JP3402406B2 - Telephone system using broadband transmission path - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone system using a coaxial transmission line. In particular, the present invention relates to a system in which a large number of telephones are connected to a coaxial transmission line and a telephone call can be made between the telephones.

[0002]

2. Description of the Related Art MC which has been put to practical use in the field of wireless
An MCA / C system is known as a communication system in which the A (multi-channel access) system is applied to a cable television network. This system divides the data signal transmission frequency band set for the up / down line into frequency slots at equal intervals, and based on the line connection request from the subscriber terminal, the MCA / C center device installed at the headend. Assign communication channels to subscriber terminals to communicate with each other.

[0003]

In the above MCA / C system, the center device constantly monitors an empty channel, and the calling terminal device uses the control channel to call the center device to the call destination terminal device. The request is transmitted, and the center device notifies the caller terminal device and the callee terminal device of the empty channel number using the control channel. Then, a call line is established between the calling source terminal device and the calling destination terminal device using the notified empty channel.

As described above, since the MCA / C system uses one control channel to establish a communication channel, when call requests from a large number of terminal devices overlap, the load on the center increases and congestion occurs. The condition easily occurs.

The present invention has been made to solve the above problems, and an object thereof is to facilitate establishment of a communication channel between telephone devices.

[0006]

The structure of the invention for solving the above-mentioned problems is, firstly, a first control channel for transmitting control data between a center device and a telephone device on a coaxial transmission line. And a second control channel for transmitting control data between the telephone devices and a plurality of call channels for performing voice communication between the telephone devices.

Secondly, the center device stores the channel management means for storing the call channel by controlling whether or not the call channel is empty and the call request control data received from the telephone device via the first control channel. The empty channel notification means for receiving and searching the empty channel from the channel management means and transmitting the number of the empty channel to the calling telephone device.

Thirdly, the telephone device receives a calling means for transmitting call request control data to an arbitrary telephone device via the first control channel and an empty channel number from the first control channel, A call notification means for notifying, by control data, that a call is to be made using the empty channel to the callee telephone device via the two control channels, and a call is made to the caller telephone device by receiving the control data from the second control channel. It is composed of a call channel forming means for establishing a channel and a telephone set for making a call operation, answering an incoming call, and making a call.

A plurality of first control channels and second control channels may be provided. In the first method, each telephone device has a unique second telephone device functioning as a telephone device to be called.
A control channel is assigned. Further, in the second method, the center device manages the idle states of the plurality of second control channels, and notifies the calling telephone device of the number of the idle second control channel.

[0010]

The channel management means of the center device manages the communication channels by storing whether each communication channel on the transmission line is empty. When each telephone device wants to talk to another telephone device, the calling means of the calling telephone device requests the first control channel to talk to any telephone device. The call request control data to that effect is transmitted.

When the center device receives the above-mentioned call request control data from the first control channel, the empty channel notifying means of the center device retrieves the number of the empty channel from the management information of the channel managing means and sets the number as the first number. Notify the calling telephone device through one control channel.

Upon receiving the above-mentioned empty channel number from the first control channel, the calling telephone device immediately releases the first control channel, and the call notification means uses the second control channel to notify the called telephone device. In order to establish a communication channel, control data including the channel number is transmitted.
The call channel forming means of the callee telephone device receiving the control data forms a channel for making a call with the caller telephone device based on the empty channel number of the control data received from the second control channel. To do. After that, a call is made between the call source telephone device and the call destination telephone device using this channel.

The above-mentioned calling operation, incoming call response, and telephone call are carried out by a telephone. As described above, since the management of the empty channels of the plurality of call channels is performed by the center device, the operation of detecting the vacancy of the call channels for each telephone device becomes unnecessary. In order to establish a call channel between telephone devices, control data is communicated using the first control channel and the second control channel, so that the exclusive time of the control channel is shortened, so that a telephone call is made between the telephone devices. The waiting time until the channel is formed is shortened, and the communication efficiency is improved. Further, since multiple calls are executed by frequency multiplexing of the coaxial transmission line, it is easy to install a telephone or expand the telephone.

