JPH10327093A - Communication network using twisted pair cable and its communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect collision and a link state while forming a 2-way bus with a transmission line in a local area network LAN using a twisted pair cable. SOLUTION: In an idle state, a detection signal transmission device 29 in a hub use interface 2 applies a voltage of +2V1 to a twisted pair cable 4. The voltage +2V1 is divided and the voltage of the twisted pair cable 4 is +V1. Detection devices 17,27 detect the voltage +V1 to discriminate a link state. In the case that a signal is sent from either of interfaces 1, 2, a signal sent from a transmitter includes a DC voltage of -V1 in average. As a result, a DC voltage level of the twisted pair cable 4 is 0V. In the case that a signal is sent simultaneously from both interfaces 1, 2, the two signals are added and the DC voltage level of the twisted pair cable 4 is -V1. The detection devices 17, 27 detect the voltage level to discriminate a collision state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a communication technique in a network using a twisted pair cable, and more particularly, to carrier detection, collision detection, and link detection in a random access local area network using a twisted pair cable. The present invention also relates to a network configuration technology for configuring a plurality of broadcast buses in parallel using a twisted pair cable, and a communication technology in the parallel broadcast bus network.

[0002]

2. Description of the Related Art FIG. 8A shows a configuration diagram of an Ethernet using a coaxial cable as a transmission medium. Each client station 311 is connected to each other via a coaxial cable 312. The signal 313 flows on the coaxial cable. The signal 313 is a binary signal including a DC component as shown in FIG. Since the signal 313 contains a DC component,
When a plurality of stations among the client stations 311 transmit at the same time, the DC voltage component of the coaxial cable becomes twice as large as that when a single station transmits. Utilizing this property, Ethernet performs collision detection.

FIG. 9 shows a CS used in Ethernet.
MA / CD (Carrier Sense Multi)
ple Access with Collision
2 shows a state transition diagram of a (Detection) protocol.
When there is a transmission request from the upper layer protocol, the client station 311 checks whether or not any signal exists on the coaxial cable 312 (carrier sense). If a carrier is sensed on the coaxial cable 312, the client station 311 waits for a random time and then attempts retransmission. If there is no carrier on the coaxial cable 312, the client station 311 starts transmitting a signal (packet).

[0004] The client station 311 receives a signal (packet).
Assuming that another station starts transmission during transmission, each station can detect the occurrence of a collision from an abnormality in the DC voltage of the coaxial cable. Upon detecting the occurrence of the collision, the station that was transmitting at that time transmits a jamming signal for a fixed time (about 50 μsec), and then attempts retransmission after waiting for a random time. Here, the transmission of the jamming signal for a predetermined time (about 50 μsec) is a procedure for informing that the collision has occurred in the entire network. If the client station 311 completes transmission of the entire packet without detecting a collision during signal (packet) transmission, it is regarded as transmission success, and the receiving station does not transmit a reply packet. Although this procedure of transmitting a jamming signal for a certain period of time has the effect of making the entire network aware of the occurrence of a collision, it has the disadvantage that the entire network cannot be used for data transmission while transmitting the jamming signal. I have.

A local area network (LAN) using a twisted pair cable (twisted pair) as a transmission medium instead of a coaxial cable has a transmission speed of 10M.
bps 10BASE-T and transmission speed 100Mbps
100BASE-T is known. In these networks, as shown in FIG. 10A, a concentrator 201 called a hub is placed at the center, and each client station 202 and the hub are connected to a set of transmission only (as viewed from the client). It is connected by a two-wire twisted pair cable 205 consisting of a line 203 and a dedicated line for reception 204 (as viewed from the client). FIG. 10B shows the structure of the client station 202. Transmitter 211,
Receiver 212 is connected to dedicated transmission line 203 and dedicated reception line 204, respectively. The transmission line 203 and the reception line 204 are terminated by terminating resistors 213 and 214, respectively.

