JPH0263237A - Data communication system - Google Patents

Abstract

PURPOSE:To decrease the effect of an obstacle standing on the way of a communication path and to ensure data communication even with a low transmission output by sending a data signal of the 1st frequency signal toward an auxiliary station from plural communication stations when the 2nd frequency signal is not outputted from the auxiliary station. CONSTITUTION:When a transmission request takes place in a communication station N1 at a time T1 and other communication stations do not make communication in this state and a communication request is generated from a transmission request means 3 in a transmission request means 3 at the time T1 in the communication station N1, an f2 signal detection means 4 receives the request to detect whether or not the 2nd frequency f2 signal is detected from an auxiliary station NO at a time T2. When the 2nd frequency signal is not detected, it is discriminated that other communication station is not communicated, an f1 signal transmission means 5 sends a data toward the auxiliary station NO by the 1st frequency signal f1 at a timer T3 or thereafter. Thus, each communication concentrates the transmission energy toward the auxiliary station to attain accurate data communication without using a large transmission power.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a data communication system that performs data communication between a plurality of communication stations using radio signals of a common frequency.
More specifically, it uses radio signals as a bus-type communication path, reduces the effects of obstacles on the communication path,
The present invention relates to a data communication system that enables reliable data communication even with low transmission power.

(Prior art) When communicating between multiple communication stations using a bus-type communication path, when one set of communication stations is using the communication path, the other communication stations use the communication path. This is not possible, because if an outside communication station were to use the same communication channel, it would interfere with communications already using that channel. For this reason, in a communication system that communicates via a bus-type communication path,
Each communication station is equipped with a function to confirm whether or not the communication channel is already in use before starting communication.

Here, in a system where the communication path is an electric wire, such a busy confirmation function can be realized with a relatively simple configuration.

On the other hand, in systems that use radio signals and have communication channels in the air, the propagation of radio signals tends to fluctuate due to disturbances, and if there are obstacles in the communication route, the signal strength becomes weak. It is not easy to realize the ToG confirmation function because it becomes difficult to directly detect the transmission output of other communication stations.

(Problems to be Solved by the Invention) The present invention was made in view of the above circumstances, and its purpose is to use radio signals as a bus-type communication path, and to An object of the present invention is to provide a data communication system that can reduce the influence of obstacles and ensure data communication even with low transmission output.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is a data communication system that performs data communication between a plurality of communication stations using a radio wave signal of a common frequency, comprising: An auxiliary station is provided that receives a first frequency signal from a communication station, converts the frequency signal into a second frequency signal, and transmits the second frequency signal to a plurality of communication stations, and the plurality of communication stations receive a first frequency signal from the auxiliary station. If the frequency signal of tube 2 is not output, the data signal of the frequency signal of tube 1 is transmitted to the auxiliary station.

(Operation) The communication station that has received the transmission request determines whether data communication is possible based on whether or not the second frequency signal f2 is being transmitted from the auxiliary station, and if the frequency signal is not detected, it determines that communication is possible and transmits the first frequency signal f2. A data signal of frequency signal f1 is transmitted toward the auxiliary station.

When the auxiliary station receives this signal, it converts it to a second frequency signal and transmits the data signal to all communication stations.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration block diagram showing an embodiment of the present invention. In FIG. It is an auxiliary station that assists the communication station in detecting. The plurality of communication stations N1 to Nn constitute a data communication system in which data communication is performed via the auxiliary station NO using radio signals having a common first frequency f1 and a second frequency f2.

In the auxiliary station No., 1 is a frequency signal detection means for detecting a signal of the first frequency f1 from one of the plurality of communication stations N1 to Nn, and 2 is a frequency signal detection means for detecting the signal of 1 at this frequency and transmitted during that period. This is a frequency signal output means that converts the signal into a signal with a second frequency f2 and outputs the signal.

