JP6930345B2 - IP phone device - Google Patents

Description

The present invention relates to a call path switching technique for switching an IP call path during a call to another call path according to deterioration of call quality.

When a voice call is made via an IP communication path formed in an IP network such as the Internet, the call quality of the voice call changes greatly depending on the communication status of the IP network. For example, when traffic is concentrated on an IP network and a failure such as packet delay, packet fluctuation, or packet loss occurs, communication errors can be recovered by taking measures such as packet retransmission in general data communication. However, in the case of a voice call, since the communication is performed in real time, the influence of these failures immediately appears as noise or a momentary interruption, and the call quality deteriorates.

Conventionally, as a technology for coping with such deterioration of call quality in an IP call path, another technology whose call quality is guaranteed in the call path during a call in response to a call path switching request from a user during a call. A technique for dynamically switching to a telephone path has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-069159

However, in such a conventional technology, since it is necessary for the user to notice the deterioration of the call quality and perform the switching operation, there is a problem that the IP call path cannot be automatically switched according to the deterioration of the call quality. there were.

Further, a method of switching the IP call path by using the call quality obtained by RTCP (Real-time Transport Control Protocol) is also conceivable. RTCP is a protocol that controls a session for sending and receiving data by RTP (Real-time Transport Protocol), and by periodically transmitting RTCP packets in the data stream to be controlled, transmission delay time and packet loss. It has a function to monitor communication quality such as rate and output it as a report.

However, since communication quality can be obtained only at intervals of about 5 seconds with RTCP, it takes a certain amount of time from the occurrence of deterioration of call quality to the switching of IP call paths, which causes discomfort to the user during that time. It will be. Also. The communication quality obtained by RTCP is the transmission delay time and the packet loss rate, and cannot be obtained for the fluctuation time. Therefore, when the call quality deteriorates due to packet fluctuation, the IP call path cannot be switched, which causes discomfort to the user.

The present invention is intended to solve such a problem, and an object of the present invention is to provide a call path switching technique capable of significantly reducing discomfort given to a user due to deterioration of call quality in an IP call path.

In order to achieve such an object, the IP telephone device according to the present invention is an IP telephone device that makes an IP call with a partner telephone device via an IP communication path formed in an IP network, and is the IP telephone device. During a call with the other party's telephone device via the call path, the call quality measurement unit that measures the call quality of the IP call path and the call quality measured by the call quality measurement unit are deteriorated from the predetermined evaluation criteria. In this case, after forming an alternative call path with the other party telephone device via an alternative network that can obtain a call quality equal to or higher than the evaluation standard, the call path with the other party telephone device is changed from the IP call path to the above. A call control unit for switching to an alternative call path is provided, and the call quality measurement unit accesses the time synchronization server connected to the IP network prior to the measurement of the call quality to access the time synchronization server connected to the IP network to the standard time of the time synchronization server. After time-synchronizing the local time of the device, the transmission time included in the RTP packet transmitted from the other party telephone device at regular intervals, the reception time based on the local time when the RTP packet is received, and the sequence of the RTP packet. The transmission delay time, fluctuation time, and packet loss rate are measured as the call quality based on the number.

Further, the IP telephone equipment according to the present invention, the call control unit, wherein when the call the speech quality measured by the quality measurement unit is degraded below a predetermined evaluation criterion, the other party telephone via said alternative network A switching instruction voice signal is transmitted via the alternative telephone path by calling the device, forming the alternative call path according to the response of the other party telephone device, and instructing the switch path switching from the IP call path to the alternative call path. After transmitting to the other party telephone device, the communication path with the other party telephone device is switched from the IP communication path to the alternative communication path.

Further, the IP telephone equipment according to the present invention, the call control unit, during a call with the other party telephone apparatus via the IP communication path, a call from the other party telephone apparatus via said alternative network In this case, after forming the alternative communication path with the other party telephone device in response to the call, the other party telephone responds to the switching instruction voice signal from the other party telephone device via the alternative communication path. The communication path to and from the device is switched from the IP communication path to the alternative communication path.