In the idle state, the hub 201 and the client station 202 transmit a link signal to each other. Therefore, each other can detect whether the hub 201 and the client station 202 are physically connected. In the case of Ethernet using a coaxial cable, such a link state is not detected, and transmission-only lines and reception-only lines have been provided in Ethernet using twisted-pair cables. .

Since the link state cannot be detected in the Ethernet using the coaxial cable, it is often impossible to detect whether the bus is empty or the physical connection with the coaxial cable is broken. I was In this regard, Ethernet using twisted pair cables has been improved. However,
This improvement is also inefficient in that it separates the two transmission media into transmission only and reception only.

[0008] In Ethernet using a twisted pair cable, collision detection is performed by the hub 201. When transmission is performed simultaneously from a plurality of client stations 202,
Signals will appear on multiple ports of hub 201 simultaneously. This state is detected, a collision is detected, and a signal having a specific pattern called a collision detection signal is transmitted to the hub 2.
01 is transmitted to each client station 202.

In Ethernet using a coaxial cable, signal transmission is performed using a single transmission medium. In Ethernet using a twisted pair cable, a transmission line 203 is used.
This means that two transmission lines, namely, the dedicated transmission line 204 and the transmission line are used. However, the two-wire twisted pair cable is thinner than the coaxial cable, and the cost per unit length is lower for the two-wire twisted pair cable, so the total system cost of the two-wire twisted pair cable is far greater. Will be cheaper.

By the way, using a twisted pair cable belonging to the so-called category 5 using a fluorine-based resin as an insulating material, a signal transmission of about 100 Mbps is performed for 100 m.
Techniques for realizing the above-mentioned distance are known (for example, see Bungo Uemura, "100 Mbps CDDI and its strategy", Computer & Network LAN, March 1993, pp. 30-38 (1993)). The key to this technology is MLT-3 (trade name or trademark of Crescendo)
This is an encoding method referred to as an encoding method. FIG. 11 shows MLT-3.
As shown in (a), the state changes for one code. 2
When the code of the value is output as NRZI (non-return to zero inverted), the power spectrum having a peak around 65 MHz is shown, whereas the MLT-3
The peak of the power spectrum can be reduced to about 16 MHz by using (see FIG. 11B). Also,
MLT-3 is designed so that the DC component becomes zero. This is because there is no need to add a DC component to the signal in the system that performs collision detection at the hub, and signals that do not include a DC component can be transmitted using a transformer, which is advantageous in mounting. is there. Category 5-2
A system that configures 100 Mbps Ethernet using a wire twisted pair cable is called 100BASE-TX.

However, when an inexpensive twisted pair cable of category 3 is used, it is difficult to transmit a signal of about 100 Mbps over a distance of about 100 m. For this reason, a technology called 100BASE-T4 has been devised (for example, “100BASE-T is converted to 100 V
G-AnyLAN will postpone, ATM25 will form its own world ", Nikkei Electronics June 5, 1995, N
o. 637, pp91-107 (1995)).

[0012] As shown in FIGS. 12A and 12B, 100BASE-T4 is a transmission-only line 281 and a reception-only line 2.
82 and a two-channel data transmission path 292 to 293 for bidirectional transmission using a pair of twisted pair cables 283 to 284. Since the transmission paths 291 to 293 of a total of three channels are formed, it is possible to obtain a total (information) signal speed of 100 Mbps by supplying a signal of 33.3 Mbps to each channel.

In FIG. 12 (a), transmitters 271, 273,
275 and receivers 272, 274, 276 are provided. Similarly, the hub interface 201 includes transmitters 261, 263, 265 and receivers 262, 264, 26.
6 are provided.

A technique of using a pair of twisted pair cables as a bidirectional bus, such as 100BASE-T4, can also be found in Japanese Patent Application Laid-Open No. 6-216925. In this prior art document, as shown in FIG. 13, a frequency band 301 for data transmission composed of frequencies f1 and f2 and a frequency band 302 for control signal transmission having a center frequency at f3 are formed. Four bidirectional transmission channels are formed using a wire twisted pair cable.