In each of the plurality of communication stations N1 to Nn, 3 indicates a transmission request means for generating a transmission request when it becomes necessary to transmit data from the communication station to the communication station in the pond, and 4 indicates the presence or absence of a second frequency signal. f2 signal detection means for detecting the frequency signal, and 5 is f1 signal transmission means for transmitting data at 1 with the first frequency signal toward the auxiliary station NO when the frequency signal is not detected by this signal detection means. .

The operation of the communication system configured as described above will be explained next.

FIG. 2 is a time chart showing an example of the operation. Now, it is assumed that a transmission request is generated at time 'l'1 in communication station N1, and that no other communication stations are communicating in this state.

In this communication station N1, when the transmission request means 3 generates a communication request at time 1'1, the f2 signal detection means 4 receives this request and detects the second frequency f2 signal from the auxiliary station NO at time T2. Determine whether or not. If the second frequency signal is not detected here, it is determined that the communication station in the pond is not communicating, and after time 1゛3, the f1 signal transmitting means 5 transmits the data to be transmitted using the first frequency signal f1. Transmit to auxiliary station number. Note that at time 1-2, the second
If a frequency signal of

In the auxiliary station NO, when the f1 detection means 1 detects the first frequency signal from the communication station N1 at time T3, the f2 output means 2 converts this signal into a second frequency signal and transmits the signal to the plurality of communication stations N1 to N1. Send to Nn.

Such operation continues while the first frequency signal is being output from the communication station N1.

In the plurality of communication stations N1 to Nn, f2 signal detection means 4
For example, it receives a second frequency signal from auxiliary station No., interprets the address therein to determine whether it is addressed to its own station, and if so, captures the transmitted data.

The frame structure of the transmitted signal is the same as that of conventional Rano.

While the communication station N1 continues to transmit, even if another communication station, for example, communication station N2, issues a transmission request at time T4, the second frequency signal has already been transmitted from the auxiliary station NO. You will have to wait until this transmission is completed.

In the communication station N2 where the transmission request has occurred, the f2 detection means 4 detects at a constant sampling period after time T4 whether or not the second frequency signal is being transmitted from the auxiliary station NO.

When the data transmission by the communication station N1 is completed at time T6, the transmission of the second frequency signal from the auxiliary station NO is also stopped at this point, and the first communication station N2 confirms this at time T7, and starts the first frequency signal from time T8. It becomes possible to transmit data using the frequency signal f1.

In the above-described embodiment, the data transmission format using the first or second frequency signal is, for example, frequency modulated and transmitted binary data using a known technique. In addition, it is desirable for the auxiliary station NO to be installed in a place where there are no obstacles between it and the plurality of communication stations N1 to Nn in order to improve the propagation conditions. If it is made large, it does not matter if there are some obstacles in the surrounding area, and since direct communication is not performed between the multiple communication stations N1 to Nn, there are no obstacles. I don't mind.

(Effects of the Invention) As described above in detail, according to the data communication system according to the present invention, in a plurality of communication stations, the auxiliary station N determines whether or not its own station can communicate.

The determination is made by detecting the presence of radio waves of the second frequency signal from the station, and data transmission is performed via the auxiliary station. Therefore, there is no need for direct radio waves to reach each other between partner stations, and the transmission and reception functions of each communication station can be simplified.

In addition, each communication station concentrates its transmission energy toward the auxiliary station, thereby eliminating the need to use large transmission power.
Accurate data communication can be performed.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure is a time chart showing an example of the operation. Figures N1 to Nn...Communication station NO...Auxiliary station 1...First frequency signal detection means 2...Second frequency signal output means 3...Transmission requesting means 4...No. 2 frequency signal detection means 5...first frequency signal transmission means Nn

Claims (1)

[Claims] A data communication system that performs data communication between a plurality of communication stations using radio signals of a common frequency, the system comprising: receiving a first frequency signal from the plurality of communication stations; An auxiliary station is provided that converts the second frequency signal into a second frequency signal and transmits it to a plurality of communication stations, and the plurality of communication stations convert the first frequency signal to a second frequency signal when the second frequency signal is not output from the auxiliary station. A data communication system configured to transmit a data signal of a signal toward the auxiliary station.