JPS62266941A - Collision detecting method for transmission line - Google Patents

Abstract

PURPOSE:To detect collision even by an equipment other than an equipment sending a signal and to suit the titled method to CATV system and the like by providing a circuit detecting power level at collision to a communication equipment. CONSTITUTION:In receiving a signal from a reception input terminal 11, only a control channel signal is sent to an operational amplifier 13 by a BPF 12, and with the signal amplified by the amplifier 13 reaching a prescribed level or over, the signal is detected by a comparator 14. Then a sampling circuit 15 receives a detection signal of the comparator 14 and in case the confirmation of the signal level exceeding a prescribed level over a prescribed period, it is regarded as the signal collision and the result is supplied to a collision detection signal output terminal 16. For example, if a collision takes place on a control channel, in case the sollision of two waves, since the level of the carrier is increased to 2<1/2> times, the collision is detected by detecting the power level at the collision by the comparator 14. Thus, even if the content of a sent signal is not accurately grasped, the collsion is detected surely.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a collision detection method on a transmission line used in a frequency multiplexed two-way communication device using an ATV line.

2. Description of the Related Art A conventional collision detection method is configured to detect the presence or absence of a collision by receiving a signal transmitted by a transmitting side and verifying whether the transmitted signal and the received signal match. FIG. 2 shows the configuration of a conventional collision detection circuit. In FIG. 2, 21 is a transmission data output terminal, 22
23 is a receiving data input terminal; 23 is a transmitting device for sending a signal to a transmission path; 24. 25 is a delay circuit, 26 is an exclusive-OR (EX-OR) gate, 27 is a collision detection signal output terminal, and 28 is a transmission path.

Next, the operation of the conventional collision detection method described above will be explained.

The transmitter 23 transmits the data sent from the transmission data output terminal 21 onto the transmission line 28. This is sent to the receiving device 24
The received data is received by the EX-OR 26 and checked to see if it matches or does not match the transmitted data delayed by the delay circuit 25. If a mismatch is detected, it is determined that a collision has occurred. In this way, a collision can also be detected using the conventional collision detection method described above.

Problems to be Solved by the Invention However, the conventional collision detection method described above has the following problems.

(1) A collision cannot be detected by any device other than the device that sent the signal.

(In the 2+ OA TV system, the signal delay time varies depending on the distance between the end and end collars, so the delay time must be adjusted for each communication device.

(3) All communication devices that send control signals must be equipped with a collision detection circuit.

It is an object of the present invention to eliminate the drawbacks of the conventional example described above, and to provide a method for detecting collisions on a transmission line, which allows collisions to be detected by devices other than those that have sent the signal, and which is compatible with 0ATV systems and the like.

Means for Solving the Problems In order to achieve the above object, the present invention provides a communication device with a circuit that detects the power level at the time of collision, so that even if the contents of the transmitted data cannot be accurately grasped, the signal can be reliably detected. This allows collisions to be detected.

Therefore, according to the present invention, even if the data content at the time of transmission cannot be accurately grasped, a collision can be detected by detecting the power level of the signal at the time of the collision.

In addition, if used in a system consisting of a center device and multiple terminal devices, by providing the above-mentioned collision detection circuit on the center side, collisions in transmission signals from the terminals can be detected by the center device. Measures for effective use of data can be taken under the control of the center device. Furthermore, it is no longer necessary to provide a collision detection circuit in each terminal device, which makes it possible to simplify functions and reduce costs.

Example FIG. 1 shows the configuration of an embodiment of the present invention.

In Fig. 1, 11 is a frequency multiplexing bidirectional 0A
A reception input terminal for a signal connected to the TV line; 12 is a bandpass filter; 13 is an Abe (op) amplifier; 14 is a comparator as an example of power increase detection means; 15 prevents false detection of signal collision due to impact noise. 16 is a collision detection signal output terminal.

Next, the operation of the above embodiment will be explained. When a signal is input to the reception input terminal 11, only the control channel signal is sent to the operational amplifier 13 by the bandpass filter 12. When the signal amplified by the operational amplifier 13 exceeds a certain level, the comparator 14 detects this. The sampling circuit 15 is configured to confirm that the output from the comparator 14 is present for a certain period of time or more in order to prevent this from becoming a signal collision when the comparator 14 detects a signal above a certain level due to impulse noise. As a result, if it is confirmed that the signal level exceeds a certain level for a certain period of time or more, it is output to the collision detection signal output terminal 16 as a signal collision.

For example, when a collision occurs on a control channel, in the case of a two-wave collision, the level of the carrier wave is null times f, so the comparator 14 detects the power level at the time of the collision. can be done.

Note that the received data is processed using a microprocessor, etc.
It will be more effective if the means for sampling bits and determining that there is a signal collision if M bits (N, M are natural numbers 82M) of which are '1'' are squared.

Effects of the Invention As is clear from the above embodiments, the present invention has the following effects.

(1) Detecting the power level at the time of transmission wave collision Since signal collision is detected by K, collision can be reliably detected even when the content of the transmission signal cannot be accurately grasped.

(2) In a communication system consisting of a center device and a plurality of terminal devices, by using the collision detection circuit of the present invention in the center device, collisions can be reliably detected. There is no need to provide a detection circuit,
Furthermore, the center device can easily utilize and manage the line effectively.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a collision detection method on a transmission line according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional collision detection circuit. DESCRIPTION OF SYMBOLS 11... Reception signal input terminal, 12... Band pass filter, 13... OI) amplifier, 14... Comparator, 15... Sampling circuit, 16... Collision detection signal output terminal, 21...・・Transmission data output terminal, 22・
... Reception data input terminal, 23 ... Transmission device, 24.
...Receiving device, 25...Delay circuit, 26...EX-
OR gate, 27...Collision detection signal output terminal, 28.
...Transmission line.

Claims (1)

[Claims] When a center device and a plurality of terminal devices are commonly connected by a transmission line and bidirectional communication is performed, a received signal of a control channel on the transmission line is received, and the power level of the received signal increases when a collision occurs. A method for detecting a collision on a transmission line, in which a collision is detected by detecting a collision using a power increase detection means.