JP2002051011A - Optical wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical wireless communication system that can avoid a communication fault due to inequality of communication opportunities. SOLUTION: A reception section 36 of a communication terminal N receives an optical signal from a collection and distribution device B and outputs the signal to a signal strength measurement section 11. The signal strength measurement section 11 measures the signal strength of the received signal and outputs the value to a transmission signal calculation section 12. The transmission signal calculation section 12 refers to a table stored in a storage section 13 to read a transmission signal strength corresponding to the received reception signal strength and controls an output control section 14 to output a transmission signal with the strength. The output control section 14 controls the signal strength of the transmission signal outputted from a transmission section 35 to have the signal strength supplied from the transmission signal calculation section 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wireless communication system in which a star type topology is formed between a collection and delivery device and a plurality of communication terminal devices to perform optical wireless half-duplex communication.

[0002]

2. Description of the Related Art In an optical wireless communication system composed of a collection and delivery device for collecting and delivering optical wireless communication signals and a plurality of communication terminals communicatively connected to the collection and delivery device as a central device when configuring a star type topology, As an access method for realizing duplex communication, CSMA / CD (Carrier S
ense Multiple Access with Collision Detection;).

In an environment of a network A including a collection and delivery device B and a plurality of communication terminals 1 to N as shown in FIG.
If there is data to be transmitted to the communication terminal N, it confirms that the transmission path is not occupied, and then transmits a transmission request signal to the collection and delivery device B. Upon recognizing the transmission request from the communication terminal N, the collection / delivery device B confirms that the transmission path can be used, and transmits a response signal indicating transmission permission to the communication terminal N within the network A as shown in FIG. To each of the communication terminals 1 to N. This collection and delivery device B
Is received by all communicable communication terminals in the network A, but the content of the transmission permission includes an ID for identifying the communication terminal N to which transmission is permitted. The communication terminal N having the matching ID acquires the transmission right. If the ID included in the transmission permission signal matches the ID of the communication terminal N, the communication terminal N starts transmitting data to the collection and delivery device B (the collection and delivery device B transmits the data to the communication terminal N).
After the data transmission is completed, the connection is terminated and the transmission path is opened. Note that while the communication terminal N is transmitting data, the transmission path is occupied and transmission from other communication terminals cannot be performed. However, after the transmission path is opened, all communication terminals 1 to N Can be transmitted. In addition, when the transmission permission is not replied or the communication terminal whose ID included in the transmission permission signal does not match the ID of the own apparatus,
Since the communication right cannot be acquired, data cannot be transmitted. At this time, the communication terminal having the data to be transmitted transmits a transmission request to the collection and delivery device B again after a predetermined time interval.

In such an access method, the acquisition of the communication right among the communication terminals 1 to N is free competition, and if it is confirmed that the transmission path is not occupied (Carrier Sense), any communication terminal transmits. It is possible to send a request (Mu
ltiple Access).

As shown in FIG. 9, when a plurality of communication terminals 1 and 2 transmit a transmission request at the same time, the transmission request signal is superimposed on the transmission path and the transmission request signal is disturbed. Can not receive the correct transmission request data and can use the transmission path,
Cannot return an appropriate transmission permission signal including the ID of the communication terminal that has requested transmission. In this case, since the collection and delivery device B does not return anything, the communication terminals 1 and 2 that have requested the transmission
By detecting that the transmission permission signal cannot be received within a predetermined time, it is possible to determine that the transmission permission signal is not transmitted due to a collision or the like.
(Collision Detection).

When it is determined that a collision has occurred between the communication terminals 1 and 2 that have requested transmission, a transmission request signal is retransmitted after a predetermined time that differs for each communication terminal (retransmission processing at the time of collision), thereby obtaining data. I try to send.

