JPH0923237A - Broad band lan communication control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect collision of transmission data without newly providing a channel. SOLUTION: The broad band LAN communication control system 50 is mainly composed of a two-way broad band network 30, plural terminal equipments A-C connected to the network 30, data processing units (a)-(c) such as personal computers connected to the terminal equipments A-C, and a head end device (HE) 10 receiving and demodulating transmission data sent from the terminal equipments A-C to an incoming CH (channel) and modulating and transmitting the modulated signal to an outgoing CH. The HE 10 modulates the received data and sends the modulated data to the outgoing CH and provides the output of command information to stop the transmission of the terminal equipments A-C by judging it to be the occurrence of data collision when an error is detected by error check information of a received pilot packet. The terminal equipments A-C stops data transmission when they receive command information or an ID included in the pilot packet sent again from the HE 10 is not its own ID or they detects an error in the error check information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control system for a bidirectional broadband LAN (local area network) used for CATV and the like.

[0002]

2. Description of the Related Art Conventionally, in a two-way broadband LAN, an upstream channel and a downstream channel are provided in different frequency bands, transmission data is placed on a carrier wave, and an upstream channel frequency transmitted from each terminal device via a headend device. Is converted into a downlink channel frequency for communication. In the CSMA / CD system which performs asynchronous multiple access on such a network, it is difficult to reliably detect and avoid transmission data collision when a plurality of terminals simultaneously start transmission.

There are two methods for knowing the collision of the transmitted data. The first method is to transmit a pilot packet for collision detection to an upstream channel before transmitting an information packet in each terminal. Then, the pilot packet, which is frequency-converted by the headend device and is transmitted back to the downlink channel, is received by the terminal device of the transmission source. When this pilot packet is normally received, it is determined that there is no collision, otherwise it is determined that transmission data collision has occurred,
Method (Japanese Patent Publication No. 6-20200). The second method is that when one of the terminals detects an abnormality, it uses a special control channel with a frequency different from the currently used channel to send data to all other terminals. This is a method of notifying that the collision has been detected, and each terminal intercepts this channel to know the collision of the transmission data (ANSI / IEEE Std 802.3b).

[0004]

However, the former method cannot necessarily detect the collision of transmission data. That is, in the broadband network, since the carrier wave communication method is used, when a plurality of terminals simultaneously perform transmission, the respective transmission levels and reception levels may differ, and it is not always possible to detect a collision of transmission data. There is a problem. In the latter method, a control channel other than the channel used for the original communication is required, and there is a problem of band utilization efficiency or a problem of complication of the device.

Therefore, the object of the present invention is to detect the collision of transmission data and notify the respective terminals of the collision information by the head-end device so that a new channel is not required and transmission data collision is surely performed. It is to provide a communication control method capable of detecting

[0006]

In order to solve the above-mentioned problems, the structure of the present invention has a bidirectional broadband network, a plurality of terminals connected to the network, and transmission from each of the terminals to an upstream channel. If there is transmission data to be transmitted, the transmission data is received and demodulated and modulated and transmitted in different frequencies in the downlink channel. If there is no carrier in the uplink channel, it is notified to each terminal device that there is no carrier. And a headend device that outputs an idle signal for notifying the downstream channel to the CSMA /
It is a communication control method for performing communication by a CD (asynchronous multiple access) method, and when a headend device receives and demodulates transmission data of an upstream channel and detects an error in the transmission data, a collision occurs in the transmission data. And outputs command information for stopping transmission to each terminal device, and each terminal device stops transmission of transmission data when receiving command information from the headend device.

According to the configuration of the second invention, the transmission data is used for a collision check including an information packet to be transmitted to a destination address and a transmission source ID and error check information transmitted prior to the information packet. Each terminal is capable of transmitting when an idle signal is received, and modulates a carrier wave with the pilot packet and the information packet to transmit to the uplink channel, and while transmitting the pilot packet. , Receiving and demodulating pilot packets of different carrier frequencies transmitted from the headend device to the downlink channel, and determining whether or not a source ID is designated and whether or not there is a collision of transmission data based on the demodulated result. When the ID is assigned to me and there is no collision of transmission data, the next information packet is transmitted,
At other times, it has the function of cutting the carrier wave and stopping the transmission.The headend device receives and demodulates the pilot packet transmitted from the terminal device to the uplink channel, re-modulates and transmits it to the downlink channel, and the error Based on the check information, it is checked whether or not the communication is normally performed. If the communication is normally performed, it is determined that there is no collision of the transmission data, and the information packet follows the pilot packet. When receiving and demodulating and modulating and transmitting to the downlink channel, if communication is abnormal, it is judged that there is a collision of transmission data and the occurrence of collision is notified to each terminal unit, and the transmission of each terminal unit is transmitted. It is characterized by transmitting command information for stopping.

