  (6) As for the correction value (adjustment value) for how fast or slow the own clock of the synchronized VoIP-TA is, the VoIP communication that has elapsed until the occurrence of buffer overrun or buffer underrun It is determined based on the time or the speed difference between the increase / decrease speed of the accumulated packet amount and the speed threshold (that is, both indicate the magnitude of the clock deviation).

  By performing the correction operation of the own clock like this, the own clock of each synchronized VoIP-TA can be synchronized with the reference clock of the synchronization destination VoIP-TA, and the clock synchronization between each target VoIP-TA Therefore, it is possible to reliably avoid the occurrence of a communication failure due to a timing shift in the BRI interface.

(Configuration example of embodiment of the present invention)
Next, an example of a VoIP-TA connection configuration according to the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating an example of a connection configuration when a business phone according to the present invention communicates using a VoIP line, and a plurality of VoIP-TAs accommodated in a main device of the same business phone. An example of the configuration is shown. The connection configuration shown in FIG. 1 is the same as the connection configuration shown in FIG. 6 as the current technology related to the present invention, and is installed in the business phone main apparatus 2 when each of the plurality of key telephones uses a telephone line. The BRI signal from each of the BRI units 20 is output to the VoIP-TA1 through the ISDN line in a synchronized state, and then converted into a VoIP signal in the VoIP-TA1, To the VoIP access line network 3.

  Here, the business phone main device 2 which is the main body of the business phone is a device having the same configuration as the current business phone main device 2A related to the present invention, and is connected to an ISDN line to realize a telephone function. And a BRI unit 20 that provides a BRI interface for connecting to an ISDN line (that is, generates a BRI signal conforming to the ISDN standard).

  The VoIP-TA 1 is an Ethernet WAN (Wide Area Network) interface (that is, a function for generating a VoIP signal) for communicating with a VoIP access line connected to the VoIP access line network 3, a business phone main apparatus 2 and an ISDN line. And a BRI interface (that is, a function of generating a BRI signal) for connection via the network, and a function of converting between an IP signal and a BRI signal. Furthermore, although details will be described later, clock synchronization between a plurality of VoIP-TA1s accommodated in the business phone main apparatus 2 using a mechanism unique to the present invention different from the current VoIP-TA1A related to the present invention. It also has the function of taking IP on an IP basis.

  Next, the internal configuration of VoIP-TA1 shown in FIG. 1 will be described in detail with reference to FIG. FIG. 2 is a block diagram showing an example of the internal configuration of VoIP-TA according to the present invention, and shows an example of the internal configuration of VoIP-TA1 shown in FIG.

  As shown in FIG. 2, the VoIP-TA1 includes a WAN interface 10, an RTP control unit 11, a jitter buffer 12, a Codec 13, an ISAC (BRIF) 14, a PLL 15, a pseudo VoIP session management unit 16, a Web setting screen control unit 17, a LAN. (Local Area Network) An interface 18 and a clock deviation detector 19 are included at least. That is, the VoIP-TA1 according to the present embodiment shown in FIG. 2 is a pseudo VoIP-TA1A shown in FIG. 8 as the current VoIP-TA related to the present invention, instead of deleting the CLK synchronization port 16A. A configuration in which the constituent elements of the VoIP session management unit 16, the Web setting screen control unit 17, the LAN interface 18, and the clock deviation detection unit 19 are added is adopted.

  The WAN interface 10 is a component that provides an interface for communicating with a VoIP access line using an IP signal, and has an Ethernet interface for transmitting and receiving VoIP packets. The RTP control unit 11 is a component that controls the operation of transmitting and receiving packets using a protocol called RTP (Real-time Transport Protocol) as a protocol for transmitting and receiving packets in real time. Using a protocol, control is performed so that transmission / reception is performed at a predetermined time interval (generally, a time interval of every 20 ms).

  The jitter buffer 12 is a buffer that accumulates packets up to a predetermined amount in order to absorb temporal fluctuations of packets that occur in an IP-based VoIP access line. That is, in the RTP protocol, as described above, packets are transmitted and received at predetermined time intervals. However, on the IP-based VoIP access line, due to the clock deviation from the communication partner, the time with the communication partner is reduced. Since a shift occurs, the packet does not always arrive at the predetermined time interval, and a temporal fluctuation of the packet occurs.