However, even when a plurality of communication terminals 1 and 2 simultaneously transmit a transmission request signal, the collection and delivery device B
If the reception strengths of the transmission request signals transmitted from the respective communication terminals at the collection and distribution device B are significantly different from each other as shown in FIG. It is recognized as correct data without being destroyed by a signal having a low reception strength.
Accordingly, the collection and delivery device B in this case transmits a transmission permission signal including the ID of the communication terminal 2 that has transmitted the transmission request signal having a high reception strength to each of the communication terminals 1 to N. As a result, the communication terminal 2 having a high reception strength at the collection and delivery device B can transmit data, but the communication terminal 1 having a low reception strength at the collection and delivery device B transmits a permission signal including its own ID. Since no transmission is made, it is determined that a collision has occurred, and transmission is refrained for a predetermined time.

In such a network environment, there are communication terminals to which transmission requests are always permitted (large occupancy rate) and communication terminals to which transmission requests are not easily granted (small occupancy rate). In a communication terminal that outputs a transmission request signal with a low reception strength, a communication failure state may occur in which transmission cannot be performed at all while holding data to be transmitted.

[0009]

The strength of the signal received by the collection and delivery device B depends on the positional relationship, distance, direction, etc. between the collection and delivery device B and each of the communication terminals 1 to N, and the transmission of each communication terminal. It is determined due to individual differences of the means.

[0010] Therefore, in an optical wireless communication system including one collection and distribution device that forms a star topology as a local area network or a part thereof and a plurality of communication terminals that are communicatively connected to the collection and distribution device, the collection and distribution device is not used. There have been communication terminals that have extremely many opportunities to obtain transmission permission due to differences in reception strength, and communication terminals that have extremely few opportunities to obtain transmission permission. As a result, in a communication terminal having extremely few transmission opportunities, even if there is data to be transmitted, a state in which the data is not actually transmitted to the collection and delivery device continues, and a communication failure may eventually occur.

[0011] Such a problem arises from the fact that, when transmission requests are sent from a plurality of communication terminals at the same time, it must be judged that a collision has occurred. If the reception strengths are significantly different, the collection and delivery device can detect only one of the transmission request signals and cannot determine that the collision has occurred. Had occurred.

Accordingly, an object of the present invention is to avoid a communication failure due to an unequal communication opportunity by using a communication terminal in which such unequal communication opportunity acquisition does not occur.

In some cases, such as when remote maintenance is performed on a device connected to the network through the network, there is a case where important and urgent communication is required from a certain communication terminal.

Therefore, the present invention not only makes it possible to avoid unequal communication opportunities under the control of the communication terminal, but also
The purpose is to give priority to communication opportunities in an emergency only by controlling the communication terminal.

[0015]

SUMMARY OF THE INVENTION As means for achieving the above object, an object is to provide an optical wireless communication system as described below.

1. A collection / delivery device for collecting / distributing data by an optical wireless signal, and a plurality of communication terminals for transmitting / receiving data to / from the collection / delivery device by an optical wireless signal, wherein the communication terminal has a terminal ID unique to its own device. Transmitting a connection request signal including the following to the collection and delivery device and starting transmission of data after receiving a transmission permission signal from the collection and delivery device, wherein the collection and delivery device simultaneously transmits the received data to each communication terminal. An optical wireless communication system for communication, wherein the communication terminal includes: a signal strength measurement unit configured to measure a signal strength of a reception signal from the collection and delivery device; and a signal strength measurement unit configured to measure a signal strength of the reception signal measured by the signal strength measurement unit. Signal strength determining means for determining the signal strength of the transmission signal, and output control means for controlling and outputting the signal strength of the transmission signal based on the output signal from the transmission signal strength determining means. Optical wireless communication systems signal strength is characterized by way, by controlling the signal strength of the transmission signal output from the communication terminal becomes a predetermined intensity when received by the pick-up device.

2. 2. The optical wireless communication system according to claim 1, wherein the communication terminal is configured to be able to control a signal strength of a transmission signal by an external control signal.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the optical wireless communication system according to the present invention will be described with reference to the drawings. Figure 1
FIG. 1 is a configuration diagram showing an embodiment of the present invention, mainly showing a configuration related to transmission signal strength control in a communication terminal N. FIG. 2 is a configuration diagram showing another embodiment of the present invention, focusing on a configuration related to transmission signal strength control in communication terminal N. FIG. 3 is a flowchart illustrating a communication procedure in a communication terminal according to another embodiment.
FIG. 4 is a diagram showing the contents of the table 16 stored in the storage unit 13 of each of the communication terminals 1 to N. FIG. 5 is a block diagram showing a configuration example of a collection and delivery device B according to an embodiment of the present invention, and FIG. 6 mainly shows a configuration for explaining a flow of data signals of communication terminals 1 to N. It is the block diagram described.

