JP3376940B2 - Voice data multiplex transmission equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the case of packetizing low bit rate audio information obtained by using, for example, a voice coding technique or a silence compression technique which does not transfer a silent portion, or these low bit rate voices. Information and 6
4kbit / s system information (existing telephone voice, FAX data, mo
dem data and the like). It can also be applied to an ATM transmission device that multiplexes these packets on a virtual channel (VC) in one asynchronous transfer mode (ATM).

[0002]

2. Description of the Related Art A method of transferring voice data compressed by a low bit rate encoding / decoding technique and a silent compression technique by a packet (including ATM, IP, frame relay, etc.) has been considered.

This method is an important technique for effectively utilizing the finite band of the transmission line. FIG. 2 is an example of such a technique, which is a method of packetizing compressed voice data in a short packet length, collecting a plurality of these channels and multiplexing them into an ATM cell. 64 used in existing telephone networks
Compared to kbit / s voice data, the packet storage time (which is called packetization delay) in the case of compressed voice data increases in proportion to the compression ratio. Therefore, in this example, the compressed voice data is temporarily stored in a packet having a short packet length to reduce the packetization delay, and the packet is multiplexed in one cell together with the packets of other channels generated at about the same time. By doing so, the cell formation delay can be shortened. That is, it is possible to reduce the total delay by reducing both the packetization and the cellization delay.

On the other hand, in the existing telephone network, similarly to voice communication, modulated data communication such as FAX communication and modem communication is in high demand. Therefore, if the modulated data is also transferred by the packet transfer method like the compressed audio data, the communication service that the user receives is not limited to the audio, and the cost of communication can be reduced by sharing the transmission path. You can

However, although voice compression is performed without degrading voice quality, there are many codecs (CODEC) that cannot correctly encode and decode modulated data. Therefore, when performing modulated data communication, the CODEC processing is bypassed. However, it is necessary to devise such as directly converting the modulated data into packets.

Therefore, as shown in FIG. 3, as a conventional technique, a technique has been developed in which a frequency detector for detecting a tone signal or a carrier frequency of modulated data communication is installed and a CODEC is bypassed when these frequencies are detected. It had been. The feature of the present technology is that, when the data input from the 64 kbit / s data lines of multiple channels is voice data, it is compressed by the codec (CODEC), passes through the multiple channel voice data lines, and is packetized by the packet processing unit. . On the other hand, in the case of modulated data, the tone detector detects the tone signal and carrier frequency, and instructs the switch to switch the transmission path to the multi-channel modulated data line. That is, the modulation data reaches the packet processing unit through the multi-channel modulation data line and is packetized.

[0007]

However, the conventional voice data multiplex transmission device has the following problems.

(1) Modulated data has a higher bit rate than compressed audio data and originally has a small packetization delay. Therefore, it may not be necessary to packetize with a shortened packet length for compressed voice data. Rather, it is more effective to increase the packet length to reduce the ratio of packet headers to the total amount of transfer data and improve transfer efficiency. Become. However, in the conventional voice data multiplex transmission device, it is impossible to distinguish the voice data and the modulated data in the packet processing unit and packetize them with a packet length suitable for each data.

(2) The bandwidth increases when the compressed voice data is changed to the modulated data. For example, 8 kbit / s CO
When DEC is used, the increase in bandwidth is 8 times. The conventional voice data multiplex transmission device does not have a function of managing the maximum number of simultaneously modulated data transferable channels and the number of channels during modulation data transfer. As a result, when the number of modulated data channels being transferred exceeds the maximum number of simultaneously modulated data transferable channels, there is a problem that the upper limit of the bandwidth of the transmission path is exceeded and the communication quality of other channels is deteriorated. Therefore, when the number of modulated data channels being transferred has reached the maximum number of simultaneously modulated data transferable channels, it is necessary to have a function of suppressing the transfer of newly generated modulated data.