[0008]

The first operation of the present invention having the above configuration is that the headend device receives and demodulates the transmission data, and when an error is detected in the transmission data, it is determined that a collision has occurred in the transmission data, Outputting command information for stopping transmission to each terminal device, each terminal device stops transmitting data when receiving command information from the headend device, and the effect is that the headend device That is, the side can judge the collision of the transmission data, and can surely detect the collision of the transmission data. (Claim 1)

The second function is that the transmission data transmitted from each terminal is composed of a collision check pilot packet including a transmission source ID and error check information, and an information packet transmitted to a destination address. Then, the headend device receives and demodulates the pilot packet, detects the collision of the transmission data from the result, and transmits the command information for stopping the transmission to each terminal device, and based on the command information, each terminal device The device stops the data transmission, and when multiple terminals are transmitting at the same time, even if a collision is not detected due to the level difference between the terminals, the ID of the normally received terminal is headed. The terminal device having a different ID transmitted by the end device recognizes that it is not its own ID and stops the transmission, thereby avoiding interference. . (Claim 2)

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. FIG. 1 is a schematic diagram showing the configuration of the first embodiment of the present invention. Broadband LAN communication control system 5
0 is mainly a two-way broadband network 3
0, a plurality of terminal devices A to C connected to the network 30, a data processing device ac including a personal computer or the like connected to each of the terminal devices A to C, and each terminal device A to C.
The head end device 10 receives and demodulates the transmission data transmitted from C to the upstream channel and modulates and transmits it to the downstream channel. This communication control system 50
It may be configured to be connected to another network system 40 via the connection device 41.

Each of the terminals A to C is connected to the RF modem unit 21 for receiving and demodulating data from the downlink channel and modulating and transmitting to the uplink channel, and to the data processing devices a to c to connect the data processing devices a to c. The communication control unit 22 is configured to access and control communication via the bidirectional broadband network 30.
A detailed configuration of the terminals A to C is shown in FIG.

The head-end device 10 includes a modem section 11 that receives and demodulates data from the upstream channel and modulates and transmits the data to the downstream channel, and a control section 12 that decodes the received data from the upstream channel and controls communication. Composed. A detailed configuration of the headend device 10 is shown in FIG.

Next, a communication method of the communication control system 50 having the above configuration will be described. FIG. 4 is an explanatory diagram showing, as an example, the content of data when the terminal A and the headend device 10 do not collide with each other and are normally transmitted and received in chronological order. In the figure, is the transmission data of the headend device 10, is the reception data of the headend device 10, is the transmission data of the terminal A, and is the terminal A.
The received data of each is shown.

The terminal device A confirms NW-IDLE (network idle: equivalent to an idle signal) (), turns on the carrier (carrier wave), and transmits PAD-IDLE (repeating 1010) to the upstream channel (). . This PAD-IDLE stabilizes after the carrier is turned ON with a delay of a stabilization time α. The PAD-IDLE transmitted from the terminal A is received by the headend device 10 with a delay of one-way transmission delay time β ().

In the headend device 10, the carrier and
When PAD-IDLE is received, it is delayed by the internal processing delay time γ.
Switch NW-IDLE to PAD-IDLE and send (). After a certain period of time, the terminal device A transmits a pilot packet composed of SA (transmission source ID), CRCC1 (pilot packet error check information), and PAD-IDLE, starting with SD (start delimiter) (). In the headend device 10,
SD, SA, CRCC1, PAD-IDLE transmitted from terminal A are sequentially received (), and SD, SA, CRCC1, PA are sent to the downlink channel.
Send D-IDLE sequentially () and check that CRCC1 has no error.

In the terminal A, from the headend device 10
SA which SD, SA and CRCC1 received () and SA sent by itself
And CRCC1 has no error, PA
Following D-IDLE, an information packet consisting of transmission information and CRCC2 (information packet error check information) and ED (end delimiter) are transmitted (). When this transmission is completed,
The terminal A turns off the carrier (). The headend device 10 receives the information packet and the ED from the terminal device A (), and sequentially transmits the data to the downlink channel ().

In the headend device 10, the carrier is OF
When it is confirmed that it is F, NW-IDLE is transmitted (). Each of the terminals A to C receives the information packet and the ED from the headend device 10 (), and after this, the NW-IDL
By receiving E (), transmission / reception of one data is completed, and the next data can be transmitted. In this way, the communication control system 50 can normally communicate.