According to the present invention, it is possible to measure a new call quality related to an IP call path in a shorter measurement time as compared with RTCP. Therefore, it is possible to shorten the time required from the occurrence of deterioration of call quality to the switching of the IP call path. Further, since the fluctuation time that cannot be obtained by RTCP is also measured, it is possible to switch from the IP call path to the alternative call path even when the call quality deteriorates due to the packet fluctuation. Therefore, it is possible to significantly reduce the discomfort given to the user due to the deterioration of the call quality on the IP communication path.

It is a block diagram which shows the structure of the IP telephone apparatus. It is a sequence diagram which shows the call path switching operation. It is explanatory drawing which shows the call path formation state in the call path switching operation.

Next, an embodiment of the present invention will be described with reference to the drawings.
[IP phone device]
First, the IP telephone device 10 according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an IP telephone device.
The IP telephone device 10 is composed of an IP telephone control device such as a main unit of a business phone and a PBX device of a PBX system as a whole, and a plurality of extension telephone terminals 20 accommodating an extension via a communication line L can be connected to the IP network NW1 or the IP network NW1 or. This is a device that is exchanged and connected to the alternative network NW2.

The IP network NW1 is a telephone network composed of an IP network such as the Internet and providing a voice call service via an IP communication path 31 based on RTP (Real-time Transport Protocol).
The alternative network NW2 consists of an existing telephone network such as an optical telephone network, ISDN (Integrated Services Digital Network), and PSTN (Public Switched Telephone Network), and is via an alternative telephone path 32 that can obtain a call quality equal to or higher than a certain evaluation standard. It is a telephone network that provides a voice call service.

The time synchronization server 30 is composed of an existing NTP (Network Time Protocol) server as a whole, and has a function of providing a time synchronization service with standard time by transmitting a time synchronization packet via the IP network NW1. doing.
In the following, the case where the IP telephone device 10 is an IP telephone control device that interchangeably connects a plurality of extension telephone terminals 20 to the IP network NW1 or the alternative network NW2 will be described as an example, but the present invention is not limited thereto. For example, it may be a single telephone terminal that makes an IP call.

As shown in FIG. 1, the IP telephone device 10 has, as main functional units, a network I / F unit 11, an extension I / F unit 12, a switch 13, a storage unit 14, a call quality measurement unit 15, and a call control unit. It has 16. Among these functional units, the call quality measurement unit 15 and the call control unit 16 are realized by the cooperation of the CPU and the program of the storage unit 14.

The network I / F unit 11 has a function of transmitting and receiving messages and signals according to the respective call control protocols between the IP network NW1 and the alternative network NW2, and voice data and voice data via the IP network NW1 or the alternative network NW2. It has a function to send and receive voice signals.
The extension I / F unit 12 has a function of transmitting and receiving control messages and voice data to and from a plurality of extension telephone terminals 20 accommodated in an extension via a communication line L.

The switch 13 has a function of exchanging and connecting a communication path between the network I / F unit 11 and the extension I / F unit 12 in response to an instruction from the call control unit 16.
The storage unit 14 is composed of a storage device such as a hard disk or a semiconductor memory, and has a function of storing various control data and programs used in the call control process and the call path switching process in the IP telephone device 10.

When the call quality measuring unit 15 forms the IP telephone path 31 via the IP network NW1, the call quality measuring unit 15 accesses the time synchronization server 30 via the network I / F unit 11 and the IP network NW1 to match the standard time of the time synchronization server 30. Transmission delay time and fluctuation based on the function of synchronizing the time with the local time of the own device and the RTP packet for transmitting and receiving voice data to and from the IP telephone device 10 of the other party via the IP communication path 31. It has a function of measuring the call quality related to the IP communication path 31 including the time and the packet loss rate.