First, the flow of data communication will be described with reference to FIGS. Collection and delivery device B shown in FIG.
A receiving unit 21 including a light receiving element such as a photodetector for receiving an optical wireless signal transmitted from the communication terminal 1 to N, and a photoelectric conversion unit for converting an optical signal received by the light receiving element into an electric signal; A terminal ID extracting unit 22 for extracting a terminal ID included in a received signal output from the receiving unit 21, and a terminal ID extracting unit 22 for transmitting a signal from one communication terminal received by the receiving unit 21 to another communication terminal. Data transfer means 23 for temporarily storing and transferring data, signal selection / generation means 24 for generating a transmission signal from the data supplied from data transfer means 23, and transmission signal supplied from signal selection / generation means 24 Is converted into an optical signal, and each of the communication terminals 1 to N
And transmission means 25 for transmitting to

The communication terminals 1 to N shown in FIG. 6 receive data transmitted from a personal computer (PC) or a work station (WS) connected to each of the communication terminals 1 to N. Interface (I /
F) a receiving means 31 such as a LAN card having a function;
A data transfer unit 32 for transferring data received by the reception unit 31 to transmit the data to the collection and delivery device B; and an ID (at least the network A
I that can individually identify each of the communication terminals 1 to N
D), a signal selecting / generating means 34 for generating a transmission signal including the ID of the terminal itself in the data supplied from the data transfer means 32, and a signal selecting / generating means 34 The transmitting means 35 converts the signal generated in the above into an optical signal, causes the light emitting element to emit light, and transmits the optical signal to the collection and distribution device B, and receives the optical signal transmitted from the collection and distribution device B by a light receiving element such as a photodetector. Receiving means 36 for converting the data received by the receiving means 36, outputting the data received by the receiving means 36, transmitting data to transmit the data to the connected PC or WS, and receiving the signal received by the receiving means 31. And a signal received by the receiving means 36, a communication state determining means 38 for determining the communication state of the own device and the transmission path, and a data based on the determination result by the communication state determining means 38. Control means 39 for performing transfer control of
And a transmission unit 40 for transmitting data output from the data transfer unit 37 to a PC or WS connected to the own device.

A network A forming a star topology is formed between the collection / distribution device B having such a configuration and the communication terminals 1 to N, and as described above with reference to FIGS. It is assumed that communication is performed between the communication terminals 1 to N via the communication terminal. For example, when data is transmitted from a PC connected to the communication terminal N and received by the receiving means 31, it is checked by the communication state determining means 38 whether the transmission path is free and the transmission path is not occupied. in case of,
A signal requesting / generating means 34 generates a connection request signal to which a terminal ID unique to the communication terminal N stored in the terminal ID storage means 33 is added, and transmits the signal from the transmitting means 35 to the collection / delivery apparatus B.

In the collection and delivery device B, the connection request signal from the communication terminal N is received by the receiving means 21 and the terminal ID extracting means 2
2, a terminal ID is extracted, a transmission permission signal including the terminal ID is generated by the signal selection / generation unit 24, and transmitted by the transmission unit 25.

When the communication terminal other than the communication terminal N receives the transmission permission signal by the receiving means 36, the communication state determining means 38 is rewritten to indicate that the other communication terminal N is occupied. Set to not send a connection request signal.

When the communication terminal N receives the transmission permission signal including the terminal ID of the own terminal by the receiving unit 36, the communication state determining unit 38 is set to the content that the own terminal occupies the transmission line, and the control is performed. The data signal from the PC is transmitted from the transmission means 35 under the control of the means 39.