When a plurality of second control channels are provided,
A unique second control channel is assigned to each call destination telephone device, or a free second control channel is notified from the center device via the first control channel. In this case, when the caller telephone device communicates with the center device through the first control channel, the caller telephone device immediately releases the first control channel and uses the second control channel. A call channel is established between the two. Since there are multiple second control channels, even if the calls overlap,
The waiting time until the call channel is established between the callee telephone devices can be extremely shortened.

[0015]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a diagram showing the overall configuration of this system. A head end 20 is connected to one end of the coaxial cable L. The head end 20, as shown in FIG.
It has a frequency conversion function of shifting the frequency of the upstream low group band to the downstream high group band by Δf. For example, the upstream channel (transmission channel) chS1 is converted to the downstream channel (reception channel) chR1 at the headend 20. With this configuration, bidirectional communication is enabled by the coaxial cable L. As shown in FIG. 6, the channel configuration includes a first control channel (chS1, chR1) and two second control channels (chS2, chR).
2, chS3, chR3) control channels and multiple call channels (c
hS4, chR4, chS5, chR5, ...). In addition, ch
S1 and chR1 are the first control channel of the uplink channel, the first control channel of the downlink channel, (chS2, chS3), (c
hR2, chR3) are the second control channel of the uplink channel and the second control channel of the downlink channel, respectively.

The coaxial cable L can transmit a frequency-multiplexed signal. The coaxial cable L has a bidirectional relay amplifier.
R1 to Rn are provided, and the telephone devices E1 to En are connected at arbitrary positions of the coaxial cable L via branching devices B1 to Bn. The center device 10 is connected to the coaxial cable L. The center device 10 is an RF modem 3
1, serial input / output interface 32, CPU 30,
ROM 33, RAM 34, input / output interface 35,
It is composed of a CRT 36 and a keyboard 37. RF
The modem 31 is a first control channel ch of a predetermined downlink channel.
The R1 high-frequency signal is received and demodulated into call request control data, and control data including an empty channel number of the call channel and data indicating whether or not the called telephone device is busy is used as the first control for the predetermined uplink channel. This is a device that modulates and sends to channel chS1. That is, in the RF modem 31, the reception channel and the transmission channel are set to different frequencies.

The center device 10 also manages the communication channels by storing empty information indicating whether or not a large number of communication channels in the coaxial cable L are empty. A call channel management table storing the empty information of this call channel is formed in the RAM 34. Further, the telephone number of the telephone device in use when the telephone channel is in use is also stored in the telephone channel management table.

On the other hand, the telephone device Ej, as shown in FIG.
RF modem 41, serial input / output interface 42,
It is composed of a CPU 40, a ROM 43, a RAM 44, an input / output interface 45, and a telephone 46. The RF modem 41 uses the first control channel chR1, which is a predetermined downlink channel,
The second downlink channel uniquely assigned to the telephone device Ej
The high frequency signal of the control channel chR2 or chR3 is received and demodulated into control data and response data including number data of the empty channel, respectively. Further, the RF modem 41 modulates the call request control data to the first control channel chS1 of the uplink channel and the call notification control data for establishing the call channel to the second control channel chS1 or chS2 of the uplink channel and sends the modulated data. Further, when a communication channel is established with another telephone device, the RF modem 41 receives a signal from the downlink communication channel and sends a modulated signal to the upstream communication channel. That is, in the RF modem 41, the reception channel and the transmission channel are set to different frequencies, and the set of these two frequencies can be variably set to the first control channel, the second control channel, and the speech channel.

Next, the operation of this system will be described with reference to the flow charts of FIGS. 2 shows the center device 1
It shows a processing procedure of the CPU 30 of 0. When the power of the center device 10 is turned on and when the device is reset, step 100 is executed. At this time, since all the call channels are not used, the call channel management table shown in FIG. 7 formed in the RAM 34 is cleared in step 100.