  Here, when the jitter buffer 12 exceeds a limit capable of absorbing the temporal fluctuation of the packet, the jitter buffer 12 causes buffer overflow. That is, when the own clock in the VoIP-TA1 of the communication partner is slower than the VoIP-TA1 of the communication partner, packets from the communication partner cannot be received, and a buffer overrun state occurs in which the buffer of the jitter buffer 12 overflows. . On the contrary, when the own clock in the VoIP-TA1 of the communication partner is faster than the VoIP-TA1 of the communication partner, a state in which a packet from the communication partner has not arrived occurs at the timing required for processing, and the jitter buffer 12 is a buffer underrun state in which there is no packet to be processed.

  The Codec 13 is a component that performs encoding / decoding of a VoIP packet. 711 μ-law or G. Encoding / decoding is performed based on the 711A-law standard. The ISAC 14 extracts the packet included in the BRI signal on the ISDN line and outputs it to the Codec 13. Conversely, the ISAC 14 receives the packet from the Codec 13 and generates a BRI-format signal via the ISDN line. It is a component that provides a BRI interface that outputs to the business phone main apparatus 2A.

  The PLL 15 is a component that constitutes a master clock as a built-in own clock, and is a voltage controlled oscillator (Phase Locked Loop) that generates a clock of VoIP-TA1, and generally uses a crystal oscillator or the like. Generate a clock. In many cases, the oscillation frequency of the own clock includes a certain amount of deviation from the desired true frequency in accordance with the applied voltage.

  The pseudo VoIP session management unit 16 is configured to generate a clock between a plurality of VoIP-TA1s connected to the same business phone main apparatus 2 based on an instruction from a user in charge of maintenance / management input from the Web setting screen control unit 17. It is a component having a function of setting and managing a pseudo VoIP session for performing synchronization. For example, when the own VoIP-TA1 is a slave VoIP-TA to be synchronized with the built-in own clock, the pseudo VoIP session management unit 16 becomes a reference when performing clock synchronization of the own clock. A function of setting a pseudo VoIP session for clock synchronization with VoIP-TA1 specified as the master VoIP-TA by using connection destination information indicating a master VoIP-TA specified in advance as a device having a reference clock At least.

  Further, the operation of the pseudo VoIP session management unit 16 will be supplementarily described. The pseudo VoIP session management unit 16 has a built-in VoIP-TA1 in which the pseudo VoIP session management unit 16 is mounted according to the designation of the user in charge of maintenance / management input from the web setting screen control unit 17, for example. The own clock is a reference clock that becomes a reference when performing clock synchronization, and is specified in advance as a device that synchronizes the clock of each of the other VoIP-TA1s connected to the same business phone main device 2 with the reference clock In the case of “synchronization destination VoIP-TA” (that is, “master VoIP-TA”), clock synchronization is performed from each of the other VoIP-TA1 on the “synchronization VoIP-TA” (that is, “slave VoIP-TA”) side. A request to start a pseudo VoIP session (setting request) is sent Fit Chi.

  When a request for starting a pseudo VoIP session (setting request) is received from the “synchronization VoIP-TA” (ie, “slave VoIP-TA”) side, the “synchronization destination VoIP-TA” and the request source “synchronization” A response permitting the establishment of a pseudo VoIP session for clock synchronization with “VoIP-TA” is returned to the requesting “synchronization VoIP-TA” (ie, “slave VoIP-TA”). As a result, a pseudo VoIP session for clock synchronization is set between the “synchronization destination VoIP-TA” and the “synchronization VoIP-TA” of the request source, and the IP base on the “synchronization VoIP-TA” side The operation to perform the clock synchronization is started. The pseudo VoIP session is continuously set until clock synchronization on the “synchronization VoIP-TA” side is completed.

  In addition, according to the designation of the user in charge of maintenance / management, the VoIP-TA 1 determines that the built-in own clock is specified in advance in the other VoIP-TA 1 connected to the same business phone main device 2. If it has been set in advance as “synchronization VoIP-TA” (ie, “slave VoIP-TA”) to be synchronized with the reference clock of “VoIP-TA” (ie, “master VoIP-TA”), A pseudo VoIP session start request (setting request) for performing clock synchronization is transmitted to “VoIP-TA”. As a result, upon receiving the response from the “synchronization destination VoIP-TA”, the pseudo VoIP session management unit 16 uses the clock synchronization for correcting the clock deviation from the reference clock of the “synchronization destination VoIP-TA”. A pseudo VoIP session is set between “synchronization destination VoIP-TA”.

  In the “synchronization VoIP-TA”, when a pseudo VoIP session for clock synchronization with the “synchronization destination VoIP-TA” is set, the pseudo VoIP session management unit 16 starts a clock synchronization operation, which will be described later. The clock deviation detector 19 is activated to monitor the buffer overrun or buffer underrun of the jitter buffer 12.

