JPH0522401A - Exchange system - Google Patents

Abstract

PURPOSE:To improve the reliability of data transfer without constructing a LAN. CONSTITUTION:Data from a digital line are diffused in spectrum by an SS transmission/receiving circuit 13, superimposed with an analog signal from an analog line network in an analog line exchanger 15 and transmitted to an extension line. On the other hand, a spectrum diffusion signal from the extension line is inverse diffused in the SS transmission/receiving circuit 13 via the analog line exchanger 15 and transmitted to a digital line via a packet control circuit 12 and a digital line exchange function block 11. The analog signal is transferred between the analog line network and the extension line via the analog line exchange 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching system for digital data communication by telephone line.

[0002]

2. Description of the Related Art Conventionally, when it is attempted to connect more telephones or terminals than the number of external lines, an analog line is constructed with an extension network centered on a PBX (Private Branch Exchange) as shown in FIG. , PBX and the outside line network were connected. On the other hand, in digital lines, as shown in Fig. 8 (b), L centering on CS (Communication Server)
This is realized by constructing an AN (local area network) and connecting the CS and the outside line network.

[0003]

SUMMARY OF THE INVENTION In the above conventional example,
When an analog line is used, the data from the terminal is connected to the line through a modem. Therefore, when the data transfer speed is increased, the data error rate increases and the reliability decreases. Further, if a digital line for transmitting data is installed and a LAN is constructed, a great deal of cost is required.

[0004]

According to the present invention, by combining the interfaces of digital lines using a spread spectrum communication system and connecting with an analog exchange, the reliability of data can be prevented from decreasing. This makes it possible to increase the transfer speed, and since the existing analog line is used, there is no need to construct a new LAN, so that the cost required can be reduced.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall construction of an embodiment of the present invention. In the figure, 1 is a switchboard carrying out the present invention, 2 is a telephone, and 3 is a terminal side interface carrying out the present invention. Unit 4 indicates a terminal.

Next, the internal configuration and functions of the exchange 1 and the terminal side interface unit 3 will be described. FIG. 2 shows the internal configuration of the exchange 1. In the figure, 11 is a digital circuit switching function block, 12 is a packet control circuit, and 1 is a packet control circuit.
3 is a transmission / reception circuit using the spread spectrum communication system (S
S transceiver circuit) 14 is a control circuit, and 15 is an analog switch having coupling for spread spectrum signals.

The control circuit 14, the packet control circuit 12, and the digital circuit switching function block 11 are CCITT Recommendation X.264.
It has a function based on 25. Further, in the embodiment of the present invention, the control circuit 14 controls the X. In addition to the function based on 25, the SS transmitter / receiver circuit 13 also has a function of supporting a spread code used in the spread spectrum communication system when transmitting data from the exchange 1 to the terminal 4.

The SS transmitter / receiver circuit 13 includes a transmitter, a receiver,
Code scanner part X. It consists of 25 interfaces.

The transmitting section spreads the data from the packet control circuit 12 with the spread code supported by the control circuit 14 and transmits the data to the terminal 4 side. Further, the transmitting unit is powered on at the time of receiving a CN (incoming call) packet from the packet control circuit 12 or at the time of receiving the synchronization pattern by the receiving unit when data is sent from the terminal. Then, after a certain period of time elapses after the transmitting unit transmits a CF (disconnection confirmation) packet to the terminal, or until a certain period of time elapses after the receiving unit receives the CF packet, RR at the link level
If no signal other than (Receive Recdy) is received, the power is turned off.

The receiving section performs spectrum despreading using the spread code whose signal has been successfully detected by the code scanner section, demodulates the data, and passes the data to the packet control circuit 12. The code scanner unit demodulates the spread code assigned to each terminal existing on the extension side of the exchange within a few cycles to check whether there is a spectrum-spread signal from the terminal side. The presence or absence of a signal is determined by the received output of the signal demodulated by the code scanner, and when it is determined that the signal is received, the spreading code used for signal detection is transmitted to the receiver. This signal detection is performed for each one or plural spread codes. X. The 25 interface is for maintaining connection with the packet control circuit 12 at the link level.

The internal structure of the terminal interface unit 4 is shown in FIG. In the figure, 31 is a coupling having the same purpose as the coupling described in the analog exchange of FIG. 2, 32 is an SS transmission / reception circuit, 33 is a packet control circuit, 34 is a control circuit, and 35 is a digital line physical interface. Control circuit 34, packet control circuit 3
3. Digital line physical interface 35 is CCIT
Recommendation X. It has a function based on 25. The SS transceiver circuit 32 includes a transmitter, a receiver, an X. It consists of 25 interfaces. These operations and functions are the same as those of the SS transmission / reception circuit 13 in the exchange 1, but the receiving section of the terminal interface unit 3 shifts from the reception mode to the signal detection mode when the connection is disconnected at the packet level. ing. Then, the signal detection is continued using the spreading code assigned to the terminal interface unit 3 until the reception output is obtained, and when the reception output is obtained, the signal detection mode is immediately switched to the reception mode.

