JPH09261180A - Space transmission communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the communication at its least level by reducing the transmission bit rate in such a case where the speech channel length is increased or the speech channel is temporarily cut and the communication is impossible at a prescribed transmission power level. SOLUTION: The signals received via a reflector are condensed on the surface of a light receiving element 1A2 of a photoelectric conversion part consisting of a photodiode, etc., via a lens 1A1. The condensed signals of the element 1A2 undergo the photoelectric conversion and are amplified by a front-end amplifier 1A3 to undergo the phase control via a phase control circuit 1A4. The circuit 1A4 sends a transmission bit rate switch control signal (d) to a terminal equipment 2 to instruct the transmitter side to change the transmission bit rate according to the change of intensity of the electric power received at a receiver 1A. The equipment 2 sends the signal (d) to the communication device of the opposite party via a transmitter 1B. When a communication circuit is defective due to an obstacle, etc., the transmission bit rate is changed to a low level to control the quantity of main beam leaking outside. Thus the communication is secured at a low bit rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an indoor and an outdoor
The present invention relates to a space transmission communication device that transmits and receives information by an electromagnetic wave signal radiated into space.

[0002]

2. Description of the Related Art For example, in a space transmission communication device that forms a network such as an optical wireless link or an optical wireless LAN to perform transmission / reception, since transmission / reception is performed through a wireless transmission path using electromagnetic waves such as infrared rays, individual transmitters / receivers are relatively small. It can be configured as a portable type that is convenient for moving.

Even in the case of using the same electromagnetic wave transmission path, particularly when light such as laser light having a short wavelength is used, broadband high-speed data communication is possible, unlike transmission using electromagnetic waves other than light. Also, since light has its own straightness,
The space area transmitted and received by the space transmission communication device is limited to a range that can be seen by a person standing at the installation place.
This type of spatial transmission communication device is a B-ISDN terminal including a wired network because it has the advantage of relatively easy management of the transmission line area and does not require a license under the Radio Law for its operation. The use as a wiring means is expected more and more.

In recent years, a computer such as a personal computer has been connected to the transmitting side, the receiving side or both the transmitting and receiving sides of communication equipment,
Various data communication has come to be performed. An optical wireless LAN connection type for performing data communication includes an optical wireless link type for performing 1: 1 communication and an optical wireless LAN type for performing 1: many communication.

1: In the optical wireless LAN type for performing a lot of communication, a master station is installed on the indoor ceiling of a building, and the master station communicates with a plurality of slave stations arranged in the room. The communication devices in the room are divided into two types, that is, a so-called diffusion type in which a parent-child type and a ceiling plate or the like are used as a light reflecting plate, and which perform mutual communication 1 :.

In any type of optical wireless LAN, since the communication devices communicate with each other via a ceiling board or a master station provided on the ceiling, the optical transmission line is used for movement of people inside the room or other equipment. A fairly wide transmit beam is used so that the arrangement does not block it. Therefore, normally, communication is not interrupted by small obstacles such as dust, and the directivity of the transmission / reception antenna, that is, the direction of the transmission beam and the reception visual field pattern, on both the transmission side and the reception side of the communication device,
It didn't have to be that strict. However, an obstacle larger than the transmission beam width temporarily interrupts the communication path to interrupt communication, and because the transmission beam width is relatively narrow, it is more susceptible to obstacles and communication is temporarily interrupted. Although it may be interrupted, if the data transmission speed is not so high, the transmission data is temporarily stored in the buffer on the transmission side until the communication path is restarted, and when the failure on the communication path is released. , It was possible to guarantee the continuation of communication by transmitting the data accumulated in the buffer.

However, on the terminal equipment side of the wireless LAN connected to the Internet or the like via the gateway device,
With the future development of B-ISDN, it is necessary to process a large amount of high-speed data, so it is practically impossible to deal with temporary interruption of communication with a simple buffer as in the past. Is.

Further, although optical transmission enables wide band transmission and can respond to speeding up of data transmission, widening the band, on the other hand, deteriorates noise resistance characteristics.
In order to maintain the S / N ratio required for optical transmission and to perform error-free data transmission, it is required to increase the power of the transmission signal.
In order to increase the power in spatial transmission by optical wireless LAN or optical wireless link, there are a method of increasing the transmission output itself with a constant transmission beam width and a method of increasing the transmission power density by narrowing the transmission beam width. is there.

On the other hand, from the viewpoint of convenience of the communication device, it is required that the transceiver be smaller and have smaller power consumption. As the output of the transmitter becomes smaller, the arrival distance of electromagnetic waves becomes shorter. Therefore, in order to secure a long communication distance even in an indoor space, the transmission beam width is narrowed to increase the transmission power density. However, since the indoor transmission optical signal in the optical wireless LAN propagates particularly in the space where the user lives, there is a limit to the increase in the transmission power, from the viewpoint of safety to the body of the user.

However, not only in the case of optical communication but also in the case of using other electromagnetic waves, the narrowing of the transmission beam width narrows the communication area and is easily affected by obstacles. Will bring the negative side.

Further, when transmitting a baseband signal conventionally, the transmitted signal reaches a low frequency band. According to the description of the document “Eye Triple E Transactions on Communications, pages 2085 to 2094 (1995)” and the like, most of the noise is a direct current ( DC) to about 500 kHz. For this reason, background light noise due to a fluorescent lamp or an incandescent lamp is superimposed on the transmission signal. Therefore, in order to effectively remove the noise, a method of premodulating a frequency higher than the transmission signal as a carrier has been adopted. However, when transmitting high-speed data exceeding 10 Mbps, the carrier frequency reaches several tens of MHz, and the band of the light source and the photodetector is insufficient, so that it is difficult to realize the pre-modulation.

[0012]

As described above, the B-I
In order to support wideband high-speed data communication such as SDN, it is necessary to narrow the beam width of optical transmission and increase the transmission power density as much as possible under the limitation of the transmission power density. Communication is likely to be interrupted even by an unexpected small obstacle such as a person crossing the transmission optical path, which is a big problem in handling high-speed data communication.