Specifically, the call quality measuring unit 15 measures the transmission delay time on the IP communication path 31 from the difference between the transmission time included in the RTP packet and the reception time of the RTP packet obtained by the own device. Further, the fluctuation time in the IP communication path 31 is measured based on the variation in the transmission delay time. Further, the packet loss rate in the IP communication path 31 is measured based on the sequence number included in the RTP packet.

There are various evaluation criteria for call quality related to IP communication paths, but in general, the following evaluation criteria examples may be used.
Transmission delay time: 150 ms or less Fluctuation time: 40 ms or less Packet loss rate: 3% or less

Generally, 50 to 100 RTP packets are required to stably measure the call quality related to the IP communication path. Since the transmission interval of the RTP packet is usually 20 ms, the call quality related to the IP call path can be stably measured in a measurement time of about 1 to 2 seconds. Therefore, since the communication quality measurement interval obtained by RTCP is 5 seconds, the communication quality measurement time can be reduced to less than half. Further, when the RTP packet whose call quality is to be measured is slid one packet at a time, a new call quality can be obtained every 20 ms, and deterioration of the call quality can be detected at shorter intervals. can.

The call control unit 16 relates to the extension telephone terminal 20 by transmitting and receiving messages and signals corresponding to the respective call control protocols with the IP network NW1 or the alternative network NW2 via the network I / F unit 11. If deterioration is found in the call quality of the IP call path 31 based on the function of performing call control such as outgoing call, incoming call, and voice call and the measurement result of the call quality measurement unit 15, the alternative network from the IP call path 31 It has a function of switching the call path to the new alternative call path 32 formed by the NW2.

Specifically, when the call quality measured by the call quality measuring unit 15 deteriorates from the predetermined evaluation standard, the call control unit 16 calls the other party's telephone device via the alternative network NW2 and responds to the other party's telephone device. A function of forming an alternative telephone path 32 accordingly, and a switching instruction voice signal such as a DTMF signal instructing the switching of the call path from the IP call path 31 to the alternative call path 32 are transmitted to the other party telephone device via the alternative call path 32. After transmission, it has a function of switching the communication path with the other party telephone device from the IP communication path 31 to the alternative communication path 32.

Further, when the call control unit 16 receives a call from the other party's telephone device via the alternative network NW2 during a call with the other party's telephone device via the IP communication path 31, the call control unit 16 responds to the call with the other party's telephone device. In response to the function of forming an alternative telephone path 32 between the telephones and the switching instruction voice signal from the other party's telephone device via the alternative telephone path 32, the call path to and from the other party's telephone device is changed from the IP call path 31 to the alternative call path. It has a function to switch to 32.

[Operation of the present embodiment]
Next, the operation of the IP telephone device 10 according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a sequence diagram showing a call path switching operation. FIG. 3 is an explanatory diagram showing a call path forming state in the call path switching operation.
Here, a case where deterioration of call quality is detected during an IP call between the IP telephone device 10A and the IP telephone device 10B via the IP communication path 31 of the IP network NW1 will be described as an example.

Note that FIG. 2 shows a case where the IP telephone device 10B measures the call quality of the IP telephone path 31 based on the RTP packet transmitted from the IP telephone device 10A to the IP telephone device 10B. It is not limited. For example, the call quality of the IP communication path 31 may be measured by the IP telephone device 10A based on the RTP packet transmitted from the IP telephone device 10B to the IP telephone device 10A, and the IP telephone device 10A and the IP telephone device 10B may be measured. The call quality of the IP communication path 31 may be measured on both sides.

When the IP telephone device 10B responds to the call from the IP telephone device 10A (step 100) (step 101), the IP telephone devices 10A and 10B access the time synchronization server 30 and synchronize the time (step 100). 102, 103). As a result, the local time of the IP telephone devices 10A and 10B is synchronized with the standard time of the time synchronization server 30, and the transmission time and the reception time of the RTP packet can be calculated and processed without any time difference, so that accurate call quality can be obtained. can.

