JP2006033261A - Private branch exchange, gateway apparatus, ip phone system, and speech quality control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a private branch exchange, a gateway apparatus, an IP phone system, and a speech quality control method thereof capable of enhancing an echo suppression amount by the gateway apparatus and obtaining an expected speech level without changing a prediction signal expected by an echo canceller. <P>SOLUTION: A gain control section 13 of a key telephone set connected to the gateway apparatus 2 including the echo canceller 25 to configure the IP phone system searches gain information denoting a gain to be attached corresponding to each line accommodated by a master unit 1 from a public line interface section 14. The searched gain information is outputted to the gateway apparatus 2 via an ISDN interface section 16. A gain control section 23 receives this gain information. The echo canceller 25 adds the received gain information to the signal received from a LAN line to calculate a pseudo echo and adaptively controls a prediction function so that a difference signal between an output signal of the echo path and the pseudo echo is minimized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an IP telephone system having a private branch exchange apparatus and a gateway (gateway) apparatus, and more particularly to a voice quality control function in an IP (Internet Protocol) telephone system.

  2. Description of the Related Art Conventionally, for example, in an IP telephone system composed of a key telephone apparatus which is a kind of private branch exchange apparatus and a gateway apparatus having an echo canceller, the main apparatus of the key telephone apparatus and the gateway apparatus add gain to each apparatus. . For this reason, the audio signal predicted by the echo canceller has been changed by the main unit. Moreover, the following techniques are disclosed as related techniques. When the telephone terminal makes a call, the voice gateway device of one of the two nodes transmits a plurality of voice level information that can be used on the channel for establishing the call to the partner node via the Internet. The voice gateway device of the counterpart node selects a voice level that can be used by the own node from the received voice level information. Then, control is performed so that a call is made at the selected voice level, and the selected voice level information is returned to the calling node. The voice gateway device of the calling node controls to make a call at the voice level received from the counterpart node (see, for example, Patent Document 1).

JP 2002-374371 A (paragraph number 0006)

  As described above, the conventional IP telephone system has the following problems. The first problem is that since the main device and the gateway device each add gain, the audio signal predicted by the echo canceller is changed by the main device, and the echo canceller function in the gateway device is fully utilized. That is, the echo cannot be erased. The second problem is that if the echo cannot be eliminated, it can be dealt with by lowering the gain of the call path connected to the gateway device, but this makes it impossible to add the expected gain. On the other hand, Patent Document 1 discloses that the fluctuation of the voice level is suppressed, but does not describe the echo suppression in the gateway device.

  An object of the present invention is to provide a private branch exchange apparatus, a gateway apparatus, and an IP telephone system capable of improving an echo suppression amount and obtaining an expected voice level in a gateway apparatus without changing a prediction signal expected in an echo canceller. And providing a voice quality control method thereof.

  The private branch exchange apparatus of the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and gain information indicating a gain to be added corresponding to a public line to be accommodated by the echo canceller. First gain control means for outputting to the gateway device for use in the echo cancellation of the above.

  The gateway apparatus of the present invention is a gateway apparatus having an echo canceller that is connected to a private branch exchange and constitutes an IP telephone system, and corresponds to a public line accommodated in the private branch exchange that is output from the private branch exchange. And second gain control means for receiving the gain information indicating the gain to be added and performing echo cancellation by the echo canceller in consideration of the gain information.

  The IP telephone system of the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and that receives gain information indicating gain added corresponding to a public line to be accommodated. A private branch exchange apparatus comprising a first gain control means for outputting to the gateway apparatus for use in echo cancellation in a canceller, and a gateway apparatus having an echo canceller connected to the private branch exchange apparatus to constitute an IP telephone system, Receiving gain information indicating a gain to be added corresponding to a public line accommodated in the private branch exchange, which is output from the private branch exchange, and performing echo cancellation by the echo canceller in consideration of the gain information And a gateway device having a gain control means.

  The IP telephone system of the present invention may be configured to include the gateway device inside the private branch exchange.