  When the occurrence of buffer overrun or buffer underrun of the jitter buffer 12 is detected as a monitoring result of the clock deviation detection unit 19, the clock deviation detection unit 19 is synchronized with the reference clock of “synchronization destination VoIP-TA”. In addition, an IP-based clock correction operation of correcting the oscillation frequency of the own clock of the “synchronized VoIP-TA” output from the PLL 15 is performed.

  Here, the pseudo VoIP session management unit 16 performs the “synchronization VoIP” until the clock synchronization of the own clock of “synchronization VoIP-TA” with the reference clock is completed by the IP-based clock correction operation as described above. The state in which the pseudo VoIP session for clock synchronization between “-TA” and “Synchronization destination VoIP-TA” is set is continued.

  Next, when the VoIP-TA1 is powered on, the Web setting screen control unit 17 sets the synchronization of the own clock of the VoIP-TA1 via the LAN interface 18 based on an instruction from the pseudo VoIP session management unit 16. A synchronization setting Web screen for performing the operation is displayed on a management device such as a PC (Personal Computer) to inquire a user in charge of maintenance and management, and control operations until receiving an instruction regarding the synchronization setting from the user. A component having at least a function. Here, regarding the synchronization setting, the Web setting screen control unit 17 determines whether or not at least the VoIP-TA1 is a target VoIP-TA (that is, a slave VoIP-TA) that performs synchronization of its own clock. Synchronization type setting means having a function of setting the synchronization type to be shown in advance is provided.

  The LAN interface 18 is a component that provides an interface for management / maintenance of devices such as VoIP-TA1, and is used by a user as a management device for management / maintenance, such as a PC, via a LAN cable. For example, based on a display instruction from the Web setting screen control unit 17, the synchronization setting Web screen is displayed on the management device.

  The clock deviation detection unit 19 is a component that enables an operation in “synchronization VoIP-TA” (that is, “slave VoIP-TA”), and has a function of detecting a deviation of its own clock of VoIP-TA1 as a clock deviation. It is a constituent element. And based on the detected clock deviation, it also has a function of correcting the oscillation frequency of the own clock by adjusting the voltage of the PLL 15 so as to eliminate the clock deviation. In other words, the clock deviation detection unit 19 on the “synchronization VoIP-TA” side monitors the VoIP-based communication status with the “synchronization destination VoIP-TA” (that is, “master VoIP-TA”) in the pseudo VoIP session. And a function of synchronizing the own clock with the reference clock of the “synchronization destination VoIP-TA” (that is, “master VoIP-TA”).

  Here, in the present embodiment, the clock deviation detection unit 19 on the “synchronization VoIP-TA” side performs VoIP with the “synchronization destination VoIP-TA” (that is, “master VoIP-TA”) in the pseudo VoIP session. As the communication status of the base, the amount of packets accumulated in the jitter buffer 12 provided to absorb temporal fluctuation of the VoIP-based packet is monitored, and the own clock and the “synchronization destination VoIP-TA” (that is, “ This shows a case where a clock deviation from a reference clock of “Master VoIP-TA”) is detected. That is, it shows a case where the amount of packets accumulated in the jitter buffer 12 is continuously monitored while the pseudo-VoIP session for clock synchronization with the “synchronization destination VoIP-TA” of the communication partner is established.

  Then, when it is detected as a monitoring result that a buffer overrun or a buffer underrun of the jitter buffer 12 has occurred before the time when the clock synchronization is estimated to be completed, that is, until the synchronization completion estimated time threshold elapses. The clock deviation detector 19 determines that there is a clock deviation from the reference clock of “synchronization destination VoIP-TA”. Then, using the correction amount (adjustment value) calculated based on the elapsed time until the buffer overrun or buffer underrun occurs, the oscillation frequency of the own clock, that is, the PLL 15 is corrected so as to eliminate the clock deviation.

  On the other hand, when the clock deviation detecting unit 19 detects that no buffer overrun or buffer underrun of the jitter buffer 12 has occurred until the synchronization completion estimated time threshold elapses, the “clock synchronization VoIP” It is estimated that the clock synchronization with the reference clock of “-TA” is completed. As a result, the pseudo VoIP session management unit 16 is notified of the completion of synchronization, whereby the pseudo VoIP for clock synchronization stretched between the “synchronized VoIP-TA” and “same VoIP-TA”. The session will be released and ended.