In the embodiment of the present invention, the exchange 1
The spread spectrum data exchanged between the terminal interface unit 3 and the terminal interface unit 3 is transmitted by using two different bands to enable full-duplex communication.

FIG. 4 shows a block diagram of the operating procedure. Figure 5,
FIG. 6 is a diagram showing the exchange of signals on a block-by-block basis in FIG. The signal indicated by (L) in the figure indicates the link level, and the other signals indicated by the alphabet indicate packet level signals.

When the power of the terminal is turned on as shown in FIG. 4, the terminal interface unit 3 which receives the clock signal from the terminal 4 as shown in FIG.
, And synchronization is established in the spread spectrum signal transmission section (SS section). When the establishment of synchronization is completed, FIG.
The procedure shifts to the link connection procedure shown in FIG. 5 and then to the packet connection procedure, packet communication period, and packet disconnection procedure shown in FIG. If the packet connection procedure or the link disconnection 1 signal shown in FIG. 6 (b) does not come within a fixed time after the completion of the packet disconnection procedure, both the exchange 1 and the terminal interface unit 3 power off their transmitters. Then
The procedure moves to the link holding procedure shown in FIG.

When connection is again made at the packet level from the state of the link holding procedure, the procedure goes to the packet connection procedure 2 shown in FIG. 6 (a). In the packet procedure 2, for example, the X.X of the terminal interface unit 3 that receives the CR (call request) packet from the terminal 4 is transmitted. The 25 interface issues support to the SS transmission / reception circuit 32 so as to synchronize the SS section with the exchange 1, and CC to the terminal 4 (connection completed).
An RNR (unreceivable) packet is returned following the packet, and data is not sent until the establishment of synchronization in the SS section is completed.

When the synchronization can be established, the receiving unit of the exchange 1 sends X. The connection signal is passed to the X.25 interface and the X. The 25 interface passes the CR packet to the digital exchange function block 11 through the packet control circuit 12. The digital exchange function block 11 which has received the CR packet is transferred to the X.X. 25. Passed the CC packet to the 25 interface and received the CC packet. 25 interface is X.25 of terminal interface unit 3 through SS section. 25 Pass the connection signal to the interface. X. of the terminal interface unit 3. When receiving the connection signal, the 25 interface sends an RR (receivable) packet to the terminal 4, terminates the packet connection procedure, and shifts to the packet communication period.

The above procedure is performed in the same manner when the exchange 1 is connected to the terminal 4.

The normal link is cut off and the terminal 4 is powered off. This procedure is shown in Fig. 6 (b) after cutting the packet.
The link is disconnected according to the link disconnection procedure 1 shown in FIG.

If the terminal is accidentally turned off during the link holding procedure, the link is disconnected according to the link disconnection procedure 2 shown in FIG. 6 (c). To briefly explain this procedure, when the terminal 4 is turned off, the connection between the terminal 4 and the terminal interface unit 3 is disconnected at the physical level. Terminal side interface unit 3
X. The 25 interface supports the SS transmitting / receiving circuit 32 to establish synchronization in the SS section as soon as the connection at the physical level is disconnected. Then, when the synchronization is established, X.X. of the terminal interface unit 3 is established. 25 interface to X.X of switch 1. 25 Send a disconnect signal to the interface. Upon receiving the disconnection signal, the X. Two
5 interface unit is a packet control circuit 12
Through the digital circuit switching function block 1 to DISC
(Disconnect) signal is passed. When receiving the DISC, the digital circuit switching function block 11 becomes X. 25 Interface (DM)
de) is returned. Upon receiving the DM, the X. 25 interface is X.25 of terminal interface unit 3 through SS section. 25. A disconnection confirmation signal is sent to the 25 interface, and both the exchange 1 and the terminal interface unit 3 power off the transmitter and disconnect the link.

Next, the system operation will be described.

Since the band of the analog line telephone which is currently used is about 4 KHz, for example, a spread code of 255 is used.
The bit rate and the chip plate are 21.42 MHz, the center frequency when transmitting from the (negative) terminal 4 to the exchange 1 side is 100 MHz, and the center frequency when transmitting from the exchange 1 to the terminal 4 side is 160 MHz. S under this condition
The state of the spectrum in the S section is shown in FIG.

The analog circuit switch 15 superimposes the spread spectrum signal and the analog signal. 4K for the interface section between the telephone 2 and the analog circuit switch 15 and the outside line
Install a low-pass filter with a cut-off frequency of Hz (kilohertz). The low-pass filter on the side of the telephone 2 has a role of not cutting the high-frequency noise generated on the line so as not to deteriorate the quality of the line. The low-pass filter on the analog circuit switch 15 side has a role of not transmitting the spread spectrum signal used for the extension line to the outside line.
Attach a high-pass filter with a cut-off frequency of 138MHz to the terminal interface unit 3.
The exchange 1 is equipped with a high-pass filter having a cut-off frequency of 78 MHz to eliminate the influence of signals on the low frequency side.

