JP3559138B2 - Two-way communication equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a two-way communication apparatus More particularly, the present invention relates to an apparatus capable of quickly searching for a target connection partner from multiple channels.
[0002]
[Prior art]
General CATV lines are unidirectional, but are switching to bidirectional in the future. In the case of a unidirectional CATV, the subscriber only receives broadcast / data transmitted from a broadcasting station, but in the case of a bidirectional CATV, only one unit can be transmitted in one channel. Subscribers can transmit broadcast / data to the center or other subscribers.
[0003]
To perform bidirectional communication on a CATV line, a bidirectional channel is set for each of the upstream and downstream bands. The number of channels to be set is determined by the number of users who can receive the interactive service at the same time, the traffic volume at the peak time, the call loss rate, the line holding time, and the like. For example, since the transmission frequency bandwidth for data communication that can be occupied by the communication terminal in one vacant channel is 6 MHz, if the communication channel bandwidth is 12.5 kHz,
6MHz ÷ 12.5kHz = 480
And 480 communication channels are theoretically obtained.
[0004]
Normally, the available channels on the CATV line are as shown in FIG. 8, but in the case of a broadcasting station that is actually operated, in addition to a normal terrestrial wave (TV broadcasting), a UHF station, a satellite broadcasting station, or an independently operated broadcasting station The number of vacant channels that can be used for multiple purposes is gradually decreasing due to broadcasting programs, emergency broadcast programs of municipalities, and the like. In order to perform various services in the limited available channels, it is necessary to connect a large number of communication terminals to a CATV line.
[0005]
Conventionally, as a method of connecting lines on a CATV line, there is a method of arranging one communication terminal A, B... Exclusively for one channel and performing one-to-one communication as shown in FIG. According to this, since one communication terminal is dedicated to one channel, the time required for connection is very short, but it cannot be used by many communication terminals due to the limitation of the number of available channels. Further, communication can be performed only between predetermined communication terminals. If you compare it to a train seat, it is not a reserved seat where anyone can make a reservation, but a fixed seat where a certain person sits.
[0006]
So MCA ( Multi A method called “Channel Access” has been considered. This divides the transmission frequency band for data communication set for the uplink / downlink into frequency slots at equal intervals and, as shown in FIG. 9 (b), the channels from the communication terminals A, B,. Based on the connection request, the center 71 searches for an empty channel, allocates the empty channel as a communication channel to the communication terminals A, B,..., And the transmitter and the receiver of each communication terminal acquire the frequency and communicate with each other. Things. MCA is likened to an unreserved seat. In the case of unreserved seats, a vacant seat is searched from the end after searching for a vacant seat.
[0007]
[Problems to be solved by the invention]
The above-described MCA has an advantage that communication can be performed between arbitrary communication terminals, but has a drawback that it takes a long time to connect depending on an increase in the number of communication terminals to be connected and the number of channels to be searched. . This means that in the case of unreserved seats, vacant seats are searched from the end, so that when there are many people, it is difficult to find vacancies.
[0008]
Considering the actual operation, for example, in the case of a home medical system using a CATV line, there is the above-mentioned CATV principle. Therefore, a host station installed in a hospital sends a number of medical communication terminals on the CATV line in order. Need to poll and collect data. In such a case, it takes a time proportional to the number of times of data collection. For example, assuming 9600 BPS, it takes about 35 seconds to communicate data of about 32 Kbytes. Assuming that the line connection loss time in the MCA is about 25 seconds, the above-mentioned about 35 seconds is added to this loss time, and the time required for data collection per case is about 1 minute. It will take about 8 hours and 20 minutes for collection. However, if the line connection loss is reduced to about 5 seconds, the same 500 data collections will be completed in about 5 hours and 30 minutes. Therefore, it is urgently desired to reduce the line connection loss.
[0009]
In the case of MCA, the number of communication terminals that can be connected to a channel is limited by the number of channels. However, the number of available communication terminals is expected to be short in the near future because available available channels are decreasing. There is a possibility that various services cannot be received.
[0010]
Further, in the case of the MCA, the center is responsible for all tasks such as searching for an empty channel at the start of communication and determining a channel for communication between communication terminals, and notifies each other of the communication terminals via the center. Therefore, there is also a problem that a large-scale facility is required in the center.
