JP2002300281A - Method for selecting speech coding in speech communication system - Google Patents

Abstract

(57) [Problem] An object of the present invention is to provide a voice communication system capable of performing voice communication with the best sound quality within a range possible for an end user and efficiently using a communication network. I do. SOLUTION: A head end holds encoding definition information in which a plurality of specific dial information and a plurality of encoding methods are associated with each other, and when a telephone starts voice communication, one of a plurality of specific dial information is started. Dialing one specific dial information, selecting a specific method of encoding voice by referring to the encoding definition information held based on the dialed specific dial information, and setting the selected encoding method to a cable. Used for modems and voice gateways.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system (Cable Television system), in which a cable modem with a telephone connected to a subscriber's home is installed and a VoIP (Voice over IP (Int)) is installed.
TECHNICAL FIELD The present invention relates to a voice communication system for performing voice communication between telephones using technology (e.g., Internet Protocol), and more particularly to selecting a voice coding method in these voice communication systems.

[0002]

2. Description of the Related Art Conventionally, in a CATV system, a cable modem having a telephone connected to a subscriber's home is installed to provide voice communication between telephones provided at the subscriber's home, or a telephone at the subscriber's home and a public telephone exchange network. It has been proposed to realize a voice communication system for performing voice communication with a telephone connected to the Internet using VoIP technology.

[0003] In such a voice communication system, compression is performed to transfer voice. When encoding the speech, a specific encoding method fixed by the system is adopted as the encoding method.

Therefore, when voice communication is performed by a telephone connected to a cable modem at a subscriber's house in a CATV system, voice exchange control is performed even if the cable modem is configured to use a plurality of encoding methods. For this purpose, speech is encoded using a specific encoding method preset in a server installed in the CATV system.

[0005] When voice communication is performed between a telephone connected to a cable modem at a subscriber's home and a telephone connected to a public telephone exchange network in a CATV system,
Even if the voice gateway installed in the cable modem and the CATV system and connected to the public switched telephone network is configured to be able to use a plurality of encoding methods, it is installed in the CATV system for performing voice exchange control. The audio is encoded using a specific encoding method preset in the server.

[0006]

As described above, in the conventional voice communication system, as the voice coding method used by the cable modem or the voice gateway, the coding method set in the server that performs the switching control is fixed. It has been adopted. As a coding method to be set in the server that performs the switching control, the communication operator that operates the voice communication system selects a coding method with a high compression rate in consideration of the time when the traffic of the communication network reaches a peak. ing.

If this high compression rate coding method is adopted,
The quality of the voice heard by the user on the telephone is degraded.
Therefore, if sound quality is emphasized, it is preferable to adopt encoding with a low compression ratio as much as possible.

For this reason, when making a call with a long-distance telephone (telephone terminal) or a mobile phone in which the sound quality tends to be degraded even in a call in which the voice is not compressed, the end user who performs the voice communication has a voice quality. It is desired that a low compression rate or an uncompressed coding method can be freely selected as a coding method used by the cable modem to improve (communication quality). However, at present, it is not possible to select a coding method. The call was made with sound quality voice.

In addition, since the coding method with a high compression rate is used, the load on the communication network is low, and even if a low compression rate or uncompressed speech coding method does not cause any problem, the high compression rate is used. Calls must be made using low-quality voice, and communication networks have not been used efficiently. The reason that this communication network is not used efficiently is that the bandwidth of the communication network is set assuming the worst case when the load on the communication network is high and the traffic is congested. This is because the use of the rate coding method increases the unused bandwidth, and the communication network is not efficiently used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and enables an end user to perform voice communication with the best possible sound quality and to efficiently use a communication network. It is an object to provide a communication system.

[0011]

A head end having a server for controlling telephone exchange, a cable modem connected to the head end, and a telephone connected to the cable modem are connected to each other. In a voice communication system configured to encode audio information from a telephone set and transmit the encoded audio information to the head end, and to decode the encoded audio information transmitted from the head end into audio information, the head end may include a plurality of specific information. It holds encoding definition information in which dial information and a plurality of encoding methods are associated with each other, and dials one of a plurality of specific dial information when starting voice communication with a telephone. Select a specific method to encode audio with reference to the encoding definition information held based on the specific dial information The selected encoding method to instruct the cable modem and characterized in that encoded on the basis of the attached specified audio information inputted from the telephone coding method.