After that, as shown in FIG. 3A, an IP communication path 31 is formed in the IP network NW1 (step 104), and an IP call is started between the IP telephone devices 10A and 10B via the IP communication path 31. (Step 105).
As a result, in order to transfer the voice data from the IP telephone device 10A to the IP telephone device 10B, RTP packets are transmitted from the IP telephone device 10A via the IP communication path 31 at regular intervals (for example, 20 ms intervals) (step). 106).

The IP telephone device 10B measures the call quality based on the RTP packet received from the IP telephone device 10A (step 107), and compares the obtained call quality of the IP telephone path 31 with a preset evaluation standard. By doing so, it is determined whether or not the call quality of the IP call path 31 is deteriorated (step 108).
Here, when it is determined that there is no deterioration (step 108: NO), the IP telephone device 10B continues to measure the call quality related to the IP communication path 31 (step 109).

On the other hand, when it is determined that there is deterioration (step 108: YES), the IP telephone device 10B selects the alternative network NW2 (step 110). At this time, when there are a plurality of alternative network NW2s, for example, the alternative network NW2 is selected in ascending order of call cost.
After that, the IP telephone device 10B calls the IP telephone device 10A via the selected alternative network NW2 (step 111), and responds to the response from the IP telephone device 10A (step 112), FIG. 3 (b). As shown in the above, an alternative telephone path 32 is formed in the alternative network NW2 (step 113).

After that, the IP telephone device 10B transmits a switching signal using a voice signal such as a DTMF signal to the IP telephone device 10A via the alternative communication path 32 (step 114), and between the IP telephone devices 10A and 10B. The call path during a call is switched from the IP call path 31 to the alternative call path 32 (step 115).
As a result, an alternative call is started between the IP telephone devices 10A and 10B via the alternative communication path 32 (step 116), and then the IP communication path 31 is disconnected as shown in FIG. 3 (c) (step 116). Step 117).

[Effect of this embodiment]
As described above, in the present embodiment, the call quality measurement unit 15 accesses the time synchronization server 30 connected to the IP network NW1 prior to the measurement of the call quality, and the standard time of the time synchronization server 30 and the own device are used. After synchronizing the local time, the transmission time included in the RTP packet transmitted from the other party's telephone device at regular intervals, the reception time based on the local time of the own device that received the RTP packet, and the sequence number of the RTP packet are set. Based on this, the transmission delay time, the fluctuation time, and the packet loss rate are measured as the call quality of the IP communication path 31.

As a result, new call quality related to the IP communication path 31 can be measured in a shorter measurement time as compared with RTCP. Therefore, the time required from the occurrence of deterioration of call quality to the switching of the IP call path 31 can be shortened. Further, since the fluctuation time that cannot be obtained by RTCP is also measured, it is possible to switch from the IP communication path 31 to the alternative communication path 32 even when the call quality deteriorates due to the packet fluctuation. Therefore, it is possible to significantly reduce the discomfort given to the user due to the deterioration of the call quality on the IP communication path 31.

Further, in the present embodiment, when the call control unit 16 calls the other party telephone device via the alternative network NW2 when the call quality measured by the call quality measurement unit 15 deteriorates from the predetermined evaluation standard, the other party telephone device is called. After forming an alternative telephone path 32 according to the response of , The communication path with the other party telephone device may be switched from the IP communication path 31 to the alternative communication path 32.

Further, in the present embodiment, when the call control unit 16 receives a call from the other party's telephone device via the alternative network NW2 during a call with the other party's telephone device via the IP communication path 31, the call control unit 16 answers the call. After forming an alternative call path 32 with the other party telephone device, an IP call is made on the call path with the other party telephone device in response to a switching instruction voice signal from the other party telephone device via the alternative call path 32. You may switch from the road 31 to the alternative telephone road 32.

As a result, when the communication path to the other party's telephone device is switched from the IP communication path 31 to the alternative communication path 32 due to the deterioration of the call quality in the IP communication path 31, the existing IP call control protocol is not changed. The call path can be smoothly switched without depending on the call control protocol of the alternative network NW2. Therefore, the present invention can be easily applied to any IP network or alternative network, and extremely high versatility can be obtained.