[0015] In 100BASE-T4, three channel transmission lines are used as parallel buses. When a plurality of transmission lines are arranged, each transmission line is regarded as an independent bus, and the protocol is further devised. It is known that transmission efficiency is improved as compared with a simple parallel bus. If carrier sensing is performed on a plurality of transmission paths and a vacant transmission path is selected at random, the transmission efficiency is improved due to the load distribution effect (Nomura et al., “Multi-channel C in Bus Local Area Network”).
SMA / CD system ", IEICE Transactions Vol. J6
7-D, no. 9, pp 949-956 (198
4)).

As shown in FIG. 14A, a plurality of buses 25
Consider a network in which client stations 251 are connected to 2 to 254. In the network shown in FIG. 14A, the client station 251 performs carrier sense on all the buses 252 to 254 before transmission, and sends out a signal (packet) to a bus selected at random from the available buses. The simulation result of the throughput in the case of adopting is described in the above-mentioned document by Nomura et al. FIG. 14B shows a load-throughput characteristic when the number of buses arranged in parallel is changed from 1 to 4 under this communication method. It can be seen that, when the load is high, the throughput is improved by about 30% when the four channels are parallelized as compared with the case of the single channel. Therefore,
Japanese Patent Application Laid-Open No.
It can be seen that the parallelization method as shown in 216925 is more desirable from the viewpoint of line utilization efficiency (improvement of throughput).

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide a collision detection method for forming a bidirectional bus with one transmission line in a local area network using twisted pair cables. .
It is another object of the present invention to provide a collision detection method capable of simultaneously detecting a link state. Another object of the present invention is to provide a collision detection method and a communication method that do not transmit a jamming signal for collision detection.

[0018]

According to the present invention, in order to achieve the above object, there is provided a concentrator having a plurality of ports, and a twisted pair cable is used as a transmission medium for connecting the ports to a station. In the communication network used, the signal propagating through the twisted pair cable is determined so as to have a DC voltage component, and the concentrator includes 1) transmitting means, 2) receiving means, 3) the transmitting means and the receiving means, And 4) a DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable, and 5) a carrier detecting means for detecting a carrier component on the twisted pair cable. , 6) collision detection means for detecting a signal collision on the twisted pair cable from the detection result of the DC voltage level detection means, and 7) collision which outputs the judgment result of the collision detection means as a change in the DC voltage component to the port. A detection signal transmitting means is provided.

In this configuration, it is possible to detect signal collision by monitoring the DC voltage level of the twisted pair cable of the transmission line while performing bidirectional signal transmission on the transmission line for one channel.

According to the present invention, in order to achieve the above-mentioned object, a communication network having a concentrator having a plurality of ports and using a twisted pair cable as a transmission medium for connecting the ports and the station is provided. Wherein the signal propagating through the twisted pair cable is determined to have a DC voltage component, and the concentrator includes: 1) transmitting means, 2) receiving means, and 3) connecting the transmitting means and the receiving means to the twisted pair cable. 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable,
5) Carrier detecting means for detecting a carrier component on the twisted pair cable; 6) Detecting a link state between the station and the concentrator from the detection result of the DC voltage level detecting means and the detection result of the carrier detecting means. And link detecting means.

In this configuration, while performing bidirectional signal transmission on the transmission path for one channel, the DC voltage level of the twisted pair cable of the transmission path can be monitored to detect the attachment / detachment of the link. Further, the detection of the carrier can be supplementarily used for the detection of the attachment / detachment of the link.