In the above embodiment, in order to extract the information packet on the receiving side, the length of the pilot packet needs to be predetermined. In the above, the NW-IDLE transmitted from the headend device 10 to the terminal device A
Can notify the terminal device A that it is ready for transmission to the uplink channel, and can provide timing information so that the terminal device A can always recover the clock synchronized with the received data. As a result, the terminal device A can always hold the synchronization clock in a stable state even if the clock reproducing means having a slow response is used.

In addition, the PAD-IDLE transmitted from the terminal A immediately after the carrier is turned ON is the headend device 10
A function of notifying all other terminals via the terminal of the start of transmission from the terminal A, calling attention not to transmit, and reproducing the synchronous clock for reception of the headend device 10. Have. Head end device 10
Requires the use of a fast response clock recovery means.

On the other hand, FIG. 5 is an explanatory diagram showing the contents of data when data collides between the two terminals A and B and the head end device 10 in chronological order. In the figure, is transmission data of the headend device 10, is reception data of the headend device 10, is transmission data of the terminal A, is reception data of the terminals A and B, is transmission data of the terminal B. Are shown respectively.

Conventionally, in the data collision determination, the data transmitted from the terminal A is received via the head end device 10, and the terminal A determines the presence or absence of the collision based on the received data. , Receive data from terminal A,
Collision is judged by the head end device 10, and the carrier O
Point to output ABRT (corresponding to command information) for FF (
Reference) is a feature of the present invention. In addition, even if data collision occurs due to the transmission of a plurality of terminals, if the data from a certain terminal is normally received, the ID of the terminal is transmitted so that the transmission of the normally received terminal is transmitted. And has a function of stopping the transmission of other terminals.

The communication method of the communication control system 50 when a data collision occurs will be described below. Terminal A is NW-IDLE
Check (), turn on the carrier, and send PAD-IDLE to the upstream channel (). Sent from terminal A
PAD-IDLE is received by the headend device 10 with a delay of one-way transmission delay time β (), and when PAD-IDLE is received,
The NW-IDLE is switched to PAD-IDLE and transmitted with a delay of internal processing delay time γ ().

Thereafter, the terminals A and B receive PAD-IDLE from the headend device 10 (), but the terminal B receives the collision window (the terminals A and B after the terminal A turns on the carrier). Until PAD-IDLE is received) within δ is NW
-Because IDLE is received, data transmission can be started (). After a certain period of time, the terminal A transmits a pilot packet composed of SA, CRCC1 and PAD-IDLE () starting from SD (), and the headend device 10 receives the data transmitted from the terminal A. (). At this time, due to the data transmission from the terminal device B, the reception data of the headend device 10 is disturbed in the shaded area in the drawing.

An error occurs in CRCC1 due to the interference by the terminal device B, and when the headend device 10 confirms the CRCC1 error, SDRT, SA, and CRCC1 are followed by ABRT one or more times (see FIG. 5).
Then send it twice). The terminals A and B receive SD, SA and CRCC1 from the headend device 10 (), and
When SA is not the SA sent by itself, when an error is detected in CRCC1 or when ABRT is received, the carrier is turned off (,).

When the terminals A and B stop transmission (,
), The headend device 10 confirms that the carrier is OFF, and transmits NW-IDLE (). Terminal A,
When B receives the NW-IDLE from the headend device 10 () and confirms the NW-IDLE, it becomes ready to start transmission again, and can wait for a stochastic time interval and start retry ().

If the transmission level of the terminal device B is lower than the transmission level of the terminal device A, an error may not be detected in the CRCC1, but if it is confirmed that the received SA is not its own, the terminal device B will Since the transmission is stopped and the terminal A continues the transmission, normal communication can be performed. As described above, the head-end device 10 detects a data collision, outputs a signal to stop transmission to each of the terminals A to C, and then transmits again, thereby reliably detecting a data collision. can do. In this example, PAD-
The IDLE transmission time is set longer than the collision window δ.

7 to 9 show procedures of data transmission / reception performed between the terminal units A and B shown in FIGS. 4 and 5 and the headend device 10. 7, FIG. 8 and FIG. 9 show flowcharts in the reception unit and the transmission unit at the time of transmission of the headend device 10 and the terminals A and B, respectively. As shown in FIG. 7, since the SD may not be able to receive due to interference or the like, in the headend device 10,
The SD may be configured to generate an error when it cannot be received within a predetermined time.

That is, at the same time when the headend device 10 receives PAD-IDLE (step 140), the timer 1 starts counting (step 150), and even if the count value of the timer 1 exceeds a predetermined value, the headend device 10 When 10 does not receive SD, it is judged as an error (step 190) and ABRT is output (step 250). With such a configuration, it is possible to deal with the case where the SD cannot be received by the headend device 10 due to interference or the like.

