JPH0677962A - Optical radio data transmission system - Google Patents

Abstract

PURPOSE:To enalarge a communication enable area and to improve communication efficiency or communication quality by linking plural equipment main bodies by optical transmission and providing both of functions for data transmission and relaying at a master equipment modem. CONSTITUTION:When an optical signal (f) from a slave equipment modem M2 is received, a master equipment modem M0) sends data addressed to the equipment itself to a temrinal equipment 8, the frequency (f) is converted to f', optical transmission is performed to the slave equipment modem over a wide range, and the master equipment modem is functioned as a repeater. In this time, light is emitted after confirming the absence of the optical signal with carrier sense so as to prevent the confusion of transmitting/receiving operations between the plural modems. Further, a callee monitors the state of a line at a carrier level measuring part and when the fault of each resistor emits light, communication velocity is switched to the optimum velocity. Thus, the communication enable area is enlarged, slave equipments can be increased, and the communication efficiency or communication quality can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wireless data transmission system for performing wireless data transmission using light such as infrared rays as a carrier (medium), and more particularly, to provide a master modem with both a relay function and a data transmission function. The present invention relates to an optical wireless data transmission system which realizes improvement of communication efficiency by expanding a service area and increasing the number of installed terminals, or by further providing a carrier sense function.

[0002]

2. Description of the Related Art In recent years, OA (Office Automa
The progress and spread of devices has been remarkable, and computers (Personal Computers) and word processors (Word Proc.
Work by installing multiple OA devices such as essor)
It is now widely practiced. In addition, it is becoming commonplace to perform personal computer communication via a communication line or the like, or to install a large-scale computer device, which is a higher-level device, to transmit data via a communication control device or a communication line.

Wired cables and the like have been conventionally used for such data transmission. Also, a personal computer, a word processor, etc. are composed of a device main body and terminals such as a keyboard, a display device, and a printer, and the main body and the terminals are generally connected by a predetermined cable to exchange signals. Of the terminal devices, the printer is relatively infrequently used, and thus one printer is often used by a plurality of personal computers and word processors.

[0004]

When one printer is used for a plurality of OA equipment, a plurality of equipment main bodies and a switching device are connected by a cable, and further the switching device and the printer are connected by a cable for use. is doing. Without such a switching device, there is the inconvenience that the device body must be removed and inserted in order to connect the cable to the printer every time a printing operation is performed. Further, even if there is a switching device, a cable between the device body and the switching device is indispensable, which hinders the appearance of the room. In addition, it is troublesome because it has to be reconnected every time the layout of the room is changed, and because the length of the cable is limited, the installation location is limited, and it is difficult to effectively use the space. It was

As an OA device capable of solving these drawbacks, a device for transmitting / receiving a signal between a device body and a printer or between device bodies such as a personal computer by using a wireless communication means instead of a cable has been used at home and abroad. It is being announced recently by various companies. As the wireless communication means, there are one using an electromagnetic wave with a specific small electric power and one using near infrared rays around 900 nm. The former is strong against obstacles in the middle of the transmission path, but has a drawback that the transmission speed (information amount per unit time) is slow and it is easily affected by electromagnetic noise from a printer or the like.
Further, the latter (conventional optical wireless device) has a drawback that it has a high transmission speed but is weak against an obstacle in the middle of the transmission path.

[0006]

An optical wireless data transmission system according to the present invention has a plurality of first modems and one or more second modems, each of which is cable-connected to each terminal. This modem receives a light output from another modem and converts it into an electric signal, and decodes the electric signal to supply it to the connected terminal device as necessary and packetize the data from the terminal device. A data processor for performing predetermined signal processing such as conversion and outputting, and the level and / or S of the electric signal
A measurement unit for measuring the N ratio and the like to check the communication quality, a communication speed control unit for controlling the output speed of the data processor according to the measurement result, and an output signal of the communication speed control unit for converting the output signal into an optical signal. The second modem, in addition to the configuration of the first modem, changes the carrier frequency of the electric signal obtained by the light receiving unit and supplies the same to the light emitting unit. The above-mentioned problem is solved by further comprising.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the optical wireless data transmission system of the present invention will be described with reference to the drawings. FIG. 1A is a basic system configuration diagram of an optical wireless data transmission system 1a of the present invention, in which M _{1 to} M ₄ are first modems and Mo.
The second modem, 8,8A～8d each modem Mo ~M ₄
Is a terminal connected to the cable. Terminals 8a-8d
For example, a word processor or a personal computer body (which may include a printer) is used, but since the modem Mo has a relay function as described later, the terminal device 8 connected to this may be only a printer, but the first If you connect a personal computer to all of the modems, you will have a system that allows personal computer communication.