(3) The compression ratio and compression processing algorithm are
It depends on the type of CODEC. Depending on the type of CODEC, a tone signal of modulated data may not be encoded and decoded correctly. When the above CODEC is used in a voice data multiplex transmission device in which only the tone signal of the modulation data or the carrier frequency is detected as an opportunity to change from the compressed voice data mode to the modulation data mode, the following problems occur, for example. To do.

FIG. 4 shows the sequence of the CED signal, which is a 2100 Hz tone signal transmitted from the called FAX terminal at the start of FAX communication.
The CED signal can be detected by the frequency detector in the voice data multiplex transmission device on the called side. However, if the CODECs on the called side and the calling side are then respectively compressed and expanded, the CED signal cannot be detected by the frequency detector of the voice data multiplex transmission device on the calling side. If the called side voice data multiplex transmission device switches to the modulation data mode during transmission of the CED signal, the CODE
Even if the C processing can be bypassed, the signal just before the switching may be missing, and the signal may have a length insufficient to be recognized as a CED signal. As a result, the calling side voice data multiplex transmission device may not be able to switch from the compressed voice data mode to the modulated data mode. That is, normal FAX communication may not be possible.

(4) For the purpose of reducing the number of detectors, as shown in FIG. 5, a voice data multiplex transmission apparatus for detecting a tone signal or carrier frequency of modulated data only in the upstream direction can be considered. In the FAX communication, one-way communication from the FAX calling side (sending side) is performed while the FAX image data for one page is being transferred after the call setting is established. Therefore, when performing FAX communication using the voice data multiplex transmission device of FIG. 5, the called side (reception side) cannot detect the carrier frequency while receiving the image data.
As a result, during the communication of the FAX data, the mode is switched to the compressed voice data mode, and the FAX data cannot be normally transmitted / received.

A voice data multiplex transmission apparatus having a function to solve some of the above problems has not existed until now.

A first object of the present invention is to provide a voice data multiplexing device for packetizing voice data and modulated data with a packet length suitable for each.

A further object of the present invention is to provide a voice data multiplexer for multiplexing within the band of the transmission path.

It is another object of the present invention to provide a voice data multiplexing device that does not hinder FAX communication.

[0017]

The structure of the present invention is shown in FIGS. According to the present invention, each of the above problems is solved by using the following means.

This means will be described with reference to FIG. The present invention provides a frequency detector (1
0) indicates that the frequency detection flag is not detected, the data transferred on the multi-channel 64 kbit / s data line is transferred to the codec (CODEC) (1
4), and transferred on the multi-channel compressed audio data line. When the frequency detection flag indicates detection, the data transferred on the multi-channel 64 kbit / s data line is transferred on the multi-channel modulated data line. This data line switching process is performed by the switching indicator (1
This is carried out by sending a switching instruction from 8) to the switching device (12).

The present invention further comprises a packet length management unit (20) for managing the packet lengths of compressed voice data and modulated data. In the compressed voice data mode, the packet processing unit packetizes the data transferred from the multi-channel compressed voice data line with the packet length for the compressed voice data managed by the packet length management unit,
In the modulation data mode, the data transferred from the multi-channel modulation data line is packetized with the packet length for modulation data. This packet length switching process is performed by sending a switching instruction from the switching indicator to the packet processing unit (16).

By the above means, compressed voice data can be transferred in short packets with emphasis on packetization delay suppression, and modulated data can be transferred with long packets with emphasis on transfer efficiency improvement.

Next, according to the present invention, the switching indicator has a function of managing the maximum number of simultaneously modulated data transferable channels and the number of channels during modulation data transfer. When the switching indicator receives the fact that the frequency detection flag of a certain channel has been newly switched to “detection”, the switching instruction line is sent only when the number of modulation data channels already being transferred is less than the maximum simultaneous modulation data transferable channel number. A data line switching instruction is sent to the switching device and the packet processing unit via.

