JPH0677961A - Optical radio data transmission system - Google Patents

Abstract

PURPOSE:To enlarge a service area, to increase a transmission enable terminal and to improve operability by connecting plural equipment main bodies by optical transmission and providing both of functions for data transmission and relaying at a master equipment modem. CONSTITUTION:At a slave equipment modem M2, prescribed processing is performed to data from a terminal member 8b, an outputted optical signal (f) is photodetected by a modem M0 of a master equipment and demodulated/decoded, and data addressed to the present equipment are sent to a terminal equipment 8. On the other hand, a reception frequency (f) is converted to f' and outputted from a light emitting part as an optical signal. In this case, light is emitted after confirming the absence of the optical signal with carrier sense so as not to confuse the transmitting/receiving operations among the plural modems and when there is any obstacle such as a partition W in the system, the master equipment modem M0 outputs the optical signal, for which not only the light reception from the modem itself but also the light reception from the other slave equipment modem M2 is frequency converted, so as to enable the carrier sense at all the slave modems. Thus, the service area can be enlarged at low cost, and communication efficiency can be improved as well.

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.
The latter (conventional optical wireless device) has a high transmission speed, but has a drawback that it is vulnerable to an obstacle in the transmission path. Further, there is a problem that the distance and spatial range in which data can be transmitted are narrow due to the structure of the light emitting portion of the modem (modulator / demodulator).

[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. The modem receives the output light from another modem and photoelectrically converts it, and decodes the photoelectrically converted signal and supplies it to the connected terminal device as necessary, while converting it to data from the terminal device. The second modem has the configuration of the first modem, which is provided with at least a data processor that performs predetermined signal processing such as packetization and outputs, and a light emitting unit that converts an output signal of the data processor into an optical signal and outputs the optical signal. In addition, the above problem is solved by providing at least a frequency converter that changes the carrier frequency of the signal photoelectrically converted by the light receiving unit and supplies the light emitting unit with the frequency converter. .

[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 portion and the light receiving portion of the parent device modem Mo are configured to be wide because they must be able to communicate with all the child device modems in the area, and the child device modems M _{1 to} M ₄ are at best the parent device modems. If only Mo can be communicated with, the function can be fulfilled, so the directional characteristics are narrowed to simplify the configuration (reduce the number of light emitting and 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 Compared to the configuration example of FIG. 1 (A), the number of slave modems and terminals is increased by two in FIG. 1 (B), and there is no difference except that the arrangement of them is wider. 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)
Is a concrete block configuration diagram of the first modem (slave unit), 2 is a decoder (decoder), 4 is a data processor,
5 is a light emitting unit, 6 is a modulator, 7 is a connector (for example, Centro specification) for connection with the terminal device 8, 9 is a carrier (carrier wave) detection circuit, 10 is a demodulator, 11 is a light receiving unit, and 20 is an encoder. (Encoder), and these are connected as shown in the figure to configure a slave unit modem.

The decoder 2 and the encoder 20 may be incorporated in the data processor 4, and in that case, they are 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. And a non-volatile memory 25 such as an EPROM for long-term storage.

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.

The master modem Mo may be configured without the connector 7 to serve as a dedicated relay operation machine. Further, the light emitting section 5, the light receiving section 11, the frequency converter 3 (and the amplifier 23).
You may comprise only only.

Next, regarding the operation of the slave modems M _{1 to} M ₄ and the data communication method, refer also to the configuration diagram of the optical packet (optical data block sent at one time) in FIG. 19 and FIG. 1 (A, B). And explain.

Data from a terminal device 8 (personal computer 8b) connected to, for example, the modem M ₂ among the slave modems is supplied to the data processor 4 via the connector 7. The data processor 4 forms a data 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 it with the encoder 20. Modulator 6
Output to. 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 determined by the carrier detection circuit 9
This is performed when the data processor 4 determines that "there is no light emission from another modem" based on the information from the.

The optical signal output in this way is caught by the light receiving section 11 of another modem (particularly, the master modem Mo) and photoelectrically converted, and then demodulated by the demodulator 10 (eg PW).
M (pulse width) demodulation}, and the decoder 2 decodes
And is supplied to the data processor 4. The data processor 4 analyzes the signal and includes the IDN included in the signal.
If o. is the same as its own ID No., it is judged that it is addressed to itself and only the data portion (D in FIG. 19) is taken out and sent to the terminal device 8 via the connector 7. 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 data packet, and the communication control according to this optical communication protocol is also performed.

