JPS61157099A - Control signal transmission system of time division multiple communication system - Google Patents

Abstract

PURPOSE:To descriminate a sound signal and a digital call control signal at a receiver side by inserting a prescribed digital call control signal which hardly occurs as the code, row of sound signal to a data pass transmitting a digital sound signal from transmission side to transmit it. CONSTITUTION:When a call is completed and a telephone set 4 becomes on hook state, an O-level signal arrives from a PBX3 through an SS line. Transmission control parts 17a and 17b detect this signal and inserts a disconnect signal to the data pass DP transferring the sound signal till then in order to output it to an opposite device. The code rows are selected so that the regenerating analog output of CODEC for receiver as a disconnect signal becomes a saturated value and signals, for example, repeating '0111' with more than 11 times are outputted. Since these code rows is scarcely possible to generate in an usual call sound signal, the transmission control part 17a at the side of receiver discriminates the arrival of the disconnect signal from call signal and detects surely the arrival of the disconnect signal. After that, it executes the disconnecting processing of outputting the disconnect signal to the PBX3 and returns to a watch and wait state.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to time and minutes? This invention relates to improvements in control signal transmission methods for J multiplex communication systems.

[Technical background of the invention]

In recent years, systems have been developed in which telephone signals are digitally encoded, time-division multiplexed, and transmitted, and thereby communications can be made between telephones. FIG. 6 shows an example of its configuration, in which 1 is a time division multiplexing device connected via a high-speed communication line 2, 3 is a private branch exchange [J (PBX), 1
．． It shows a telephone connected to the PBX3.

The time division multiplexing device 1 includes, for example, as shown in FIG. 7, audio interfaces 11a and 11b for transmission and reception that time division multiplex and reproduce telephone signals, and transmits multiplex control information such as transmission rate designation information. It is composed of a multiplexing control section 12 and a main control section 13 that controls the operation of each of the audio interfaces 11a, 11b and the multiplexing control section 12. By allocating telephone signals and multiplex control information to predetermined logical paths, signal transmission with other devices is performed.

Diagram M8 shows the frame structure of the transmission signal. This transmission signal is composed of one control path CP and a plurality of data paths DP, and the control path CP contains control information between the time division multiplexers. , and a digitized telephone voice signal is inserted into each arbitrary data path DP.

Incidentally, in such a system, in addition to voice signals, it is necessary to transmit call control signals such as calling, answering, and disconnecting calls as telephone signals. Conventionally, transmission of call control signals has been carried out as follows, for example.

In other words, conventional control signal transmission methods include an out-channel method in which the control signal is transmitted on a logical path separate from the data path DP that transmits the audio signal, and an in-channel method in which the control signal is inserted into the data path DP together with the audio signal and transmitted. Out-channel methods include a control path method and a dedicated control signal path method.

In the control path method, as shown in FIG. 9, a call control signal is supplied to the multiplexing controller 12.
It is transmitted by allocating it to the control path CP. Further, in the dedicated control signal path method, a control signal interface 14 is newly provided as shown in FIG. The control signal interface 14 provides a control signal path T.
It is transmitted by assigning it to P.

As the -5 in-channel method, the LSBS Nasr method is known. This method transmits a call control signal by periodically pit-staying the least significant pit (LSB) of a digitized audio signal.

[Problems with background technology]

However, each of these conventional control signal transmission systems has the following drawbacks.

■ In the case of the control path method, all call control signals are sent through the control path CP, so
The control procedure and control contents of the multiplexing control unit 12 are complicated, and the call control signal must be transmitted in a short time due to the response time limit specified by the telephone protocol, so a control unit with a high processing speed is required. is necessary,
Therefore, the multiplexing control section 12 becomes expensive.

■ In the case of a dedicated control signal path method, a new interface for call control signals must be provided, which complicates the device configuration. The number of DPs decreases, leading to a decrease in multiplexing efficiency. This decrease in multiplexing efficiency is caused by the fact that in a system where multiple time division multiplexers are connected to one time division multiplexer, control signal paths for the multiple units must be provided. This becomes a particular problem because the number of data paths diverted to control signal paths increases.