The RF modem 31 demodulates the high frequency signal of the first control channel chR1 of the downlink channel and outputs the data to the CPU 34 via the serial input / output interface 32. In step 102, data is input from the serial input / output interface 32, and in step 104,
It is determined whether the data is call request control data. If the data is call request control data, in step 106, the call channel management table of FIG. 7 is searched from the telephone number of the call destination telephone device included in the call request control data, and the call destination telephone device is in use. It is determined whether or not.
Then, if the called telephone device is in use, control data indicating that it is in use is output to the RF modem 31 via the serial input / output interface 32 in step 108. As a result, the RF modem 31 modulates the above control data to the first control channel chS1 of the upstream channel and sends it out. Then, the process returns to step 102, and the signal of the first control channel chR1 of the downlink channel is monitored.

When it is determined in step 106 that the called telephone device is not in use, the empty channel number is retrieved from the call channel management table shown in FIG. Then, in step 112, the numbers of the two empty channels are output to the serial input / output interface 32. As a result, the RF modem 31 modulates the control data including the number of the empty channel and the number of the second control channel uniquely assigned to the destination telephone device, and then outputs the modulated control data to the first control channel chS1 of the upstream channel. . Incidentally, the telephone number of the called telephone device and the number of the second control channel uniquely assigned are managed by the center device 10 as a table.

As a result, the number of the empty call channel and the second
The control channel number and the number have been transmitted to the calling telephone device. Then, in step 114, in the call channel management table of the RAM 34, a symbol indicating that the two call channels contacting the call source telephone device are “in use”,
The telephone numbers of the call source telephone device and the call destination telephone device that use the call channel are recorded. And step 1
Returning to 02, the above process is repeated.

If it is determined in step 104 that the data is not call request control data, it is determined in step 116 whether the received data is call completion control data. If it is determined to be call completion control data, in step 118, "empty" is entered in the column of the call channel management table corresponding to the channel number included in the control data.
Is recorded, and the telephone number of the telephone device in use is deleted. Then, the process returns to step 102.

If it is determined in step 116 that the data is not the call completion control data, it means that no control data has been received from the first downlink control channel chR1, and therefore the process returns to step 102. That is, the loop of steps 102, 104, and 116 is repeatedly executed until the control data is received.

Next, a processing procedure of the CPU 40 of the arbitrary telephone device Ej will be described with reference to FIG. The program of FIG. 3 is activated using an off-hook signal when the receiver of the telephone 46 is removed and an on-hook signal when the receiver is placed as an interrupt signal. Further, when an on-hook signal and an off-hook signal are generated during execution of this program, the execution is interrupted and the program is executed from the beginning. In the initial state when the power is turned on, the telephone device Ej needs to wait for a call from another telephone device. Therefore, the transmission channel and the reception channel of the RF modem 41 are uniquely assigned to the device. The second control channel chS2 or chS3 of the acquired upstream channel,
It is set to the second control channel chR2 or chR3 of the downlink channel.

In step 200, a signal is input from the input / output interface 45 and it is determined whether or not the signal is an off-hook signal indicating that the handset of the telephone 46 has been picked up. Subsequently, the telephone 46 outputs a telephone number signal for identifying the telephone device of the call destination. This telephone number signal is converted into binary data at the input / output interface 45. In step 202, the telephone number converted into binary data is read from the input / output interface 45.

Next, in step 204, the frequency of the transmission channel of the RF modem 41 is set to the frequency of the first control channel chS1 of the upstream channel, and the frequency of the reception channel is set to the frequency of the first control channel chR1 of the downstream channel. . Next, in step 206, call request control data including the telephone number of the call destination telephone device is output to the serial input / output interface 42. As a result, the RF modem 41 FSK-modulates the call request control data and outputs it to the first control channel chS1 of the upstream channel. This signal is determined in the center device 10 in step 104 of FIG.

Next, in step 208, the process waits until control data is received from the serial input / output interface 42. That is, the process waits until the data indicating the busy state output to the first control channel or the control data including the number of the idle call channel is received in steps 108 and 112 of FIG. When the control data is input, it is determined in step 210 whether the control data includes data indicating that the control data is being used. If the called telephone device is in use, in step 212, a control signal is output to the input / output interface 45 so that the telephone 46 outputs a busy tone. This allows the caller to hear the busy tone from the handset until the handset is placed.