The second modem Mo converts the carrier frequency f of a signal obtained by receiving near-infrared rays having a wavelength of around 900 nm and photoelectrically converting it into a different frequency f ', which will be described later, and outputting it in real time. , Called a base unit (base unit modem) because it has a function of relaying communication between other units,
Other modem M ₁ ~M ₄ is called because there is no relay function cordless handset (the handset modem). As described above, the optical wireless data transmission system 1 includes at least a plurality of slave units and one or more master units. The directional characteristics of the light emitting part and the light receiving part of the master unit modem Mo are configured to be wide because they have to be able to communicate with all the slave unit modems in the area. Since the function can be achieved, the directional characteristics are narrowed to simplify the configuration (reduce the number of light emitting elements and light receiving elements) and save power.

Generally, an LED (light emitting diode) is used for the light emitting portion, and a phototransistor is used for the light receiving portion. Particularly, since the LED has a relatively narrow directivity, it is used as the light emitting portion of a slave modem. It suffices to install one to several wires in the same direction. On the other hand, it is necessary to widen the directional characteristics of the light emitting unit and the light receiving unit in the base unit modem. For that purpose, the number and direction (mounting angle) of the light emitting elements of the light emitting unit and the light receiving elements of the light receiving unit are increased. . In particular,
A plurality of LEDs and phototransistors are vertically arranged in a fan shape (in the case of FIG. 1 (A)) or in a radial shape (in the case of FIG. 1 (B)) on a cylindrical surface of an appropriate size at substantially equal intervals. Furthermore, by providing a plurality of lens-shaped visible light cut filters in front of each LED and phototransistor,
It is possible to obtain a wide directional characteristic with an improved ratio.

As shown in FIG. 1 (A), the cordless handset is placed around the base unit.
° In a system configuration example that exists within the range below,
The directional characteristics of the master unit modem Mo need to be close to 180 °, and in the system configuration example where the slave unit exists within the range of 180 ° or more around the base unit as shown in Fig. 1 (B), it needs to be close to 360 °. Becomes It should be noted that in FIG. 1 (B), the number of handset modems and terminals is increased by two compared to the configuration example of FIG. So
Detailed description thereof will be omitted. If the cylinder also serves as a heat dissipation housing, a good heat dissipation effect can be obtained.

As long as the signal light arrives, it is possible to communicate between the slave unit modems without going through the master unit modem Mo. In that case, the direct light from the slave unit modem and the master unit Since the carrier frequency is different from that of the indirect light via the machine modem Mo (f, f '), the collision (interference) phenomenon does not occur between the two. However, since the slave unit modems communicate with each other using the light of the same carrier frequency, regardless of whether the master unit modem Mo is used or not, when two or more sets of slave unit modems communicate with each other almost simultaneously. As the number of modems increases, the possibility of collision increases. Therefore, as will be apparent from the description below, measures have been taken to prevent interference.

By the way, the modem M ₂ among the plurality of modems in FIG. 1A is drawn so as to face the modem Mo side. However, in this way, the modem or at least the light emitting portion (or the light receiving portion to this) is provided. If the modem is configured so that the mechanically combined light emitting / receiving section) can be directed manually or electrically in the direction of transmission, it will be possible to reliably communicate even if the directivity of the light emitting section or the light receiving section is narrow. It is convenient.

Next, a concrete configuration example of the modem, which is the main part of the device of the present invention, will be described with reference to FIG. Figure 2 (A)
1 is a concrete block configuration diagram of a first modem (slave modem), 2 is a decoder (decoder), 4 is a data processor, 5 is a light emitting unit, 6 is a modulator, and 7 is a terminal device 8. A connector for connection (for example, Centronics specification), 9 is a carrier detection circuit, 10 is a demodulator, 11 is a light receiving part, and 20 is an encoder (encoder). Is configured.

The decoder 2 and the encoder 20 may be incorporated in the data processor 4, and in that case, they are often not shown. Further, when the terminal device 8 is desired to be a printer only (especially in the case of a master modem), since the printer generally does not have a memory function, a RAM for temporarily storing the input data from the light receiving unit 11 via the data processor 4. Volatile memory 24, etc., or for long-term storage
A non-volatile memory 25 such as EPROM is provided.

Further, FIG. 2B shows a second modem (master device) M.
It is a block diagram of o, and further comprises a frequency converter 3 and an amplifier 23 in addition to the above configuration of the slave modem.
Therefore, the carrier frequency f ′ of the signal light output from the master unit
Is different from the carrier frequency f (for example, 2.5 MHz) of the output signal light from the slave unit which is input from the light receiving unit 11. The frequency converter 3 can be realized relatively easily by using, for example, a square circuit, and in that case, f '= 2f is naturally obtained. As a result, in the slave unit modem, is the signal light supplied to the light receiving unit 11 a signal relayed by the master unit modem? Or, it becomes possible to identify whether the signal light is from another slave unit modem.

Next, regarding the operation of the slave modems M _{1 to} M ₄ and the data communication method, the packet (optical packet;
Block diagram of optical data block sent at one time) and Fig. 1 (A),
It will be described with reference to (B) as well.