[0011]
The above-mentioned problem is not limited to the bidirectional CATV line, but is also common to the bidirectional wireless line.
[0012]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art and to achieve a short-time line connection loss and a high-speed bi-directional line communication capable of searching for a connection partner. apparatus Is to provide. Another object of the present invention is to provide a bidirectional communication system capable of using a small number of channels with a large number of communication terminals. apparatus Is to provide. Another object of the present invention is to provide a bidirectional communication system in which the center can be operated with simple equipment by making a part of the work of the center burdened on a communication terminal. apparatus Is to provide. A further object of the present invention is to provide a bi-directional communication system capable of automatically switching from a CATV line to a general line (NTT) when the CATV line cannot be used. apparatus Is to provide.
[0013]
The first invention is A data communication transmission frequency band for performing bidirectional communication is set for each of the up / down vacant lines of the CATV line, and a plurality of centers connected to the CATV line using the data communication transmission frequency band are used using the data communication transmission frequency band. In a two-way system in which two-way communication is performed between communication terminals or between a plurality of terminals, a transmission frequency band for data communication set for each of the up / down vacant lines is equally divided by a communication channel bandwidth. Thus, a call channel for making a call is set to n lines, an inquiry channel for making an inquiry for a call is set to at least one line, and a unique identification number is assigned to each of the plurality of communication terminals. Is assigned to each communication terminal with an identification number, and the identification number of each communication terminal corresponds to the assigned communication channel. The database was set to the center.
[0014]
When the communication terminal on the calling side of the call is A and the communication terminal on the receiving side is G, the communication terminal A communicates with the center through the inquiry channel in order to know the communication channel allocated to the communication terminal G. The center notified of the identification number of the terminal G, and notified of the identification number of the communication terminal G, searches the database for a communication channel corresponding to the identification number of the communication terminal G, and corresponds to the identification number of the communication terminal G. When a communication channel is found and the communication terminal G having the identification number corresponding to the communication channel is not busy, the communication channel of the communication terminal G is notified to the communication terminal A, and the communication channel of the communication terminal G is received. The communication terminal A makes a call to the communication terminal G via the communication channel of the communication terminal G.
[0015]
When the communication terminal G receives a call, the communication terminal A notifies the communication terminal G of the communication channel corresponding to the identification number of the communication terminal A, and the communication terminal G notified of the communication channel transmits the communication channel of the communication terminal A. Communication between the communication terminal A and the communication terminal G by performing a transmission operation to the communication terminal A through apparatus It is.
[0016]
In a second aspect, in the first aspect, When the number of communication terminals in the entire system increases beyond the n-channel communication channels, a plurality of communication terminals are allocated to one communication channel by rewriting the database, and the communication terminals are grouped. When another communication terminal B in the group is using the communication channel assigned to the group when the communication terminal A performs the calling operation, the communication terminal A sets the communication channel assigned to the group to ± 1. ~ ± m (M is an integer smaller than n and is a value within a moving range of the frequency of the one communication channel) It confirms the availability of the communication channel within the range of the added channel, and if it is available, changes the communication channel of the communication terminal A to the available communication channel.
[0017]
Along with this change, the communication terminal A notifies the center of the changed communication channel of the communication terminal A through the inquiry channel, updates the database, and makes a call operation to the communication terminal G using the communication channel. The communication terminal A on the calling side and the communication terminal G on the receiving side confirm the identification numbers unique to each other, and when they match, conduct a call between the communication terminal A and the communication terminal G. A two-way communication in which the changed communication channel and database of the communication terminal A are returned to the original communication channel after the communication is completed and after the communication of the communication terminal B is completed. apparatus It is.
[0018]
According to a third aspect of the present invention, in the first or second aspect, when the communication terminal G on the receiving side is not in a call or when all communication channels are in use, the CATV line is given priority over the general telephone line. A general telephone line is connected to the communication terminal in addition to the CATV line so that the communication terminal G on the receiving side can use the communication terminal G when the communication terminal G is in a call or all the communication channels are in use. -Line communication with automatic switching from telephone to general telephone line apparatus It is.