(2) In the case of the LSB pit-stealing method, a synchronization signal is required for pit-stealing, and therefore a synchronization circuit must be provided, which complicates the configuration of the device. In addition, the audio signal is lost due to hit-staying, resulting in deterioration of audio quality. This has a large effect, especially when audio signals are encoded using the ADPCM method and transmitted, and is extremely undesirable.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a control signal transmission method for a time division multiplex communication system that does not cause complication of control or configuration or decrease in multiplexing efficiency, and statistically shows very little deterioration in voice quality. shall be.

[Summary of the invention]

In order to achieve the above object, the present invention inserts a digitized call control signal composed of a predetermined digital code string that is unlikely to occur as a code string of an audio signal from the transmitting side into a data path that transmits the digitized audio signal. The digitized voice signal and the digitized telephone call control signal are discriminated by transmitting the signal and detecting a predetermined digital code string transmitted by the data path on the receiving side.

[Embodiments of the invention]

FIG. 1 shows the configuration of a time division multiplex communication system to which a control signal transmission method according to an embodiment of the present invention is applied. In this figure, the same parts as those in FIGS. 8 to 10 are given the same reference numerals and detailed explanations will be omitted.

Audio interface 15a, 1 of time division multiplexer 10
5b is an ADPCM codec (for example, 32 kbps) that performs time division multiplexing and reproduction of audio signals, respectively.
16a, 16b, transmission control units 17a, 17b, and the codec 16a according to switching instructions from the transmission control unit 17a, 917b.

16b and transmission control units 17a and 17b, respectively, and a switch circuit (SW) 18a that selectively connects them to the data path.
, 18b. Transmission control unit 17b for transmission
The call control signal consisting of the outgoing signal, the dial signal output from the PBX 3, the disconnection signal, and the response signal, and the digitized voice signal multiplexed by the codec 16b are processed as described above according to a predetermined call control procedure for outgoing and incoming calls. It is provided with control means for selectively inserting into the data path OP by switching the switch circuit 18b. In addition, the receiving transmission control unit 17a switches the switch circuit 18a according to preset incoming and outgoing call control procedures to control various call control signals and digitized voice signals that are inserted into the data path DP and arrive from the other party's device. A control means is provided for inputting the respective signals and detecting a call control signal from these signals while distinguishing it from a voice signal.

Next, the control signal transmission system of this embodiment will be explained based on the above configuration. First, in the standby state, the transmission control section 17b for transmission inserts a disconnection state signal into the data path DP and sends it out, as shown in FIG. 2, for example.

Now, if telephone 4 goes off-hook in this state, the PBX
3 outputs a signal of ``1'' level to the SS line. Then, as shown in FIG. 4, the transmission control section 17b switches the switch circuit 18b to
With the SS line set to the side, the level of the SS line is determined in step 4b, and when this ssm reaches 1 level, the process moves to step 4C, where a transmission signal is inserted into the data path DP as shown in Figure 2, and the transmission signal is transmitted to the other party. It is sent to the device.In addition, in the SS line level judgment operation in step 4b above, 5ssii is "
o'', the process moves to step 4d, where the reception transmission control unit 17a monitors the arrival of the transmission signal from the partner device.

After transmitting the outgoing signal in step 4C, the transmission control units 17a and 17b then monitor the arrival of a dial signal in step 4e, and when a dial signal arrives from the PBX 3 in this state, the transmission control unit 17a, 17b performs dialing from the other party's device in step 4f. The receiver monitors the arrival of signals. When the dial receiver detects the arrival of the signal, it determines that the other device can now receive the dial signal, and moves to step 4q.
In this step 4q, a dial signal is inserted into the data path OP as shown in FIG. 2 and sent to the partner device.