  The private branch exchange apparatus according to the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and that receives gain information indicating gain to be added corresponding to a public line accommodated therein. A button telephone device comprising first gain control means for outputting to the gateway device to be used for echo cancellation in a canceller.

  The private branch exchange apparatus of the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and has public information that has gain information for adding gain to each public line and accommodates each public line. A first line interface unit for interfacing with a line; a second line interface unit connected to the gateway device; and a time division switch connected to the first and second line interface units to form a speech path First, when the first line interface unit is captured, the gain information of the public line is retrieved and output to the gateway device for use in echo cancellation by the echo canceller via the second line interface unit. Gain control means, and a control circuit for controlling the respective units.

  The gateway device of the present invention is a gateway device that is connected to a private branch exchange and constitutes an IP telephone system, and includes a third line interface unit that interfaces with the private branch exchange, and the third line interface. And an echo canceller for connecting to the echo canceller and receiving the gain information indicating the gain added corresponding to the public line accommodated in the private branch exchange connected to the echo canceller and output from the private branch exchange A second gain control means for performing echo cancellation by the echo canceller in consideration of the gain information; a voice compression section for voice-compressing an output gain-controlled by the second gain control means; and the voice compression Interface unit for outputting the output of the unit to the LAN line, the network from the LAN line The input audio signal via the interface unit and an audio decompression unit for speech stretching.

  The gateway device of the present invention is a gateway device that is connected to a private branch exchange and constitutes an IP telephone system, and includes a third line interface unit that interfaces with the private branch exchange, and the third line interface. And an echo canceller for connecting to the echo canceller and receiving the gain information indicating the gain added corresponding to the public line accommodated in the private branch exchange connected to the echo canceller and output from the private branch exchange A second gain control means for performing echo cancellation by the echo canceller in consideration of the gain information; a voice compression section for voice-compressing an output gain-controlled by the second gain control means; and the voice compression Interface unit for outputting the output of the unit to the LAN line, the network from the LAN line A voice expansion unit that expands a voice signal input via the interface unit, and the echo canceller has a gain information table that stores gain information received from the private branch exchange, and is input from the LAN line. A pseudo echo is calculated by adding the gain information of the line to the received signal, and the prediction function is adaptively controlled so that the difference signal between the output signal of the echo path and the pseudo echo is minimized.

  The IP telephone system of the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and has public information that has gain information for adding gain to each public line. A first line interface unit for interfacing with a line; a second line interface unit connected to the gateway device; and a time division switch connected to the first and second line interface units to form a speech path First, when the first line interface unit is captured, the gain information of the public line is retrieved and output to the gateway device for use in echo cancellation by the echo canceller via the second line interface unit. A private branch exchange apparatus comprising: a gain control means; and a control circuit for controlling the respective units; and a private branch exchange apparatus Is a gateway device that configures an IP telephone system by connecting to a third line interface unit that interfaces with the private branch exchange, and an echo canceller that connects to the third line interface unit and cancels echo And receiving the gain information indicating the gain to be added corresponding to the public line accommodated in the private branch exchange connected to the echo canceller and output from the private branch exchange, and taking the gain information into account, A second gain control means for performing echo cancellation, a voice compression section for voice-compressing the output gain-controlled by the second gain control means, and a network interface section for outputting the output of the voice compression section to a LAN line Voice signals input from the LAN line via the network interface unit And a gateway device and an audio decompression unit for decompressing.

  The IP telephone system of the present invention is a private branch exchange apparatus that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, and has public information that has gain information for adding gain to each public line. A first line interface unit for interfacing with a line; a second line interface unit connected to the gateway device; and a time division switch connected to the first and second line interface units to form a speech path First, when the first line interface unit is captured, the gain information of the public line is retrieved and output to the gateway device for use in echo cancellation by the echo canceller via the second line interface unit. A private branch exchange apparatus comprising: a gain control means; and a control circuit for controlling the respective units; and a private branch exchange apparatus Is a gateway device that configures an IP telephone system by connecting to a third line interface unit that interfaces with the private branch exchange, and an echo canceller that connects to the third line interface unit and cancels echo And receiving the gain information indicating the gain to be added corresponding to the public line accommodated in the private branch exchange connected to the echo canceller and output from the private branch exchange, and taking the gain information into account, A second gain control means for performing echo cancellation, a voice compression section for voice-compressing the output gain-controlled by the second gain control means, and a network interface section for outputting the output of the voice compression section to a LAN line Voice signals input from the LAN line via the network interface unit A decompression unit, and the echo canceller includes a gain information table for storing gain information received from the private branch exchange, and the gain information of the line is added to a signal input from the LAN line. And a gateway device that adaptively controls the prediction function so as to calculate a pseudo echo and minimize a difference signal between the output signal of the echo path and the pseudo echo.