If the number of modulation data channels that are already being transferred is equal to the maximum number of channels that can simultaneously transfer modulation data, the switching instruction is not sent. As a result, since the channel for newly starting the transfer of the modulated data is still passing through the CODEC, the modulated data communication cannot be established and the automatic disconnection can be performed as the protocol for the modulated data communication.

By the above means, it is possible to comply with the maximum number of simultaneous transfer channels of modulated data communication and prevent the bandwidth of the transmission line from exceeding its upper limit.

Further, in the present invention, the packet processing unit in FIG. 1 has a function of identifying the packet length of a packet sent from the packet transfer line and notifying the switching indicator of the presence or absence of switching. That is, when the packet to be received is a packet for compressed audio data, the packet processing unit notifies the switching instruction device that the compressed audio data is being received through the packet length switching notification line. When the received packet is a modulation data packet, it notifies that modulation data is being received.

The switching indicator issues a data mode switching instruction to the switching device and the packet processing section through the switching instruction line in accordance with the notified data type (compressed voice data or modulated data). Here, the switching processing in the packet processing unit can be performed at the time when the packet length of the packet to be received is switched before receiving the instruction from the switching instruction device. However, like the means for solving the problem 2, the switching indicator has a function of managing the maximum number of simultaneously modulated data transferable channels and the number of channels in which modulated data is being transferred. In the case of preventing, the packet processing unit performs the switching process according to the instruction from the switching indicator.

By the above means, for example, the calling side voice data multiplex transmission device in FAX communication can switch from the compressed voice data mode to the modulated data mode based on the packet length of the packet to be received.

However, when this means is implemented, the following problems are added. Due to the data transmission time between the calling side and the called side voice data multiplex transmission device, there is a difference between the time when the carrier frequency is not detected, in other words, the time when the modulation data mode is switched to the compressed voice data mode. Therefore, as shown in FIG. 6, the voice data multiplex transmission device that first switches to the compressed voice data mode may receive the modulated data packet after the switching. This causes a problem of switching to the FAX data mode again even though the FAX communication is completed.

This problem can be solved by adding the following means. It is assumed that the FAX communication ends, the frequency detection flag becomes undetected, and the switching instruction is transmitted.
In the present means, after the start of the compressed voice data mode, the packet processing unit sends the packet length switching notification even if the packet of the modulation data packet length is received again at least until the time that is twice the transmission time has elapsed. It does not have a function, namely, compressed voice data protection time. As a result, the other voice data multiplex transmission device can also switch to the compressed voice data mode within the protection time, so that the modulated data packet is not received after the protection time. That is, it is possible to prevent an erroneous operation of switching to the modulation data mode again after the completion of the modulation data communication. As an alternative to this means, it is possible to provide the switching indicator with a compressed voice data protection time.

Further, in the present invention, in the modulated data mode, from the time when the carrier frequency is not transferred in the multi-channel 64 kbit / s data line (upstream direction) of FIG.
The frequency detector continues to indicate the frequency detection flag as detection for a time period longer than one page image transfer (undetected timer). Alternatively, as an alternative means, the switching indicator sends the switching instruction with a delay of at least the time corresponding to one page of image data transferred.

In the FAX communication, the carrier frequency for confirming the delivery of the image data is transferred in both the up and down directions every time the transfer of one page is completed. Therefore, the undetected timer can be reset each time. Therefore, by this means, the modulated data mode can be maintained until the FAX communication is completed, and the FAX data can be normally transmitted and received.

As a modification of FIG. 1, the configuration shown in FIG. 7 can be considered. The operation processing contents of each functional unit are the same as those shown in FIG. 1, but the means of FIG.
The point is different from the case of FIG.

The first point is that the switching processing in the switching device is limited to the downward direction, and the processing amount is reduced. In the upstream direction, a bus connection is adopted, and data is always sent to both the CODEC and the multi-channel modulation data lines. The switching processing in the upstream direction is performed only by the packet processing unit, and the data line corresponding to the mode is selected.
Since the packet processing unit also performs the switching processing in FIG. 1, the operation is the same as that of the packet processing unit in FIG. 7. That is, the processing amount of the audio data multiplex transmission apparatus as a whole is reduced by the amount of the processing of the switching unit being reduced.