If it is determined in step 210 that the called telephone is not in use, in step 214,
The frequency of the transmission channel of the RF modem 41 is set to the center device 1
Second control channel chS2 of the upstream channel notified from 0
Alternatively, the frequency of the receiving channel is set to the frequency of chS3 and the frequency of the second control channel chR2 or chR3 of the downlink channel.

Next, in step 216, the call notification control data including the number of the empty call channel received from the center device 10 in step 208 and the telephone number is output to the input / output interface 42. As a result, the call notification control data is the second control channel chS2 of the uplink channel that is uniquely assigned to the call destination telephone device from the RF modem 41.
Alternatively, the signal is modulated to chS3 and output.

Next, in step 218, after waiting for a predetermined time until the call destination telephone device responds to the call notification control data, in step 220, it is determined whether or not the response data is received. This response data is
This data is output from the call destination telephone device in response to the call notification control data output in step 216. If no response data is received, a control signal is output to the input / output interface 45 to cause the telephone 46 to output a ringing tone in step 222 until the response data is received. This allows the caller to hear the ringing tone from the handset of the telephone 46.

The center device 10 has a first call channel for transmitting a voice signal from the call source telephone device to the call destination telephone device, and a second call channel for transmitting a voice signal from the call destination telephone device to the call source telephone device. Channels and two channels (two sets of channels, one set for upstream and one for downlink) are allocated. Therefore, when functioning as a calling telephone device,
In step 224, the transmission channel and the reception channel of the RF modem 41 are set to the upstream channel of the first communication channel and the downstream channel of the second communication channel instructed by the center device 10, respectively, and in step 226, the telephone set 46 and the RF modem 41 are connected via the input / output interface 45. As a result, the call source telephone set and the call destination telephone set are in a callable state. Next, in step 228, the CPU 40 goes into a standby state.

On the other hand, when an on-hook signal generated when the handset is placed is generated, execution is forcibly started from step 200, and after the judgment of step 200, the communication channel is currently being established in step 230. It is determined whether or not. In the case where the call is terminated to a destination telephone set and the handset is placed, or when the handset is placed after the control data including the empty channel is received from the center device 10 in step 208, the Since the device 10 sets the two communication channels as “in use”, it is necessary to notify the center device 10 of the cancellation of the two. For this reason, if it is determined in step 230 that the telephone device is in the process of establishing a call channel, in step 232, in step 204, in order to communicate with the center device 10.
Similarly, the transmission channel and the reception channel of the RF modem 41 are set to the first control channels chS1 and chR1 of the up channel and the down channel, respectively.

Next, in step 234, the call completion control data is output to the RF modem 41 via the serial input / output interface 42. As a result, the center device 10 rewrites the two call channel columns in the call channel management table from "in use" to "empty" in step 114 of FIG. By erasing, the call channel is opened to other telephone devices, and those telephone devices are managed as the unused state.

Further, in step 236, the telephone device is
Ej executes the process of waiting for reception. That is, in step 236, the transmission channel and the reception channel of the RF modem 41 are respectively set to the second control channel chS of the upstream channel.
2, set to the second control channel chR2 of the downlink channel.
Also, if it is determined in step 230 that the telephone channel is not being established, this telephone device must be in the reception waiting state, and therefore the process of step 236 is executed.

In the reception waiting state, it is determined in step 238 whether or not the call notification control data including the telephone number and the call channel number has been received. While the data is not received, the waiting state is set in that step. If it is determined that the call notification control data has been received, the telephone number is analyzed in step 240 to determine whether or not the call is addressed to itself. If not, the process returns to step 238 and the next call notification control data is sent. It will be in a standby state until it is received.