  The voice quality control method in the IP telephone system according to the present invention is a voice quality control method in an IP telephone system that controls voice quality in an IP telephone system that includes a private branch exchange apparatus and a gateway apparatus that has an echo canceller and accommodates the IP telephone apparatus. In the control method, the private branch exchange apparatus has gain information for adding gain to each public line to be accommodated, and after establishing a voice path, the gain information of the public line is searched and the echo is canceled by the echo canceller. Outputting to the gateway device for use in erasure; receiving the gain information in the gateway device; and adding the received gain information of the line to the signal input from the IP telephone device, the echo canceller The difference between the echo path output signal and the pseudo echo And a step signal is adaptively controlled prediction function to minimize. The gain information is transmitted through a control channel.

  According to the present invention, a private branch exchange system such as a key telephone apparatus having a gain addition function and a gateway apparatus equipped with an echo canceller that is connected to this system and cancels an echo from a public line are added by the private branch exchange system. The gain is transmitted to the gateway device, and this gateway device takes this gain into account and performs echo cancellation. Thereby, the echo suppression effect of the echo canceller in the IP call can be improved.

  As described above, according to the present invention, the gain of the main device is transmitted to the gateway device, and this echo is added to cancel the echo. As a result, the echo suppression amount can be improved and the expected voice level can be obtained by the gateway device without changing the prediction signal expected by the echo canceller.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  Referring to FIG. 1 (a), an IP telephone system including a main apparatus 1 of a button telephone system, a gateway apparatus 2 having an echo canceller (not shown), and an IP telephone apparatus 3 as an embodiment of the present invention. It is shown. The IP telephone device 3 includes a microphone 31 and a speaker 32 for calling. The main apparatus 1 and the gateway apparatus 2 are connected by an ISDN line, but the connection method is not limited to the ISDN line, and for example, E & M or a unique interface may be used.

  In FIG. 1A, the main device 1 is connected to the gateway device 2. The gateway device 2 accommodates the IP telephone device 3 via a local area network (LAN), converts a voice signal from the main device 1 into an IP packet, and vice versa. The main device 1 and the gateway device 2 each have a gain control unit (not shown).

  FIG. 1B is a diagram showing the configuration of the main part of the main device 1. Referring to FIG. 1B, the main device 1 includes a time switch 11, a gain control unit 12, a VoIP gateway signal transmission unit 13, a public line interface unit 14, a button telephone extension interface unit 15, and an ISDN interface unit. 16 and a control circuit 10 for controlling the above-described units. The time switch 11 is connected to the public line interface unit 14 and the ISDN interface unit 16 to form a speech path. The public line interface unit 14 holds gain information of each public line and performs an interface with each public line accommodated therein. The ISDN interface unit 16 is connected to the gateway device. The gain control unit 12 searches the public line gain information of the public line interface unit 14 when the main apparatus 1 establishes a call path according to an instruction from the control circuit 10. The VoIP gateway gain signal sending unit 13 sends the gain information of the public line received from the gain control unit 12 to the gateway device 2 for use in echo cancellation in the gateway device 2.

  FIG. 1C is a diagram illustrating the configuration of the gateway device 2. Referring to FIG. 1C, the gateway device 2 includes a network interface unit 21, a voice compression unit 22, a voice expansion unit 23, a gain control unit 24, an echo canceller 25, and a main device interface unit 26. Prepare. The main apparatus interface unit 26 has a voice channel and a control channel connected to the control circuit 10 of the main apparatus 1, and interfaces with the time switch 11 via the ISDN interface unit 16 of the main apparatus 1 by these channels. The echo canceller 25 is connected to the main apparatus interface unit 26 and is used to cancel the echo of the audio signal from the time switch 11 of the main apparatus 1.