(Description of the operation of the embodiment of the present invention)
Next, the operation of VoIP-TA1 shown in FIG. 2 as an embodiment of the present invention will be described in detail with reference to the flowchart of FIG. FIG. 3 is a flowchart for explaining an example of the operation of the VoIP-TA 1 shown in FIG. 2 as an embodiment of the present invention, and performs clock synchronization of each VoIP-TA 1 connected to the same business phone main apparatus 2. An example of the operation is shown.

  In the flowchart shown in FIG. 3, first, when the power of each VoIP-TA1 connected to the same business phone main apparatus 2 is turned on (step S1), under the control of the pseudo VoIP session management unit 16, the Web The setting screen control unit 17 is activated, and a login Web screen is displayed on the screen of the management device, for example, the PC, via the LAN interface 18.

  When a user who performs maintenance / management of VoIP-TA1 enters the user authentication information (user ID, password, etc.) of the user on the login Web screen displayed on the screen and logs in (step S2), the VoIP-TA1 The web setting screen control unit 17 confirms the input user authentication information. When the user authentication is obtained, the Web setting screen control unit 17 uses the LAN interface 18 to preset the requirements for performing the clock synchronization operation as the synchronization setting of the VoIP-TA1, as shown in FIG. A synchronization setting Web screen as shown is displayed on a management device such as a PC to inquire the user.

  FIG. 4 is a schematic diagram showing an example of the synchronization setting Web screen displayed on the maintenance / management PC. The synchronization setting Web screen 30 shown in FIG. 4 includes a synchronization type setting field 31 and a synchronization connection destination setting field 32.

The synchronization type setting column 31 is a column for setting information regarding the synchronization type of the VoIP-TA1, and this VoIP-TA1 is
(1) “synchronized side”: “synchronization destination” on the side that synchronizes the own clock of each of the other VoIP-TA1s connected to the same business phone main device 2 with the clock of this VoIP-TA1 (that is, the reference clock) “VoIP-TA”, that is, “master VoIP-TA” is designated.
(2) “Synchronizing side”: the side that synchronizes its own clock of this VoIP-TA1 with the reference clock of “synchronization destination VoIP-TA”, that is, “master VoIP-TA” connected to the same business phone main device 2 “Synchronization VoIP-TA”, that is, “slave VoIP-TA”.
(3) “Do not synchronize”: Designate that the VoIP-TA1 is not subject to clock synchronization processing.
This is a column that allows the user to select which of the synchronization types. After the user selects one of the synchronization types, the user operates the “set” button to set and register the synchronization type.

  The synchronous connection destination setting field 32 sets a pseudo VoIP session when the VoIP-TA1 is “synchronizing side” (that is, “synchronization VoIP-TA”, in other words, “slave VoIP-TA”). This is a column for setting information indicating “synchronization destination VoIP-TA” (in other words, “master VoIP-TA”) (that is, connection destination information indicating a connection destination) used when performing the above. In other words, in order to perform clock synchronization processing, connection destination information indicating a “synchronization destination VoIP-TA”, that is, “master VoIP-TA” as a communication destination for establishing a pseudo VoIP session for clock synchronization, for example, a telephone number After the user inputs, a “synchronization” button is operated to open a pseudo-VoIP session for clock synchronization with the connection destination and start IP-based communication.

  Returning to the description of the flowchart of FIG. 3, when the synchronization setting Web screen 30 shown in FIG. 4 is displayed on the screen, the user selects the synchronization type of the VoIP-TA 1 from the synchronization type setting column 31 and clicks “Setting”. By operating the button, the VoIP-TA1 is instructed to register settings. When the Web setting screen control unit 17 of VoIP-TA1 receives the installation registration instruction from the user, the pseudo VoIP session management unit 16 notifies the pseudo VoIP session management unit 16 to that effect, whereby the synchronization is instructed. The type is set and registered (step S3). As a result, one of the plurality of VoIP-TA1 connected to the same business phone main apparatus 2 is “synchronized side” (that is, “synchronization destination VoIP-TA”, in other words, “master VoIP-TA”. ), And all other VoIP-TA1 are set as “synchronizing side” (that is, “synchronized VoIP-TA”, in other words, “slave VoIP-TA”).

  Furthermore, the synchronization type of the synchronization setting Web screen 30 is selected by selecting “synchronizing side” (that is, “synchronization VoIP-TA” in other words, “slave VoIP-TA”) in the synchronization type setting field 31 VoIP-TA1 set and registered. With respect to the information, the user can obtain information on “synchronization destination VoIP-TA”, that is, “master VoIP-TA” to be a connection destination for clock synchronization (in this embodiment, as shown in FIG. Information) is input to the input field of the synchronous connection destination setting field 32, and the “connect” button is operated, so that the “side to be synchronized” with the VoIP-TA1 (that is, “synchronization destination VoIP-TA”). Master VoIP-TA ”)) is instructed to connect to VoIP-TA1.