In this embodiment, the pilot packet and the information packet are grouped together and sandwiched between SD and ED for transmission. However, as shown in FIG. 6, each packet is sandwiched between SD and ED. It may be configured. At this time, in order to identify the packet type, by inserting the identification code CF after SD, the CF can be checked on the receiving side to identify the packet type.

The information packet is the information part that should be transmitted between the terminals, and the destination address and the like are included in this packet. For example, as the structure of the information packet, the same configuration as IEEE Std 802.3 can be used.

As indicated above, according to the present invention,
The transmission data transmitted from each terminal is composed of a pilot packet for collision inspection including a transmission source ID and error check information, and an information packet transmitted to a destination address, and the head end device receives the pilot packet. It demodulates, detects the collision of the transmission data from the result, and transmits the command information for stopping the transmission to each terminal, and based on the command information or by checking the sender ID or CRCC1, Each terminal device can reliably transmit and receive data by stopping the data transmission.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment according to the present invention.

FIG. 2 is a block diagram showing the configuration of a terminal device according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing the configuration of a headend device in a first embodiment according to the present invention.

FIG. 4 is a schematic diagram showing the contents of data when data is normally transmitted and received in the first embodiment according to the present invention in chronological order.

FIG. 5 is a schematic diagram showing the contents of data transmitted and received when data collide in the first embodiment according to the present invention in chronological order.

FIG. 6 is a schematic diagram showing the contents of data used in another embodiment of the present invention in chronological order.

FIG. 7 is a flowchart showing a processing procedure of the headend device in the first embodiment according to the present invention.

FIG. 8 is a flowchart showing a processing procedure of the receiving unit of the terminal device at the time of transmission in the first embodiment according to the present invention.

FIG. 9 is a flowchart showing a processing procedure of a transmitter of the terminal in the first embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 headend device AC terminal device ac data processing device 21 RF modem unit 22 communication control unit 30 bidirectional broadband network 50 broadband LAN communication control system

Claims (2)

[Claims] 1. When there is a bidirectional broadband network, a plurality of terminals connected to the network, and transmission data to be transmitted from each of the terminals to an upstream channel, the transmission data is received and demodulated for downlink. A head-end device that outputs an idle signal to the downlink channel, which is modulated and transmitted at a different frequency to the channel, and when there is no carrier in the uplink channel, to notify the terminals that there is no carrier. And a communication control method for performing communication by a CSMA / CD (asynchronous multiple access) method, wherein the headend device receives and demodulates the transmission data of the uplink channel and detects an error in the transmission data. Determining that a collision has occurred in the transmission data, outputting command information for stopping transmission to each of the terminals, Terminal unit receives the instruction information from the headend, broadband LAN communication control method, characterized in that stops transmission of the transmission data. 2. When there is a bidirectional broadband network, a plurality of terminals connected to the network, and transmission data transmitted from each of the terminals to an upstream channel, the transmission data is received and demodulated for downlink. A head-end device that outputs an idle signal to the downlink channel, which is modulated and transmitted at a different frequency to the channel, and when there is no carrier in the uplink channel, to notify the terminals that there is no carrier. And a communication control method for performing communication by a CSMA / CD (asynchronous multiple access) method, wherein the transmission data is an information packet to be transmitted to a destination address, and a transmission source to be transmitted prior to the information packet. I
D and a pilot packet for collision check including error check information, each of the terminals can transmit when the idle signal is received, and modulates a carrier wave with the pilot packet and the information packet. Then, while transmitting to the uplink channel, during transmission of the pilot packet,
The pilot packet of different carrier frequency transmitted from the headend device to the downlink channel is received and demodulated, and the transmission source I is demodulated based on the demodulated result.
The presence / absence of the designation of D and the presence / absence of collision of the transmission data are determined. When the transmission source ID is designated by itself and there is no collision of the transmission data, the next information packet is transmitted, and otherwise, the information packet is transmitted. It has a function of cutting the carrier wave and stopping the transmission, the headend device receives and demodulates the pilot packet transmitted from the terminal to the uplink channel, and re-modulates and transmits to the downlink channel, and Based on the error check information, check whether communication is normally performed, and if communication is normally performed,
It is determined that there is no collision of the transmission data, and the information packet is received and demodulated following the pilot packet and modulated and transmitted to the downlink channel. When communication is abnormal, there is a collision of the transmission data. A broadband LAN communication control system, characterized in that it determines and notifies each of the terminals that a collision has occurred, and transmits command information for stopping the transmission of each of the terminals.