Data from the terminal device 8 (personal computer 8b) connected to the modem M ₂ of the slave modems is supplied to the data processor 4 via the connector 7. The data processor 4 forms a packet, for example, as shown in FIG. 19 according to the data format of the optical communication protocol, by grouping a predetermined number (for example, 256 bytes) of data, and then encodes and modulates it by the encoder 20. Output to the container 6. The coded signal is modulated by the carrier (carrier wave) by the modulator 6, and emitted from the light emitting unit 5 as an optical signal and output. Such an optical signal is sometimes called a carrier, and its light emission timing is performed when the data processor 4 determines based on the information from the carrier detection circuit 9 that "the light emission by the other modem does not exist".

The optical signal output in this manner is captured by the light receiving portion 11 of another modem (particularly the master modem) and photoelectrically converted, and then demodulated by the demodulator 10 (for example, PWM (pulse width) demodulation). }, And is decoded by the decoder 2 and supplied to the data processor 4. The data processor 4 analyzes the signal, and if the ID No. contained therein is the same as its own ID No., it judges that it is addressed to itself and extracts only the data portion (D in FIG. 19), and the connector 7
To the terminal device 8 via. At this time, a response packet is created by the data processor 4 as needed, and the light emitting unit 5 emits light through the encoder 20 and the modulator 6. That is, in the data processor 4, the communication command response of the optical communication protocol is also formed by the same packet, and the communication control according to this optical communication protocol is also performed.

Next, the operation peculiar to the master modem M _o will be described with reference to the block diagram of FIG. 2B, as shown in FIGS.
It will be described with reference to FIG. The signal light (carrier frequency = f) caught by the light receiving unit 11 is photoelectrically converted here, and then demodulator 10, carrier detection circuit 9, and amplifier 2
It is supplied to the frequency converter 3 via 3. The frequency converter 3 converts (changes) the carrier frequency to a frequency f ′ (for example, 2f), photoelectrically converts it in the light emitting unit 5, and outputs it in real time.

After the demodulator 10, almost the same processing as that of the slave modem is performed. That is, the demodulator 10 demodulates the signal, and the decoder 2 decodes the signal.
It is supplied to the data processor 4. Data processor 4
Analyzes the data, and the terminal device 8 connected to itself or
If it is destined for the destination, the data format is converted as necessary and sent to the terminal device 8 via the connector 7. The data processor 4 also analyzes the data sent from the terminal device 8 via the connector 7 and converts the data format as necessary, and the encoder 20 and the modulator 6 respectively perform the same signal processing as described above. After applying, frequency converter 3
Is converted into a frequency f ', and converted into an optical signal by the light emitting section 5 and output.

The data processor 4 further includes a terminal device 8
The data sent from the connector 7 is converted into the packet format and supplied to the encoder 20. Then, the same signal processing as described above is performed and the data is output from the light emitting unit 5. The light emission timing is performed when the data processor 4 determines that "there is no light emission from another modem" based on the information from the carrier detection circuit 9, as in the case of the slave modem.

By the way, in a system including a plurality of terminals and modems such as the optical wireless data transmission systems 1a and 1d of the present invention shown in FIGS. It is indispensable to perform orderly transmission / reception without causing confusion (optical data collision) in the transmission / reception operation, and the systems 1a and 1d of the present invention prevent optical data collision as follows.

That is, in FIG. 1A, the modems M _1, M _2,
When M _{3 and the} like are going to emit (transmit), the carrier detection circuit 9 shown in FIG. 2 performs carrier sensing (determines whether or not signal light exists in the space), and the light is present. If not, the light emission is started after waiting for a predetermined random number time (time set by the random number generator in the device). Specifically, for example, the upper and lower bits of the lower 5 bits of a free running counter (not shown) in the CPU are replaced with each other for 3 ms.
The product of ec and the random time.

Here, the system (area) is shown in FIG.
If there is a partition W _1, W _2, W _3, such as, modem M _1, M _2,
M ₃ is a partition W ₁ even if a modem other than yourself is emitting light
There is a possibility that two or more modems will start to emit light because they cannot be sensed by being blocked by or W ₂ .
At that time, light collision occurs. In order to prevent this, the master modem Mo performs not only data transmission with its own terminal 8 but also the light received from another slave modem (modem M _{2 in} the example in the figure). By spreading it over a wide range (for example, 360 °) like a double line or a broken line, it has the function of enabling all the slave modems to perform carrier sense.

In the case of optical communication, even if the directivity is strong, the strength decreases in inverse proportion to the square of the distance. Therefore, even if the area is not blocked by a wall, the optical communication range ( Area) has a limit. For example, in FIGS. 1A and 1B, when the modem M ₂ to the modem Mo can communicate but the light does not reach the modem M ₄ , the modem M ₂ to the modem M ₄ via the modem Mo. Since it is communicated, it is clear that the modem Mo acts as a relay device.

Here, if there is an obstacle (such as a pillar) X as shown in FIG. 3 between the modem M ₂ and the modem Mo, the light does not reach from the modem M ₂ to the master modem Mo, Therefore, optical communication with the modem M ₄ cannot be performed. In that case, another master unit modem M ₇ is installed at a position as shown in FIG. 3 to configure the system 1b (second embodiment of the system of the present invention), so that the modem M ₂ can operate as the modem M ₇ Optical communication with the modem M ₄ can be performed via the via.