Further, in the case of the spread-type LAN, even if the signal has a narrow transmission beam width and a large transmission power density, the transmission wave is diffused by the ceiling plate or the reflection plate provided on the ceiling wall. The power received at is small. Therefore, since the effective service area becomes short, there is a problem that many gateway devices connected to the wired network must be provided in order to obtain an external database or the like.

When transmitting a baseband signal,
There is also a problem that background light noise is superimposed on a transmission signal, and it is difficult to effectively remove the noise.

[0015]

In order to solve the above-mentioned conventional problems, the first invention is a transmitter for converting data into an electromagnetic wave signal having a predetermined bit rate and radiating the electromagnetic wave signal into space.
In a spatial transmission communication device comprising a receiver that receives an electromagnetic wave signal radiated by this transmitter and reproduces the data, a reception strength detection unit that detects a reception strength of the received electromagnetic wave signal, and a reception strength detection unit. And a bit rate changing means for changing the transmitting bit rate, and a receiving means for changing the receiving bit rate or the receiving operation of the electromagnetic wave signal according to the transmitting bit rate changed by the bit rate changing means. It is characterized by doing.

That is, the spatial transmission communication device according to the first aspect of the invention has a function of changing the transmission bit rate on the transmitter side and a reception function corresponding to the transmission bit rate on the receiver side.

Since the first invention device is configured as described above, when some obstacle enters the signal transmission path and as a result, the reception strength weakens, the transmission side lowers the transmission bit rate and transmits the signal. To do. On the other hand, on the receiving side that receives the transmission signal, the receiving operation is performed according to the transmission bit rate. Therefore, the reception bit rate is first changed. The reception field pattern is broadened with respect to the rate of reception.

As described above, since the device of the first aspect handles signals of a plurality of bit rates during transmission and reception, during high-speed data communication at a high bit rate, the transmission path is temporarily cut off and reception is performed at the required reception power. When it becomes impossible, the transmission bit rate is reduced by switching operation, and it is possible to switch to low-speed transmission that can communicate even in the transmission beam area with a low power density (beam area in the peripheral part away from the center). By avoiding the influence, at least the minimum required communication is continuously ensured, and the interruption of communication is avoided.

Further, since the device according to the first aspect of the present invention is merely a switching operation of the transmission signals having different bit rates, when the obstacle is removed, high-speed data transmission having a long communication distance can be immediately recovered. It is not necessary to previously install a large number of gateway devices connected to an external wired network as in the conventional case.

In a second aspect of the present invention, in a space transmission communication device for converting data into an optical signal, radiating the same to space, and capturing an optical signal propagating in the space to reproduce the data, the data to be transmitted is a baseband signal. Yes, this baseband signal is aB1C (a: natural number: a> 1) or bBc
B (b, c: natural number; c = b + 1) or DdB1
M (d: natural number; d> 1) is coded, and the low frequency band of the receiver is cut off.

That is, the spatial transmission communication device according to the second aspect of the present invention encodes the baseband transmission signal in the spatial transmission communication device in which the transmission bit rate is not changed according to the reception intensity, and performs background optical noise. Good data can be transmitted and received even if the low frequency band where is present is cut.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a space transmission communication device according to the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing an optical wireless LAN to which the spatial transmission communication device according to the first embodiment is applied. That is, a plurality of optical transceivers 1 in the room
(11, 12, ... 1N) are respectively connected to a terminal device 2 (21, 22, ... 2N) consisting of a personal computer or a gateway device to form an optical wireless LAN capable of digital transmission at a transmission speed of 100 Mbps. ing. Communication between the optical transceivers 1 (11, 12, ..., 1N) is performed by the diffused transmission signal reflected by the reflector 3 on the ceiling.

This optical wireless LAN of the diffusion type is different from the one of the parent-child type in that it does not require a specially active device to be mounted on the ceiling, and therefore can be easily constructed. Each optical transceiver 1
Each of (11, 12, ... 1N) is configured so that an optical signal is emitted toward the reflecting plate 3 on the ceiling and the reflected light from the reflecting plate 3 is received. In addition, a plurality of terminal devices 2
At least one of (21, 22, ... 2N) is composed of a gateway device (gateway device 23 in FIG. 1), and is connected to the Internet or the like via a wired network (not shown).

FIG. 2 shows each optical transceiver 1 (11, 1) of FIG.
It is a block diagram which shows 2, ... 1N). Optical transceiver 1 (1
It is assumed that the receiver 1A, which constitutes 1, 12, ... 1N), receives an optical signal modulated by RZ-encoded high-speed data. A transmission light signal received via the reflection plate 3 in FIG. 1 passes through the lens 1A1 and is condensed on the surface of the light receiving element 1A2 of the photoelectric conversion unit including a PD (photodiode) or the like. In the light receiving element 1A2, the optical signal is converted into an electric signal and amplified by the front end amplifier 1A3, and then the phase control circuit 1A4 and the first changeover switch 1A.
5 is supplied.

The phase control circuit 1A4 determines the bit rate of the input signal, derives the switching control signal a based on the determination result, and controls the first changeover switch 1A5.

A plurality of band limiting filters 1A6 (two filters 1A61, 1A62 in this embodiment) are connected to the first changeover switch 1A5.
Upon receiving the switching control signal a from the phase control circuit 1A4,
Selectively connect the filter corresponding to the bit rate of the input signal. The input signal from which the noise component has been removed by the selectively connected filter 1A6 is supplied to the discriminator 1A7.

A plurality of oscillators 1A9 (two oscillators 1A91, 1A92 in this embodiment) are connected to the phase control circuit 1A4 via a second changeover switch 1A8. The second changeover switch 1A8 receives the changeover control signal a based on the bit rate discrimination result from the phase control circuit 1A4 and selectively connects the oscillators corresponding to the bit rate of the input signal from the plurality of oscillators 1A9. The circuit 1A4 introduces an oscillation frequency signal corresponding to the bit rate of the input signal from the oscillator 1A9, generates a clock signal b whose phase is matched with the input signal, and supplies the clock signal b to the discriminator 1A7. The discriminator 1A7 introduces the received signal that has passed through the filter 1A6 and the clock signal b from the phase control circuit 1A4 to reproduce a 0/1 digital signal c,
It is supplied to the terminal device 2.