  When receiving the connection instruction from the user, the Web setting screen control unit 17 of VoIP-TA1 notifies the pseudo VoIP session management unit 16 so that the pseudo VoIP session management unit 16 “slave VoIP-”. VoIP-TA1 corresponding to “TA” sets and registers the telephone number of VoIP-TA1 corresponding to “master VoIP-TA”, which is the connection destination for clock synchronization (step S4). At the same time, the pseudo VoIP session management unit 16 sends a synchronization VoIP session start request as a “synchronization VoIP session start request as a pseudo VoIP session for clock synchronization with the VoIP-TA 1 corresponding to the“ master VoIP-TA ”. It transmits with respect to VoIP-TA1 applicable to TA. Thereafter, upon receiving a response to the start request from VoIP-TA1 corresponding to “Master VoIP-TA”, the pseudo VoIP session management unit 16 and VoIP-TA1 corresponding to “Slave VoIP-TA” and “Master VoIP- A pseudo-VoIP session for clock synchronization (synchronization VoIP session) is set between the VoIP-TA1 corresponding to “TA” and the VoIP-TA1 corresponding to “slave VoIP-TA” is IP-based. Shift to a state of starting the clock synchronization operation (step S5).

  That is, the pseudo VoIP session management unit 16 of the VoIP-TA 1 corresponding to “synchronization VoIP-TA”, that is, “slave VoIP-TA” activates the clock deviation detection unit 19. As a result, the clock deviation detection unit 19 performs the buffering of the jitter buffer 12 while the synchronization VoIP session with the VoIP-TA1 corresponding to the “synchronization destination VoIP-TA”, that is, the “master VoIP-TA” is continued. Start the operation to continue monitoring the occurrence of overrun or buffer underrun. As long as there is a clock deviation from VoIP-TA1 corresponding to “Master VoIP-TA”, buffer overrun or buffer underrun of jitter buffer 12 occurs. When the clock deviation detecting unit 19 of the VoIP-TA1 corresponding to the “slave VoIP-TA” detects the occurrence of buffer overrun or buffer underrun of the jitter buffer 12, the buffer is used when the time has elapsed. Detection information indicating whether an overrun or a buffer underrun has occurred is acquired (step S6).

  The VoIP-TA1 clock deviation detector 19 corresponding to “slave VoIP-TA” corrects the oscillation frequency of the own clock, that is, the PLL 15 in the VoIP-TA1, based on the acquired detection information, The clock deviation from the VoIP-TA1 clock (reference clock) corresponding to “VoIP-TA” is adjusted (step S7).

  Here, regarding a specific correction amount (adjustment amount) for correcting the own clock of the “slave VoIP-TA”, that is, the oscillation frequency of the PLL 15, for example, a packet corresponding to a communication time corresponding to a communication time of 100 msec. In the case of the amount, the following correction amount may be applied.

  (A) When a buffer overrun of the jitter buffer 12 occurs in the communication time of 1 second, the own clock in the own “slave VoIP-TA” is slower than the opposite “master VoIP-TA” by 0.1 Hz (PLL15 Therefore, the self-clock is increased by 0.1 Hz (the oscillation frequency of the PLL 15 is increased).

  (B) When a buffer overrun of the jitter buffer 12 occurs in a communication time of 100 seconds, the own clock in the own “slave VoIP-TA” is slower than the opposite “master VoIP-TA” by 0.001 Hz (PLL15 Therefore, the self-clock is increased by 0.001 Hz (the oscillation frequency of the PLL 15 is increased).

  (C) When a buffer underrun of the jitter buffer 12 occurs in a communication time of 1 second, the own clock in the own “slave VoIP-TA” is faster than the opposite “master VoIP-TA” by 0.1 Hz (PLL15 Therefore, the own clock is delayed by 0.1 Hz (the oscillation frequency of the PLL 15 is lowered).

  (D) When a buffer underrun of the jitter buffer 12 occurs in a communication time of 100 seconds, the own “slave VoIP-TA” in the own “slave VoIP-TA” is more than 0.001 Hz than the opposite “master VoIP-TA”. Therefore, the own clock is fast (the oscillation frequency of the PLL 15 is high), so that the own clock is delayed by 0.001 Hz (the oscillation frequency of the PLL 15 is lowered).