Next, regarding the operation peculiar to the master modem M _o , referring to the block diagram of FIG. 2 (B), FIG. 1 (A, B), FIG.
Will also be described. 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 23.
Is supplied to the frequency converter 3 via. Frequency converter 3
Then, the carrier frequency is converted (changed) to a frequency of f ′ (for example, 2f), photoelectrically converted by the light emitting unit 5, and emitted and output 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 data packet format and supplied to the encoder 20,
Thereafter, the same signal processing as described above is performed and the light is emitted 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 above-mentioned slave unit 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, in the system (communication area), as shown in FIG.
If there are partitions W _1, W _2, W _{3 such as} (A), the modem M _1,
Also M _2, M ₃ is not emit light a modem other than your own, it is not possible to carrier sense is blocked by the partition W ₁ and W _2, could start to emit light with two or more of the modem is there, 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.

By the way, in the case of optical communication, even if the directivity is narrow, the strength decreases substantially in inverse proportion to the square of the distance.
There is a limit to the range in which optical communication is possible (communication area) even within the range where the wall is not blocked. For example, Figures 1 (A) and (B)
In, also from the modem M ₂ up modem Mo can communicate reachable light, until the modem M ₄ in the case where the light does not reach is communicated to the modem M ₄ from the modem M ₂ via the modem Mo, modem Mo is Functions 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, 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 increase the number of terminals on the master side, another 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, when 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 receiving 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. 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 can be configured to monitor the line status and automatically switch the communication speed so that the communication can continue without interruption even if the line quality deteriorates.

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, who received the signal, photoelectrically converts the return light in the light receiving section 11, and then the carrier level of the signal,
The line quality is judged by measuring the SN ratio, jitter, etc., and the optimum communication speed V (for example, 38.4 kBPS, 76.8 kBPS, etc.) is determined by the communication speed control unit 13 in FIG. Then, in the data processor 4, "link setting OK" is given to the calling party.
The information of the optimum speed V is put in the reply packet of and returned. The calling party receiving this returns a "reception OK" reply 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 caller then sends the data thereafter at the optimum speed V
To do.

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 can be incorporated in the data processor 4.

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.

[0038] In system 1c shown in FIG. 6, handset modem M ₂ if you want to transmit data to any one of the modems of the other handset modem M _1, M ₃ ~M _6, 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 a 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

By the way, the data processor 4 has, in addition to the above-mentioned various functions, a function of dividing a series of data sequentially output from a terminal connected to a cable into a plurality of packets. The specific method is shown in FIGS.
The timing chart of No. 1 will be described.

As a conventional method, the packet data length (for example, 256 bytes) is fixed, and the data sent from a terminal such as a personal computer momentarily (FIG. 20 (A)).
When 256 references are accumulated, they are output as packets as shown in (B) and (C) of the same figure. If no data is output from the terminal device for the time-out T1 or more, it is considered that the print data is completed, and the optical communication is disconnected (finished) {see (C) in the figure}. This is because the print data from the terminal device does not indicate the end of the data, and therefore the end can be determined only by a timeout.

The timeout T1 can be set only in seconds (for example, 10 seconds) in consideration of the processing speed of the terminal and the data output timing of the printing software, and the current spreadsheet software outputs the data while performing the calculation. Therefore, there may be a few seconds or more between data (T3 in the same figure (A)). Therefore,
If the packet length of the final data is less than 256 bytes,
This packet will be output after the timeout T1. Therefore, when the processing speed of the printer connected to the called party's modem is high, a few seconds of vacant time is required until the final data is printed, resulting in lost time.

Therefore, a timer is provided inside or outside the data processor 4, and the modem (data processor) is provided with a function of packetizing the input data when the timer times out, and the time interval of the packet output is set. At the same time, setting the time from the output of the final packet to the disconnection of the link is also one of the features of the present invention.

Specifically, in addition to the time-out T1, a packetization time-out T2 (several 10 to several 100 ms) is provided as shown in FIG. By performing this in units, the final packet can be output in at least T2 seconds or less, and the occurrence of the above loss time is resolved. For example, T2 = 256 / terminal unit average data transfer rate [bps] is determined. If the terminal data transfer rate is 10 kbps, T2 = 256 / 10k = 25.6 ms
become.

The optical transmission in the area (space) in the system is crowded, and the transfer (transmission) speed in the space is T.
If it is 2 or more, the packet length may be 256 bytes as before. The terminal device data transfer rate in the above equation is calculated by the data processor 4 from the number of data output in a certain time. That is, the data processor 4 has a function of measuring the data transfer rate of the terminal device. Then, by updating this value once every several seconds, efficient packetization becomes possible.

The timing of packetization (transmission) is not limited to the above T2, and the data processor 4 is configured to output a packet when a special control code such as CR (line feed), LF (page break) is received. It is easy to configure in software.