With this configuration, the end user can perform voice communication with the best possible sound quality and can use the communication network efficiently.

[0013]

FIG. 1 is a diagram showing a cable modem voice communication system according to an embodiment of the present invention. The cable modem voice communication system 10 includes a head end (HE) 13 in a CATV system,
Cable modem (CM) 21, 2 installed at subscriber's house
4. Coaxial cable 20 for connecting the head end 13 and the cable modem. The cable modem 21 has a telephone 22 and a personal computer (P
C) 23 are connected. Similarly, cable modem 2
4 includes a telephone 25 and a personal computer (P
C) 26 is connected. In the head end 13,
A LAN (Local Area Network) 19 is provided. The LAN 19 includes a voice gateway 14, a server 15, and a cable modem terminator (CMTS: Cable
Modem Terminal System) 17 is connected.

The voice gateway 14 is connected to a public switched telephone network (PSTN) via a line 18.
telephone (22 or 25) provided at each subscriber's house in the voice communication system 10 and a telephone (voice) between the telephone 12 connected to the public telephone exchange network 11. It has a function to perform protocol conversion for communication. Cable modem termination device 17
Is also called a headend modem (HM),
It is connected to the coaxial cable 20 and has a function of controlling a band on the coaxial cable when performing data communication between the cable modem and the head end. Therefore, the cable modems 21 and 24 and the cable modem termination device 17 are configured to communicate via the coaxial cable 20.

The server computer 15 (hereinafter, referred to as a server) has a function of switching a line for a telephone call (voice communication). The server 15 connects a magnetic disk device 16 as an external storage device. The telephone numbers of telephones connected to each cable modem in the cable modem voice communication system 10 are registered in the external storage device 16.

The operation of the thus configured cable modem voice communication system 10 will be described with reference to the flowchart shown in FIG. First, a process until the telephone set 22 connected to the cable modem 21 connects to the telephone set 12 connected to the public switched telephone network 11 will be described.

When the receiver of the telephone set 22 goes off-hook (S1), the cable modem 21 detects this off-hook (S2). When the cable modem 21 detects the off-hook of the telephone 22, the cable modem termination device 17
Request a channel for voice communication to
3). Upon receiving this channel request, the cable modem terminating device 17 allocates an available channel to the cable modem 21 and notifies the cable modem 21 of the request source (S4). The cable modem 21 having received the notification of the channel sends a dial tone to prompt the telephone set 22 for dial input (S).
5). Here, after confirming that the dial tone is generated from the receiver of the telephone set 22, the user inputs the telephone number of the telephone set 12 connected to the public telephone exchange network 11 (S6).

When the cable modem 21 detects the dial signal output from the telephone 22 in response to the input of the telephone number (S7), it transmits the telephone number of the destination to the server 15 via the cable modem terminating device 17 (S7). S
8). The server 15 determines whether the telephone to which the received telephone number is given is a telephone connected to the cable modem voice communication system 10 or not.
The determination is made by referring to the telephone number list registered in No. 6. If the telephone to which the destination telephone number is assigned is not a telephone connected to the cable modem voice communication system 10, the server 15 requests the voice gateway 14 to make a call to the public switched telephone network 11 (S9). ). The voice gateway 14 makes a call request to the public switched telephone network 11 via the line 18 according to the request from the server 15.

The public telephone exchange network 11 that has accepted the outgoing call request
Starts calling the destination telephone 12 (A10) and transmits a call acceptance signal to the voice gateway 14 (S11). The voice gateway 14 that has received the call acceptance signal notifies the server 15 of the call acceptance (S1).
2) Then, the server 15 notifies the transmission origin cable modem 21 of the reception of the transmission (S13). As a result, the cable modem 21 starts transmitting a ringback tone to the calling telephone set 22 (S14).
Here, when the destination telephone 12 connected to the public telephone exchange network 11 answers (S15), the public telephone exchange network 11 responds.
Transmits a response signal to the voice gateway 14 (S16).