[0019]
According to a fourth invention, in the first to third inventions, communication of a bidirectional line is performed, in which a wireless line is used instead of the CATV line. apparatus It is.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The communication of the two-way line of the present invention is described below. apparatus An embodiment in which the present invention is applied to a bidirectional CATV line will be described with reference to the drawings.
[0021]
As shown in FIG. 7, a signal (uplink signal) from a communication terminal to a broadcasting station and a signal (downlink signal) from a broadcasting station to a communication terminal are distinguished at a boundary of 60 MHz. Broadcasts such as TV broadcast programs and satellite broadcast programs are downlink signals, and reports related to home security, home medical system data, home video games and communication karaoke requests are uplink signals. In order to perform bidirectional communication between a center connected by a CATV line and a plurality of communication terminals or between a plurality of terminals, as shown by a dotted line in FIG. An upstream data communication transmission frequency band 51 for performing communication and a downstream data communication transmission frequency band 52 are set.
[0022]
By dividing the set transmission frequency bandwidth for data communication at equal intervals by the bandwidth of the communication channel, a large number of channels are obtained. Among them, a communication channel for making a call is set to n lines, and at least one inquiry channel for transferring information of the communication channel from each communication terminal is set. Assuming that the transmission frequency bandwidth for data communication is 6 MHz and the communication channel bandwidth is 12.5 kHz, the number of obtained channels is 480, as described above. Is a communication channel.
[0023]
Here, as shown in FIG. 1 (a), in order to search for an unspecified communication partner on the CATV line, one communication channel is used while the number of communication terminals A, B.
One communication terminal is allocated to (transmission / reception communication channel). Where S ₁ ~ S _n Is the call channel, R ₁ Is an inquiry channel.
[0024]
When the number of communication terminals A, B... Of the entire system increases more than the n-channel communication channels S1 to Sn, as shown in FIG. Assign multiple units, Think of this as a group. An example For example, two or three It is.
[0025]
The assignment of such communication channels to the communication terminals is managed by a database described later.
[0026]
Each communication terminal is assigned a unique identification number ID. And n-channel communication channel S ₁ ~ S _n Are assigned to the unique identification numbers ID of the communication terminals A, B,..., A database 3 is created in which the assigned communication channels correspond to the identification numbers, and the database 3 is set on the system management computer 2 of the center 1. .
[0027]
FIG. 2 shows a specific example of the database 3 corresponding to FIG. Each of the two free channels is divided into 480 channels, and the reception / transmission frequency is assigned to the identification number ID of each communication terminal. The reception frequency and the transmission frequency are paired, and the reception frequency is obtained by frequency-converting the transmission frequency at a fixed rate. This fixed ratio is not common to all broadcasting stations, but is a value specific to the broadcasting station to be installed. In the case of FIG. 2, the frequency obtained by adding 94 MHz to the upstream frequency is returned as the downstream.
[0028]
In the table, the reception / transmission frequencies assigned to ID 0000 0000 to 0000 0007 are used for an inquiry frequency, for system management, and for emergency broadcast. In addition, when considering the home medical system, the unique identification number ID of the communication terminal is very easy to understand if it is common to the last eight digits (39814131) of the home telephone number (for example, 03 (3981) 4131). Cheap.
[0029]
In FIG. 1A, when the communication terminal on the calling side of a call is A and the communication terminal on the receiving side is G, the communication channel allocated to the communication terminal G from the communication terminal A to the center 1 is shown. S ₇ To know the inquiry channel R ₁ The communication terminal G is notified of the identification number 007 via the communication terminal. The center 1 notified of the identification number 007 of the communication terminal G sends the communication channel S corresponding to the identification number 007 of the communication terminal G from the database 3. ₇ And the communication channel S corresponding to the identification number 007 of the communication terminal G ₇ Is found and the call channel S ₇ Is not busy, the communication channel G of the communication terminal G is not busy. ₇ To the communication terminal A.