According to the present invention, in order to achieve the above object, a communication network having a concentrator having a plurality of ports and using a twisted pair cable as a transmission medium for connecting the ports and the station is provided. Wherein the signal propagating through the twisted pair cable is determined to have a DC voltage component, and the station comprises:
2) receiving means, 3) connection switching means for switching and connecting the transmitting means and the receiving means to the twisted pair cable, 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable, 5)
A carrier detecting means for detecting a carrier component on the twisted pair cable; and 6) a collision detecting means for detecting a collision of a signal on the twisted pair cable from a detection result of the DC voltage level detecting means.

In this configuration, it is possible to detect a signal collision by monitoring the DC voltage level of the twisted pair cable of the transmission line while performing bidirectional signal transmission on the transmission line for one channel.

According to the present invention, in order to achieve the above-mentioned object, a communication network having a concentrator having a plurality of ports and using a twisted pair cable as a transmission medium for connecting the ports and the station is provided. Wherein the signal propagating through the twisted pair cable is determined to have a DC voltage component, and the station comprises:
2) receiving means, 3) connection switching means for switching and connecting the transmitting means and the receiving means to the twisted pair cable, 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable, 5 A) a carrier detecting means for detecting a carrier component on the twisted pair cable; and 6) a link for detecting a link state between the station and the concentrator based on a detection result of the DC voltage level detecting means and a detection result of the carrier detecting means. It has a detecting means.

Also in this configuration, while bidirectional signal transmission is performed on the transmission path for one channel, the DC voltage level of the twisted pair cable of the transmission path can be monitored to detect the attachment / detachment of the link. Further, the detection of the carrier can be supplementarily used for the detection of the attachment / detachment of the link.

According to the present invention, in order to achieve the above-mentioned object, in a communication network capable of detecting the above-mentioned collision, the transmitting station immediately stops transmitting when a collision is detected. You are going to do the steps. Further, the line concentrator executes a procedure for immediately stopping signal relay when a collision is detected. After the collision is detected, the concentrator stops transmitting the collision detection signal after the carriers from all the ports are no longer detected.

In this configuration, since the line concentrator determines the collision of signals, it is not necessary to generate a jamming signal in a LAN using a coaxial cable for a predetermined time after the collision is detected. That is, in a LAN using a coaxial cable, it is necessary to generate a jamming signal to ensure that a collision is detected at one station even after a collision is detected at one station. According to the present invention, since the concentrator directly performs the detection, the signal transmission can be immediately stopped without generating such a jamming signal.

According to the present invention, in a communication network including the above-described concentrator and the station, when the port and the station are not properly linked, the DC voltage levels of the port and the station are respectively set to the first level. DC voltage level and the second DC voltage level, and the signal propagating through the twisted pair cable is determined to have a DC voltage component. When the signal collides in the twisted pair cable, the DC voltage level of the twisted pair cable is The third DC voltage level is set.

In this configuration, by monitoring the DC voltage, it is possible to monitor the collision of signals and the attachment / detachment of the link.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a network configuration according to the present invention will be described with reference to FIGS. FIG. 1 shows an interface 1 for a client station and an interface 2 for a hub.
FIG. 3 is a diagram showing a detailed structure of connection with the maker. FIG. 2 is a diagram showing voltage waveforms on the twisted pair cable 3 connecting the client station interface 1 and the hub interface 2 in each state. FIG. 3A shows the hub 41.
FIG. 2 is a diagram showing an overall configuration of the embodiment. The hub 41 is connected to the client station 42 by a two-wire twisted pair cable 45. Twisted pair cables 43 to 44 are included in the two-wire twisted pair cable 45. Although the twisted pair cables 43 to 44 are substantially equivalent to the twisted pair cable 3 in FIG. 1, the reference numerals are distinguished for convenience of explanation. FIG. 3 (b)
Is a diagram showing that the client 42 includes client station interfaces 1a and 1b. Interface 1a or 1b for client station
Is the interface 1 for the client station in FIG.
Is substantially equivalent to FIG. 3C shows hub interfaces 2 a through 2 b for a certain port in the hub 43.
It is a figure showing that b was included. The hub interfaces 2a and 2b are also substantially equivalent to the client station hub interface 2 in FIG.
FIG. 4 is a diagram showing the internal configuration of the hub 41. A pair of interfaces 2a and 2b are provided for each port, and controllers 46 and 47 are provided to form a two-system bus.