Voice gateway 14 receiving the response signal
Notifies the server 15 of the response (S17), and the server 15 notifies the response to the transmission source cable modem 21 (S18). At this time, the encoding method used at the time of voice communication is specified from the server 15 to the cable modem 21 and the voice gateway 14. The details of the setting of the specified encoding method will be described later. This allows
The voice from the calling telephone 22 is transmitted to the cable modem 21.
And the coaxial cable 2
0, sent to the voice gateway 14 via the cable modem termination device 17 and the LAN 19,
After being decrypted in step 4, it is transmitted to the telephone 12 of the other party through the public telephone exchange network 11.

On the other hand, the voice from the telephone set 12 is also transmitted to the voice gateway 14 via the public switched telephone network 11, and the voice gateway 14 encodes the voice according to the specified coding method, and then the LAN 19 and the cable modem termination device. 1
7. The data is transmitted to the cable modem 21 via the coaxial cable 20. In the cable modem 21, the received voice data is decoded by the specified coding method, and then transmitted to the telephone set 22. According to the procedure described above, a telephone call between the telephone set 22 connected to the cable modem 21 and the telephone set 12 connected to the public switched telephone network 11 is started (S19).
FIG. 3 shows a sequence diagram of the above procedure.

Next, the operation of the process for selecting and specifying the audio coding method will be described. Here, it is assumed that the cable modems 21 and 24 and the voice gateway 14 support the following three methods as encoding methods.

As a speech coding method, ITU-T (Int
ernational Telecommunication Union Telecommunicati
on Standardization Sector (International Telecommunication Union Telecommunications Standardization Sector). 711, G.R. 726, G.R. 728 shall be used. G. FIG. 711 is 64 kbps
(64 kiro bit per second) PCM (Pulse Code
Moduration: pulse code modulation) A speech coding method.
G. FIG. 726 is an AD of 40, 32, 24, 16 kbps
PCM (Adaptive Differential Pulse Cod Moduratio
n: adaptive differential pulse code modulation) This is a speech coding method.
In the present invention, G. As 726, an encoding method of 32 kbps is adopted. G. FIG. 728 is 16kbps CELP
(Code Exited Linear Predication Compression) A speech coding method.

In the magnetic disk device 15 connected to the server 15, as shown in FIG. 4, dial information for selecting and instructing an encoding method is registered as an encoding method registration table. In the coding method registration table shown in FIG. 4, the coding method "G.711 (64 kbps)" is registered corresponding to the dial information "* 1". Similarly, the encoding method “G.726 (32 kbps)” is registered corresponding to the dial information “* 2”. Further, an encoding method “G.728 (16 kbps)” is registered corresponding to the dial information “* 3”. In addition, as a default (default), G.264 is used as an encoding method. 729A (8 kbps) is registered. As for the correspondence between the dial information and the encoding method, "*
When dialing "1", the server 15 determines that "G.711 (64 kbps)" has been selected and designated as the encoding system by referring to the encoding system registration table shown in FIG. It should be noted that the telephone 12 connected to the public telephone exchange network 11 has a telephone number "06-1234-".
5678 ". Similarly, cable modem 2
The telephone 25 connected to the telephone number 4 has the telephone number “03”.
−1234-5678 ”. If the input of the dial information of the number specifying the encoding method is omitted, the G.264 registered as the encoding method by default. 729A (8 kbps) is determined to be specified.

Here, the telephone set 22 connected to the cable modem 21 is transmitted from the telephone set 25 connected to the cable modem 24 to the telephone set 25 as G. The operation in the case of selecting / instructing 711 and making a call to make a telephone call (voice communication) will be described. When the receiver of the telephone set 22 goes off-hook, the cable modem 21 detects this and requests the channel to be used for the cable modem terminating device 17 to secure the channel to be used and to transmit a dial tone to the telephone set 22. . Here, first, dial information "* 1" is dialed in to select and instruct an encoding method from the telephone set 22. Then, the phone number of the called party "0
3-1234-5678 ". Then, the cable modem 21 transmits the dial information “* 10312345678” inputted from the telephone 22 to the server 1.
5 is transmitted. The server 15 recognizes that an instruction to select an encoding method has been given since the dial information received from the cable modem 21 has "*" at the beginning. In response to this recognition, the server 15 refers to the encoding method registration table registered in the magnetic disk device 16 based on the dial information “* 1”, and encodes the encoding method “* 1” corresponding to the dial information “* 1”. G.711 ".