[0030]
Communication channel S of communication terminal G ₇ Is received by the communication terminal A, the communication channel S of the communication terminal G is received. ₇ To the communication terminal G through the terminal. When the communication terminal G performs the receiving operation, the communication terminal A sets the communication channel S corresponding to the identification number 000 of the communication terminal A. ₁ To the communication terminal G. Call channel S ₁ Is notified, the communication channel G of the communication terminal A ₁ The communication operation between the communication terminal A and the communication terminal G is realized by performing a transmission operation to the communication terminal A through.
[0031]
Also, in FIG. 1B, when the communication terminal A performs a calling operation in the group and the communication channel S4 assigned to this group is used by another communication terminal B in the group, the communication is performed. The terminal A is connected to the communication channel S4 assigned to the group by ± 1 to ± m. (M is an integer smaller than n and is a value within the range of movement of the frequency of the one communication channel) Check the availability of call channels within the range of adding channels. If the communication channel is not vacant, the communication channel S4 of the communication terminal A is changed back to the vacant communication channel, for example, S3, and the center 1 is notified of the changed communication channel S3 of the communication terminal A via the inquiry channel R1, The call is transmitted to the communication terminal G. Thereafter, the communication terminals A on the calling side and the communication terminal G on the receiving side confirm the identification numbers 000 and 026 unique to each other, and when they match, a call between the communication terminal A and the communication terminal G is made. carry out. After the end of the call and after the end of communication of the other communication terminal B in the group, the changed communication channel S3 of the communication terminal A is returned to the original communication channel S4, and at the same time, the database 3 of the center 1 is used using the inquiry channel. To update.
[0032]
In the present invention, when compared to train seats, the seats are just reserved seats. FIG. 1A shows a case where only one person has reserved for one channel. However, since communication is not usually performed all day, it is not preferable from the viewpoint of efficiency that one person always occupies one channel. Therefore, as shown in FIG. 1B, reserved seats are treated like group seats. By looking at the traffic volume per channel, several reservations are allocated to one channel. Look at the reserved seat, and if no one is using it, use it as it is. If someone has used it first, search for a vacancy near the reserved seat. Even if your reserved seat is in use, the seats nearby are often vacant with a high probability. In this case, the longer the search range is, the longer it takes to find an “empty”, but the narrower the search range is, the shorter it takes to find an “empty”.
[0033]
Here, when the communication channel S4 assigned to the group is used by another communication terminal B in the group, the number of channels to be moved in addition to the communication channel S4 assigned to the group is ± 1 to ± m. (M is an integer smaller than n and is a value within the range of movement of the frequency of the one communication channel) The reason is that the connection loss is reduced to speed up the search by reducing the connection loss. When m = n, the connection loss becomes the same as that of the MCA, and when m = 0, the connection loss increases as shown in FIG. It is because it does not change from the state of. Practically, about ± 1 to ± 3 is preferable.
[0034]
According to the present invention, the communication terminal A, not the center, is searched for a vacant channel at the start of communication, the communication channel G corresponding to the identification number 000 of the communication terminal A is notified to the communication terminal G, and the communication terminal ± 1 to ± m on channel S4 (M is an integer smaller than n and is a value within the range of movement of the frequency of the one communication channel) The burden of the center is reduced because the center is responsible for confirming the availability of a communication channel within the range of the added channel and for determining the channel for communication between communication terminals instead of the center. Can be operated with simple equipment. This increases the burden on the communication terminal, which can be easily absorbed by the sophistication, higher function, and lower cost of the electronic devices that make up the communication terminal.
[0035]
Hereinafter, a communication system of a bidirectional CATV line will be specifically described.
[0036]
As shown in FIG. 3, the center 1 has a CATV broadcasting facility 4 and a management computer 2. A plurality of communication terminals 6 are connected to the center 1 via a wireless or wired CATV line 5. The plurality of communication terminals 6 have a function of transmitting / receiving data between arbitrary communication terminals 6 and transmitting / receiving data in response to communication from the management computer 2 of the center 1. The communication terminal 6 has at least a transmission frequency and a reception frequency, software that is independently installed in the CPU, or a mechanism that can be set from a management computer, for example, a preset mechanism for fixing a specific frequency to a PLL.