Conventionally, a dedicated repeater has performed this role. Therefore, when it is desired to connect a terminal device also to the master side, one modem is required in addition to the repeater, and the modem needs to be installed at a position where optical communication with the repeater is possible. In this respect, the master modem of the device of the present invention has the functions of both a repeater and an optical transmission device, so it suffices to connect a terminal to the place where the modem M _{7 in} the figure is installed, and purchase an extra modem. There is an advantage that the space of the room can be effectively used without doing.

Now, when a certain modem M _n (n is a natural number of 3 or more) transmits data to a terminal of another vacant (not in use) modem, the link setting partner is arbitrary. The modem M _n makes a link connection to the modem M _x (x is a natural number of 3 or more) that first answers. Here, for example, the terminal device 8 (printer included in) of FIGS. 1 (A) and 1 (B) has failed, and for the time being the modem M
Consider the case of using o as a repeater. Modem M
If the emission timing of o is lucky and the fastest, the modem Mo
Responds to the modem M _n coming to the link connection, but includes the status of terminal failure (or no connection) in the response message.

As a result, the modem M _{n that} has received this status must wait for a response from another modem without making a link connection with the modem Mo. Due to such extra replies, the line efficiency becomes poor. Therefore, when the terminal 8 breaks down, a signal indicating the failure is given to the connector 7
Data is supplied to the data processor 4 via a terminal, or the user sets the identification number of the modem Mo to a specific address (for example, address 0), so that data transmission / reception with the terminal device 8 is not performed at all. The modem Mo (the data processor 4 and the like of the modem) is configured to perform only the operation. This can alleviate the decrease in line efficiency.

By the way, as is well known, the communicable distance becomes short in inverse proportion to the square root of the communication speed (baud rate).
Between modems communicating over a certain distance, the communication may not be possible on the way due to deterioration of the SN ratio of light (effect of external light, etc.), generation of jitter, and reduction of carrier level. The modem in the system of the present invention monitors the state of the line and automatically switches the communication speed, that is, the amount of information per unit time, for example, by changing the clock frequency to prevent the deterioration of the line quality. Can be configured so that communication can continue without interruption.

Speed change protocol (specification) in that case
An example will be described with reference to FIG. FIG. 4 is a principle diagram showing an example of a speed change protocol in the system of the present invention. First, the calling party (modem M ₂ etc.) issues a link setting request to the called party (modem Mo etc.) at the lowest speed (for example, 9.6 kBPS) which is the speed with the best communication quality. The called party naturally waits for a link setup request from the calling party at this minimum speed.

The called party receiving this judges the line quality based on the carrier level, SN ratio, jitter, etc. included in the reply optical signal, and determines the optimum communication speed V (for example, 38.4 kBPS or 7
6.8kBPS, etc.) Then, the information of the optimum speed V is put in the reply packet of "link setting OK" and returned to the caller. The caller who received this received "Receive O
A reply of "K" is returned to the called party. The called party switches the optical communication speed to the optimum speed V at the moment of receiving this, and waits for data from the calling party. The delivery is performed at the optimum speed V.

As described above, the modem M capable of changing the communication speed has the SN ratio, the jitter, and the like as shown in the configuration example of FIG.
A carrier level measuring unit (hereinafter abbreviated as “level measuring unit”) 12 for measuring a carrier level and the like and a communication speed control unit 13 are further provided. The other components are the same as those in the configuration example shown in FIG. 2B, and therefore, the same reference numerals are given and detailed description thereof is omitted. Note that this configuration example is compatible with the master modem, and in the case of compatible with the slave modem, FIG.
As is clear from (A), there is no frequency converter 3, and the light is directly output from the modulator 6 to the light emitting unit 5.

The input signal photoelectrically converted by the light receiving section 11 is supplied to the level measuring section 12, where the SN ratio, jitter, carrier level and the like are measured by a known method. The measurement result is A / D converted if necessary, and then supplied to the communication speed control unit 13. As a result, the output signal (packet data) from the terminal device 8 via the data processor 4 is controlled so that the communication speed thereof is an optimum speed for the degree of the line quality, and the light emitting unit via the encoder 20 and the modulator 6. Light emission is output from 5.

The communication speed control unit 13 is incorporated in the data processor 4, or the communication speed control unit 13 is used.
It is also possible to provide the data processor 4 with the information on the communication speed set in step 1. In that case, the following merits occur. That is, in the packet of the output signal formed by the data processor 4, the communication speed control unit 1
The data processor has the function of including the communication speed set in step 3, and the information of the communication speed included in the signal sent from the modem of the communication partner is decoded and the two are compared, By providing the data processor with the function of adjusting the set value (baud rate) of the communication speed control unit to the slower one, more reliable data communication can be performed. The reason will be described below.