Subsequently, the server 15 refers to the telephone number registered in the magnetic disk device 16 based on the dial information “0312345678”, and uses the telephone 25 connected to the cable modem 24 as the destination telephone. It recognizes that there is, and sends an incoming message to the cable modem 24. At this time, the server 15 transmits a call acceptance message to the cable modem 21 of the call origin. Upon receiving the call acceptance message, the cable modem 15 sends a ringback tone to the telephone set 22. Next, the cable modem 24 that has received the incoming message causes the telephone 25 to be called to ring. Then, when the receiver of the telephone set 25 is picked up and off-hook and the telephone set 25 answers, the cable modem 24 transmits the response message to the response message server 15. On server 15,
When a response message is received from the destination cable modem 24, the encoding system (G.711) and packet size (data in the packet) necessary for voice communication are transmitted to the transmission source cable modem 21 and the destination cable modem 24. Size) and information about the other party.
As a result, voice communication is performed between the source cable modem 21 and the destination cable modem 24 using the encoding method designated by the server 15, and a telephone call between the telephones 22 and 25 is possible. Become.

Next, the telephone set 22 connected to the cable modem 21 and the telephone set 12 connected to the public switched telephone network 11
However, a case will be described in which G.726 is selected as the encoding method and a call is made. When the receiver of the telephone set 22 goes off-hook, the cable modem 21 detects this and requests a channel to be used by the cable modem terminating device 17 to secure the channel, and sends a dial tone to the telephone set 22. I do. Here, first, dial information “* 2” for selecting an encoding method from the telephone set 22 and the telephone number “06-1234-567” of the destination telephone set 12.
Dial "8". The cable modem 21 transmits the dial information “* 20612345” input from the telephone 22.
678 ”to the server 15. Server 1
In step S5, based on the dial information received from the cable modem 21, "G.726" is selected as the encoding method used for voice communication, and
2 judges that it is connected to the public switched telephone network 11 and transmits an outgoing message including the telephone number “06-1234-5678” to the voice gateway 14. At this time, the server 15 transmits a call acceptance message to the cable modem 21 of the call origin. When the cable modem 21 receives the call acceptance message, it sends out a ringback tone to the telephone set 22.

Next, the voice gateway 14 which has received the outgoing message performs a calling process to the public telephone exchange network 11, and the public telephone exchange network 11 makes the telephone number "06-1234".
5678 "to make the called telephone 12 ring. Then, when the telephone 12 picks up the receiver and goes off-hook to respond, the public switched telephone network 11 transmits a response signal to the voice gateway 14. The voice gateway 14 that has received the response signal transmits a response message to the server 15. Upon receiving the response message, the server 15 instructs the transmission source cable modem 21 and the voice gateway 14 to perform an encoding method (G.7) necessary for voice communication.
28) Notify the packet size, information about the other party, etc. As a result, voice communication is performed between the transmission source cable modem 21 and the voice gateway 14 using the encoding method designated by the server 15, and a telephone call between the telephone set 22 and the telephone set 12 becomes possible.

Next, a description will be given of a process for changing the speech coding method for each communication time zone. The manager of the voice communication system registers the encoding system management table for each time period shown in FIG. 5 in the magnetic disk device 16 connected to the server 15. In the encoding method management table for each time period shown in FIG. 5, the encoding method used for each time period is set and registered as follows. Between 8:00 a.m. and 7:00 p.m. on a weekday, the encoding method G. 728 is registered to be used. 7 weekday afternoon
In the time period from time till 8:00 am of the next day, the encoding method G. 729 is registered. Further, in the time zone of 8:00 am to 7:00 pm on Saturday and Sunday, the encoding method G. 729 is registered. In the time zone from 7:00 pm on Saturday and Sunday to 8:00 am on the following day, the encoding method G. 729 is registered.