Further, the phase control circuit 1A4 derives the transmission bit rate switching control signal d in order to instruct the transmission side to switch and change the transmission bit rate in accordance with the intensity change of the received power in the receiver 1A. , To the terminal device 2 side. On the side of the terminal device 2 that has received the transmission bit rate switching control signal d, a transmission bit rate switching change instruction signal is transmitted to the partner communication device via the transmitter 1B. The transmission bit rate switching control signal d
Is not generated on the side of the phase control circuit 1A4, but is generated on the contrary on the side of the terminal device 2 or based on the transmission bit rate switching notification from the communication device on the other side,
By supplying it to the phase control circuit 1A4, the first and second changeover switches 1A5 and 1A8 may be switch-controlled.

Next, in the transmitter 1B, the information signal e to be transmitted is received from the terminal device 2 side and is temporarily stored in the buffer 1B1.
The signals are sequentially read according to the transmission control signal f from the side and supplied to the driver circuit 1B3. The driver circuit 1B3 is
A laser diode (LD) 1 generates a current according to the information signal e.
It is supplied to B4, and a transmission optical signal corresponding to the information signal e is generated and derived from the laser diode (LD) 1B4. The transmission optical signal is controlled by the lens 1B5 to have a transmission beam diameter required for transmission and is emitted to the reflector 3.

A bias current is supplied to the laser diode 1B4 from a bias power source 1B6. Further, the lens 1B5 is provided for the receiver 1 in order to reduce the size of the transceiver 1.
It may be configured to be shared with the A lens 1A1. Further, normally, all the signals accumulated in the buffer 1B1 are read by the selection circuit 1B2 and supplied to the driver circuit 1B3. However, when the bit rate control signal d indicates low bit rate transmission, A minimum required signal or a high priority signal is selected and read by the selection circuit 1B2 and supplied to the driver circuit 1B3.

The information for selection at this time may be given from the terminal device 2 as the signal g, or may be given to the terminal device 2 the signal g which is judged by the selection circuit 1B2 and notifies the information of transmission or discard. . in this way,
Since the sent information and the other information can be surely grasped by the terminal device 2, the reliability of communication is ensured and the retransmission becomes easy.

When the communication line is defective due to the presence of obstacles or the like, the transmission is switched from the high bit rate to the low bit rate, and the low bit rate transmission is mainly used during normal transmission. Center of the existing beam (main beam)
The outer light beam is utilized. Therefore, transmitter 1B
Also in this case, by controlling the amount of light leaking to the outside of the main beam, low bit rate communication can be made more reliable.

That is, even in the module of the ordinary transmitter 1B, since the components around the laser diode 1B4 diffusely reflect the light from the laser diode 1B4, a light beam propagating to the reflector 3 through an optical path slightly different from the main beam. There is. However, these rays tend to have large level fluctuations due to temperature changes, and there is also a tendency for the variations in the light amount among modules to become large. Therefore, in the transmitter 1B of FIG. 2, a part of the light from the laser diode 1B4 is provided with a reflector 1B7, and the optical transmission power is intentionally distributed around the main beam so that the minimum transmission power can be guaranteed. Configured. In this case, the intensity pattern of the light beam is slightly distorted, but ideally, it is desirable that the stepwise intensity pattern of the light beam can be formed as shown in FIG. This can be realized by using a hologram for the lens.

According to the first embodiment, the transmitter 1B on the other end of the communication prepares a plurality of types of transmission bit rates in advance, but the receiver 1A receiving the transmission bit rate has an obstacle. In many cases, the reception intensity changes drastically depending on the situation, and therefore, the transmitter 1B on the other side generally has a transmission rate of 100 Mbps, 1.5 Mbps, 64, for example.
It is enough to set about 3 categories like kbps,
Even if it is set so finely, a bit rate that is hardly used remains, or even if the bit rate is switched, there is practically no difference in the reception level. Furthermore, on the receiver 1A side, filters configured by the number of the bit rate types are used. It is often difficult to set many bit rates because provision of 1A6 may be difficult in practice.

The transmission bit rate switching condition determined by the phase control circuit 1A4, that is, the formation condition of the transmission bit rate switching control signal a, may be fixed in advance by mutual agreement with the other communication device. well,
Further, a reception power detection circuit for detecting the reception intensity is provided at the output part of the front end amplifier 1A3 of the receiver 1A, the output power of the front end amplifier 1A3 is monitored, and the partner transmission side is arranged so as to respond to the change in the received optical power. The transmission bit rate may be changed.

Therefore, it is assumed that the receiver 1A is in a state of receiving a signal with a constant transmission power from the partner communication device. If the receiver 1A moves and the distance from the reflector 3 becomes long, the optical power received by the receiver 1A becomes small, and in that state, the reception at the transmission rate of 100 Mbps cannot be maintained. On the side, for example, 384 kbp
The transmission speed is reduced to s and transmitted. In the receiver 1A that has received the transmission signal, the phase control circuit 1A4 determines the transmission bit rate, and switches and selects the band-limited filter 1A6 by the switching control signal a.

Due to the switching of the transmission rate drop, the receiver 1A usually has a margin of reception sensitivity of 20 dB or more and the communicable distance becomes long. Therefore, it is difficult to transmit information having a large amount of data such as image information. However, communication can be maintained for voice information and a small amount of data.

Therefore, according to the receiver 1A according to the first embodiment, if the receiver 1A is normally installed mainly in the communication of a small amount of data and the received signal strength is weak, the receiver 1A is operated. If the receiver 1A needs to receive information having a large amount of data such as a moving image, the receiver 1A should be placed at a position closer to the reflector 3 up to a distance where the required reception intensity can be obtained. Can be moved and received.

Further, a plurality of optical transceivers 1 (11, 12,
.. 1N) is arranged, the optical transceiver 1 (1, 12, ... 1N), which requires wideband transmission of high-speed data relatively frequently among them, is differentiated from other transceivers of low-speed data to reflect it. By centrally arranging the devices at a position closer to the device 3, it is possible to improve the utilization efficiency of the area within the limited range of the room supported by one optical wireless LAN.