  The gain control unit 24 is connected to the echo canceller 25 and receives gain information indicating a gain to be added corresponding to the public line accommodated in the main device 1 from the main device interface unit 16. The gain control unit 24 causes the echo canceller 25 to perform echo cancellation by adding the gain information of the line to the signal input from the LAN line. The audio compression unit 22 compresses the output whose gain is controlled by the gain control unit 24. The network interface unit 25 converts the output of the voice compression unit 22 into packet data and outputs it to the LAN line according to the IP protocol. The voice decompression unit 23 decompresses a voice signal input from the LAN line via the network interface unit 21 according to the IP protocol.

  FIG. 4 is a diagram showing an example of the gain information format. In FIG. 4, Total Length is the length of the message, Resource No. Is the channel number, length is the message length from Octet4, Tx-Gain is the gain in the gateway device → main device direction (for example, −14 to +14 dB), and Rx-Gain is the gain in the main device → gateway device direction (for example, −14 to +14 dB) respectively. Tx-Gain / Rx-Gain indicates the value of the gain (gain) in the main apparatus 1 and is added to the public line interface unit 14 (FIG. 1) of the main apparatus 1.

  FIG. 2A is a diagram for explaining the configuration of the echo canceller. In FIG. 2A, the echo canceller estimates an echo path from the input signal x (n) input from the microphone 31 (FIG. 1), and estimates a pseudo echo e ′ (n). The echo canceller adaptively applies the prediction function of the echo predictor 251 so that the difference signal y (n) between the output signal e (n) of the actual echo path and the pseudo echo e ′ (n) is minimized. To control.

  FIG. 2B is a diagram showing a gain information table, and shows an example of gain information of each channel. The gain information from the main apparatus 1 is stored in the gain information table 252 of the echo canceller 25 via the main apparatus interface unit 26 of the gateway apparatus 2. The echo canceller 25 performs echo cancellation with an echo cancellation algorithm that takes into account the values in the gain information table 252. When gain information is sent from the main apparatus 1 to the gateway apparatus 2, gain information of each channel shown in FIG. 2B is set in the gain information table 252.

  For example, in the echo predictor 251, if Tx / Rx = 4/4 dB, the gain information table 252 is referred to the pseudo echo e ′ (n) calculated by calculation, and the value of Tx / Rx is set to e ′ (n). = 4 + 4 + e ′ (n) is added to minimize the difference signal y (n). That is, Tx-Gain is a gain in the gateway device → main device direction, but is added to the level of the transmission side to the public side by the main device 1 as a response to the public line, and Rx-Gain is the main gain. Device → gateway device direction gain, which is added by the main device 1 as a receiving side gain from the public side, and this Tx / Rx is added to the pseudo echo of e ′ (n) and y (n) Cancel the echo.

  In the above-described embodiment, the gateway device 2 and the main device 1 are separated from each other. However, the gateway device 2 may be included in the main device 1.

  Next, the operation of the best mode for carrying out the present invention will be described with reference to FIGS.

  When voice input is performed from the microphone 31 toward the public line, the IP telephone apparatus 3 performs necessary processing such as sampling processing on the input voice signal. As a result of the processing, packet data is transmitted from the IP telephone device 3 to the gateway device 2. Each packet data is assembled in order in the network interface unit 21 of the gateway device 2, and the voice decompression unit 23 performs voice decompression. The expanded audio data is selectively added with the gain as the gateway device 2 by the gain control unit 24, and is transmitted as PCM data to the ISDN interface unit 16 of the main device 1 through the main device interface unit 26. The converted PCM data gives gain information of the line currently connected by the time switch 11 to the PCM data, and the voice is output to the public line via the public line interface unit 14 based on an instruction from the control circuit 10. . That is, the gain control unit 24 of the gateway device 2 selects a gain based on the above-described gain information (not shown) of the gateway device 2. The main apparatus 1 side has “Tx-Gain / Rx-Gain” in the public line interface unit 14 (FIG. 1), and these gains are added to output the voice to the public line. Gain information is added to PCM data and output to the public line.