Referring to FIG. 1, the client station interface 1 and the hub interface 2 will be described in detail. In FIG. 1, a client station interface 1 is connected to a hub interface 2 via a twisted pair cable 3, and a bidirectional signal 3 is transmitted on the twisted pair cable 4. The controller 11 and the transmitter 1 are inside the client station interface 1.
2. Receiver 13, transmission / reception switch 14, carrier detection mechanism 16, link state detection / collision detection mechanism 1
7, including the terminating resistor 18. On the other hand, the controller 21 and the transmitter 2
2, receiver 23, transmission / reception changeover switch 24, carrier detection mechanism 26, link state detection mechanism and collision detection mechanism 2
7, a terminating resistor 28, and a link state signal / collision detection signal transmitting mechanism 29.

The carrier detection mechanisms 16 to 26 include a band-pass filter and a detection mechanism. For example, when the MLT-3 code is employed, a frequency region having the highest power spectrum density around 16 MHz is detected (FIG. 1).
1 (b)). Link state detection mechanism and collision detection mechanism 1
Reference numerals 7 to 27 each include a low-pass filter and a DC voltage level detecting mechanism, and have a function of checking the DC voltage state of the twisted pair cable 4 as a transmission medium.

In the idle state, the link state signal / collision detection signal transmission mechanism 29 in the hub interface 2 applies a voltage of + 2V1 to the twisted pair cable 4.
Since the voltage of + 2V1 is branched by the terminating resistors 18 and 28, the voltage on the twisted pair cable 4 becomes + V1 (see FIG. 2A). The link state is detected by detecting the voltage of + V1 by the link state detection mechanism / collision detection mechanisms 17 to 27. if,
If the twisted pair cable 4 is disconnected, the link state detection mechanism / collision detection mechanism 17 detects a voltage of 0V, and the link state detection mechanism / collision detection mechanism 27 detects a voltage of + 2V1. In the idle state, the carrier detection mechanisms 16 to 26 cannot detect any signal. In addition,
Here, it is assumed that the terminating resistors 18 and 28 have substantially the same resistance value.

It is assumed that a signal is transmitted from the client station interface 1 side. In this case, the signal transmitted from the transmitter 12 has an average of -V as shown in FIG.
A signal containing one DC voltage is transmitted. This signal is added to the + V1 voltage applied to the twisted pair cable 4 to form a waveform pattern as shown in FIG.
That is, the DC voltage level of the twisted pair cable 4 is 0V. In this state, if only the DC voltage level is monitored, the client cannot distinguish between a state in which the link has been disconnected and a state in which a signal has been applied to the twisted pair cable. However, in the above-mentioned state, the carrier detection mechanisms 16 to 26 are configured to output the carrier component (for example, 1
(A power component around 6 MHz), so that the link state detection mechanism / collision detection mechanism 17 and the carrier detection mechanism 16 can be detected.
By using both of the results, the link state and the carrier detection state can be identified. When a signal is transmitted from the hub interface 2 side, carrier detection and link detection can be identified in the same manner as described above.

Next, consider the case where signals are simultaneously transmitted from both the interface 1 for the client station and the interface 2 for the hub. In this case, as shown in FIG. 2D, the DC voltage level of the twisted pair cable 4 becomes -V1 by adding the two signals. The collision state can be detected by detecting the voltage level by the link state detection mechanism / collision detection mechanisms 17 to 27. At the time of collision detection, the presence or absence of carrier sense is ignored, and if the DC voltage level on the twisted pair cable 4 is -V1 or less, it is considered that a collision has occurred.