Furthermore, the terminal device 2 (21, 22, ... 2)
N) is used to perform multimedia communication such as PC video conference via optical wireless LAN,
Even if a part of the light beam is blocked by a passerby and communication at a transmission rate of 100 Mbps is temporarily disabled, the application of the terminal device 2 (21, 22, ... It is possible to suspend the transmission of information having a large transmission capacity such as image information such as drawings and drawings, and maintain and continue only small capacity information such as voice and text by narrow band transmission.

By the way, in the case of diffusion type spatial transmission optical communication using the reflecting plate 3 on the ceiling, since the magnification of the lens 1A1 is limited, the light is collected by the lens 1A1 and the light receiving element 1A.
The light image formed on the second light receiving surface tends to be large. Further, when the transmitted light is reflected by the reflector 3 on the ceiling,
The coherency of light is impaired, and the image on the light receiving surface tends to spread.

However, in the case of an optical wireless link having a transmission speed of several tens of Mbps or more, when the light receiving element 1A2 is a photodiode or the like, a light receiving surface having a small diameter has a property of easily operating at high speed data. It is desirable that the diameter of 1A2 be set as small as possible. However, since the light receiving element 1A2 having a small diameter narrows the range of the incident direction of the receivable optical signal and narrows the field of view of the reception, when an obstacle obstructs the main part (main beam) of the transmission optical path, the obstacle is obstructed. Even if there is a transmission signal incident via the outside of the object, there is a risk that it will not be imaged on the normal light receiving surface and will not be received.

Even if the reception field pattern of the receiver 1A is not so narrow, this phenomenon also occurs when the transmission optical path is partially blocked by an obstacle that blocks a main portion of the transmission optical path. In such a case, the phase control circuit 1
Even if the transmission bit rate is switched and lowered by the fall back function by the bit rate switching control signal d derived from A4, the signal cannot be received.

FIG. 4 is a perspective view showing a light receiving element 1A2 formed of a photodiode. In FIG.
In the photoelectric conversion portion of the light receiving element 1A2, not only the light receiving surface portion 1A2b that receives the normal main beam A on the substrate 1A2a, but also a portion 1A2c formed by expanding the rectangular shape on the outside thereof.
Wiring is also provided on the outside so that the signal B incident on the outside can be received. The light receiving element 1A2 has the same structure as the substrate 1A2a except for the normal element portion. When the electrode 1A2d is provided, the photoelectric conversion action is performed although the efficiency is somewhat deteriorated.

The electrode 1A2e, which is a terminal on the current output side, is commonly connected to the front end amplifier 1A3 by a wiring pattern 1A2f. In the other terminal, the normal light-receiving surface portion 1A2b at the center is reverse-biased via the electrode 1A2g, but the peripheral portion is grounded by the electrode 1A2d. Therefore, the central portion of the beam, that is, the main beam A normally responds to high-power signals and high-speed signals, while the signal B incident on the peripheral portion of the beam, that is, outside the main beam, responds to these high-input power and high-speed signals. Responds only to low power signals and low speed signals. By using the light receiving element 1A2 having such a configuration, a high-speed signal is usually received by photoelectric conversion in the central portion, and the main part of the beam of the optical signal as described above is blocked by an obstacle on the optical path, Even if only the signal that has passed through the surrounding area can be received, the light is imaged on the outer portion 1A2c and photoelectrically converted, so that the reception visual field pattern is equivalently expanded, and a weak low-speed signal is generated. However, it is possible to continue reception.

As described above, by providing the receiving means for low-speed communication in the periphery of the main receiving area, that is, in the periphery of the transmitting beam, the receiving means for low speed communication is not particularly required, and even in the case of optical transmission. Therefore, the complicated configuration of the photoelectric conversion unit and the front end amplifier can be suppressed to the minimum, and the device can be downsized.

In the light receiving element 1A2 shown in FIG. 4, wiring is provided on a portion 1A2c outside the normal light receiving surface portion 1A2b,
Although the receiving field pattern is configured to be wide so that the signal B incident on the outer portion can also be received, the receiving field pattern can be widened even if a large number of photodiodes are arranged in an array.

(Second Embodiment) That is, FIG. 5 illustrates a second embodiment of the space transmission communication device according to the present invention, and in particular, its configuration is different from that of the first embodiment. It is a principal part perspective view which took out and showed the light receiving element 1A2 which does. That is, a large number of photodiode elements 1A2h1, 1A2h2, ... 1A2h7 are arrayed on the substrate 1A2a.
Arranged and biased photodiode element 1
The range of A2h1, 1A2h2, ... 1A2h7 is divided,
Further, by arbitrarily switching, it is possible to obtain the same function as that of the light receiving element 1A2 shown in FIG.

In this case, each of the photodiode elements 1A2h1, 1A2h2, ... 1A2h7 has its own photoelectric conversion efficiency and receives high-speed data independently of each other. The reception sensitivity when the signal is widened can be higher than that in the case of the first embodiment shown in FIG.

Further, each photodiode element 1A2h1,
1A2h2, ... 1A2h7 are provided with light receiving power detection circuits respectively on the output side, and when bias is applied only to the photodiode element in the portion where the received light power is high, the incident angle of the optical signal is slightly deviated or the incident beam diameter is changed. The field of view of the receiver 1A can be equivalently controlled even when the field of view is slightly changed or when strong interfering light such as sunlight enters the field of view of the receiver.
It is possible to enhance the photoelectric conversion efficiency for the optical signal by aligning 2 with the direction of the transmitted light beam or by aligning the portion with less interfering light.

The first and second wireless optical LANs
In the spatial transmission communication device according to the embodiment of the present invention, when a plurality of signals having different bit rates are mixed, in order to prevent the transmission of one optical signal from colliding with the transmission of another optical signal, Regardless of the type of bit rate,
It is necessary to be able to easily detect the transmission signal of another communication device.