In general, the directional characteristics of the light-receiving portion 11 and the light-emitting portion 5 in the slave modem are narrow, and the arrangement (direction) of the light-receiving portion 11 and the light-emitting portion 5 or variations in hardware performance may cause
The quality of light received and emitted varies between modems of both handset units during communication. For this reason, when the communication baud rate is set, if only one of the receiving performances is judged, if the other receiving performance is inferior, the communication becomes impossible. Therefore, this problem is solved by confirming the baud rate by both parties and setting it to the slower one.

Further, although communication is possible with a short packet such as communication for the link setting procedure, for example, data stored in advance in the non-volatile memory 25 is included in the packet, and the data amount (packet length) is calculated. If you make it longer,
The number of errors suddenly starts to occur frequently, and the line efficiency may drop due to repeated retransmission operations. Therefore, if you try to send an optical packet of the length actually used for data communication, and if you can communicate normally, perform the subsequent communication at that baud rate, and if you cannot communicate normally, set the baud rate to 1 rank. Lower it for subsequent communication. Note that when communicating by relaying not the slave units but the master unit, communication is performed in accordance with the slowest baud rate of the three parties, which enables more reliable communication.

In the baud rate judgment, when the line quality is judged only by the carrier level without using the SN ratio, jitter, etc. of the received light, the master modem amplifies the received light with the amplifier 23 as described above. Since the relay is performed, the actual light level from the personal computer side slave unit modem cannot be known to the printer side slave unit modem. Therefore, an incorrect baud rate may be set depending on the layout of the slave modem. Therefore, by providing the master modem (the data processor 4 of the master modem) with a function of determining the appropriate baud rate from the received light levels from both slaves and notifying both slaves of the master modem, which acts as a relay, Can be resolved. Further, the data processor 4 may be configured by software so as to dynamically switch the baud rate not only at the time of call setting but also during the data communication procedure.

Here, a concrete configuration example of the communication speed control unit 13 and a method of switching the communication speed will be described with reference to FIG. FIG. 9 is a specific block diagram of the communication speed control unit 13, and the band limiting filter 15 is configured by a cutoff variable filter such as a switched capacitor. The clock control unit 17 generates an appropriate clock signal according to the communication speed control signal from the data processor 4 and supplies it to the band limiting filter 15. The filter 15 removes the high frequency component of the input signal at the cutoff frequency set by the clock signal. Then, the communication speed is changed by changing the cutoff frequency according to the communication speed. In addition, LPF (low pass filter) 1
Reference numeral 6 serves to remove unnecessary high frequency components generated by the switching of the filter 15.

Here, when the slave modem serving as a caller is set up for a call (callee setup), if the slave modem serving as a setting partner is arbitrary, the callee who first replies is called. A method and a principle thereof that can save the trouble of setting a communication partner by link connection will be described with reference to the configuration example of FIG. FIG. 6 is a system configuration diagram of a third embodiment 1c of the present invention system. In this figure, the same components as those of the first and second embodiments shown in FIGS. Detailed description thereof will be omitted.

In the system 1c shown in FIG. 6, when the slave unit modem M ₂ wants to transmit data to any one of the other slave unit modems M _1, M _{3 to} M ₆ , the modem M ₂
First of all, the call setup is started by arbitrarily setting the other party. The modems M _{1 to} M that have received such a signal via the master modem M ₇
After waiting for random time different from each other, ₆ confirms that there is no carrier, and then replies. For example, if modem M ₄ replies first, modem M ₂ will link to modem M ₄ .

Such a function is convenient, for example, when a personal computer or word processor having no printer wants to print on any of the printers in standby (not in use). If it terminal unit 8d of the modem M ₄ is out of order, because it returns an error status to the modem M _2, the modem M ₂ is not link connection to the modem M ₄ sometimes from other modems in the following replies To wait for

Further, it is convenient if the slave unit modem and the master unit modem that are in communication are configured so that adjacent packets can be separated by an arbitrary time so that communication can be performed between other slave units and the master unit (or between slave units). . Specifically, for example, in FIG.
After transmitting one optical packet, the master unit stops the transmission for the time Tw. If no communication (optical signal output) is made by another slave or master during that time, the optical packet is sent again. In addition, FIG. 10 shows a plurality of sets of slave units in the system of the present invention.
6 is a timing chart showing the principle of a method for performing data communication between master devices without light collision.

On the other hand, it can be seen from the detection result of the level measuring section 12 of FIG. 5 that the other carriers and masters have run out of carriers at time To when the slaves and masters stop data communication. After waiting for a predetermined (random number) time, if there is no more carrier, transmission is started. The same is done at time T ₁ , which enables a plurality of sets of communications to be performed without interference or collision even in data communications using light of the same frequency. On the other hand, if there is no communication between the other child device and the parent device, opening Tw for a long time leads to a decrease in communication efficiency. Therefore, in such a case, the communication efficiency (line efficiency) can be improved by shortening Tw in proportion to the time.