[0037]
From the communication terminal 6, transmission data is transmitted from the CPU 7 through the modem 8. The transmission data enters the LPF 9 through the modem 8, removes unnecessary high-frequency components by the LPF 9, and then FM-modulates the signal to the designated FM broadcast band by the FM modulator 10. The FM signal passes through the BPF 11 to transmit unnecessary waves. Is removed. The signal from which the unnecessary wave has been removed is mixed by the mixer 12 with the oscillation signal of the VCO 14 adjusted to the transmission frequency setting signal by the PLL 13 and converted into a frequency for adjustment set in advance by CATV. After the conversion, the high-frequency unnecessary components are removed by the LPF 15 and then sent to the RFAMP 16 to be amplified to a predetermined level necessary for sending to the center 1. The gain of the RFAMP 16 is controlled by an AGC voltage supplied from the CPU 7 through the modem 8. The amplified signal passes through the RF GATESWITCH 17 for protecting from transmission errors due to ingress noise that is closed and controlled by the transmission control signal, passes through the DUPLEXER 18, and is sent to the center 1 through the CATV line 5.
[0038]
On the other hand, the data signal output from the center 1 is input from the DUPLEXER 18 to the communication terminal 6 and mixed with the signal of the oscillator 20 by the mixer 19, and when the carrier of the data signal matches the set reception frequency, the mixer 19 Taken out of Note that the frequency of the oscillator 20 is controlled by phase-detecting the local oscillation signal and the reception frequency setting signal generated by the oscillator 20 by the PLL 21, extracting an error voltage thereof, and feeding it back to the oscillator 20.
[0039]
From the signal output from the mixer 19, the first intermediate frequency signal (10.7 MHz) is extracted by passing through the first stage BPF 22, and then the IF center frequency ± 455 kHz for removing adjacent interference in the second stage BPF 23. , A selectivity characteristic higher than a predetermined level can be obtained. A change in frequency is detected as a change in voltage by the FMDT 24, a part of the detection signal is subjected to unnecessary noise removal by a squelch circuit 25, and unnecessary components in a high frequency band are removed through an LPF 26. Is taken into the CPU 7 and processed.
[0040]
In the case where a plurality of communication terminals are connected to one channel as shown in FIG. 1B on a CATV line in which the environment as described above is maintained, a communication terminal on the transmitting side (hereinafter referred to as a call station) is actually used. The procedure for connecting the receiving side communication terminal (hereinafter referred to as a called station) by connecting a line to perform communication with the receiving side communication terminal (hereinafter referred to as a called station) is partially omitted, but is approximately as shown in FIG. Here, for convenience, the uplink / downlink assigned to a channel is referred to as transmission / reception, and a channel without transmission / reception limitation means both transmission / reception.
[0041]
(1) The calling station starts transmission (401), selects a called station (402), and assigns the receiving frequency to one of several transmission inquiry channels to which the receiving side is assigned in advance. The PLL 21 is set (preset), the CPU 7 determines the presence or absence of a carrier received through the DUPLEXER 18, and checks whether the transmission inquiry channel of one frequency is used by another communication terminal (403). This must be confirmed when a plurality of communication terminals are assigned to one communication channel, because one or more communication terminals cannot transmit to the same channel at the same time. If in use, the reception frequency is set to the next frequency of the transmission inquiry channel, and the same check is performed.
[0042]
Here, if an unused transmission inquiry channel can be confirmed, the confirmation is stopped, the frequency of the transmission inquiry channel is stored in the CPU 7, a frequency having the same value is set as the transmission frequency in the PLL 13 on the transmission side, and the transmission is performed. Transmission operation is enabled for the inquiry channel. In addition, in order to set a reception inquiry channel on the reception side, a reception frequency obtained by frequency-converting the transmission frequency at a fixed rate is set in the PLL 21 on the reception side to prepare for reception of an inquiry response. If all are in use, the user of the calling station is notified that the terminal is busy, and the process ends (405).
[0043]
{Circle over (2)} The calling station transmits the inquiry data on the frequency of the called station to the center 1 via the DUPLEXER 18 through the transmission inquiry channel described above (404). In the center, information on the receiving / transmitting communication channel of the called station and information on whether or not the called station is currently in a call are transmitted from the database on the system management computer 2 to the CPU 7 from the receiving side through the reception inquiry channel. (406). At this point, it is determined whether the called station exists (412) or the called station is not in use (413). If the called station is unregistered or busy, both are determined. The user of the calling station is notified that the telephone is busy, and the process ends (405).