The second point is that the frequency detector is a switching device and a COD.
It is located between ECs, and frequency detection is performed only in the upstream direction. Since the upstream is bus wiring, the frequency can be detected regardless of whether the mode is compressed audio data or modulated data. By applying this configuration, it is possible to store the frequency detection function in the CODEC, and a reduction in the amount of hardware can be expected.
Further, the number of detectors can be reduced in the same manner as the reason shown in Problem 4 (FIG. 5).

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] Assuming modem communication, an embodiment of the present invention will be described with reference to FIG. The called modem terminal transmits an answer tone signal of 2100 Hz at the start of modem communication. Here, the packet lengths of the compressed voice data packet and the modulated data packet are 13 bytes and 43 bytes including the header length, respectively. Further, these packets are transferred through the ATM transfer line by the ATM cell forming method shown in FIG. The frequency detector is a device capable of detecting the frequencies of the answer tone signal and the carrier wave.

First, the processing at the time of starting the connection of the modem communication will be described. When the setting of the transmission path is established between the calling modem terminal and the called modem terminal, the called modem terminal sends the answer tone signal. Answer tone signal is sent to the voice data multiplex device on the called side
This frequency is detected by (1) and the internal frequency detector (2). The frequency detector outputs "1" to the frequency detection flag line while receiving this frequency (3).
When the instruction switch receives "1" from the frequency detection flag line, it recognizes that modulation data communication has started, increases the number of channels under control of modulated data transfer by one, and sends a switch and packet processing through the switch instruction line. Instruct the department to switch the modem mode (4). As a result, the switch switches the downlink data transmission path from the multi-channel compressed voice data line to the multi-channel modulated data line. Further, the packet processing unit also performs the same switching, and also switches the packet length to be transmitted from 13 bytes to 43 bytes (5).

On the other hand, in the voice data multiplex transmission apparatus on the calling side, when a packet of 43 bytes is received (6), the packet processing unit informs the instruction switching unit through the packet length switching notification line that the modulated data communication is requested. Notify (7).
The instruction switcher increases the number of channels under control of modulated data transfer by 1, and instructs the switcher and the packet processing unit to switch the modulation data mode through the switching instruction line (8). The operations of the switching unit and the packet processing unit according to the switching instruction are the same as in the case of the voice data multiplex transmission device of the modem communication called side.

By the above operation, the voice data multiplex transmission apparatus on both the calling side and the called side is switched from the compressed voice mode to the modulated data mode. After the answer tone signal,
The frequency switches to the carrier frequency, but the frequency detector is still detectable, so the data bypasses the CODEC process and 43 bytes of packetization are maintained.

Next, the processing at the end of the connection of the modem communication will be described. In the voice data multiplex transmission device of the modem communication calling side, when the carrier frequency is not received from the multi-channel 64 kbit / s data line (9), the frequency detector sets the output of the frequency detection flag line to “0” (1
0). The instruction switch is "0" on the frequency detection flag line.
When it receives the message, it recognizes the end of the modulated data communication, reduces the number of channels under control of modulated data transfer by one, and instructs the switching device and the packet processing unit to switch the compressed voice mode through the switching instruction line (8). . As a result, the switcher switches the data transmission path in the downstream direction from the multi-channel modulation data line to the multi-channel compressed voice data line. The packet processing unit also performs the same switching, and the packet length to be transmitted is from 43 bytes to 13 bytes.
Switch to byte (6).

On the other hand, in the voice data multiplex transmission apparatus on the called side as well as on the calling side, the reception of the carrier frequency from the multi-channel 64 kbit / s data line is eliminated (1), and the frequency detection flag line is output from the frequency detector. Became "0"
At the time (3), the instruction switch recognizes that the modulated data communication has ended. Subsequent processing is the same as that of the calling side.