For example, if there is a transmitter / receiver performing low bit rate communication, the other transmitter / receiver
It may appear as if a signalless state continues for a long time, and a new transmission may be started to cause an interference state. Therefore, in order to prevent such interference, when it corresponds to “0” in low bit rate transmission (data signal “1”).
"Light ON" at the time of, and "light OFF" at the time of data signal "0"), for example, 100 at intervals of several μs.
A pulse signal corresponding to Mbps may be inserted so that another transceiver can know that the transmission path is in use. The insertion of an extra pulse signal of this level (a pulse signal corresponding to 100 Mbps at intervals of several μs) has a short pulse width on the communication side, which is performed at a low bit rate.
Since the transmission power is also small, it does not cause any trouble. In addition, by limiting the transmission packet length during low bit rate transmission, when another node has only a buffer with a normal 1 ms delay, the buffer is filled up immediately by occupying the transmission path due to low bit rate transmission. Can be avoided.

Further, in the first embodiment shown in FIG. 4,
The output electrode 1A2e of the light receiving element 1A2 is configured to be connected to one front end amplifier 1A3 in common with the normal light receiving surface portion 1A2b and the outer portion 1A2c. The same effect can be obtained by separating the portion 1A2b and the light receiving portion 1A2c outside the portion 1A2b and connecting them to separate front end amplifiers 1A3.

(Third Embodiment) That is, FIG. 6 is a block diagram of a receiver 1A for explaining a third embodiment of the spatial transmission communication device according to the present invention. In a receiver 1A shown in FIG. 6, a main light receiving element 1A21 and a sub light receiving element 1A22 are provided.
Are the first and second front end amplifiers 1A3, respectively.
1, 1A32 is connected.

The first front-end amplifier 1A31 is directly connected to the first front-end amplifier 1A32, and the second front-end amplifier 1A32 is connected to the synthesizing circuit 1A11 via the switch 1A10.
The output from A32 is combined as necessary, and then supplied to the discriminator 1A7 via the filter 1A51.

The switch 1A10 is a phase control circuit 1
In response to the switching control signal a from A4, the light receiving element 1A2
Since the output signals of 1 and 1A22 are supplied to the synthesizing circuit 1A11, the switching control thereof removes the influence from the parasitic capacitance of the light receiving element 1A22 from the signal from the main light receiving element 1A21 for high-speed signal reception. ,
A signal with stable reception characteristics can be obtained. Further, the band of the second front end amplifier 1A32 corresponding to the subordinate light receiving element 1A22 is set from the beginning to, for example, a transmission rate of 384.
By adjusting to Kbps, noise in a high frequency band is suppressed, so that switching of the filter required in the configuration of FIG. 2 is not necessary and the configuration is simplified.

Further, in the configuration shown in FIG. 6, the first and second
Although the outputs of the front-end amplifiers 1A31 and 1A32 are selectively combined, the switches 1A10 may be omitted and the signals may be constantly combined. Further, in this embodiment, the first and second front end amplifiers 1A3
Although the outputs of the two systems of 1 and 1A32 are configured to be combined in the preceding stage of the filter 1A5, the outputs of the two systems are configured to be extended to the filter 1A51 or the discriminator 1A7 due to IC integration or the like, and then combined. Alternatively, it may be configured to switch.

According to this configuration, although the number of front-end amplifiers 1A31, 1A32 and the switch 1A10 increases, the main light receiving element 1A21 and the sub light receiving element 1A2.
2, and first and second front end amplifiers 1A3
By monolithicizing the 1 and 1A32, it is possible to avoid an increase in wiring and complication of the configuration.

In each of the above-described embodiments, the receiving operation according to the change of the transmission bit rate in the receiver 1A is based on the selective switching of the light-receiving field pattern by the light-receiving portion of the light-receiving element 1A2 or the synthesis. As shown in FIG. 7, the same function and effect can be obtained by moving the position of the receiving lens 1A according to the change of the transmission bit rate.

(Fourth Embodiment) That is, FIG. 7 is a block diagram showing a receiver for explaining a fourth embodiment of the space transmission communication device according to the present invention. That is, the lens 1A1 that collects the incident signal light on the light receiving element 1A2 is configured so that the position of the lens 1A1 can be finely moved in the arrow Y direction intersecting the optical axis by the adjusting mechanism 1A12. The light receiving area of the light receiving element 1A2 is only one part of the main part.
Even if the direction of the lens 1A1 is moved by the control of the adjusting mechanism 1A12, the focus position of the lens 1A1 is always the light receiving element 1
It is configured to be on A2, and is configured to be able to follow the light signal incident at an angle slightly displaced from the normal and convert the received light. Therefore, the receiver 1A detects the received optical power in the power detection circuit 1A13, and based on the detection signal, the adjustment mechanism 1A12 is controlled via the control unit 1A14 so that the optical power to the light receiving surface is always maximized. To adjust the lens 1A1.

When the optical transmission line is blocked by an obstacle, the control section 1A14 moves the lens 1A1 so that the optical transmission signal leaking through the outside of the obstacle and reaching the light receiving element 1A2 is condensed more. Control. That is, lens 1
By moving A1 to slightly shift the direction of the reception visual field pattern of the receiver 1A toward the outside of the obstacle, reception of the transmission signal at a low bit rate is ensured.

In this case, the light receiving element 1 shown in FIG.
Unlike the case where A2 is adopted, there is no change in the location where the received light pattern of the receiver 1A is obtained. Also,
The adjusting mechanism 1A12 and the like for finely moving the lens 1A1 can be configured by a servo mechanism using a known feedback circuit. Further, it is desirable that the lens 1A1 can move in any of the directions of up, down, left, and right around the optical axis, but considering that the blocking of the transmission path in an indoor wireless LAN is often due to the movement of a person. , Lens 1
The moving direction of A1 may be adjusted so as to be specified in the moving direction of the person, that is, the horizontal direction. Also, the reception path of the low bit rate transmission signal was selected by moving the lens 1A1.
Since it is determined by the relative optical positional relationship between A1 and the light receiving element 1A2, the lens 1A1 is fixed and the light receiving element 1A is fixed.
Even if the control system is configured to slightly move 2, the same function and effect can be obtained.