[0044]
(3) The calling station then makes the pre-assigned outgoing call channel the main, and checks in the same manner as in (1) whether the outgoing call channel is being used by another communication terminal in the same group. I do. This also needs to be confirmed when a plurality of communication terminals are assigned to one communication channel because one or more communication terminals cannot transmit to the same channel at the same time.
[0045]
{Circle around (4)} When the transmission call channel is being used, the reception frequency set value of the PLL 21 on the receiving side is moved, and several channels before and after the main transmission call channel, for example, ± The use states of the channels in the range of 1 to ± 3 channels are sequentially checked, and the unused transmission call channels are detected and determined from among them (see FIG. 1B). If all are busy at this point, the user of the calling station is notified that the terminal is busy, and the process ends.
[0046]
{Circle around (5)} The calling station stores the communication channel in the CPU 7, sets the frequency of the transmission communication channel as the transmission frequency in the PLL 13, and is assigned to the called station which is the communication partner notified from the system management computer 2. An outgoing call operation is performed for the current call channel (407).
[0047]
The data to be transmitted to establish the communication here includes a unique identification number ID of the calling station, a unique identification number ID of the called station, a transmission / reception communication channel of the calling station, spare data for future expansion, and communication. Checksum data for confirming the accuracy of the contents. Here, the calling station sends the ID of the other party and its own ID because the used application sometimes uses them.
[0048]
{Circle around (6)} The called station B in the reception standby state (415) receives the data from the calling station (416), checks the transmitted unique identification number ID (417), and finds that ID is its own. If it does not match the unique identification number ID, the incoming call is abandoned and the system waits for the next frame with the unique identification number ID. The matched called station notifies the calling station that the start of the call has been permitted (418). At the same time, information such as the transmission / reception communication channel of the called station is also notified. Here, the called station confirms the ID because there is a possibility that another communication terminal is connected to one communication channel, and it is necessary to select a target one from among them.
[0049]
In the case where a plurality of communication terminals are connected to the receiving side, when the received plurality of communication terminals come to a terminal other than their own IDs, the following (a) will be continued until the communication of the communication line ends. Alternatively, the operation of (b) is performed.
[0050]
(A) When you want to send
As described above, a vacancy is searched for in a range of about ± 1 to ± 3 of the set communication channel, and the operation shifts to a calling operation.
[0051]
(B) Waiting for reception
It continues to receive using the paging channel set in the inquiry channel and waits until it is called. Here, if the call is not called from another communication terminal, if the call on the originally assigned communication channel is completed, the communication terminal waits on the assigned communication channel. When a call is made from another communication terminal, a search is made for a vacancy in the range of ± 1 to ± 3 of the allocated communication channel using the paging channel, and the result is reported to the center. Receive and wait to be called. When the call is completed, the next call is awaited on the originally assigned call channel.
[0052]
{Circle around (7)} When the calling station receives the permission notification from the called station, both the calling station and the called station open the line (409, 419) and start talking / communication (410, 420).
[0053]
(8) After the end of the call, the call channel to which the calling station has moved is returned to the original set value. Here, the reason why the communication channel is returned to the original set value is to prevent the channel allocated to the communication terminal subscribed to the CATV broadcasting station from being shifted. If the “vacant” seats that happen to be set are set as the reserved seats, the number of seats reserved for one seat can be shifted, which is inconvenient.
[0054]
As described above, the correspondence between the unique identification number of the communication terminal and the frequency is stored in a database on the computer 2 that manages the communication system, and the communication related to the communication terminal of the connection partner is performed in response to a request from the communication terminal. Necessary data is transferred using a database, so that the target connection partner can be searched at high speed.
[0055]
Further, since the connection relation of the communication terminals can be easily changed only by rewriting the contents of the database, an unspecified communication partner can be searched from the CATV line. One channel can be allocated to one channel, and as the number increases, two or three communication terminals can be allocated to one channel. In particular, when a plurality of communication terminals are allocated to one channel, more communication terminals than the number of channels can be connected. Can also respond.