  Thereafter, the process returns to step S6 to continue monitoring the occurrence of buffer overrun or buffer underrun of the jitter buffer 12, and until the time preset as the synchronization completion estimated time threshold elapses, the buffer of the jitter buffer 12 When overrun or buffer underrun occurs again, the operation of correcting the oscillation frequency of the PLL 15 again is repeated.

  On the other hand, when the buffer overrun or the buffer underrun of the jitter buffer 12 does not occur until the time corresponding to the synchronization completion estimated time threshold elapses, the clock deviation detecting unit 19 determines that “slave VoIP-TA”. It is estimated that the own clock of the VoIP-TA1 corresponding to the VoIP-TA1 has been synchronized with the reference clock of the VoIP-TA1 corresponding to the “master VoIP-TA” and has reached a state where there is no clock deviation. The pseudo VoIP session management unit 16 is notified of the completion of the conversion. Upon receiving the notification, the pseudo VoIP session management unit 16 terminates the pseudo VoIP session for clock synchronization with the VoIP-TA1 corresponding to the “master VoIP-TA”.

  As described above, in this embodiment, each of a plurality of VoIP-TA1 accommodated in the same business phone main apparatus 2 includes a pseudo VoIP session management unit 16, a web setting screen control unit 17, a LAN interface 18, and clock deviation detection. By providing the unit 19, it is possible to perform clock synchronization between each VoIP-TA1 on an IP basis, eliminating the need to provide a CLK synchronization port that is essential in the current technology related to the present invention, A more economical VoIP-TA can be realized.

  In other words, in the present embodiment, when the VoIP-TA1 is powered on, the Web setting screen control unit 17 and the LAN interface 18 make one of the VoIP-TA1 specified by the user “synchronized”. The VoIP-TA, that is, “master VoIP-TA” is specified in advance, and the remaining VoIP-TA is set in advance as the “synchronizing side” VoIP-TA, that is, “slave VoIP-TA”. Furthermore, pseudo VoIP for clock synchronization is established between each VoIP-TA1 set as “slave VoIP-TA” and VoIP-TA1 previously specified as “master VoIP-TA” by the pseudo VoIP session management unit 16. After establishing a VoIP session for synchronization as a session, the clock deviation detecting unit 19 is activated to start clock synchronization processing in “slave VoIP-TA”.

  Then, the clock deviation detecting unit 19 continues to monitor the occurrence of buffer overrun or buffer underrun of the jitter buffer 12 while the synchronization pseudo VoIP session continues, and based on the monitored result, the “master VoIP” The operation of detecting the degree of clock deviation from the reference clock of “−TA” and correcting the oscillation frequency of the own clock, that is, the PLL 15 according to the degree of the clock deviation is repeated. On the other hand, if the buffer overrun or the buffer underrun of the jitter buffer 12 does not occur until the predetermined time as the synchronization completion estimated time threshold elapses, the own clock is the reference of “master VoIP-TA”. It is determined that clock synchronization with the clock has been obtained, and the pseudo VoIP session management unit 16 releases the pseudo VoIP session for synchronization between the “slave VoIP-TA” and the “master VoIP-TA”. , Completing the synchronization process.

  The IP-based clock synchronization operation as described above is performed in all the VoIP-TA1s accommodated in the same business phone main apparatus 2, so that all the “slaves” are included in the clock (reference clock) of the “master VoIP-TA”. The own clock of “VoIP-TA” can be synchronized.

  In the above-described embodiment, in the synchronous connection destination setting field 32 of the synchronous setting Web screen 30 shown in FIG. 4, the synchronous connection corresponding to the “synchronized side” VoIP-TA1, that is, “master VoIP-TA”. An example is shown in which a telephone number is used as connection destination information indicating “master VoIP-TA” when a destination is specified. However, the present invention is not limited to such a case, and an IP address may be used instead of a telephone number as connection destination information indicating “master VoIP-TA”. Furthermore, VoIP-TA1 corresponding to “synchronizing side” VoIP-TA1, ie, “slave VoIP-TA”, and VoIP-TA1 corresponding to “synchronizing side”, ie, VoIP-TA1 corresponding to “master VoIP-TA” Are present in the same network, a MAC address may be used as connection destination information indicating “master VoIP-TA”.