Here, the telephone set 22 connected to the cable modem 21 and the telephone set 1 connected to the public switched telephone network 11
A case will be described in which a call is made at 1 pm on Monday. When the receiver of the telephone set 22 is picked up and goes off-hook, and the cable modem 21 detects this, the cable modem 21 requests the channel to be used by the cable modem terminating device 17 to secure the channel and dials the telephone set 22. Transmits a tone (Dial Tone). Here, when the telephone number “06-1234-5678” of the destination telephone set 12 is dialed in from the telephone set 22, the cable modem 21 transmits the dial information input from the telephone set 22 to the server 15. In the server 15, based on the dial information received from the cable modem 21, the called telephone 12 is switched to the public telephone exchange network 11.
Is determined to be connected to the telephone number "06-1234".
-5678 "to the voice gateway 14. At this time, the server 15 transmits a call acceptance message to the cable modem 21 of the call origin. When the cable modem 21 receives the call acceptance message, the cable modem 21 issues a ringback tone to the telephone 22.
e) is sent.

Next, the voice gateway 14 that has received the outgoing message performs an outgoing call processing to the public switched telephone network 11. The public switched telephone network 11 has a telephone number "06-1234".
5678 ", the called telephone 12 is made to ring. When the telephone 12 picks up the telephone and answers, the public switched telephone network 11 sends a response signal to the voice gateway 14. The voice gateway 14 that has received the response signal transmits a response message to the server 15. Upon receiving the response message, the server 15 selects an encoding method (G.728) necessary for voice communication by referring to the encoding method management table based on the current time, and information on the packet size, the communication partner, and the like. At the same time, it notifies the transmission source cable modem 21 and the voice gateway 14.
As a result, voice communication is performed between the transmission source cable modem 21 and the voice gateway 14 using the encoding method specified by the server 15, and the telephones 22 and
Call is possible. Similarly, when the call is made at 1:00 pm on Saturday, by referring to the voice coding method management table, G.100 is set as the voice coding method. 729 is selected.

Next, a process for selecting an encoding method from past network traffic will be described.
The server 15 is provided with a function of collecting statistical information such as the number of calls per unit time (for example, the number of calls per hour) and the holding time (the number of calls per call). For example, when the bandwidth that can be used for voice communication is 1 Mbps, G.264 is used as the encoding method. 711 (64 kbps) can be used and 8 calls can be made at the same time. In addition, G. 728 (16 kb
ps), 4 times 32 calls, G. 729 (8 kb
In ps), 64 calls, which is eight times as large, are possible.

Here, as statistics information collected by the server 15, the number of calls from 9 pm to 10 pm on Monday is up to 20 at the same time.
In case of a call, the available bandwidth is 1Mbps
Therefore, the server 15 uses G.264 as the audio encoding method.
728 (16 kbps) or G.728. 729 (8 kbp
s). Also, from 5:00 am on Monday
If the number of calls during 6:00 am is a maximum of 5 simultaneous calls,
Similarly, the server 15 has the G. 711 (64 kbps) can be selected. The server 15 selects a speech coding method based on the statistical information (traffic for each past time period) thus collected.

[0034]

According to the present invention, voice communication can be performed with the best sound quality within the range possible for the end user, and the communication network can be used efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cable modem voice communication system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for explaining the operation of the cable modem voice communication system 10.

FIG. 3 is a sequence diagram for explaining a procedure for starting a telephone call between the telephone set 22 and the telephone set 12;

FIG. 4 is a diagram showing an encoding system registration table in which dial information for selecting and instructing an encoding system is registered.

FIG. 5 is a diagram illustrating an encoding system management table.