When the transmission of the dial signal is finished, the transmission control units 17a and 17b monitor the arrival of a response signal from the partner device in step 4h, and when the response signal arrives, step 4
1, a "1" level signal is sent to the PBX3 via the SR line.Then, in step 4j, the switch circuits 18a and 18b are
The transmission control unit 17. After both a, 17b and codecs 16a, 16b are connected to the data path DP, the communication signal transmission/reception operation in step 4k is started. Here, in the transmission operation of this call signal, the voice signal sent from the telephone 4 via the PBX 3 is ADPCM encoded by the codec 16b, and then the data path DP
The reception operation of the call signal is performed by decoding and reproducing the ADPCM encoded audio signal that has arrived from the other party's device by being inserted into the data path DP, and then transmitting the call signal via the PBX 3! Sent on 14th,
It is done by doing. Control is then performed up to the transition to the talking state, but the procedure for the above control operations is stipulated in advance as a convention between the sending and receiving parties.
The receiving transmission control unit 17a can easily determine that the signal inserted into the data path DP is a call control signal, and there is no particular need to distinguish it from a call signal.

Now, in this state, for example, the telephone 4 ends the call and goes on-hook, which causes the PBX 3 to transmit the message "
o” level signal arrives, the transmission control unit 17a,
17b detects this bill in step 42 and moves to step 4m, where it inserts a disconnection signal into the data path DP that has been transmitting audio signals up to that point and sends it to the other party's device.

By the way, the disconnection signal is sent when the calling PBX detects disconnection, but if a code similar to that present in the voice signal is used as the disconnection signal, the receiving transmission control unit may confuse it with the call signal. It is impossible to detect them separately. Therefore, in this embodiment, a code string is selected as the disconnection signal such that the reproduced analog output of the receiving codec becomes the saturation value of A, DPCM. For example, the '0111' signal, which is a code that positively saturates the reproduced analog output, is
As shown in the figure, the message is sent repeatedly over 11 times. like this'
A code string in which the ``0111'' signal is repeated 11 times or more is almost impossible to occur in a normal telephone voice signal.
7a, the arrival of the disconnection signal can be reliably detected in step 40 by distinguishing it from the call signal. When the arrival of this disconnection signal is detected, the process moves to step 4n, where a disconnection process such as sending a disconnection signal to the PBX 3 is performed, and the standby state is returned. In addition, if a disconnection signal is sent in step 4m, step 4 is performed after sending out this disconnection signal.
The process moves to n and performs cutting processing. In this way, the control (lvJ operation) when making a call is completed.

On the other hand, if there is an incoming call from the other party's device, that is, if an outgoing signal from the other party's device is detected in step 4d,
The transmission control units 17a and 17b perform control according to the procedure shown in FIG. That is, first, in step 5a, the dial receiver inserts a signal into the data path OP and sends it out, and then, in step 5b, the arrival of the dial signal is monitored. When a dial signal arrives, this dial signal is received in step 5C and output to the PBX 3, and when all dial signals have been received, a response signal is inserted into the data path DP in step 5d, so that the calling side device Send to.

After sending out this response signal, the switch circuit 18a is activated in step 5e.

By replacing 18b with 1i7J, the transmission control section 17a.

17b and the codecs 16a and 16b are respectively connected to the data path DP, and then, in step 5f, transmission and reception of call signals are started. Below, the sending and detecting operation of the disconnection signal after the end of the call operation (steps 50 to 5i) will be described.
), the operation when the call is made (step 41
Steps 2 to 4n) are exactly the same.