The collision between the interface 1 for the client station and the interface 2 for the hub has been described above. However, a collision may occur at another port of the hub 41 in FIG. In this case, the controllers 46 to 47 in the hub 41 shown in FIG. Is generated (see FIG. 2E). Then, a DC component of -V1 is applied on the twisted pair cable 4, and the occurrence of the collision can be transmitted to the client station.

A specific example of the communication system of the present invention will be described with reference to FIGS. In the network described with reference to FIGS. 1 to 4, this communication method is applicable. FIG. 5 is a state transition diagram of a communication system (protocol) applied to the client station (for example, 42 shown in FIG. 3). On the other hand, FIG. 6 shows a hub (for example, 4 shown in FIG. 3).
It is a state transition diagram of the communication system (protocol) applied to 1). As shown in FIG. 5, the protocol applied to the client station stops transmission immediately after a collision is detected during transmission and enters a wait for a random time. In the protocol applied to the hub, as shown in FIG. 6, when a collision is detected, signal relay is immediately stopped, and a collision detection signal is transmitted to all ports. Then, when the carrier is not detected from all the ports, the transmission of the collision detection is released.

The features of the present invention become clear when compared with the state transition diagram of the protocol in the prior art shown in FIG. That is, there is no procedure of transmitting a jamming signal for a fixed time, but instead, a procedure of immediately stopping signal transmission is included. In Ethernet using a coaxial cable, a collision notification is generated in the form of interference between two signals, so it is necessary to transmit a jamming signal for a predetermined time longer than the maximum round-trip propagation delay time of the bus. On the other hand, in the network of the present invention, collision detection is performed in the hub, and notification of collision detection to each client is notified from the hub in the form of a DC voltage level. There is no need to take. In a conventional Ethernet using a twisted pair cable, collision detection is performed by a hub. However, since the notification of the collision detection signal is performed in the form of a specific collision detection signal, it is necessary to transmit the collision detection signal for a certain period of time.

In the network and communication system of the present invention, the collision detection is detected by the DC voltage of the transmission medium (twisted pair cable), and the notification of the collision detection to the entire network is notified by the DC voltage of the transmission medium. Features. Further, the cancellation of the collision state is determined based on the disappearance of the carrier signal, and the transmission of the collision detection signal is canceled. Together, these features make it possible to introduce into the protocol the procedure of immediate transmission of transmission or signal relay following collision detection.

FIG. 7 shows a network configuration when the present invention is applied when connection between hubs is performed. Even when the hub 51 and the hub 52 are directly connected, the collision detection using the voltage levels shown in FIG. 2 is possible. However,
When connecting hubs, it is necessary to slightly change the function of the interface 2-1 of one hub (the hub 52 in FIG. 7). When the hub interfaces 2 shown in FIG. 1 are connected to each other, the link state signal / collision detection signal transmitting mechanism 2
9, a signal of -2V1 is transmitted, and the voltage level on the twisted pair cable 57 during idle is -2V1.
It is because it becomes. Therefore, it is necessary to change one of the interfaces 2-1 so that a voltage of 0 V is transmitted from the link state signal / collision detection signal transmitting mechanism 29 at the time of idle, but the other points need to be changed. is not.

In the network shown in FIG. 7, the communication system based on the state transition diagram shown in FIGS. 5 and 6 is applicable.

[0042]

According to the present invention, collision detection and link state detection can be performed while forming a bidirectional bus using a pair of twisted pair cables. Therefore, if two-wire twisted pair cables are used, two independent bidirectional buses can be configured using four-wire twisted pair cables. The communication capacity can be expanded and new functions can be added using the plurality of independent bidirectional buses. Further, according to the present invention, the collision detection is notified by the DC voltage level, so that the entire network can be made aware of the collision state without performing a procedure of transmitting a jamming signal for a predetermined time. Therefore, the time during which the network cannot be used for data transmission by transmitting the jamming signal for a certain time can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an internal structure and a connection state of a client station interface 1 and a hub interface 2 in an embodiment of the present invention.