By the above operation, the voice data multiplex transmission apparatus on both the calling side and the called side are switched from the modulation data mode to the compressed voice mode, and thereafter, the data is CODEC.
And is transferred by the 13-byte packet on the ATM transfer line.

[Embodiment 2] Assuming FAX communication, an embodiment of the present invention will be described. In this example, the called FAX terminal is 2
Consider a case where the tone signal CED of 100 Hz is transmitted, while the FAX terminal on the calling side does not transmit the tone signal CNG of 1100 Hz. In this case, if the CED signal is replaced with the answer tone signal of the first embodiment, the first embodiment will be described.
FAX communication becomes possible by the same operation as.

In the FAX communication, CNG is used in addition to this example.
Several cases are conceivable, such as a case where only a signal is sent or a case where neither is sent. However, when only the CNG signal is transmitted as the tone signal, the same operation as that of the first embodiment is performed if the frequency detector for 1100 Hz is provided. Further, when neither the CED signal nor the CNG signal is sent out, only the frequency detector for the carrier frequency is sufficient, and the operation is the same as that of the first embodiment.

However, in the case of FAX, one page worth of FAX
Since the one-way communication from the FAX transmission side is performed during the transfer of the image data, the FAX called side voice data multiplex transmission apparatus transfers the FAX image data for one page into the frequency detector. The frequency detection flag can be kept at "1" even during the image data transfer by operating the undetected timer set to the time or longer. Thereby, the FAX mode processing is continued from the start to the end of the FAX communication.

[Embodiment 3] An embodiment of the present invention will be described on the assumption of FAX communication using the apparatus configuration shown in FIG. A feature of the configuration shown in this figure is that it has a frequency detection function in both the up and down directions. In this case, the undetected timer in the frequency detector described in the second embodiment is not necessary, and the FAX called-side voice data multiplex transmission apparatus detects the frequency in the downlink direction during image data transfer to detect the frequency. The flag can be kept at "1". Thereby, the FAX mode processing is continued from the start to the end of the FAX communication.

[Embodiment 4] Using the sequence shown in FIG. 9, an embodiment at the end of FAX will be described. At the end of the FAX communication, the called side of the FAX communication terminal sends an MCF signal and the calling side sends a DCN signal. Depending on these signal time lengths and the signal transmission time between the calling side and called side voice data multiplex transmission devices, a difference in carrier wave non-detection time occurs between the calling side and the called side.

In the case of this example, the called side first enters the undetected state and switches to the compressed voice mode. After switching the compressed voice mode in the voice data multiplex transmission device on the callee side, the packet processing unit of FIG. 1 sends a call from the caller side within a time period longer than the undetected time difference (this time is called a compressed voice data protection time). Even if the packet for modulated data arrives, the packet length switching notification is not sent. As a result, re-switching to the modulated data mode is suppressed.

On the other hand, the calling side voice data multiplex transmission apparatus also
While the compressed voice data protection time has elapsed, the undetected state is entered and the mode is switched to the compressed voice mode. Therefore, after the compressed voice data protection time has elapsed, both the calling side and the called side are switched to the compressed voice mode, and packets for compressed voice data are sent to each other. That is, both the calling side and the called side can normally end the modulated data mode after the FAX communication ends and the voice data protection time elapses.

[0048]

The voice data multiplex transmission apparatus of the present invention enables both compressed voice data and modulated data to be communicated only by the processing for detecting the frequency of the tone signal and the carrier wave in the modulated data communication. Therefore, compared to devices that monitor detailed protocols for modulated data, throughput,
That is, there is an advantage that the amount of hardware can be small.

As a second advantage of the present invention, since packet lengths suitable for communication of compressed voice data and modulated data can be adopted, communication is possible if delay and efficiency are balanced. Further, since the maximum number of simultaneous transfer channels of modulated data communication is observed, it is possible to prevent the bandwidth of the transmission path from exceeding its upper limit and maintain the communication quality.

[Brief description of drawings]

FIG. 1 is a block diagram of a cell assembly device of the present invention.