Next, as shown in FIG.
Can also be configured to determine the packet length from the amount of data that it has been able to send to the parent device within the specified time. Note that the inter-packet waiting time Tw is constant.
The more crowded the line, the smaller the amount of data that can be sent by itself, so the packet length should be shortened as shown in the figure.
In this figure, L1 (ι), L2 (m), and L3 (n) are packet lengths determined by the amount of data that the transmitting modem could send within the specified time. In this way, the communication efficiency between each child device and the parent device becomes equal. Moreover, since the packet length becomes long when the line is not busy, the influence of the waiting time Tw on the transmission efficiency becomes small.

In the optical communication protocol, there is a means for preventing data loss by retransmitting in case of data reception error. If the communication state is bad, the number of times of retransmission is increased, so that the communication efficiency is deteriorated in proportion to the packet length. Therefore, it is preferable to improve communication efficiency by shortening the packet length when the communication state is poor. The communication status is determined based on the number of past retransmissions and the level of the carrier level.

By the way, without increasing the applied voltage for light emission,
As is well known, in order to increase the communicable distance, it is effective to narrow the directivity of the output light from the light emitting unit. Therefore, if the system scale is small (for example, if the modem is 2-4
In the case of individual devices), it is not necessary to secure a wide service area, so it is economical to configure the system with only the slave unit, without using the master unit, by making the light emitting part of the modem for the slave unit a narrow directivity. is there. FIG. 7 is a block diagram showing a system configuration example in the case where the system scale is small. In that case, if the transmission frequency and the reception frequency are both f ′ for inter-slave communication, the frequency converter 3 constituting the modem is also unnecessary. Becomes

On the other hand, the master unit is configured to have a wide directivity (for example, 360 °) in order to obtain a wide communication range. FIG. 8 is a block diagram showing a system configuration example in the case where the system scale is large, and as shown in the figure, a plurality of parent devices are used. Then, the transmission frequency between the slave units is f, and the reception frequency is f ',
With the reception frequency of the base unit as f and the transmission frequency as f ', a service area as wide as possible is secured. The transmission frequencies of the slave unit and the master unit are made different from each other as shown by f and f ', respectively, even if the direct light from the slave unit and the light transmitted from the master unit which is the repeater are output at the same time. This is to prevent it from happening.

When it is not necessary to increase the communicable distance, the output light from the light emitting unit 5 and the directivity of the light receiving unit 11 are opposite to those in the above even in the slave unit which is a modem having no relay function. By making it possible to perform carrier sensing with each other, there is an advantage that it is possible to prevent collision (interference) of lights having the same transmission frequency.
However, with respect to a plurality of slave units installed in places hidden from each other by walls or partitions, it is impossible to take measures to prevent optical collisions only by expanding the directivity.

Therefore, as an example of preventive measures, a command of LINKON is used to connect the link and a command of LINKOFF is used to disconnect the link. As shown in the system configuration diagram for explaining measures against hidden slave units in FIG. 12, for example, the slave unit M ₂ sends a command to the master unit Mo.
When the link is set by LINKON, even if the directivity of the outgoing light of the temporary handset M ₂ is wide, the handset M _{1 and} M ₃ cannot perform carrier sense because of the partitions W _{1 and} W ₂ , and the link is set. May start working. To prevent this, the master Mo receiving the command LINKON emits a signal light including the command LINKON to notify the other slaves M _{1 and} M ₃ that the link connection with the slave M ₂ has been made. The slaves M _{1 and} M ₃ that detect this are
The link setting operation is performed on the master unit Mo until the slave unit M ₂ outputs the command LINKOFF to the master unit Mo and the master unit Mo that receives the command outputs the command LINKOFF to all the slave units. The data processor 4 of the child device is designed as software so as not to perform it. As a result, it is possible to implement measures against hidden child devices in the system of the present invention.

Next, even if the base station modem does not have the relay function or the function of the hidden handset countermeasure described above, when there is a handset modem that cannot carry out carrier sense, deterioration of communication traffic due to collision is minimized. Explain how to stop it. If a response from the master unit is not received within the specified time, the slave unit that has entered the link setting determines that a collision with the light transmitted from another unit has occurred, and extends the time until the link setting operation is restarted. In addition, I guess that there is a child machine that can not carry out carrier sense, and extend the retransmission interval from myself,
Gives a chance to link to a child device that cannot carry out carrier sense. The data processor 4 is configured so that the extension time also gradually increases in proportion to the number of retransmissions in the past.

That is, in the case where the parent machine does not have the relay function or the function of the above-mentioned hidden child machine, and there is a child machine which cannot carry out carrier sense, when a collision occurs, the situation shown in FIG. As shown in the timing chart for explaining the operation when the communication between the printers is the Centronics specification}, if the retransmission interval T ₂ is extended only on the slave unit (M ₂ ) side, the slave unit and the master unit (Mo) are connected. The decrease in transmission efficiency can be minimized. In the example of FIG. 13, the parent device is also a separate combination, but it is also effective when the parent device is common.