In this example, the in-channel method is adopted in which the call control signal is inserted into the data path DP together with the voice signal for transmission, and the call control signal is transmitted according to the call control procedure when making and receiving calls. Since it is inserted and transmitted temporally separately from the call signal, it may complicate the control procedure and control content of the multiplex control unit for the control path as in the out-channel method, and it may require a new ink for control signals. This method does not complicate the device in which the face is provided, and since the control signal is not inserted into the audio signal as in the LS8 Steel system, the quality of the audio signal does not deteriorate. Furthermore, among the call control signals, the disconnection signal that is sent mixed with the call signal is composed of a code string that is unlikely to exist in a voice signal, so it is possible to clearly distinguish this disconnection signal from the call signal and detect it. As a result, cutting instructions can be reliably conveyed and cutting can be performed reliably.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the disconnection signal is sent to the transmission control unit 1 on the receiving side.
7a's playback analog output saturates in the positive direction '0111
Although the signal is a continuous code string of 111[1 or more, a code string of 11 or more consecutive '1000' signals that saturate in the negative direction may be used instead. Also these '01
It is almost impossible for an audio signal to have 11 or more consecutive 11" or "1000" signals, and it can be used as is, but it cannot be said that these code strings are completely absent from the audio signal. In order to further increase the certainty of discrimination, the above "0111""signal" 1000
After 10 consecutive "'0110'signals," for example, a preset "0110" signal may be inserted into the 11th signal, and the disconnection signal may be detected by detecting this signal. The column pattern may be of any type as long as it does not exist or is difficult to exist in the voice signal, and if necessary, it may be applied to other call control signals such as outgoing signals and response signals.Others , the control procedure and control contents of the transmission control unit, the encoding method of the audio signal,
The configuration of the audio interface and the like can be modified in various ways without departing from the gist of the present invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, a digitized call control signal composed of a predetermined digital code string that is unlikely to occur in a coded string of an audio signal is sent from the transmitting side to a data path for transmitting a digitized audio signal. By inserting and transmitting the signal and detecting a predetermined digital code string transmitted by the data path on the receiving side, the digitized voice signal and the digitized call control signal are discriminated.
It is possible to provide a control signal transmission method for a time division multiplex communication system that does not cause complication of control or configuration or deterioration of multiplexing efficiency, and statistically shows very little deterioration in voice quality.

[Brief explanation of drawings]

1 to 5 are for explaining a control signal transmission method according to an embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of a time division multiplex communication system to which the method is applied, and FIG. The figure is a schematic diagram showing the state of insertion of control signals and audio signals into the data path according to this method, Figure 3 is a schematic diagram showing the configuration of the disconnection signal, and Figures 4 and 5 are the control procedures of the transmission control unit, respectively. 6 to 10 are flowcharts showing control contents, and are used to explain the conventional technology. FIG. 6 is a schematic configuration diagram of a time division multiplex communication system, and FIG.
The figure is a circuit block diagram showing an example of the configuration of a time division multiplexing device, Figure 8 is a frame configuration diagram of a transmission signal, and Figures 9 and 10 are time division multiplexing systems using different conventional control signal transmission methods. FIG. 1 is a block diagram showing the configuration of a communication system. 3...Private branch exchange (PBX), 4...Telephone, 10
. . . Time division multiplexing device, 12 . . . Multiplexing control unit, 1
3... Main control unit, 15a, 15b... Audio interface, 16a, 16b/ADPCM codec, 17
a, 17b...Transmission control unit, 18a, 18b-...Switch circuit, CP...Control path, DP...
data path. Applicant's representative Patent attorney Takehiko Suzue Figure 6 Figure 7 Figure 8 Figure 9 Figure 1-1 Figure 10

Claims (1)

[Claims] A time division multiplex communication system in which a voice signal and a call control signal are each digitally encoded and time division multiplexed transmitted between communication devices to which a voice communication path is connected, thereby allowing a call to be made via the voice communication path, From the transmitting side, a digitized call control signal composed of a predetermined digital code string that is unlikely to occur as a digital coded string of the audio signal is inserted into the data path for transmitting the digitized audio signal, and the receiving side transmits the above data. Control of a time division multiplex communication system, characterized in that the digitized voice signal and the digitized call control signal are discriminated by detecting the predetermined digital code string transmitted via a path. Signal transmission method.