When the receiving / receiving device B receives the data from the communication terminal N by the receiving means 21, it outputs the data to the signal selecting / generating means 24 via the data transferring means 23, and the network A
The data received from the transmission means 25 is transmitted to all of the communication terminals 1 to N in the server.

The communication terminals other than the communication terminal N are
When receiving the data from the receiving unit 36, the receiving unit 36 transmits the data via the data transfer unit 37 and the transmission unit 40 to the PC / WS to which each communication terminal is connected. Each of the communication terminals 1 to N receives the transmission path release notification signal transmitted from the collection and delivery device B after receiving the data, rewrites the contents of the communication state determination means 38, and connects when the data comes from the PC / WS. A request signal can be transmitted.

In the case where the half-duplex communication is performed in this manner, depending on the distance to the collection and delivery device B and the presence of a communication obstacle, even if the transmission signals of the same strength are output from the communication terminals 1 to N, the collection and delivery device B Has a different value for each communication terminal. Therefore, unfairness of the communication opportunity has occurred between the communication terminals 1 to N. In the present invention, the reception intensity at the collection and delivery device B is the same for all the communication terminals 1 to N,
The transmission signal strength at each of the communication terminals 1 to N is controlled.

The control means of the transmission signal strength in each of the communication terminals 1 to N will be described with reference to FIG.

In FIG. 1, when a data signal or a communication permission signal is transmitted from the collection and delivery device B to each of the communication terminals 1 to N, for example, in the communication terminal N, the receiving unit (receiving means) 36
Receives the optical signal, converts it into an electric signal, and outputs it to the signal strength measuring unit 11. The signal strength measuring section 11 measures the signal strength of the received signal and outputs the value to the transmission signal calculating section 12. In the transmission signal calculation unit 12, the storage unit 1
The control unit 14 reads out the transmission signal strength corresponding to the supplied reception signal strength with reference to the table 16 stored in the control unit 3 and controls the output control unit 14 to output the transmission signal at the strength. The output control unit 14 controls the signal strength of the transmission signal output from the transmission unit 35 to the signal strength supplied from the transmission signal calculation unit 12. With such control, the communication terminal N
When data is sent from a PC or the like connected to the communication device, a connection request signal is output with the signal strength output from the transmission signal calculation unit 12.

Here, the table 16 stored in the storage unit 13 stores values such that the transmission signal strength decreases as the reception signal strength from the collection and distribution device B increases. That is, when the reception intensity is high, the collection and delivery device B
It is considered that the distance to the communication device is small, so that the signal is output with a small transmission signal. If the reception intensity is small, the distance to the collection and delivery device B is considered to be long, so that the signal is output with a large transmission signal. A value set so that the reception intensity when the transmission signal from the terminal is received by the collection and delivery device B is always the same (predetermined value) regardless of the position of the communication terminal is stored.

The above control is performed by each communication terminal 1.
To N, the reception intensities received by the collection and delivery device B are all the same (predetermined value), and it is possible to prevent communication failure due to unfair communication opportunities.

FIG. 2 shows another embodiment of the present invention.
The description of the same control parts as in the embodiment described above with reference to FIG. 1 will be omitted. In a state where the reception strengths of the signals received by the collection and delivery apparatus B are controlled to be the same (predetermined value) in each of the communication terminals 1 to N, the data such as the PC includes the priority control signal 15 or the like. Alternatively, a mechanical signal of a switch or the like on a communication terminal, a signal generated on software, or the like, but not limited thereto, may be obtained by other means. When the priority control signal 15 is supplied, control is performed so that the signal strength of the connection request signal transmitted from the transmission unit 35 is set to the maximum level.

By controlling in this way, the signal strength of the connection request signal transmitted from this communication terminal N is greater than that of the other communication terminals since the received signal strength when received by the collection and delivery device B is higher than that of the other communication terminals. Even if the connection request signal is transmitted at the same time as the communication terminal, the communication terminal N is given priority and can receive the communication permission signal having the terminal ID of the terminal itself. Therefore, when an important communication such as an emergency communication is to be performed, the priority control signal 15 is supplied to the transmission signal calculating unit 12 so that the line is occupied with a higher priority than other communication terminals. it can. Of course, when transmitting low priority data, the priority control signal 15 is supplied to the transmission signal calculation unit 12 to output a transmission signal having a signal strength lower than the value set as the signal strength in the normal state. And the priority may be lowered.