  In the above description, the clock deviation detecting unit 19 corrects the own clock, that is, the jitter before the time set in advance as the synchronization completion estimated time threshold elapses as an opportunity to correct the oscillation frequency of the PLL 15. Although the case where occurrence of buffer overrun or buffer underrun of the buffer 12 is detected has been described, the present invention is not limited to such a case. For example, the amount of packets accumulated in the jitter buffer 12 is measured at predetermined time intervals, and the increase / decrease rate of the accumulated amount of packets is calculated. Then, it is determined whether or not the increase / decrease speed of the accumulated packet amount exceeds the speed range of the increase / decrease speed set in advance as the synchronization completion estimated speed threshold. The own clock may be corrected, that is, the oscillation frequency of the PLL 15 may be corrected according to the magnitude of the speed deviation between the synchronization completion estimated speed threshold and both. Note that the rate of increase / decrease in the amount of packets accumulated in the jitter buffer 12 before the time corresponding to the synchronization completion estimated time threshold elapses is within the speed range of the synchronization completion estimated speed threshold. If it is not detected that the clock has been exceeded, it is determined that the clock synchronization of the own clock has been obtained, and the clock synchronization set with the “master VoIP-TA” by the pseudo VoIP session management unit 16 The pseudo VoIP session management unit 16 for use releases the pseudo VoIP session and ends the clock synchronization operation.

(Description of the effect of this embodiment)
As described in detail above, the following effects can be achieved in the present embodiment.

  When a plurality of VoIP-TA1s are accommodated in the same business phone main device 2, each VoIP-TA1 does not have a CLK (clock) synchronization port which is essential in the current technology related to the present invention. Thus, clock synchronization between each VoIP-TA1 can be ensured, and loss of synchronization of the BRI interface due to clock deviation between each VoIP-TA1 can be reliably avoided. The reason is that a device having a reference clock when performing clock synchronization, that is, one VoIP-TA1 specified in advance as “master VoIP-TA” and “slave” that is a target of clock synchronization of the built-in own clock. A pseudo-VoIP session for clock synchronization is set with another VoIP-TA1 that is “VoIP-TA”, and the own clock incorporated in each “slave VoIP-TA” is set to “Master VoIP-” on an IP basis. In other words, a clock synchronization process is performed to synchronize with a reference clock prepared for TA.

  Thus, in the present invention, not only the VoIP-TA device cost increases due to the provision of the CLK synchronization port, but also the connection work of each VoIP-TA associated with the provision of the CLK synchronization port and the increase in the cost of the connection cable. Problems in the current technology related to the invention can be solved.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

1 VoIP-TA
1 VoIP-TA
2 Business Phone Main Device 2A Business Phone Main Device 3 VoIP Access Line Network 4 ISDN Access Line Network 10 WAN Interface 10A WAN Interface 11 RTP Control Unit 11A RTP Control Unit 12 Jitter Buffer 12A Jitter Buffer 13 Codec
13A Codec
14 ISAC (BRIF)
14A ISAC (BRIF)
15 PLL
15A PLL
16 pseudo VoIP session management unit 16A CLK synchronization port 17 Web setting screen control unit 18 LAN interface 19 clock deviation detection unit 20 BRI unit 20A BRI unit 30 synchronization setting Web screen 31 synchronization type setting field 32 synchronization connection destination setting field

Claims (10)

