SU1479936A1 - Method and adapter for detecting collisions in digital communication line - Google Patents

Abstract

The invention relates to the field of digital communications for creating local area networks of computers with a multiple access line and collision detection. The purpose of the invention is to increase the reliability of receiving information. The goal is achieved by stretching the transmitted pulse before comparing with the time taken to compensate for the delay in the elements connected to the communication line. 2 sec. and 1 z. p. f-ly, 2 ill.

Description

one

This invention relates to digital communications for creating local area networks of computers with a community access and collision looping network.

The purpose of the invention is to increase the reliability of receiving information.

Fig. 1 shows the first embodiment of an adapter block diagram implementing the proposed collision detection method; figure 2 - the same, the second option.

The adapter (Figures 1 and 2) contains a transmitter 1, a receiver 2, information output 3, element 4, and node 5 of a pulse stretching.

The essence of the invention is that collision detection is performed by comparing a pulse transmitted to the communication line with a pulse received from it. But in order to compensate for the instability of the receiver latency,

WITH

the transmitter and the communication line before comparing the transmitted impulse is stretched so that the received impulse is invested in growth. For ease of implementation of the reference node (element I), the expanded pulse is inverted, since logical subtraction is performed

With R / S

(one)

where C is the signal produced by the collision detector; R is the signal received from the line; S - delayed and extended

transmitted signal. The magnitude of the required lengthening of the pulses is chosen based on the maximum possible instability of the delay times of the transmitter, receiver and delay circuit.

V vJ

with

CO SO

CD

transmitted signal, and it can lie in the range from 1 to 10-20% of the duration of the transmitted pulses. In the case of transmission in the absence of collisions, the pulse of the received signal due to the instability of the element delay time may not coincide with the delayed transmitted pulse. Stretching a delayed transmitted pulse provides a guarantee that the received pulse will be embedded in it. In this case, the logical subtraction by formula (1) will give C 0, i.e. will show no collisions. If there is a real collision, there will appear impulses uncorrelated with the transmitted device in the communication line, t. e. at some time instants S 0, a R 1 From formula (1) it follows that in this case C 1, i.e., a collision was detected in the communication line. Moreover, if at some time, due to interference or hardware C R O, and S 1, then, according to the formula (1), C 0, whereas in a similar situation, the method implemented by the prototype is fixed oval would clash.

Thus, the proposed method provides reliable detection of collisions in a line under the conditions of temperature and time instability of the parameters of the elements of the implementing scheme.

The adapter works as follows.

The transmitted pulses arrive at the inputs of transmitter 1 and node 5. The transmitter transmits pulses to the line, and receiver 2 receives them from the line. From the output of the receiver, the received pulses arrive at the first input of the element I 4, the second input of which receives the delayed, stretched and inverted pulses from the output of the node. In the absence of extraneous pulses in the line, the signal at the output of the element I is zero, since the pulses of the direct polarity at the first input become time nested in the pulses of inverse half at the second input. If there are extraneous pulses in the line,

five

0

five

0

five

0

five

0

corrected with the transmitted signals, the signal at the first input of the AND element turns out to be equal to one in the absence of the INB of the RSNO pulse at the second input. In this case, the detector generates a single signal at the output of the error indication. In the receive mode, the pulses from the receiver output (Fig. 1) are fed to the information output of the adapter.

Claims (3)

1. A method for collision detection in a digital access link with multiple access, which consists in comparing the received pulse from the communication link with the delayed transmitted into a communication line by impulse and fixing errors when they do not match, characterized in that, in order to increase the reliability of receiving information, the transmitted pulse is stretched before comparison by an amount greater than the maximum total delay in the transmit and receive elements and inverted, produced by the conjunction operation. 2. A collision detection adapter in digital multiple access communication, comprising a receiver and a transmitter, the transmitter output being connected to the receiver input and connected to the adapter input-output, the information input adapter being connected to the transmitter input, characterized in that reliability of reception of information, the element is entered into it And the pulse stretcher node, the adapter input being connected to the pulse stretcher node input, the output of which is connected to the first input of the element AND whose output is connected to the output of the adapter error indication, the receiver output is the information output of the adapter and . 3. The adapter according to claim 2, wherein, in order to simplify the adapter, the output of the AND element is the information output of the adapter. Phie.1 FIG. 2