  Here, it is generally known that a phenomenon called echo occurs. The PCM signal output from the public line interface unit 14 is input as voice in the direction from the main apparatus 1 to the gateway apparatus 2 due to impedance mismatch (2-wire to 4-wire conversion) of the public line. The voice in this case is output as voice from the speaker 32 of the IP telephone device 3 via the main device 1 and the gateway device 2 and forms a loop. A transmission delay occurs in a path (echo path) that generates this echo. That is, the caller of the IP telephone device 3 listens to the sound input from the microphone 31 through the speaker 32 with a slight delay. Therefore, the echo canceller 25 is used in the gateway device 2.

  In the conventional system, the pseudo echo e ′ (n) predicted by the echo canceller 25 is calculated from the input signal x (n). If gain is added by the main apparatus 1, the output signal e (n) of the echo path is greatly out of sync with the pseudo echo e ′ (n), and it becomes difficult to minimize the differential signal y (n). . That is, when the difference signal y (n) is large, the audio signal from the microphone 31 of the IP telephone apparatus 3 can be heard from the speaker 32.

  In order to solve this, the gain information of the main device 1 is sent to the gateway device 2, and the received gain information is taken into account when the gateway device 2 performs echo cancellation. When the voice path connection between the IP telephone apparatus 3 and the public line is established, the main apparatus 1 transmits the gain information of the public line via the VoIP gateway signal transmission unit 13. The gateway device 2 calculates and predicts a pseudo echo from the received gain information of the public line and the input signal x (n) from the microphone.

  The echo canceller 25 predicts a signal returning as an echo from the received signal based on signal processing, and cancels the echo by adding the predicted signal to the transmitted signal. Therefore, if gain is added by a device that does not have an echo canceller (main device 1 in this case), a signal different from the signal predicted by the echo canceller 25 is input to the echo canceller, and the echo cannot be erased correctly. On the other hand, when gain is added by the gateway device 2, the gain added by the gateway device 2 by the echo canceller 25 can be known. Therefore, the prediction signal can also be performed with gain added.

  If the gain is lowered, it is natural that the return echo also decreases. Conversely, if the gain is increased, the return echo is large. Lowering the gain also lowers the original audio signal gain. In the present invention, the gain information in the system (in this case, the main apparatus 1) in which the echo canceller is not mounted is sent to the gateway apparatus 2 in which the echo canceller is mounted, and the gain information is taken into account, that is, in the pseudo echo. In addition, the echo is canceled and a gain is added by the gateway device 2 to maintain a required audio signal gain.

  FIG. 3 is a diagram for explaining the operation of the embodiment of the present invention. The public line interface unit of the main apparatus has gain information for adding gain to each accommodated line. After establishing the voice path, the main device searches for gain information of the public line and transmits the gain information to the gateway device. The gateway apparatus receives this gain information, and calculates a pseudo echo e ′ (n) in the echo predictor of the echo canceller from this information and the input signal x (n). That is, the gain information added by the key telephone system is transmitted to the gateway device, and this gateway device takes this gain information into account to perform the echo canceling operation. The above-described transmission of gain information uses a control channel of an interface to which the main apparatus and the gateway apparatus are connected.

  As described above, according to the present invention, it is possible to obtain an expected prediction signal without changing the voice predicted by the echo canceller of the gateway device in the main device. Therefore, the maximum echo suppression amount can be obtained by the gateway device. In this embodiment, an example using a button telephone system has been described, but the present invention can also be applied to a PBX system.