FIG. 2 shows voltage waveforms in each state on a twisted pair cable connecting a client station interface 1 and a hub interface 2 in the above embodiment.

FIG. 3 is a schematic diagram showing an overall configuration of a hub 41 according to the embodiment.

FIG. 4 is a schematic diagram showing an internal configuration of a hub 41 according to the embodiment.

FIG. 5 is a state transition diagram on the client station side showing a control procedure of the communication method according to the embodiment.

FIG. 6 is a state transition diagram on the hub side illustrating a control procedure of the communication method according to the embodiment.

FIG. 7 is a schematic diagram showing connection between hubs in the above embodiment.

FIG. 8 is a schematic diagram showing a configuration of an Ethernet using a conventional coaxial cable and a voltage waveform on the coaxial cable.

FIG. 9 shows CSMA / adopted in conventional Ethernet.
It is a state transition diagram of a CD protocol.

FIG. 10 is a schematic diagram showing a configuration of an Ethernet using a conventional twisted pair cable.

FIG. 11 is a schematic diagram showing a waveform pattern and a power spectrum of an MLT-3 code used for a conventional 100BASE-TX or the like.

FIG. 12 is a schematic diagram showing how a twisted pair cable is used in a conventional 100BASE-T4.

FIG. 13 is a schematic diagram showing a relationship between a data communication channel and a control channel in a prior art document.

FIG. 14 is a schematic diagram showing a configuration of a multi-channel Ethernet (CSMA / CD) in another prior art document and its effect.

[Explanation of symbols]

1: Client interface, 2, 2a, 2
b: hub interface, 3: signal propagating over twisted pair cable 4, 4 ... twisted pair cable, 1
DESCRIPTION OF SYMBOLS 1 ... Controller, 12 ... Transmitter, 13 ... Receiver, 14
... Transmission / reception changeover switch, 15 ... Transmission / reception switching control control signal, 16 ... Carrier detection mechanism, 17 ... Link state detection mechanism, collision detection mechanism, 18 ... Terminal resistor, 21 ... Controller, 22 ... Transmitter, 23 ... Receiver, 24 ... Transmission and reception changeover switch, 25 ... Transmission and reception changeover control signal, 2
6 Carrier detection mechanism, 27 Link status detection mechanism, collision detection mechanism, 28 Terminating resistor, 29 Link status detection mechanism, collision detection signal transmission mechanism, 41 Hub, 42 Client station, 43-44 Twisted pair cable , 45 ...
2-wire twisted pair cable, 46-47 ... controller, 51-52 ... hub, 53-54 ... twisted pair cable connecting between the client station and the hub, 55-56
.., A signal propagating on a twisted pair cable, 57... A signal propagating on a twisted pair cable connecting between hubs, 58.
62 client station, 201 hub, 202 client station, 203-204 twisted pair cable, 2
05: two-wire twisted pair cable, 211: transmitter,
212 ... receiver, 213-214 ... terminator, 261,
263, 265: hub-side transmitters, 262, 264, 2
66: Receiver on the hub side, 271, 273, 275: Transmitter on the client station side, 272, 274, 276: Receiver on the client station side, 281-284 ... Twisted pair cable, 291 ... Channel-1, 292 ... Channel −
2, 293 ... channel-3, 311 ... (client)
Station, 312 ... coaxial cable, 313 ... signal propagating on the coaxial cable

Claims (8)