Further, in each of the above-mentioned embodiments, the received signal passed through the front end amplifier 1A3 is the phase control circuit 1A.
Although the data signal is reproduced by analog processing using the clock signal b from 4, the same effect can be obtained by processing and reproducing the received signal that has passed through the front end amplifier 1A3 by the digital arithmetic circuit.

(Fifth Embodiment) FIG. 8 is a block diagram showing an optical receiver 1A for explaining a fifth embodiment of the space transmission communication device according to the present invention. This optical receiver 1A has a digital arithmetic circuit 1A1 at the output of a front end amplifier 1A3.
By connecting 5 and changing the operation program, it is possible to easily cope with the change of the transmission bit rate and the transmission coding format.

That is, the optical reception signal received through the lens 1A1 and the light receiving element 1A2 is the front end amplifier 1
After being amplified by A3, it is supplied to the digital arithmetic circuit 1A15.

In the digital arithmetic circuit 1A15, the input signal is first quantized by the high speed A / D converter 1A15a.
At this point in time, the signal is a signal before discrimination including signal noise, and therefore the A / D converter 1A15a is assumed to have a sufficient sampling speed, a dynamic range, and required accuracy. Based on the output of the A / D converter 1A15a, a DSP (Digital Signal P) which is a main arithmetic circuit.
necessary calculation is performed in the processor 1A15b.

The DSP 1A15b first determines the bit rate of the received signal, then limits the band according to the bit rate and reproduces the digital information signal. The reproduced information signal is converted into a serial signal by the parallel-serial converter (PS) 1A15c, output, and supplied to the terminal device 2. Also DSP1A15
b controls the clock generation circuit 1A15d to generate a clock signal according to the transmission bit rate and similarly supplies it to the terminal device 2. Further, it also exchanges necessary information such as a bit rate control signal. In this receiver 1A, by providing a plurality of A / D converters 1A15a, the configuration of the optical receiver as shown in FIG. 6 is possible, and as shown in FIG. 7, the fine movement control of the lens is collectively calculated. It can also be performed by the circuit 1A15.

In each of the above-described first to fifth embodiments, the case where light is used for the transmission signal has been described as an example, but the embodiment where radio waves such as millimeter waves and microwaves are used will be described. .

(Sixth Embodiment) That is, FIG. 9 is a block diagram showing a sixth embodiment of the device of the present invention.
The signal receiving circuit 1A16 of the above is a high-frequency stage including an antenna and an RF unit, captures a transmission radio wave, converts it into an electric signal, and performs signal amplification, frequency conversion, etc. as necessary, and a switching control circuit 1A17 and a first changeover switch. Supplied to 1A5. The switching control circuit 1A17 determines the transmission rate of the received signal, derives the switching control signal a to control the first changeover switch 1A5, and also generates the transmission bit rate switching control signal d and supplies it to the terminal device 2. .

A signal processing circuit 1A18 is connected to the first change-over switch 1A5, and a plurality of signal processing circuits 1A18 are provided (corresponding to the first and the second in this embodiment) corresponding to the number of divisions of the transmission transmission rate which is assumed in advance. 2 signal processing circuit 1A18
1, 1A182) are provided, and the received signal is reproduced by noise removal and demodulation / identification by filters and a local oscillator provided inside, respectively, and the reproduced digital signal c
And the local clock signal b are supplied to the terminal device 2 via the first changeover switch 1A5, respectively.

The switching control circuit 1A17 is configured to introduce the reception signal from the signal receiving circuit 1A16 and generate and derive the switching control signal a according to the transmission bit rate thereof. Similarly to the above, the switching control signal a may be generated and derived by receiving the transmission bit rate switching control signal d from the terminal device 2, and further,
Although not shown, the digital signal c reproduced by the signal processing circuit 1A18 may be introduced, and on the basis of the monitoring of the digital signal c, on the contrary, the switching control signal a may be derived and supplied to the first changeover switch 1A5. good. However, in the configuration of the first changeover switch 1A5 in this case, the changeover switch section between the signal receiving circuit 1A16 and the signal processing circuit 1A18 is omitted, and the received signal is common to the first and second signals.
Signal processing circuits 1A181 and 1A182.

Further, the signal processing circuit 1A18 can be replaced with the digital arithmetic circuit 1A15 shown in FIG. 8 of the fifth embodiment, and in that case, the changeover switch 1A5 becomes unnecessary.

In any case, since the receiver 1A is constructed as described above, a failure occurs in the spatial transmission line,
The switching signal when the normal high-speed transmission becomes impossible and the transmission speed needs to be switched down is the switching control circuit 1A.
17 or generated and derived by supply from the terminal device 2.

On the other hand, the transmitter 1B receives the information signal e to be transmitted from the terminal device 2 side, temporarily stores it in the buffer 1B1, and successively in the selection circuit 1B2 in accordance with the transmission control signal f from the terminal device 2 side. It is read and supplied to the transmission signal generation circuit 1B8.

A plurality of transmission signal generation circuits 1B8 are provided in correspondence with the number of divisions of the transmission bit rate (two in this embodiment, the first and second signal generation circuits 1B81 and 1B82).
Since the transmission signal is generated by the transmission rate and the modulation method determined respectively, the generated transmission signal is transmitted from the signal transmission circuit 1B10 including the transmission antenna to the reflector 3 or the like via the transmission changeover switch 1B9. Radiated to the space. Also in this embodiment, as in the case of using light,
By configuring the radiation angle and the transmission beam pattern of the transmission antenna that configures the signal transmission circuit 1B10 according to the transmission transmission speed, it is possible to more effectively respond to the occurrence of a failure in the transmission path. Other than that, the signal transmission / reception relationship between the selection circuit 1B2 and the terminal device 2 is the same as the configuration shown in FIG.

(Seventh Embodiment) In each of the above embodiments, transmission of RZ (Return to Zero) encoded data has been mainly described. However, not only RZ code but also NRZ (Non Return to Zero) is used.
It is also possible to transmit an o) code, and further, a ternary or quaternary multilevel encoded signal. In transmitting these signals,
Scramble or BSI to remove background light noise
(Bit Sequence Independence
e) Various encoding techniques for assurance can be applied. The scrambling and BSI guarantee coding technology was developed to prevent the same code of signal marks and spaces from being unable to extract the timing clock continuously. In the seventh embodiment, while maintaining this advantage, background light noise existing in the low frequency range can be effectively removed.