(A) is a figure for demonstrating embodiment of the IP telephone system of this invention. (B) is a figure which shows the structure of the principal part of the key telephone system main apparatus in (a). (C) is a figure which shows the structure of the gateway apparatus in (a). (A) is a figure for demonstrating the structure of an echo canceller. (B) is a figure which shows a gain information table. It is a figure for demonstrating the operation | movement of embodiment of this invention. FIG. 4 is a diagram showing an example of the gain information format.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main apparatus 2 Gateway apparatus 3 IP telephone apparatus 10 Control circuit 11 Time switch 12, 24 Gain control part 13 VoIP gateway gain signal transmission part 14 Public line interface part 15 Button telephone extension interface part 16 ISDN interface part 21 Network interface part 22 Voice Compression unit 23 Speech expansion unit 25 Echo canceller 26 Main device interface unit 31 Microphone 32 Speaker 251 Echo predictor 252 Gain information table

Claims (11)

A private branch exchange that is connected to a gateway apparatus having an echo canceller to constitute an IP telephone system, wherein the private branch exchange sends an echo information gain indicating a gain to be added corresponding to a public line to be accommodated by the echo canceller. A private branch exchange apparatus comprising first gain control means for outputting to the gateway device for use in erasure. A gateway apparatus having an echo canceller that is connected to a private branch exchange and constitutes an IP telephone system, the gateway apparatus being added corresponding to a public line accommodated in the private branch exchange that is output from the private branch exchange A gateway apparatus comprising: second gain control means for receiving gain information indicating a gain, and performing echo cancellation by the echo canceller in consideration of the gain information. An IP telephone system comprising the private branch exchange apparatus according to claim 1 and the gateway apparatus according to claim 2. An IP telephone system comprising the gateway apparatus according to claim 2 inside the private branch exchange apparatus according to claim 1. 2. The private branch exchange apparatus according to claim 1, wherein the private branch exchange apparatus is a key telephone apparatus. A private branch exchange connected to a gateway device having an echo canceller to constitute an IP telephone system, wherein the private branch exchange has an interface with each public line having gain information for adding gain to each public line. A first line interface unit for performing communication, a second line interface unit connected to the gateway device, a time division switch connected to the first and second line interface units to form a communication path, and the first First gain control means for retrieving the gain information of the public line when the line interface unit is captured and outputting it to the gateway device for use in echo cancellation by the echo canceller via the second line interface unit And a private branch exchange apparatus comprising: a control circuit that controls each of the units. A gateway device connected to a private branch exchange to constitute an IP telephone system, wherein the gateway device is connected to a third line interface unit for interfacing with the private branch exchange device and the third line interface unit. An echo canceller for canceling echo, and gain information indicating gain added corresponding to a public line accommodated in the private branch exchange connected to the echo canceller and output from the private branch exchange, and the gain information The second gain control means for performing echo cancellation by the echo canceller, a voice compression section for voice compression of the output gain-controlled by the second gain control means, and the output of the voice compression section A network interface unit for outputting to a LAN line, and the network interface from the LAN line The input audio signals through the scan unit gateway apparatus characterized by comprising an audio decompression unit for speech stretching. The echo canceller has a gain information table for storing gain information received from the private branch exchange, calculates a pseudo echo by adding the gain information of the line to a signal input from the LAN line, The gateway apparatus according to claim 7, wherein the prediction function is adaptively controlled so that a difference signal between a path output signal and the pseudo echo is minimized. An IP telephone system comprising the private branch exchange apparatus according to claim 6 and the gateway apparatus according to any one of claims 7 and 8. A voice quality control method in an IP telephone system for controlling voice quality in an IP telephone system comprising a private branch exchange apparatus and a gateway apparatus having an echo canceller and accommodating an IP telephone apparatus, wherein each of the private branch exchange apparatuses accommodates the voice quality control method. The gain information for adding gain to the public line, and after the establishment of the voice path, the gain information of the public line is retrieved and output to the gateway device for use in echo cancellation by the echo canceller; and the gateway The apparatus receives the gain information, and adds the received gain information of the line to the signal input from the IP telephone apparatus, calculates a pseudo echo in the echo canceller, and outputs an echo path output signal and the pseudo echo Adaptively controlling the prediction function to minimize the difference signal from Voice Quality control method in the IP telephone system and having a. 11. The voice quality control method in an IP telephone system according to claim 10, wherein the gain information is transmitted through a control channel.

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