[0056]
Further, when two or three communication terminals are assigned to one channel, and when a channel set in advance according to the use state of the line is used, the channel moves by itself and finds an empty channel within the movement range. As a result, a target connection partner can be searched at a higher speed as compared with an MCA that moves through all channels. For this reason, for example, in a home medical system using a CATV line, even when a host station installed in a hospital needs to sequentially poll a number of medical communication terminals on the CATV line and collect data, a line connection loss may occur. Because it is shortened, data collection does not take much time.
[0057]
Further, the present invention is not limited to a bidirectional CATV line, but can be applied to a bidirectional wireless line. This is because there is only a difference between wired and wireless and no difference in circuit / configuration.
[0058]
In the above embodiment, a plurality of communication terminals are assigned to one communication channel to form a group, but this group is not fixed. Allocation of communication terminals to channels can be freely changed by rewriting the database, and the change can be made flexibly according to the frequency of use of CATV. In an extreme case, if a communication terminal of a certain channel uses a majority of the time for communication in a day, the channel is allocated to only one communication terminal, and the frequency of use of the other channel is almost zero. It is also possible to assign several communication terminals to a channel having no channel. The management computer 2 of the center 1 plans the channel assignment in this way so that all communication terminals can talk at the same chance.
[0059]
In addition, in the embodiment shown in FIG. 1B, the case where only one communication terminal Z is connected to the channel on the receiving side has been described for convenience, but the transmitting side where a plurality of communication terminals A and B are connected is described. Similarly to the above, the present invention can be applied to a case where a plurality of communication terminals other than the communication terminal Z are connected to the receiving side.
[0060]
By the way, in the communication procedure of FIG. 4 described above, when all the communication channels are in use or the other party is busy, the user of the calling station is notified that the communication is busy and ends. However, in this case, it is very convenient to automatically switch from a closed CATV line to a general telephone line (NTT) instead of terminating the communication. Therefore, the main part of the communication terminal 6 was improved as shown in FIG. 5, and a general telephone line modem 27 was connected to the CPU 7 in the communication terminal 6 in FIG. This connection allows the CATV line 5 to be used preferentially with respect to the general telephone line 28. If the other party on the CATV line 5 is busy, or if all communication channels are in use, the general telephone line 28 is used. Automatically switch to calling. The flow of the switching process will be described with reference to FIG. In FIG. 6, parts corresponding to those in FIG. 4 are denoted by the same reference numerals.
[0061]
When the called station is not in use (413), the center notifies the called station of the channel of the called station (414) as in the case of FIG. However, when the called station is in use, that is, when the called station is in a call or when all the communication channels of the CATV line are in use, the center searches for the telephone number of the general public line from the already registered database. A notification is made to the calling station (421). The calling station receives the retrieved telephone number of the general public line (422). Here, the call station notifies the user that "it is busy and will be connected to the general public line" (423), and then terminates the CATV line (424). The calling station automatically makes a call to the general public telephone number received at 422 (425). Subsequent steps are the same as the normal telephone processing.
[0062]
As described above, when the CATV line is blocked, the system is automatically switched to the general public line. Even if the CATV line is blocked, the call / communication can be secured, so that the service can be further improved and very convenient.
[0063]
【The invention's effect】
According to the present invention, a communication channel is allocated to an identification number assigned to each communication terminal, and this is stored in a database for connection management. Therefore, a line connection loss is short, and a connection partner can be searched at high speed. Never let the user wait.
[0064]
Further, according to the present invention, when the number of communication terminals increases, a plurality of communication terminals are allocated to one communication channel, and a channel moves by itself in addition to the allocated communication channel depending on the usage state of the communication channel. As a result, a wide range of channel connections is provided, so that a small number of channels can be used by a large number of communication terminals, and a connection partner can be searched at high speed, so that users do not have to wait. In addition, the initial investment required for this can be made inexpensively because it is only necessary to install a database in the center and change the contents according to the situation.
[0065]
Further, according to the present invention, a part of the work of the center is borne by the communication terminal, so that the equipment of the center can be simplified and the center can be constructed at low cost.
[0066]
Further, according to the present invention, when the CATV line is fully used, or when the communication terminal on the receiving side is busy, the general public line is automatically switched, so that the communication service can be further improved.