FIG. 2 is a diagram showing a multi-channel voice packet multiple cell system.

FIG. 3 is a diagram showing a voice data multiplex transmission device capable of transferring modulated data according to a conventional technique.

FIG. 4 is a diagram showing a sequence example in the case where the calling side voice data multiplex transmission device cannot receive a single tone signal in FAX communication.

FIG. 5 is a diagram showing a voice data multiplex transmission device (FAX receiving side) that detects a tone signal of modulated data or a carrier frequency only in the upstream direction.

FIG. 6 is a diagram showing a problem in the case of performing data mode switching depending on a packet length of a received packet.

FIG. 7 is a diagram showing a modified example of FIG.

FIG. 8 is a diagram showing an example of the present invention.

FIG. 9 is a diagram showing a sequence example at the time of FAX termination in the embodiment of the present invention.

[Explanation of symbols]

10 frequency detector 12 switch 14 Codec 16 Packet processing unit 18 Switching indicator 20 Packet length management unit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 2000-165413 (JP, A) JP 6-70049 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 12/56 300

Claims (7)

(57) [Claims] 1. A codec means for compressing or expanding audio data of a plurality of channels, a means for detecting a tone signal of modulated data or a carrier frequency of modulated data in a transmission line, and a detection or non-detection of the tone signal or carrier frequency. And a switching means for processing the transmission / reception data by the codec means when the notification means indicates non-detection and for diverting the transmission / reception data from the codec means when the notification means indicates detection. In the audio data multiplex transmission device having, packet processing means for packetizing arbitrary data including compressed audio data with an arbitrary packet length for each channel; A packet length management means for managing the packet length, the packet length management means comprising: When the notification means indicates undetected, the packet processing means is caused to process with a packet length for compressed voice data, and when the notification means indicates detection, it is caused to process with a packet length for modulated data. A voice data multiplex transmission device. 2. The voice data multiplex transmission apparatus according to claim 1, wherein the maximum number of simultaneously modulated data transferable channels and the number of channels during modulation data transfer are managed, and the notification means of a certain channel is newly detected. When shown, only when the number of modulation data channels that are already being transferred is less than the maximum number of channels that can be simultaneously modulated data transfer, send / receive data is diverted from the above codec, and send data is packetized with a packet length for modulated data. An audio data multiplex transmission apparatus comprising: 3. The voice data multiplex transmission apparatus according to claim 1, wherein when the packet length of a packet to be received changes during transmission / reception of a packet for compressed voice data to a packet length for modulated data, the transmitted / received data is transmitted from the codec. An audio data multiplex transmission device having means for diverting and packetizing transmission data with a packet length for modulated data. 4. The voice data multiplex transmission apparatus according to claim 2, wherein when the packet length of a packet to be received changes during transmission / reception of a packet for compressed voice data to a packet length for modulated data, the modulated data already being transferred. Voice data characterized by having means for diverting transmitted / received data from the above codec and packetizing the transmitted data with a packet length for modulated data only when the number of channels is less than the maximum number of simultaneously modulated data transferable channels Multiplexer. 5. The voice data multiplex transmission apparatus according to claim 1, claim 2, claim 3, or claim 4, wherein after the carrier frequency of the modulated data is undetected,
An audio data multiplex transmission apparatus comprising means for delaying the time at which the notification means indicates undetected time by a previously specified undetected timer time. 6. The voice data multiplex transmission apparatus according to claim 3 or 4, wherein after the notification means indicates undetected, packetization is started with a packet length for compressed voice data, and then specified in advance. Means for maintaining the operation of processing the transmitted / received data by the codec and packetizing with the packet length for the compressed voice data, even if the modulated data packet is received again, until the compressed voice data protection time has passed. An audio data multiplex transmission device comprising: 7. A voice data multiplex transmission apparatus according to claim 1, wherein said means for detecting a tone signal of modulated data or a carrier frequency of modulated data is provided only in one direction.