In addition, if it is desired that the slave unit that has caused the collision be able to perform communication in the same manner as the slave unit, FIG. 14 {reduces the deterioration of communication traffic due to the collision and enables both parties involved in the collision to communicate. As shown in {Principle diagram showing the method of the above method}, the collided slave unit side also extends the retransmission interval to give the slave unit many opportunities to emit light. If the slave unit can carry out carrier sense, once the slave unit emits light, the packet at this time is transmitted to the master unit without a collision due to the waiting time Tw shown in the figure. In FIGS. 13 and 14, the mark x indicates that a collision has occurred between the upper and lower packets, and n and m indicate the number of past retransmissions.

Finally, another configuration example M'of the modem in the system of the present invention will be described with reference to the block diagram of FIG. In this figure, 19 is an A / D converter, 21 is a display drive circuit such as an LED driver, 22 is a display portion such as a 7-segment LED, and other components shown in FIG. 2 (B) and FIG. The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted. Note that this configuration example is also compatible with the master modem, and when compatible with the slave modem, the frequency converter 3 is not provided as in FIG. 2A, and the modulator 6 directly outputs the light to the light emitting unit 5.

The level of the signal received and photoelectrically converted by the light receiving unit 11 is measured by the carrier level measuring unit 12, the measured value is converted into a digital value by the A / D converter 19, and the data processor 4 is operated. Supply to. The data processor 4 converts this value into a value for 7-segment LED display, outputs it to the display drive circuit 21, and displays it on the display unit 22. If the frequency converter 3, the light emitting unit 5, and the modulator 6 are provided, the same function as that of the modem M shown in FIG. 2 can be provided. Further, when the terminal 8 is connected to the connector 7, a signal from the terminal 8 (for example, power ON, OFF, etc.) can be displayed, but a typical use example is to improve reception efficiency as follows.

In order for the master unit to most efficiently receive the outgoing light from the slave unit, it is essential to optimize the direction of the outgoing light from the slave unit. Therefore, it is convenient to inform the user of the reception efficiency based on the received carrier level. To this end, in FIG. 18, the carrier level from the light receiving unit 11 is A / D converted by the A / D converter 19 and input to the data processor 4. The data processor 4 displays the A / D converted numerical value on the 7-segment display unit 22 in real time. The better the reception, the higher the carrier level, that is, the display value of the display unit 22, so that the user can know the optimum direction. Specifically, the dummy data is repeatedly transmitted and received by the test program between the transmitting and receiving modems at fixed time intervals, during which the light emitting unit, the light receiving unit, or the light emitting and receiving unit that mechanically combines both is manually operated. Alternatively, it may be electrically driven to search for the direction in which the carrier level display is maximized.

Further, as shown in FIG. 16, the wired communication between the parent device Mo and the printer 8e connected thereto as shown in FIG. If the specification is such that it knows that it has received the data, if the response does not come within the specified time, the master unit (Mo) judges that the printer power is off and uses this information as a slave unit (M ₁ ) Send it back to. The child device (M ₁ ) informs the user of this by lighting the display unit 22 on the panel of the child device (M ₁ ). FIG. 15 is a block diagram for explaining the status confirmation method of the master unit from the slave unit, and FIG.
FIG. 4 is a timing chart for explaining a data transfer confirmation method between the master unit and the terminal.

FIG. 17 is a timing chart for explaining the operation when the communication between the master unit and the printer is the Centronics specification. In the Centronics specification, when data or a STROBE signal is sent from the base unit to the printer, a BUSY (acceptance impossible) signal or ACKNLG (acceptance possible) signal for response is returned. If this reply is not received within the stipulated time, the main unit will display "Printer power
"OFF".

[0059]

Since the optical wireless data transmission system of the present invention is constructed as described above, it has various excellent features as follows. (1) Since the master modem has the functions of both a repeater and a data transmission device, it is possible to expand the communication area and increase the number of terminals by adding slave modems. (2) The communication quality and communication quality can be improved by providing the communication quality determination means and the communication speed varying means.

(3) It is possible to enable a plurality of sets of simultaneous communication by not transmitting continuously during communication but by transmitting a predetermined time interval between adjacent packets. (4) Communication efficiency can be improved by varying the packet length, the open time between packets, and the waiting time according to the quality of communication and the congestion of lines. (5) At least the called party's modem has a function to display the received light level, and if the level is displayed according to the intensity of the output light from the calling party, the direction of the modem (receiver or light emitter) can be changed. You can adjust the optimum direction by increasing or decreasing the level when you do.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a first embodiment of an optical wireless data transmission system of the present invention.

FIG. 2 is a block diagram showing a configuration example of a modem which is a main part of the system of the present invention.

FIG. 3 is a system configuration diagram showing a second embodiment of the system of the present invention.

FIG. 4 is a principle diagram showing an example of a speed change protocol in the system of the present invention.

FIG. 5 is a block diagram showing another configuration example of a modem which is a main part of the system of the present invention.

FIG. 6 is a system configuration diagram showing a third embodiment of the system of the present invention.