Now, various encoding methods for BSI guarantee applicable to the present invention will be described.

As a typical encoding method, aB1C (a
Binary with 1 Complement
insertion) encoding (a: natural number).
This is to add one complementary bit for each a bit to the immediately preceding bit.

Another coding method is bBcB coding (b, c: natural number). This means that the mark rate is ½ for a block of a c-bit binary code of a binary sequence for every b bits.
It is converted so that it approaches.

Furthermore, DdB1M (Different
ial d Binary with 1 Mark
insertion) coding (d: natural number). A coding method in which 1 bit of a mark signal is inserted for every d bits into a signal sequence (original sequence) to be transmitted, and the signal sequence and the transmission code 1 bit before are summed to generate a mark signal. is there.

In addition, eB1P (e Binary
with 1 Parity) encoding (e: natural number) or PMSI (Periodic Mark and Sp)
ace Insertion) encoding, and further C
Encoding methods such as MI and DMI are also applicable. However, redundancy is a problem with these encodings.

For example, in the case of aB1C encoding, the original information rate is a / (a + 1) of the bit rate, and bBc
In the case of B encoding, the original information rate is the bit rate b /
c, the original information rate d / (d + in the case of DdB1M encoding
1) respectively. However, for these three encoding methods, a> 1, c = b + 1, d>, respectively.
If the condition of 1 is added, the increase rate of the bit rate can be suppressed to a small level and the background light noise can be cut.

On the other hand, it is not preferable to use bi-phase coding such as CMI and DMI in which the original information rate is 1/2 of the bit rate in a system that uses the data transmission band compactly.

However, even when the various BSI guarantee coding schemes are used as described above, deterioration due to low-frequency cutoff during repeated pattern transmission may occur. In order to avoid this, it is extremely effective to provide the receiver with a low-frequency cutoff compensation circuit, and a clamp circuit can be used as an example. This clamp circuit can perform peak and bottom hold with a time constant sufficiently longer than the bit length to determine the mark or space discrimination level.

Further, in a system using scrambling alone, the maximum homo-code continuity can be specified only stochastically, but the maximum homo-code continuity can be specified by using scrambling and various BSI guarantee coding systems together. Further, since it is possible to prevent the repeated pattern from being generated easily, the background light noise can be more effectively cut.

The effect of low-frequency cutoff of the coded signal will be described with reference to FIG. FIG. 10a) is a time waveform of the original signal. As an example, a case where a mark continues for a sufficiently long bit number and then a space continues for a sufficiently long bit number is shown. FIG. 1 shows the case where aB1C encoding is performed on this original signal.
0b) (a = 5 in the figure). This aB1C
FIG. 10c) shows the low-frequency cutoff of the encoded signal of FIG. 10b). FIG. 10c) shows that since the signal does not include a DC component, the mark / space level fluctuates immediately after switching from mark to space. The speed of this fluctuation depends on the cutoff frequency of the low frequency cutoff.

Further, in the low-frequency cutoff compensation clamp circuit of the receiver, the time constants for peak and bottom detection for determining the discrimination level are made sufficiently large in order to withstand the same sign continuity.
Therefore, assuming that the level fluctuation at a-bit continuous is m, if the level fluctuation due to low frequency cutoff is (0.5 + m / 2) or less at a-bit continuous, no identification error occurs.

Here, assuming that the bit rate is R, the time interval for a bits is a / R, and the time constant τ of level fluctuation due to low frequency cutoff is

[Equation 1] Becomes For example, the bit rate R is 100 Mbps (R =
100 × 10 ⁶ ), if the level fluctuation m of a-bit continuous in the clamp circuit is 10% (m = 0.1), 10B1C
Can cut to 950 kHz and 5B1C to 1.9 MHz. However, this is limited to the case where the received light power is large and the S / N is sufficiently high. In practice, it is desirable to secure the low frequency range up to about 1/2 of the cutoff frequency f given by the equation (1).

Further, an LD (Laser Diode) is particularly suitable for a high-speed spatial transmission communication device because it can perform high-speed modulation and high output as compared with an LED (light-emitting diode). Therefore, if LD is used as a light emitting element in the transmitter and an encoding technique is used, efficient communication becomes possible. Of course, an LED may be used.

The encoding is effective even if the transmission bit rate is changed. In this case, several methods are possible. First, even if the transmission bit rate is changed, the same encoding method is used. In this case, the circuit configuration is relatively simple. Also, when changing to a low bit rate, there is a method of increasing the redundancy of coding. Eg 1
By changing from 0B1C to 2B1C, background light noise can be effectively removed regardless of the transmission bit rate. When the bit rate becomes lower, the background light noise cannot be removed even by encoding. In such a case, there is a method such as not performing encoding, or switching to a pre-modulation communication system with a carrier higher than the band of background light noise.

In each of the above-described embodiments, when low-bit-rate transmission is performed by the transmitting side, if there is no output for a certain period of time or longer, the receiving side performing communication at a high bit-rate from the transmitting side. A function to insert and send out a transmission signal that can be detected only by the machine is added, and even if high bit rate communication and low bit rate communication may be performed at the same time on 1: transmission lines, they will collide with each other. It can be configured to avoid and communicate. In addition, good data can be transmitted and received even if the low frequency band where the background light noise exists is cut by encoding the baseband transmission signal.

Further, the device of the present invention is compatible with the transceivers 1A and 1A.
In both B, the transmission bit rate changing process that is performed in response to the occurrence of a transmission failure in the communication path is performed quickly and appropriately, and it is described as being capable of supporting high-speed data communication and the like. It also means that an apparatus having a transmission and reception function capable of handling this transmission bit rate change processing can immediately respond to the transmission and reception functions of the other party. Therefore, the device of the present invention is naturally applied to the existing transmitter or receiver having only the function of high-speed data transmission, and further to the transmitter or receiver having only the function of only low-speed data transmission, its communication format and network. As long as there is consistency in the processing format of, communication can be performed without any trouble.