[Explanation of symbols]

 10 Cable modem voice communication system 11 Public telephone network 14 Voice gateway 15 Server 21 Cable modem 22 Telephone

Continued on the front page F-term (reference)

Claims (7)

[Claims] 1. A head end having a server for performing telephone exchange control, a cable modem connected to the head end, and a telephone connected to the cable modem, wherein the cable modem is connected to the telephone. A voice communication system configured to encode audio information from and transmit the encoded audio information to the head end, and to decode the encoded audio information transmitted from the head end into audio information. Holding encoding definition information in which the specific dial information and the plurality of encoding methods are associated with each other, and when starting voice communication with the telephone, dialing one specific dial information of the plurality of specific dial information; The voice is encoded by referring to the held encoding definition information based on the dialed specific dial information. Selecting a specific method, instructing the cable modem on the selected encoding method, and encoding the voice information input from the connected telephone based on the specified encoding method. A method for selecting speech coding in a speech communication system. 2. The head end is connected to a public telephone network and encodes an audio signal from the public telephone network, outputs the encoded signal to the cable modem, and decodes encoded audio information from the cable modem. A voice gateway for outputting to the public telephone network, and when starting voice communication from the telephone to a telephone connected to the public telephone network, the selected specific encoding method is transmitted through the cable. And instructing the modem and the voice gateway, the cable modem encodes voice information input from the connected telephone based on the indicated encoding method, and the voice gateway encodes the code output from the cable modem. Decoding the converted speech information based on a designated encoding method and outputting the decoded information to the public telephone network. The method for selecting speech coding in the speech communication system according to claim 1. 3. A head end having a server for performing telephone exchange control, a cable modem connected to the head end, and a telephone connected to the cable modem, wherein the cable modem is connected to the telephone. A voice communication system configured to encode audio information from and transmit the encoded audio information to the head end, and to decode the encoded audio information transmitted from the head end into audio information. Holds encoding definition information in which a plurality of specific time zones specified by a combination of time zones and a plurality of encoding methods are associated with each other. A specific encoding method for encoding audio with reference to the encoding definition information on the basis of the selected encoding method. Selection method of speech coding in voice communication system for causing encoded based instructs the modem to the connected to the specified audio information inputted from the telephone coding method. 4. The head end is connected to a public telephone network and encodes an audio signal from the public telephone network, outputs the encoded signal to the cable modem, and decodes encoded audio information from the cable modem. A voice gateway for outputting to the public telephone network, and when starting voice communication from the telephone to a telephone connected to the public telephone network, the selected encoding method is defined as the cable modem. Instructing the voice gateway,
The cable modem encodes voice information input from the connected telephone based on a specified coding method, and the voice gateway is instructed by the coded voice information output from the cable modem. 4. The method according to claim 3, wherein decoding is performed based on the coding method and the decoded data is output to the public telephone network. 5. A head end having a server for performing telephone exchange control, a cable modem connected to the head end, and a telephone connected to the cable modem, wherein the cable modem is connected to the telephone. A voice communication system configured to encode audio information from the head end and transmit the encoded audio information to the head end, and to decode the encoded audio information transmitted from the head end into audio information. Measure information, select a specific encoding method from a plurality of types of encoding methods based on the measured load information when starting voice communication in the telephone, based on the selected encoding method The cable modem encodes audio information input from the connected telephone based on the selected encoding method. Selection method of speech coding in speech communication system characterized by and. 6. The head end is connected to a public telephone network and encodes an audio signal from the public telephone network, outputs the encoded audio signal to the cable modem, and decodes encoded audio information from the cable modem. A voice gateway for outputting to the public telephone network, and when starting voice communication from the telephone to a telephone connected to the public telephone network, the selected encoding method is defined as the cable modem. Instructing the voice gateway,
The cable modem encodes voice information input from the connected telephone based on a specified coding method, and the voice gateway is instructed by the coded voice information output from the cable modem. 6. The method according to claim 5, wherein decoding is performed on the basis of the coding method and the decoded data is output to the public telephone network. 7. The head end is connected to a public telephone network and encodes an audio signal from the public telephone network, outputs the encoded signal to the cable modem, and decodes encoded audio information from the cable modem. Having an audio gateway that outputs to the public telephone network, when the audio gateway receives audio information from the public telephone network, it receives the audio information from the public telephone network based on the selected encoding method. The method for selecting speech coding in a speech communication system according to claim 5, wherein the speech information is encoded and output.