[Claims] 1. A concentrator having a plurality of ports,
In a communication network using a twisted pair cable as a transmission medium for connecting the port and the station, a signal propagating through the twisted pair cable is determined to have a DC voltage component, and the concentrator has the following components. A communication network characterized by the following. 1) Transmission means. 2) Receiving means. 3) connection switching means for switching the transmission means and the reception means to the twisted pair cable for connection; 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6) Collision detecting means for detecting a collision of signals on the twisted pair cable from a detection result of the DC voltage level detecting means. 7) Collision detection signal transmitting means for outputting the result of determination by the collision detection means as a change in the DC voltage component to the port. 2. A line concentrator having a plurality of ports,
In a communication network using a twisted pair cable as a transmission medium for connecting the port and the station, a signal propagating through the twisted pair cable is determined to have a DC voltage component, and the concentrator has the following components. A communication network characterized by the following. 1) Transmission means. 2) Receiving means. 3) connection switching means for switching the transmission means and the reception means to the twisted pair cable for connection; 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6) Link detection means for detecting a link state between the station and the concentrator from the detection result of the DC voltage level detection means and the detection result of the carrier detection means. 3. A concentrator having a plurality of ports,
In a communication network using a twisted pair cable as a transmission medium for connecting the port and the station, a signal propagating through the twisted pair cable is determined to have a DC voltage component, and the station has the following components. Characteristic communication network. 1) Transmission means. 2) Receiving means. 3) connection switching means for switching the transmission means and the reception means to the twisted pair cable for connection; 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6) Collision detecting means for detecting a collision of signals on the twisted pair cable from a detection result of the DC voltage level detecting means. 4. A concentrator having a plurality of ports,
In a communication network using a twisted pair cable as a transmission medium for connecting the port and the station, a signal propagating through the twisted pair cable is determined to have a DC voltage component, and the station has the following components. Characteristic communication network. 1) Transmission means. 2) Receiving means. 3) connection switching means for switching the transmission means and the reception means to the twisted pair cable for connection; 4) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6) Link detection means for detecting a link state between the station and the concentrator from the detection result of the DC voltage level detection means and the detection result of the carrier detection means. 5. The communication method used in the communication network according to claim 1, wherein the transmitting station executes a procedure for immediately stopping the transmission when a collision is detected. Communication method to be used. 6. The communication method used in the communication network according to claim 1, wherein said concentrator executes a procedure for immediately stopping signal relay when a collision is detected. Method. 7. A communication method used in a communication network according to claim 1, wherein said concentrator stops transmission of a collision detection signal after carriers from all ports are not detected after collision detection. A communication method, comprising: 8. A concentrator having a plurality of ports,
In a communication network using a twisted pair cable as a transmission medium for connecting the port and the station, when the port and the station are not properly linked, the DC voltage levels of the port and the station are respectively set to the first level.
And a second DC voltage level of
Further, the signal propagating through the twisted pair cable is determined to have a DC voltage component. When a signal collides in the twisted pair cable, the DC voltage level of the twisted pair cable becomes a third DC voltage level, and the concentrator is It comprises the following components: 1a) Transmission means. 2a) Receiving means. 3a) connection switching means for switching the transmission means and the reception means to the twisted pair cable for connection; 4a) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5a) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6a) Collision detection means for detecting a collision of signals on the twisted pair cable when the DC voltage level detection means detects the third DC voltage level. 7a) Link detecting means for determining a link state between the station and the concentrator when the DC voltage level detecting means does not detect the first DC voltage level. 8a) Collision detection signal sending means for outputting the result of the judgment by the collision detection means to the port as a change in the DC voltage component.
A communication network, wherein the station has the following components. 1b) Transmission means. 2b) Receiving means. 3b) connection switching means for switching and connecting the transmitting means and the receiving means to the twisted pair cable. 4b) DC voltage level detecting means for detecting a DC voltage level on the twisted pair cable. 5b) Carrier detecting means for detecting a carrier component on the twisted pair cable. 6b) Collision detection means for detecting a collision of signals on the twisted pair cable when the DC voltage level detection means detects the third DC voltage level. 7b) Link detecting means for judging a link state between the station and the concentrator when the DC voltage level detecting means does not detect the second DC voltage level.