[0067]
Further, according to the present invention, the present invention is not limited to a bidirectional CATV line, but can be applied to a bidirectional wireless line.
[Brief description of the drawings]
FIG. 1 shows a bidirectional line communication of the present invention. apparatus FIG. 3A is a diagram illustrating the principle of the system, wherein FIG. 4A is an explanatory diagram in the case where one communication terminal is assigned to one communication channel, and FIG. FIG. 4 is an explanatory diagram in a case where a plurality of communication terminals are assigned to one call channel.
FIG. 2 is a correspondence table of a communication terminal specific number (ID), a reception frequency, and a transmission frequency, showing a specific example of a database according to the present embodiment.
FIG. 3 shows communication on a bidirectional line according to the embodiment. apparatus FIG. 1 is a system configuration diagram of a center side and a communication terminal side connected by a CATV line for implementing the above.
FIG. 4 is an explanatory diagram showing a flow of processing until a communication terminal on the transmitting side according to the present embodiment connects to a communication terminal on the receiving side via a center.
FIG. 5 is a main part configuration diagram of a communication terminal to which a general telephone line modem according to the present embodiment is added.
6 is an explanatory diagram showing a flow of processing for automatically switching and connecting a CATV line to a general public line when the CATV line is fully used or during a call according to the embodiment of FIG. 5;
FIG. 7 is an explanatory diagram showing an example of band division of a bidirectional transmission line in Japan.
FIG. 8 is a list of reception frequencies of channel CATV in Japan.
9A and 9B show principle diagrams of a conventional system, in which FIG. 9A shows a one-to-one system and FIG. 9B shows an MCA system.
[Explanation of symbols]
1 center
3 database
A, B ... Z communication terminal
S ₁ ~ S _n Call channel
R ₁ There is no change to the substantive contents of the specification except for the inquiry channel correction command items.

Claims (2)

In a bidirectional communication device for performing bidirectional communication via a center between a plurality of communication terminals connected to a CATV line,
The transmission frequency band for data communication is set to the up / down vacant line of the above CATV line by dividing the transmission frequency band for data communication at equal intervals by the communication channel bandwidth, and the n-channel communication channel for performing the communication and the communication channel of the communication are set. At least one inquiry channel for making an inquiry for
The communication center is set in the center, and a unique identification number is assigned to each of the plurality of communication terminals, and the communication channel of the n-line is assigned to each of the communication terminals assigned the identification numbers. A database in which a plurality of communication terminals are assigned to one communication channel by rewriting data contents when the number of communication terminals of the entire system increases beyond the n-channel communication channels. A database having data that assigns A and B, and groups them.
When the communication terminal A performs an outgoing call operation to another communication terminal G in the group, the other communication terminal B in the group uses the one communication channel assigned to the group. , ± 1 to ± m (m is an integer smaller than n and a value within a moving range of the frequency of the one communication channel) having frequencies before and after the one communication channel assigned to the group. In the range including the communication channel of the communication channel, a search is made for a free communication channel, and when there is a free communication channel in the communication channel in the above range, the communication channel of the communication terminal A is used by another communication terminal B. from the communication channels are, together with the re-changed first in one call channel found among the speech channel vacant, the communication terminal to the center through the query channel Notifying the changed call channel of terminal A, updating the database, and making a call operation to communication terminal G using the changed call channel,
The center confirms the unique identification number ID between the communication terminal A on the calling side and the communication terminal G on the called side, and if the ID numbers match, the communication between the communication terminal A and the communication terminal G is performed. After the end of the call and after the communication of the communication terminal B ends, the changed communication channel and database of the communication terminal A are returned to the original communication channel,
When the communication terminal G on the receiving side is not in a call or when all communication channels are in use, the communication terminal is added to the CATV line in addition to the CATV line so that the CATV line can be used preferentially over the general telephone line. A line is connected, and the communication terminal G on the receiving side is automatically switched from a CATV line to a general telephone line when the communication terminal G on the receiving side is busy on a call or when all communication channels are in use.
A two-way communication device. 2. The communication device according to claim 1 , wherein the CATV line is replaced by a wireless line .

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