Some printers perform error processing such as discarding the command due to reception timeout between control command bytes. For example, if the control command has a format such as A (control command code) + B (command type) + C (argument): 3 bytes, the output timing to the printer side is A to B, B.
If there is a long free time between C and C, the printer may discard A or A + B at timeout T2. Then, B and C input next are regarded as normal characters, and as a result, abnormal characters are printed on the printer side.

Therefore, according to the present invention, the contents of the packet are constantly monitored, and when the final data of the packet is in the middle of the command sequence, the data before A is output as one packet, thereby solving the above problem. is doing. As an example, a method of monitoring and packetizing the ESC (Escape) / P code is shown in the flowchart of FIG. It is convenient for the data processor 4 to have such a function of monitoring the content of the input data.

Further, it is more convenient if the slave unit modem and the master unit modem which 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 the slave units). Become. Specifically, for example, in FIG. 10, the slave unit and the master unit stop transmitting for one time Tw after transmitting one data packet. If no communication (optical signal output) is made by another slave or master during that time, the data packet is sent again. 10. 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 master unit in the system of the present invention without light collision.

On the other hand, the other slave units and the master unit indicate that the carrier is lost at the time To when the slave unit or the master unit stops the data communication, or the carrier detection circuit 9 of FIG.
As can be seen from the detection result of the level measuring unit 12, the transmission is started if there is no carrier generated from another device after waiting a predetermined (random number) time. The same thing happens at time T ₁
However, even in data communication using light of the same frequency, it becomes possible to perform a plurality of sets of communication without interference or collision. 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. So in this case,
By shortening Tw in proportion to time, the line efficiency can be improved.

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 in the case of a base station modem that does not have a relay function or the above-mentioned hidden handset countermeasure function, 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, when the base unit does not have a relay function or a function of the above-mentioned hidden handset, and there is a handset that cannot carry out carrier sense, when a collision occurs, the state 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 communicate similarly to the slave unit, FIG. 14 {to reduce the deterioration of the communication traffic due to the collision and to enable 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 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 light emitted from the slave unit, it is essential to optimize the direction of the light emitted 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".

[0065]

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 increase the number of terminals that can be transmitted along with the expansion of the service area by adding a slave. (2) Since one model of the master unit is equivalent to two conventional models (a repeater and a data transmission device), it can be manufactured at a lower cost than the price of two models and model management is easy.

(3) By setting an address of a specific numerical value in the base unit modem, if the data exchange with the terminal connected to the cable is interrupted and only the relay operation is performed, the terminal can be operated. It does not reduce the line efficiency when it cannot be used. (4) Instead of fixing the packet data length (information amount) as the packet division method, a timer is provided in the data processor, and the data from the terminal device is packetized when this timer times out. In this case, since the final data packet is also quickly emitted, the loss time does not occur even if the called party printer has a high processing speed. (5) The communication efficiency can be improved by varying the packet length, the open time between packets, and the waiting time according to the congestion of the communication line.

[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 unit from a slave unit.

FIG. 16 is a timing chart for explaining a data transfer confirmation method between a master unit and a terminal (printer).

FIG. 17 is a timing chart for explaining the operation when the communication between the master unit and the printer is 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 block diagram showing still another configuration example of the modem in the system of the present invention.

FIG. 20 is a timing chart for explaining a conventional example of a method of dividing a series of output data from a terminal device into a plurality of packets by a data processor.

FIG. 21 is a timing chart for explaining the operation of dividing a series of output data from a terminal device into a plurality of packets in the system of the present invention.

FIG. 22 is a flowchart for explaining the operation of monitoring the content of output data from the terminal device to the modem and packetizing the data by the data processor.

[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, 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 (3)

[Claims] 1. A plurality of first modems and one or more second modems, each of which is connected to each terminal by a cable, are provided.
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 light output from another modem and photoelectrically converts it. And a data processor that decodes the photoelectrically converted signal and supplies it to a connected terminal device as necessary, while performing predetermined signal processing such as packetization on the data from the terminal device and outputting the data. At least a light emitting unit for converting the output signal of the data processor into an optical signal and outputting the optical signal is provided. An optical wireless data transmission system, comprising at least a frequency converter for changing a carrier frequency and supplying the light emitting section to perform a relay operation. 2. When a specific address number is supplied to the second modem as its identification number, the modem does not exchange data with the terminal connected to the cable but only performs a relay operation. The optical wireless data transmission system according to claim 1, wherein the optical wireless data transmission system is configured. 3. A timer for counting time and a storage unit for temporarily storing a series of data from a terminal connected to a cable are further provided in at least the first modem, and are stored in the storage unit. The data processor is provided with a function of sequentially outputting the data that is being generated as one packet at a time interval set by the timer, or a function of sequentially outputting as one packet when a special control code is input. The optical wireless data transmission system according to claim 1.