FIG. 7 is a system configuration diagram showing an example of a small system scale.

FIG. 8 is a system configuration diagram showing an example of a large system scale.

FIG. 9 is a specific block diagram of a communication speed control unit in the modem.

FIG. 10 is a timing chart showing the principle of a method of performing data communication between a plurality of sets of slave units and a master unit in the system of the present invention without light collision.

FIG. 11 is a timing chart showing the principle of a method for improving communication efficiency while equalizing communication efficiency between a plurality of sets of slave units and master unit in the system of the present invention.

FIG. 12 is a block diagram for explaining measures against hidden child devices in the system of the present invention.

FIG. 13 is a principle diagram showing a method for preventing deterioration of communication traffic due to collision to a minimum in the system of the present invention.

FIG. 14 is a principle diagram showing a method of reducing deterioration of communication traffic due to a collision and enabling communication between both parties involved in the collision.

FIG. 15 is a block diagram for explaining a status confirmation method of a master modem from a slave modem.

FIG. 16 is a timing chart for explaining a data transfer confirmation method between a master modem and a terminal.

FIG. 17 is a timing chart for explaining the operation when the communication between the master device modem and the terminal device is the Centronics specification.

FIG. 18 is a block diagram showing still another configuration example of the modem in the system of the present invention.

FIG. 19 is a schematic diagram showing the contents (configuration example) of an optical packet used in the system of the present invention.

[Explanation of symbols]

1a to 1d ... Optical wireless data transmission system, 2 ... Decoder (decoder), 3 ... Frequency converter, 4 ... Data processor, 5 ... Light emitting unit, 6 ... Modulator, 7 ... Connector, 8, 8a
8n ... Terminal device, 9 ... Carrier detection circuit, 10 ... Demodulator, 11 ... Light receiving unit, 12 ... Carrier level measuring unit, 1
3 ... Communication speed control unit, 14, 16 ... LPF (low pass filter), 15 ... Band limiting filter, 17 ... Clock control unit, 19 ... A / D converter, 20 ... Encoder, 21 ... Display drive circuit, 22 ... display unit (light emitting diode), 24, 25 ... memory, M, Mo ~M _n ... modem, W ₁ ~ W ₃ ... partition, X ... obstacle.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H04B 10/22 (72) Inventor Takami Shiramizu 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Japan Victor Co., Ltd. (72) Inventor Susumu Katayama 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Japan Victor Co., Ltd. (72) Inventor Hiroshi Takano 3-12 Moriya-cho, Kanagawa-ku, Yokohama Japan Victor Co., Ltd.

Claims (7)

[Claims] 1. A plurality of first modems and one or more second modems, each of which is connected to each terminal by a cable, respectively.
Is a system for performing wireless data transmission using light as a medium between the modems or between the first and second modems, wherein the first modem receives output light from another modem and converts it into an electric signal. A light-receiving unit, a data processor that decodes the electric signal and supplies it to a connected terminal device as necessary, and performs predetermined signal processing such as packetization on data from the terminal device and outputs the data. A measuring unit for measuring a signal level and / or an SN ratio or the like to check communication quality, a communication speed control unit for controlling an output speed of the data processor according to a measurement result of the measuring unit, and the communication speed control And a light emitting unit for converting the output signal of the unit to an optical signal and outputting the optical signal. The second modem has, in addition to the configuration of the first modem, a carrier of an electric signal obtained by the light receiving unit. Change frequency Characterized by being configured further comprising a frequency converter for supplying to the light emitting portion Te, the optical wireless data transmission system. 2. The optical wireless data transmission system according to claim 1, wherein the communication speed control unit comprises a cutoff frequency variable filter for changing the cutoff frequency according to a measurement result of the measurement unit. . 3. A carrier detection circuit for detecting the presence or absence of an electric signal obtained by a light receiving section and supplying the detection result to a data processor is provided in at least a second modem of the two types of modems. The optical wireless data transmission system according to claim 1. 4. A data processor further comprising a storage unit for temporarily storing data sent from a cable-connected terminal device, and having a function of intermittently outputting the temporarily stored data into packets by a predetermined amount. The optical wireless data transmission system according to claim 1 or 3, wherein the optical wireless data transmission system is provided. 5. A detection result of the carrier detection circuit and / or
5. The optical processor according to claim 4, wherein the data processor has a function of appropriately adjusting the amount of data to be packetized and / or the time interval of intermittent output according to the measurement result of the measuring unit. Wireless data transmission system. 6. A function of including the information of the communication speed set by the communication speed control unit in the output signal data, and the information of the communication speed included in the signal transmitted from the modem of the communication partner. The optical processor according to claim 1 or 4, wherein the data processor further has a function of decoding and comparing the two, and adjusting the set value of the communication speed control unit to the slower of the two communication speeds. Wireless data transmission system. 7. The optical wireless data transmission according to claim 1, further comprising a display unit for displaying the level of the electric signal measured by the measuring unit, the first and / or second modem. system.