[Extension of Embodiment]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made within the scope of the present invention in the configuration and details of the present invention.

10, 10A, 10B ... IP telephone device, 11 ... network I / F unit, 12 ... extension I / F unit, 13 ... switch, 14 ... storage unit, 15 ... call quality measurement unit, 16 ... call control unit, 20 ... Extension telephone terminal, 30 ... time synchronization server, 31 ... IP telephone path, 32 ... alternative telephone path, NW1 ... IP network, NW2 ... alternative network.

Claims (3)

An IP telephone device that makes an IP call with the other party's telephone device via an IP communication path formed in the IP network.
A call quality measuring unit that measures the call quality of the IP telephone path during a call with the other party's telephone device via the IP telephone path, and a call quality measuring unit.
When the call quality measured by the call quality measuring unit deteriorates from a predetermined evaluation standard, an alternative call path is formed with the other party telephone device via an alternative network that can obtain a call quality equal to or higher than the evaluation standard. After that, a call control unit for switching the call path to the other party telephone device from the IP call path to the alternative call path is provided.
Prior to measuring the call quality, the call quality measuring unit accesses the time synchronization server connected to the IP network, synchronizes the standard time of the time synchronization server with the local time of the own device, and then synchronizes the time with the other party. Transmission delay as the call quality based on the transmission time included in the RTP packet transmitted from the telephone device at regular intervals, the reception time based on the local time when the RTP packet was received, and the sequence number of the RTP packet. Measuring time, fluctuation time, and packet loss rate ,
When the call quality measured by the call quality measuring unit deteriorates from a predetermined evaluation standard, the call control unit calls the other party's telephone device via the alternative network, and responds to the response of the other party's telephone device. After forming the alternative call path and transmitting a switching instruction voice signal instructing the change path switching from the IP call path to the alternative call path to the other party telephone device via the alternative call path, the other party telephone An IP telephone device, characterized in that the communication path to and from the device is switched from the IP communication path to the alternative communication path. An IP telephone device that makes an IP call with the other party's telephone device via an IP communication path formed in the IP network.
A call quality measuring unit that measures the call quality of the IP telephone path during a call with the other party's telephone device via the IP telephone path, and a call quality measuring unit.
When the call quality measured by the call quality measuring unit deteriorates from a predetermined evaluation standard, an alternative call path is formed with the other party telephone device via an alternative network that can obtain a call quality equal to or higher than the evaluation standard. After that, a call control unit for switching the call path to the other party telephone device from the IP call path to the alternative call path is provided.
Prior to measuring the call quality, the call quality measuring unit accesses the time synchronization server connected to the IP network, synchronizes the standard time of the time synchronization server with the local time of the own device, and then synchronizes the time with the other party. Transmission delay as the call quality based on the transmission time included in the RTP packet transmitted from the telephone device at regular intervals, the reception time based on the local time when the RTP packet was received, and the sequence number of the RTP packet. Measuring time, fluctuation time, and packet loss rate ,
When the call control unit receives a call from the other party's telephone device via the alternative network during a call with the other party's telephone device via the IP communication path, the call control unit responds to the call and the other party's telephone device. After forming the alternative call path with the other party, the call path to and from the other party telephone device is changed from the IP call path in response to the switching instruction voice signal from the other party telephone device via the alternative call path. An IP telephone device characterized by switching to the alternative telephone path. In the IP telephone device according to claim 1,
When the call control unit receives a call from the other party's telephone device via the alternative network during a call with the other party's telephone device via the IP communication path, the call control unit responds to the call and the other party's telephone device. After forming the alternative call path with the other party, the call path to and from the other party telephone device is changed from the IP call path in response to the switching instruction voice signal from the other party telephone device via the alternative call path. Switching to the alternative call path
An IP telephone device characterized by.

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