The above control can be performed only on the communication terminal side. The flow on the communication terminal side will be described with reference to FIG. 3. First, when entering the network A (or when power is turned on), the output control unit 14
Are set to the standard level (step 101). Then, when a received signal from the collection and delivery device B is detected (Step 102 → Y), the received signal strength is measured, the table 16 is referred to, and the set value of the output control unit 14 is set to the transmission signal strength corresponding to the received signal strength. (Step 103).
When data is sent from a connected PC etc.
(Step 104 → Y), it is checked whether or not a priority signal is coming (Step 105). If there is no priority signal (Step 105 → N), the setting value of the output control unit 14 is set. The connection request signal is output by controlling the strength of the transmission signal (step 107). If the priority order signal is supplied (step 105 → Y), the output control unit 14
Is set to the maximum level (step 106), and a connection request signal is output at the maximum level strength (step 1).
07).

[0035]

According to the optical wireless communication system of the present invention, the transmission intensity of each communication terminal is controlled so that the reception intensity at the collection and distribution device becomes the same. It is possible to reduce the inequality in acquiring the transmission right caused by the difference in strength.

Further, the present invention has an effect that the priority of transmission right acquisition is controlled by simply controlling the communication terminal side, so that emergency communication and the like can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an optical wireless communication system according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the optical wireless communication system of the present invention.

FIG. 3 is a flowchart illustrating a communication procedure according to another embodiment of the present invention.

FIG. 4 is a diagram showing an example of a table stored in a storage unit of the communication terminal according to the present invention.

FIG. 5 is a schematic configuration diagram of a collection and delivery device according to the present invention.

FIG. 6 is a schematic configuration diagram of a communication terminal according to the present invention.

FIG. 7 is a schematic diagram showing a state in which data is transmitted from a communication terminal N to a collection and delivery device B in a network A.

FIG. 8 is a schematic diagram illustrating a state in which data is transmitted from the collection and delivery device B in the network A to the communication terminals 1 to N.

FIG. 9 is a schematic diagram for explaining a case where a signal collision occurs.

FIG. 10 is a schematic diagram for explaining a case where reception strengths at the collection and delivery device B are different.

[Explanation of symbols]

 1 to N communication terminal A network B collection and delivery device 11 signal strength measurement unit (signal strength measurement means) 12 transmission signal calculation unit (transmission signal strength determination means) 13 storage unit 14 output control unit (output control means) 15 priority control signal (External control signal) 35 Transmitter (transmitter) 36 Receiver (receiver)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04B 10/14 10/06 10/04 H04L 12/28

Claims (2)

[Claims] An information processing apparatus, comprising: a collection and delivery device for collecting and delivering data by an optical wireless signal; and a plurality of communication terminals for transmitting and receiving data by an optical wireless signal to and from the collection and delivery device. A transmission of a connection request signal including a terminal ID unique to the collection and delivery device, and starting transmission of data after receiving a transmission permission signal from the collection and delivery device, the collection and delivery device simultaneously transmits the received data to each communication terminal. An optical wireless communication system of half-duplex communication for transmitting, wherein the communication terminal is a signal strength measuring means for measuring a signal strength of a signal received from the collection and delivery device; and a reception signal measured by the signal strength measuring means. Transmission signal strength determining means for determining the signal strength of the transmission signal based on the signal strength of the transmission signal; and an output control means for controlling and outputting the signal strength of the transmission signal based on the output signal from the transmission signal strength determination means. And means, optical wireless communication system, wherein the signal strength to a predetermined intensity, to control the signal strength of the transmission signal output from the communication terminal when receiving in the collection and delivery device. 2. An optical wireless communication system according to claim 1, wherein said communication terminal is configured to be able to control the signal strength of a transmission signal by an external control signal. .