VoIP-TA (TA: terminal adapter) that performs conversion between a BRI (Basic Rate Interface) -based signal compliant with ISDN (Integrated Service Digital Network) standard and a VoIP (Voice over Internet Protocol) -based signal,
A synchronization type setting means having a function of setting in advance a synchronization type indicating whether or not the VoIP-TA is a target to be synchronized with its own clock;
When the synchronization type is a slave VoIP-TA to be synchronized with the built-in own clock, the synchronization type is specified in advance as a device having a reference clock serving as a reference when performing clock synchronization of the own clock. Pseudo VoIP session management means having a function of setting a pseudo VoIP session for clock synchronization with the master VoIP-TA using connection destination information indicating the master VoIP-TA,
Based on the monitoring result of the VoIP-based communication status with the master VoIP-TA in the pseudo VoIP session set by the pseudo VoIP session management means, the own clock is used as the reference clock of the master VoIP-TA. VoIP-TA, which is synchronized with the VoIP-TA. Packets accumulated in a jitter buffer provided for absorbing temporal fluctuations of a VoIP-based packet as a target for monitoring a VoIP-based communication status with the master VoIP-TA in the pseudo VoIP session A clock deviation detecting means for monitoring a quantity and detecting a clock deviation between the own clock and the reference clock of the master VoIP-TA based on a monitoring result of the packet quantity;
2. The VoIP-TA according to claim 1, wherein the oscillation frequency of the own clock is corrected so as to eliminate the clock deviation based on the clock deviation detected by the clock deviation detecting means.   When the clock deviation detecting means corrects the oscillation frequency of the own clock until a time corresponding to a predetermined synchronization completion estimated time threshold elapses, a buffer overrun or buffer underrun of the jitter buffer is performed. Or the rate of increase / decrease in the amount of packets accumulated in the jitter buffer exceeds the speed range of a predetermined synchronization completion estimated speed threshold. The VoIP-TA according to claim 2, wherein the VoIP-TA is used.   When the clock deviation detecting means detects that the buffer buffer is overrun or the increase rate of the amount of packets accumulated in the jitter buffer exceeds the speed range of the synchronization completion estimated speed threshold, Correction is made to increase the oscillation frequency of the own clock, and the buffer underrun of the jitter buffer or the rate of decrease in the amount of packets accumulated in the jitter buffer exceeds the speed range of the synchronization completion estimated speed threshold. The VoIP-TA according to claim 3, wherein when detected, the VoIP-TA is corrected so as to slow down an oscillation frequency of the own clock.   The correction amount for correcting the oscillation frequency of the own clock is the time elapsed until the buffer overrun or buffer underrun of the jitter buffer occurs, or the rate of increase / decrease of the packet amount accumulated in the jitter buffer and the synchronization 5. The VoIP-TA according to claim 3, wherein the VoIP-TA is determined based on a magnitude of a speed deviation between the estimated completion speed threshold and both.   When the clock deviation detecting unit does not detect occurrence of buffer overrun or buffer underrun of the jitter buffer until a time corresponding to the synchronization completion estimated time threshold elapses, or the jitter buffer If the increase / decrease rate of the packet amount accumulated in the packet does not exceed the synchronization completion estimated speed threshold speed range, the pseudo VoIP session management means is set between the master VoIP-TA and The VoIP-TA according to claim 3, wherein the pseudo VoIP session is released. As the synchronization type setting means, when the power is turned on, information regarding the synchronization type indicating whether the master VoIP-TA or the slave VoIP-TA and the pseudo VoIP session are set. Web setting screen having a function to display a synchronization setting Web screen for inquiring of a user who performs maintenance / management of the connection destination information indicating the master VoIP-TA to be used on a maintenance device used by the user who performs the maintenance / management With control means,
7. The connection destination information indicating the master VoIP-TA is acquired based on a response from the maintenance device, and the connection destination information indicating the master VoIP-TA is acquired. VoIP-TA as described.   The VoIP-TA according to claim 7, wherein the connection destination information indicating the master VoIP-TA is one of a telephone number, an IP address, or a MAC address of the master VoIP-TA. The BRI-based signal and VoIP (Voice over Internet Protocol) are connected to each of a plurality of ISDN lines that communicate in a clock-synchronized state using a BRI (Basic Rate Interface) -based signal compliant with the ISDN (Integrated Service Digital Network) standard. A business phone that connects a VoIP-TA that performs conversion to and from a base signal and performs VoIP communication using a plurality of VoIP access lines,
Any one of the plurality of VoIP-TAs is set as a master VloIP-TA specified in advance as a device having a reference clock that serves as a reference when performing clock synchronization between the VoIP-TAs, and the remaining other VoIP-TAs The VoIP-TA is a slave VoIP-TA that is to be synchronized so that its own clock incorporated in the VoIP-TA matches the reference clock of the master VoIP-TA, and the master VoIP-TA and the slave VoIP-TA By setting a pseudo VoIP session for clock synchronization between each TA, the own clock of each slave VoIP-TA is synchronized with the reference clock of the master VoIP-TA. Business phone. To synchronize a clock built in VoIP-TA that performs conversion between a BRI (Basic Rate Interface) -based signal compliant with ISDN (Integrated Service Digital Network) standard and a VoIP (Voice over Internet Protocol) -based signal A clock synchronization method,
A synchronization type setting step having a function of setting in advance a synchronization type indicating whether or not the VoIP-TA is a target for synchronization of the built-in own clock;
When the synchronization type is a slave VoIP-TA to be synchronized with the built-in own clock, the synchronization type is specified in advance as a device having a reference clock serving as a reference when performing clock synchronization of the own clock. A pseudo VoIP session management step having a function of setting a pseudo VoIP session for clock synchronization with the master VoIP-TA using connection destination information indicating the master VoIP-TA,
Based on the monitoring result of the VoIP-based communication status with the master VoIP-TA in the pseudo VoIP session set in the pseudo VoIP session management step, the own clock is used as the reference clock of the master VoIP-TA. A clock synchronization method characterized by synchronizing with each other.

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