Even if a spread spectrum signal is transmitted during a telephone call, it can be removed by the low-pass filter of the telephone, so that the spread spectrum signal does not disturb the call. Similarly, the spread spectrum signal can be removed by a high pass filter from the influence of the spread spectrum signal on the telephone line or the low frequency side.

Since the influence of the signals can be removed by the filter in this way, the analog line signal and the spread spectrum digital line signal can be transmitted on the same line,
Moreover, it is possible to use them at the same time.

That is, in the present embodiment, the data from the digital line is spectrum spread by the SS transmission / reception circuit 13, superposed on the analog signal from the analog line network in the analog line exchange 15, and sent to the extension line. On the other hand, the spread spectrum signal from the extension line is despread by the SS transmission / reception circuit 13 via the analog line exchange 15 and sent to the digital line via the packet control circuit 12 and the digital line exchange function block 11.

The analog signal is communicated with the analog circuit network and the extension network via the analog circuit switch 15.

In the above embodiment, one spreading code is assigned to one terminal interface unit, but this is adopted by adopting a method of assigning one spreading code to one user. Good.

That is, a memory for storing which code has which user exists in which line is added to the digital line switching function block inside the exchange. In addition, the control circuit of the terminal interface unit, the spreading code sent from the reading device of the storage medium recording the spreading code of the user, or the spreading code input to the terminal is used as a clue. A memory is added to store the spread code specified by a numerical value.

After powering on the terminal, first the spreading code is stored in the control circuit in the terminal interface unit, and then the synchronization procedure and the link connection procedure follow. However, since the information on the line used by the user is sent from the terminal interface unit during the first packet communication period, signals from the exchange side until that time do not use the digital line switching function block. Transmitted to the line. The subsequent operation is the same as that of the previous embodiment until the link is disconnected. When the link is disconnected, the digital circuit switching function block stores the line that has been used up to now as an unused line and deletes the spread code stored in the control circuit in the terminal interface unit.

In the case of the present embodiment, it is possible to send and receive data without any problem regardless of which terminal the user uses.

Also, a system in which some of a large number of spreading codes are used as control channels can be adopted. As an example, to explain the case where the control channel has three codes, one of the three codes is a channel dedicated to calling from the exchange to the terminal interface unit, and the other two are channels dedicated to calling from the terminal interface unit to the switching. To do. Further, the SS transmitting / receiving circuit of the terminal interface unit passes through the code scanner, the control circuit holds an extension number instead of the spreading code, and has a memory for separately storing the spreading code instructed by the exchange.
The code interface section of the terminal interface unit and the exchange checks the transmission / reception state of the three codes of the control channel.

Next, additional points of the operation procedure will be described. When sending data from the terminal interface unit to the exchange,
The terminal interface unit examines the exchange call-dedicated channel and establishes the synchronization of the SS section by using the transmittable control channel and the exchange-dedicated control channel. After the synchronization is established, the spread code used for actual communication is transmitted from the exchange, and the exchange on the control channel is completed.
After that, data communication is performed by the same operation procedure as that of the embodiment using the spreading code instructed by the exchange. The same applies when calling the terminal interface unit from the exchange, but the exchange transmits the extension number after synchronization is established with all the terminal interface units. Except for the corresponding unit, synchronization is deviated, and upon receipt of the response signal from the corresponding unit, the exchange instructs the currently unused spreading code. After that, the spread code is used to perform data communication by the same method as the operation means of the embodiment.

[0033]

As described above, by using the exchange and the terminal interface unit according to the present invention, it is possible to perform high-speed data communication with high reliability even on an analog line and, at the same time, perform full operation on the analog line. By enabling duplex communication, it is more effective to reduce the cost than constructing a new LAN.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of an exchange according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a terminal interface unit according to an embodiment of the present invention.

FIG. 4 is a schematic operation procedure diagram of the embodiment of the present invention.

FIG. 5 is a first detailed operational procedure diagram of the embodiment of the present invention.

FIG. 6 is a second detailed operational procedure diagram of the embodiment of the present invention.

FIG. 7 is a spectrum diagram of an example of the present invention.

FIG. 8 is a configuration diagram of a conventional circuit network.

[Explanation of symbols]

 1 Switch 2 Telephone 3 Terminal Physical Interface 4 Terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04Q 3/58 101 9076-5K

Claims (1)

Claim: What is claimed is: 1. A digital circuit switching means connected to a digital circuit network, a means for modulating and demodulating the exchanged digital data by a spread spectrum communication system, and an analog switching means connected to an analog circuit network. And a means for superposing the spread spectrum signal and the analog signal, a means for connecting the superposed signal to an extension network, and a means for separating the distributed superposed signal on the terminal side.