JPH09252284A - Burst signal collision detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit to detect collision of a burst signal in a burst data transmission system. SOLUTION: The collision detection circuit having a level monitor 15 measuring a level of a reception signal 11 and a comparator 17 comparing a level of the reception signal with a threshold level signal is provided with a means using a level of burst signals while switching the level of the plural signals received normally for a threshold level to be fed to the comparator 17. In more details, the detection circuit has a storage device 16 that stores only a level of a normal state and provides an output of a level of a preceding normal state in parallel based on a normal state signal 14 denoting the normally received burst signal subject to time division for each sender according to a switching signal 12 to inform an expected sender among the plural senders.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burst signal collision detection circuit, and is particularly suitable for use in a burst transmission system when signals from a plurality of optical transmitters are time-divisionally received by a single receiver. The present invention relates to a burst signal collision detection circuit.

[0002]

2. Description of the Related Art As a prior art of this kind of burst signal collision detection circuit, for example, Japanese Patent Laid-Open No. 59-236 discloses.
A collision detection device installed adjacent to the star coupler monitors the reception level, and when two or more stations simultaneously output optical signals, the collision detection device detects the occurrence of a collision and all connected A method has been proposed in which an alarm signal is sent to the station to notify the occurrence of a collision.

Various control methods have been proposed and put to practical use as data access control methods for LAN (local area network). Among them, CSMA /
CD (Carrier Sense Multi-Access Collision Detection) is known as ETHERNET (Ethernet, registered trademark), and is used in various LANs that use the CSMA / CD system as an optical transmission line. Japanese Patent Publication No. 2-37144 proposes a configuration of an optical network system using a CSMA / CD system capable of reliably detecting collisions of transmission signals from a plurality of stations without converting an optical signal into an electric signal. There is. This system is an optical network system in which a plurality of stations are connected to a star coupler device via an optical transmission line, and each station transmits an optical data signal having a wavelength λ _{1 or} a wavelength λ ₂ according to its binary state. And a means for receiving the optical transmission signal from another station via a star coupler device that emits light, and at the time of reception, a constant optical signal of wavelengths λ ₁ and λ ₂ is provided. When the overlap for more than a time is detected, the transmission signals from a plurality of stations are in a collision state.

FIG. 4 shows the configuration of an optical transmission line using the CSMA / CD system. In this system, the function of receiving the burst signal of its own at the time when the source transmits the burst signal. The receiver 43, which is provided in advance and detects a collision with the transmitter 41, is physically provided at the same location.

FIG. 3 is a block diagram showing a circuit configuration of a conventional receiver (optical receiver). 31 is a received signal, 32 is a threshold signal, 34 is an optical level monitoring device, and 35 is a comparison. Reference numeral 33 indicates a collision detection signal.

In the conventional receiver shown in FIG. 3, collision detection is performed as follows.

The optical level monitoring device 34 converts the received signal 31, which is an optical signal in the transmission line, from an optical signal to an electric signal, and the comparator 35 converts the electric signal into a threshold value which is a presumed reception level value. Compared with the signal 32, a collision is detected when a large level exceeding the threshold signal 32 is input, and a collision detection signal 33 is output. Here, the threshold signal 32 is
It is proportional to the transmission level.

[0008]

In the conventional burst transmission method described above, in the burst signal collision detection circuit in the case where signals from a plurality of transmitters are received by one receiver in a time division manner, the transmission source is In a transmission method in which there is no correlation between the burst signal transmitted at the same time and the burst signal received, it is a serious problem if a new receiver for collision detection is provided. Becomes

The present invention has been made in view of the above problems, and the receiver expects the transmission order of the transmitters in which there is no correlation between the burst signal transmitted by the transmitter and the burst signal received by the transmitter at the same time. It is an object of the present invention to provide burst signal collision detection in a possible burst transmission scheme.

[0010]

In order to achieve the above object, the present invention stores only the reception level of a normal reception state of a burst signal, and when the next burst signal is received, the stored reception level is exceeded. Provided is a burst signal collision detection circuit, which is characterized by detecting a signal collision when there is an input.

Further, in the present invention, preferably, a reception level storing operation in a normal reception state of a burst signal,
It is characterized in that the operation of comparing the reception level read from the storage device with the reception level of the current burst signal is performed at the same time.

Further, the present invention is characterized in that a plurality of transmission sources of burst signals are time-divisionally processed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, the embodiment of the present invention includes a received signal 11, an optical level monitor 15 for measuring the level of the received signal 11, and a comparator 17 for comparing the level of the received signal 11 with a threshold signal. In the case of using the collision detection circuit having the above, the collision detection circuit is provided with means for switching a plurality of burst signal levels when normally received as a threshold signal.

That is, in the embodiment of the present invention, the burst signal is normally received by time division for each transmission source according to the switching signal 12 from a plurality of transmission sources for notifying the transmission sources. Normal reception status signal 1 indicating that
By 4, only the level of the normal state is memorized, and at the same time,
In parallel with this, it has a memory 16 for outputting the level of the previous normal state.