As described above, the spatial transmission communication device according to the present invention effectively utilizes the power distribution of the transmission beam by the switching control, and the receiver side is better able to receive the low bit rate during the high speed transmission. It can be done reliably.

Further, the transmitting side is provided with the function of separately forming the peripheral beam portion having the transmission power required for transmission at the low transmission bit rate around the central portion of the transmission beam forming the transmission signal. , It is possible to remarkably reduce the influence on transmission line failure, and future B-ISD
This is a large effect that can be obtained as N terminal wiring means.

Further, in the space transmission communication device in which the transmission bit rate is not changed according to the reception intensity, the baseband transmission signal is coded to cut the low frequency band where the background light noise exists. You can send and receive good data.

[0097]

According to the first aspect of the present invention, since a single receiver can switch and demodulate signals of a plurality of bit rates, it is necessary when the communication path becomes long and the communication path is temporarily interrupted. When communication with a predetermined transmission power becomes impossible, the minimum communication can be secured by lowering the transmission bit rate.

Further, in a system using a receiver for high-speed communication with a narrow field of view, a light-receiving surface for low-speed communication is formed around the main light-receiving element even when the main part of the light beam cannot be received by the receiver. As a result, the receiver can receive by using the peripheral portion of the light beam with a field pattern different from that in the normal time, and thus it is possible to secure the minimum communication in which the transmission bit rate is also reduced.

Also, by controlling the power distribution of the light beam, it is possible to secure the required amount of power in the peripheral portion of the beam, so that it is possible to effectively realize low bit rate reception at the receiver side, etc. The practically remarkable effect is obtained.

The spatial transmission communication device according to the second aspect of the present invention encodes the baseband transmission signal in the spatial transmission communication device in which the transmission bit rate is not changed according to the reception intensity, and the presence of background optical noise is present. Good data can be transmitted and received even if the low frequency range is cut.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical wireless LAN to which a first embodiment of a space transmission communication device according to the present invention is applied.

2 is a block diagram showing an optical transceiver of the spatial transmission communication device shown in FIG. 1. FIG.

3 is an intensity pattern diagram of a light beam emitted from an optical transmission unit of the optical transceiver shown in FIG.

FIG. 4 is a perspective view showing a light receiving element of the optical transceiver shown in FIG.

FIG. 5 is a perspective view showing a light receiving element adopted in an optical receiver according to a second embodiment of a space transmission communication device according to the present invention.

FIG. 6 is a block diagram showing an optical receiver according to a third embodiment of a space transmission communication device according to the present invention.

FIG. 7 is a configuration diagram showing an optical receiver according to a fourth embodiment of a space transmission communication device according to the present invention.

FIG. 8 is a block diagram showing an optical receiver according to a fifth embodiment of the spatial transmission communication device according to the present invention.

FIG. 9 is a block diagram showing a radio wave transmitter / receiver according to a sixth exemplary embodiment of a spatial transmission communication device according to the present invention.

FIG. 10 is a diagram for explaining the influence of low-frequency cutoff of a coded signal according to the present invention.

[Explanation of symbols]

 1, 11, 12, ... 1N Optical transceiver 1A Receiver 1A1 Lens 1A2 Light receiving element 1A3 Front end amplifier 1A4 Phase control circuit 1A6 Filter 1A7 Discriminator 1A8 Transmission signal generation circuit 1A9 Oscillator 1A12 Adjustment mechanism 1A13 Power detection circuit 1A15 Digital arithmetic circuit 1A17 switching control circuit 1A18 signal processing circuit 1B transmitter 1B1 buffer 1B2 selection circuit 1B4 laser diode 1B5 lens 1B7 reflection plate 2, 21, 22, ... 2N terminal equipment 23 gateway device 3 reflection plate a switching control signal c digital signal d transmission bit Rate switching control signal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04B 10/00

Claims (8)

[Claims] 1. A space including a transmitter for converting data into an electromagnetic wave signal having a predetermined bit rate and radiating the electromagnetic wave to space, and a receiver for receiving the electromagnetic wave signal radiated by the transmitter and reproducing the data. In the transmission communication device,
Reception intensity detecting means for detecting the reception intensity of the received electromagnetic wave signal, bit rate changing means for changing the transmission bit rate according to the reception intensity, and the transmission bit rate changed by the bit rate changing means. And a receiving unit that changes the reception bit rate or the reception operation of the electromagnetic wave signal in accordance with the above. 2. The space transmission communication device according to claim 1, wherein the electromagnetic wave signal is an optical signal. 3. The spatial transmission communication device according to claim 1, wherein the receiving means includes a plurality of receiving elements forming mutually different electromagnetic wave receiving areas. 4. The transmitter further comprises: first transmitting means for forming a transmitting main beam; and radiation power generated by the transmitting main beam outside the transmitting main beam formed by the first transmitting means. The spatial transmission communication device according to any one of claims 1 to 3, further comprising a second transmission unit that forms a transmission sub-beam with a small power. 5. The transmitter transmits a signal that can be detected only by the receiver that is receiving an electromagnetic wave signal of a high bit rate while the transmitter is transmitting an electromagnetic wave signal of a low bit rate. The spatial transmission communication device according to any one of claims 1 to 4, wherein the spatial transmission communication device transmits the electromagnetic wave signal with a low bit rate. 6. The data is a baseband signal,
This baseband signal is aB1C (a: natural number; a>
1) or bBcB (b, c: natural number; c = b +
The spatial transmission communication device according to claim 2, wherein the spatial transmission communication device is encoded according to 1) or DdB1M (d: natural number; d> 1), and blocks the low frequency range of the receiver. 7. The spatial transmission communication device according to claim 6, wherein the light emitting element for outputting the optical signal in the transmitter is a laser diode. 8. In a space transmission communication device for converting data into an optical signal, radiating the optical signal to space, and capturing an optical signal propagating in the space to reproduce the data, the data to be transmitted is a baseband signal, Band signal is aB1
C (a: natural number: a> 1) or bBcB (b,
c: natural number; c = b + 1), or DdB1M (d:
A spatial transmission communication device which is encoded by a natural number; d> 1) and cuts off a low frequency band of a receiver.