On the other hand, if it is determined that the data is the self-addressed data, the response data is output through the second control channel in step 242. Next, in step 244, the transmission channel and the reception channel of the RF modem 41 are respectively set to the upstream channel of the second communication channel and the downstream channel of the first communication channel designated by the communication notification control data. . In this state, this telephone device functions as a called station. That is, the telephone device of the called station receives the voice signal from the calling telephone device from the downlink channel of the first call channel and sends its own voice signal to the uplink channel of the second call channel. On the other hand, the calling telephone device functions as a calling station, and the telephone device of the calling station receives the voice signal from the called telephone device (called station) from the downlink channel of the second call channel and makes the first call. The own audio signal is transmitted to the upstream channel. In this way, simultaneous two-way communication is possible using two voice channels.

In the above embodiment, the channel management means is the CPU 30 of the center device 10, the RAM 34, the channel management table of FIG. 7, steps 114 and 116 of FIG.
It is realized by 118. The empty channel notification means is the CPU 30 of the center device 10, the RAM 34, step 1 of FIG.
It is realized by 04, 110 and 112. The calling means of the telephone device is the CPU 40, steps 202 to 2 of FIG.
It is realized in 06. The call notification means is the CPU 40,
This is realized in steps 208 to 216 in FIG. The call channel forming means is the CPU 40, step 22 in FIG.
It is realized by 0-226.

In the above embodiment, whether or not the call channel is in the empty state is determined by setting the system to the empty state in the initial state, and managing the empty state of the call channel according to the subsequent call request and the call completion. Center device 10
In the above, it may be possible to manage whether or not it is empty by detecting the carrier of each communication channel.

In the above embodiment, the first control channel,
Each second control channel is formed by one set of channels (one set of uplink and downlink channels).
It may be formed by a pair of channels. That is, in the communication between A and B, the channel from A to B and the channel from B to A may be different channels. By doing so, the control data can be transmitted and received at the same time.

In the above embodiment, the second control channel is composed of a plurality of sets, but the first control channel may be composed of a plurality of sets of channels. In this case, the call waiting time can be shortened by making a call even if the call operations overlap.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a specific example system of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a CPU of a center device.

FIG. 3 is a flowchart showing a processing procedure of a CPU of the telephone device.

FIG. 4 is a flowchart showing a processing procedure of a CPU of the telephone device.

FIG. 5 is a flowchart showing a processing procedure of a CPU of the telephone device.

FIG. 6 is an explanatory diagram showing a channel arrangement of the system of this embodiment.

FIG. 7 is an explanatory diagram showing a channel management table in the system of the present embodiment.

[Explanation of symbols]

L: Coaxial cable (coaxial transmission line) 10 ... Center device Ej ... telephone device 30, 40 ... CPU 31, 41 ... RF modem

Claims (4)

(57) [Claims] 1. A coaxial transmission line for transmitting a signal by frequency multiplexing, a head end connected to an end of the coaxial transmission line for frequency-converting an up-channel signal into a down-channel signal, and the coaxial transmission line. In a telephone system having a connected center device and a plurality of telephone devices, a first control channel for transmitting control data between the center device and the telephone device on the coaxial transmission line, and the telephone device. A second control channel for transmitting control data between the telephone devices and a plurality of call channels for performing voice communication between the telephone devices, and the center device determines whether or not the call channel is empty. Channel management means for storing and managing the call channel; and a call request control data received from the telephone device via the first control channel. And an empty channel notifying means for receiving an empty channel from the channel management means and transmitting the number of the empty channel to the calling telephone device, wherein the telephone device uses the first control channel. Calling means for transmitting call request control data to an arbitrary telephone device via the telephone, receiving the number of the empty channel from the first control channel, and transmitting the idle number to the called telephone device via the second control channel. A call notification means for notifying by control data that a call is made using a channel, and receiving the control data from the second control channel,
A telephone system comprising: a call channel forming means for establishing a call channel with a call source telephone device; and a telephone device for performing a call operation, an incoming call response, and a call. 2. The telephone system according to claim 1, wherein the second control channel comprises a plurality of channels, and each second control channel is assigned to the telephone device as a telephone device to be called. . 3. The second control channel comprises a plurality of channels, the center device manages an idle channel of the second control channel, and the idle second control channel number for the calling telephone device. 2. The telephone system according to claim 1, wherein the telephone system is transmitted via the first control channel. 4. The telephone system according to claim 1, wherein the first control channel comprises a plurality of channels.