As described above, in the embodiment of the present invention, the threshold value of the normally received burst signal level is determined in advance by using the received signal level during operation for collision detection of burst signals. It is unnecessary to leave it.

Examples will be described below in order to describe the above-described embodiment of the present invention in more detail. FIG. 1 is a block diagram showing a burst signal collision detection circuit according to an embodiment of the present invention, in which 11 is a received signal, 12 is a switching signal, 13 is a collision detection signal, and 14 is a normal reception state signal.
Reference numeral 15 is an optical level monitor, 16 is a memory, and 17 is a comparator. The burst signal collision detection circuit according to the embodiment of the present invention further includes a memory 16 in addition to the optical level monitor 15 and the comparator 17. Here, the normal reception state signal 14 is a signal output from an error detection circuit (not shown) that receives the reception signal 11 and monitors its quality. Further, in the TDMA (Time Division Multiple Access) method, it is scheduled that the received signal arrives in advance within a certain time range, and the switching signal 12 is thereby generated.

In the embodiment of the present invention, burst signal collision detection is performed as follows.

Received signal 1 which is an optical burst signal on the transmission path
1 is input, the optical level is quantified by the optical level monitor 15, and only when the burst signal indicated by the normal reception status signal 14 is received without error, the area indicated by the switching signal 12 is stored in the memory 16. Write. That is, the optical level of the reception signal transmitted by the TDMA method in the normal reception state is written in a predetermined area of the storage device 16, respectively.

In parallel with this, when the optical burst signal on the transmission line is input, the storage device 16 outputs the reception level in the normal state stored earlier from the area designated by the switching signal 12.

The comparator 17 detects a collision when the level of the electric signal output from the optical level monitor 15 is much larger than the value read from the memory 16, the collision detection signal 13 detected as a collision. Is output.

The comparator 17 operates in a time division manner by the switching signal 12 from a plurality of transmission sources, which indicates the transmission source.

FIG. 2 is a diagram showing an embodiment in which the burst signal collision detection circuit according to the present invention is applied to a PDS (passive double star) type optical communication system. Optical transmission lines (optical fibers) 24b to 24e from a plurality of transmitters 21 are connected to a receiver 23 via an optical fiber 24a via a coupler (star coupler) 22. In this PDS method, when an optical signal from a plurality of optical transmitters is to be received by one receiver in a time-division manner, the reception level from each optical transmitter is stored as a history and the optical transmitters from each optical transmitter are stored. When receiving the optical signal of, the reception level from the previous optical transmitter is read from the storage device and set as the threshold value of the comparator, and the reception level this time changes (increases) rapidly with respect to the previous reception level.
Then, the collision of the optical burst signals is detected.

[0023]

As described above, the present invention has an effect that it is not necessary to previously determine the threshold value of the reception level of the normally received burst signal. This is because the received level during operation was used for burst signal collision detection.

Further, according to the present invention, since the time division processing is performed, there is an advantage that only one receiver needs to detect a collision with respect to a plurality of transmitters. That is, according to the present invention, for each of the received signals from the plurality of transmitters, the number of comparators for collision detection may be one, and it is not necessary to predetermine the threshold value, and the circuit configuration can be improved. It's simplified.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an embodiment of a transmission system to which the present invention is applied.

FIG. 3 is a diagram showing a configuration of a conventional collision detection circuit.

FIG. 4 is a diagram showing a configuration of a conventional transmission method (CSMA / CD method).

[Explanation of symbols]

 11 Received Signal 12 Switching Signal 13 Collision Detection Signal 14 Normal Reception Status Signal 15 Optical Level Monitor 16 Memory 17 Comparator 21 Transmitter 22 Coupler 23 Receiver 24a to 24e Transmission Line 31 Received Signal 32 Switching Signal 33 Collision Detection Signal 34 Optical level monitor 35 Comparator 41 Transmitter 42 Coupler 43 Receiver 44a to 44e Transmission line

Claims (5)

[Claims] 1. A method of storing only a reception level of a normal reception state of a burst signal, and detecting a signal collision when there is an input exceeding the stored reception level at the next reception of the burst signal. Burst signal collision detection circuit. 2. The operation of storing the reception level of the burst signal in the normal reception state and the operation of comparing the reception level read from the storage device with the reception level of the current burst signal are performed at the same time. The burst signal collision detection circuit according to claim 1. 3. The burst signal collision detection circuit according to claim 1, wherein a plurality of transmission sources of the burst signal are time-divisionally processed. 4. An optical level monitoring means for monitoring a received signal and measuring the level of the received signal, and a comparing means for comparing the level of the received signal with a threshold value and detecting a collision based on the comparison result. In the collision detection circuit, the reception level of the burst signal when normally received from a plurality of transmission stations is stored as history information, and the reception level of the burst signal received this time corresponds to the stored reception level. A burst signal collision detection circuit characterized in that a level is read out and used as a threshold value of the comparison means. 5. The comparison means according to claim 4, wherein the comparison means compares the reception levels of burst signals from a plurality of transmitting stations with the stored levels in a time division manner for each transmitting station. Burst signal collision detection circuit.